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Overview
Chapter One: Cameras
The cinematographer's most basic tool is the motion picture camera. This piece of precision machinery comprises scores of coordinated functions, each of which demands understanding and care if the camera is to produce the best and most consistent results. The beginning cinematographer's goal should be to become thoroughly familiar and comfortable with the camera's operation, so that he or she can concentrate on the more creative aspects of cinematography.
This chapter covers many isolated bits of practical information. However, once you become familiar with camera operation, you will be able to move on to the substance of the cinematographer's craft in subsequent chapters. In the meantime, you are well advised to try to absorb each operation-oriented detail presented in this chapter, because operating a camera is all details. If any detail is neglected, the quality of the work may be impaired.
The film movement mechanism is what really distinguishes a cinema camera from a still camera. The illusion of image motion is created by a rapid succession of still photographs. To arrest every frame for the time of exposure, the principle of an intermittent mechanism was borrowed from clocks and sewing machines. Almost all general-purpose motion picture cameras employ the intermittent principle.
Intermittent mechanisms vary in design. All have a pull-down claw and pressure plate. Some have a registration pin as well. The pull-down claw engages the film perforation and moves the film down one frame. It then disengages and goes back up to pull down the next frame. While the claw is disengaged, the pressure plate holds the film steady for the period of exposure. Some cameras have a registration pin that enters the film perforation for extra steadiness while the exposure is made.
Whatever mechanism is employed requires the best materials and machining possible, which is one reason good cameras are expensive. The film gate (the part of the camera where the pressure plate, pull-down claw, and registration pin engage the film) needs a good deal of attention during cleaning and threading. The film gate is never too clean. This is the area where the exposure takes place, so any particles of dirt or hair will show on the exposed film and perhaps scratch it. In addition to miscellaneous debris such as sand, hair, and dust, sometimes a small amount of emulsion comes off the passing film and collects in the gate. It must be removed. This point is essential. On feature films, some camera assistants clean the gate after every shot. They know that one grain of sand or bit of emulsion can ruin a day's work.
The gate should first be cleaned with a rubber-bulb syringe or compressed air to blow foreign particles away. Cans of compressed air must be used in an upright position; otherwise they will spray a gluey substance into the camera. When blowing out the aperture, it is recommended that you spray from the open lens port side, with the mirror shutter cleared out of the way, through the aperture, rather than from inside the threading area into the aperture. This helps prevent blowing particles into the mirror area. An orangewood stick, available wherever cosmetics are sold, can then be used to remove any sticky emulsion buildup. There is also an ARRI plastic "skewer" for this job, bent at the end to allow you to get the inner edges of the aperture better. The gate and pressure plate should also be wiped with a clean chamois cloth -- never with linen. Never use metal tools for cleaning the gate, or, for that matter, for cleaning any part of the film movement mechanism, because these may cause abrasions that in turn will scratch the passing film. Do not use Q-tips either, as these will leave lint behind.
The gate should be cleaned every time the camera is reloaded. At the same time, the surrounding camera interior and magazine should also be cleaned to ensure that no dirt will find its way to the gate while the camera is running.
The intermittent movement requires the film to be slack so that as it alternately stops and jerks ahead in one-frame advances, there will be no strain on it. Therefore, one or two sprocket rollers are provided to maintain two loops, one before and one after the gate. In some cameras (such as the Bolex and Canon Scoopic), a self-threading mechanism forms the loops automatically. In Super-8 cassettes and cartridges, the loops are already formed by the manufacturer. On manually threaded cameras, the film path showing loop size is usually marked.
Too small a loop will not absorb the jerks of the intermittent movement, resulting in picture unsteadiness, scratched film, broken perforations, and possibly a camera jam. An oversize loop may vibrate against the camera interior and also cause an unsteady picture and scratched film. Either too large or too small a loop will also contribute to camera noise.
Camera Speeds
The speed at which the intermittent movement advances the film is expressed in frames per second (fps). Each frame exposed is a single sample of a moving subject, so the higher the sampling rate, that is, the faster the frame rate, the smoother the motion will be reproduced. To reproduce movement on the screen faithfully, the film must be projected at the same speed as it was shot. Standard shooting and projection speed for 16mm and 35mm is 24 fps; standard speeds for 8mm and Super-8 are 24 fps for sound and 18 fps (or 24 fps) for silent.
If both the camera and the projector are run at the same speeds, say 24 fps, then the action will be faithfully reproduced. However, if the camera runs slower than the projector, the action will appear to move faster on the screen than it did in real life. For example, an action takes place in four seconds (real time) and it is photographed at 12 fps. That means that the four seconds of action is recorded over forty-eight frames. If it is now projected at standard sound speed of 24 fps, it will take only two seconds to project. Therefore, the action that took four seconds in real life is sped up to two seconds on the screen because the camera ran slower than the projector.
The opposite is also true. If the camera runs faster than the projector, the action will be slowed down in projection. So to obtain slow motion, speed the camera up; to obtain fast motion, slow the camera down.
This variable speed principle has several applications. Time-lapse photography can compress time and make very slow movement visible, such as the growth of a flower or the movement of clouds across the sky. Photographing slow-moving clouds at a rate of, say, one frame every three seconds will make them appear to be rushing through the screen when the film is projected at 24 fps. On the other hand, movements filmed at 36 fps or faster acquire a slow, dreamy quality at 24 fps on the screen. Such effects can be used to create a mood or analyze a movement. A very practical use of slow motion is to smooth out a jerky camera movement such as a rough traveling shot. The jolts are less prominent in slow motion.
To protect the intermittent movement, never run the camera at high speeds when it is not loaded.
When sound movies arrived in 1927, 24 fps was firmly established as the standard shooting and projection rate, although it was a frame rate occasionally used by Silent Era filmmakers. It is not actually the ideal frame rate for the recreation of motion, as it provides barely enough individual motion samples over time to create the sensation of smooth, continuous motion when played back. However, it's become the frame rate that audiences are most accustomed to seeing in movies and has become an integral part of the "film look" that many people discuss these days as they attempt to get video technology to emulate film. The main artifacts to this fairly low frame rate are strobing and flicker. Strobing is the effect of sensing that the motion is made up of too few samples and therefore does not feel continuous. One of the ramifications is that it is sometimes necessary to minimize fast movement, such as when panning the camera across a landscape; otherwise the motion seems too staccato, too jumpy. Flicker happens when the series of still images are not being flashed quickly enough for the viewer to perceive the light and image as being continuously "on." The solution generally has been for film projectors to use a twin-bladed shutter to double the number of times the same film frame is flashed before the next frame is shown. So even if the movie was shot and then projected at 24 fps, the viewer is seeing forty-eight flashes per second on the screen.
A change in camera speed will cause a change in shutter speed. In most cameras the shutter consists of a rotating disk with a 180* cutout (a half circle). As the disk rotates it closes over the aperture, stopping exposure and allowing the movement to advance the film to the next frame. Rotating further, the cutout portion allows the new frame to be exposed and then covers it again for the next pull-down. The shutter rotates constantly, and therefore the film is exposed half the time and covered the other half. So when the camera is running at 24 fps, the actual period of exposure for each frame is 1/48 second (half of 1/24). Varying the speed of the camera also changes the exposure time. For example, by slowing the movement by half, or to 12 fps, we increase the exposure period for each frame, from 1/48 to 1/24 second. Similarly, by speeding up the movement, doubling it from the normal 24 fps to 48 fps, we reduce the exposure period from 1/48 to 1/96 second. Knowing these relationships, we can adjust the f-stop to compensate for the change in exposure time when filming fast or slow motion.
A change in the speed of film movement can be useful when filming at low light levels. For example, suppose you are filming a cityscape at dusk and there is not enough light. By reducing your speed to 12 fps, you can double the exposure period for each frame, giving you an extra stop of light that may save your shot. Of course, this technique would be unacceptable if there were any pedestrians or moving cars in view; they would be unnaturally sped up if the film were projected.
Some cameras are equipped with a variable shutter. By varying the angle of the cutout we can regulate the exposure. For example, a 90° shutter opening transmits half as much light as a 180° opening. Some amateurs make fade-outs and fade-ins on their original film by using the variable shutter, assuming it can be changed smoothly while the camera is running. Professionals generally have all such effects done in the lab.
Since changing the camera speed also changes the exposure, you can compensate for a speed change in midshot (called speed ramping) by adjusting either the f-stop or the shutter to maintain the correct exposure. For example, a speed change from 24 fps to 12 fps would cause twice as much light to reach the film by the time it was running at 12 fps, so you could simultaneously close down the shutter angle from 180° to 90° as the frame changes, thus counteracting the exposure increase. However, the rendition of motion will be different when you alter the shutter angle, not just when you alter the frame rates.
Shutter movement is directly responsible for the stroboscopic effect. Take the example of the spokes of a turning wheel. Our intermittent exposures may catch each succeeding spoke in the same place in the frame, making the spinning wheel appear to be motionless. The camera may even catch each spoke in a position counterclockwise to the previous spoke captured, making the wheel look like it is running in reverse. Another variation, called skipping, results from movement past parallel lines or objects, such as the railings of a fence. They may appear to be vibrating. These effects will increase with faster movement and with a narrower shutter angle.
Exposure time controls the amount of motion blur recorded on each frame; due to the low sampling rate of 24 fps, a certain amount of blur is needed to make a moving object on one frame visually "blend" with the next frame. Too little blur and the motion seems too "sharp" and the viewer becomes more aware as to how few motion samples there really are; it no longer feels continuous but instead "steppy." Therefore, shooting at 24 fps with a closed-down shutter, like at a 45° or 90° angle, will cause faster motion to strobe heavily. This has been used as a creative effect by some filmmakers, since it adds a certain nervous, jittery energy to action scenes. The movie Saving Private Ryan is the most famous example of this technique; many of the battle scenes were shot handheld with a 45° shutter angle. It's also a useful technique when shooting spraying water or falling rain, if you want to see each droplet more clearly.
There are other reasons to use a shutter angle other than 180°, such as for filming TV screens or lights that pulse with their AC current. (See chapter 8.)
In many cameras the shutter performs a vital role in the viewing system. The front of the shutter has a mirror surface that reflects the image into the viewfinder when the shutter is closed. The great advantage of this reflex system is that all the light goes alternately to the film and to the camera operator's eye, providing the brightest image possible. The surface of the mirror shutter should be cleaned only with an air syringe or gently with compressed air; nothing should be allowed to touch it.
Other systems (such as the Bolex Reflex) use a prism between the lens and the shutter so that a certain percentage of the light is constantly diverted to the viewfinder. The disadvantage is that it reduces the amount of light going both to the viewfinder and to the film, since the beam is split. An exposure compensation is required to allow for the light "stolen" from the film by the viewing system. It is usually very slight. For example, in the Bolex Rex-5 the loss is about a third of a stop. You should consult the operator's manual for the specific camera to learn the exact compensation.
Be aware that just as the reflex camera allows light coming through the lens to reach both the film and the camera operator, it also allows light coming back through the eyepiece to reach the film. Therefore, you must keep your eye pressed against the viewfinder while filming to prevent any light-leak from fogging your image; if you are not planning on looking through the viewfinder during the take, you must seal off the eyepiece.
The viewing systems discussed so far allow the cameraperson to look through the taking lens. Many cameras of older design do not have a reflex viewfinding system. As a result, the film in the camera may not receive exactly the same image that the separate viewfinder (usually off to one side of the camera) sees. Referred to as parallax, this is especially a problem when shooting close with a wide-angle lens. However, most nonreflex cameras have an adjustment that can partly correct for parallax.
Video Assist
Also referred to as a video tap, this is a system where some of the light going to the viewfinder is also received by a tiny internal video camera; that image can then be sent to a TV monitor, either with cables or transmitted by UHF (by using an additional device). This signal can even be recorded to videotape for temporary playback on the set. The image quality of this video image is generally very poor, but it allows you to see the framing without actually looking through the viewfinder. This is mainly done so that people other than the camera operator can see the exact shot during the take. However, it is also useful when it is physically impossible to look through the camera viewfinder during the take, like when the camera is mounted on a moving vehicle, a Steadicam, or a remote-controlled crane. Occasionally the camera assistant will have a small LCD monitor mounted to the camera, which enables the assistant to see what the operator is framing. This can come in handy when shooting a scene on a telephoto or macro lens in which the operator is panning from one object to another and the focus needs to be adjusted as each object comes into view. The portable LCD screen can even be used by the operator when doing a complex dolly move, perhaps with an extreme boom up or down combined with a pan, when it may be too difficult to continually keep the eye against the viewfinder.
The film transport mechanism, the shutter, and other moving camera parts are operated by the motor. There are two basic types of motors, spring-wound and electric. Spring-wound cameras run approximately twenty to forty feet of film per wind. The advantages include a compact design and reliable performance under difficult conditions such as cold weather.
Electric motors are available in a variety of designs. The five types that are generally used are: (1) variable speed ("wild"); (2) interlocked; (3) stop frame (time-lapse); (4) constant speed; and (5) crystal speed, which is the most commonly used, especially for sync-sound production. Variable speed motors have an adjustable speed control that may range from 2 to 64 fps or more. (Above 64 fps are considered high-speed motors.) The interlocked motor synchronizes the camera with other devices, such as back or front projectors. The stop frame or time-lapse motor is usually connected with an intervalometer to allow the setting up of whatever exposure intervals are needed for time-lapse photography (such as filming the growth of plants). The constant speed motor is designed to run at a set speed, such as 24 fps, with some precision.
The most advanced type of synchronous speed motor is designed with a crystal control to regulate the speed with extreme precision. When the camera motor and the tape recorder are both equipped with crystal controls, you can film "in sync" with no cables connecting the camera to the recorder. Furthermore, several crystal control cameras can be held in sync to one or more crystal recorders, allowing for multicamera coverage with no cables to restrict the distances between them. Some crystal control motors even combine several functions, allowing the operator to change from constant speed crystal-sync to variable "wild" speeds or single frame at the touch of a switch. The best controls allow a wide variety of speeds to be shot precisely at crystal-sync, necessary for filming under certain pulsing AC light sources at high frame rates for a slow-motion shot.
Most 16mm camera motors operate on DC current supplied by batteries. Nickel-cadmium (NiCad) and nickel metal hydride (NiMH) are widely used; lithium ion batteries are becoming more common. Their life expectancy varies, depending on the conditions of use and maintenance, but on the average about five hundred cycles of recharging and discharging should be expected.
There are slow "overnight" chargers that require fourteen to sixteen hours, quick chargers that will charge batteries in half this time, and truly fast chargers that can do the job in one hour.
It is essential to familiarize yourself with the charger on hand. Some chargers will damage a battery when left to charge for longer than required. It is advisable to have at least four charged batteries on hand so that they can be rotated with enough time for slow charging.
Batteries come in three types: belt, block, and on-board. The battery belt, consisting of built-in nickel-cadmium cells, is a convenient power source for portable 16mm and 35mm cameras, especially when shooting handheld. In situations where mobility is less of an issue, longer-lasting but heavier block batteries may be used. Many modern 16mm cameras use small on-board batteries that clip onto the rear or side of the camera. All Super-8 cameras house the batteries (usually AAs) inside the camera body.
Make sure the voltage of the battery used matches what your camera motor uses. The 16mm Arri SR1 and SR2, and the Aaton XTRprod and A-Minima, for example, use a 12-volt battery, but the Arri SR3 uses a 24-volt battery (as do many 35mm cameras). Many battery belts and block batteries can be switched between 12V and 24V, or between 12V and 16V. Plug into the correct voltage connector on these batteries.
Most of the smaller 16mm cameras will house up to 100-foot loads (on metal daylight spools) inside the camera body. Modern 16mm cameras are usually equipped with film magazines capable of holding up to four hundred feet of film on a plastic core instead of a metal spool. Four hundred feet of film stock in a camera running at 24 fps will give you eleven minutes of footage. The Aaton A-Minima uses a unique 200-foot plastic spool design that must be loaded in darkness. There is an optional 1,200-foot magazine for the 16mm Panaflex Elaine and an 800-foot magazine made for the Aaton XTRprod and Arri SR3 cameras.
Having several magazines allows for a more efficient production, particularly when more than one type of film stock is used on a given day. The camera assistant loads several magazines in advance so that the magazine change will slow down the production minimally.
Remember, when considering magazines, the two decisive factors are capacity and design. The shape and placement of the magazine is sometimes important too. For most shooting situations it doesn't matter, but when you are shooting in cramped quarters, such as from the cockpit of a plane or from under a car, the bulkiness of the camera can make a difference. Here a cameraperson may want a camera with magazines that are smaller or that mount to the back rather than the top. The operator may even want to use one of the smaller cameras that only allow the 100-foot daylight spool loads.
Most magazines have to be loaded in total darkness. The smaller loads available on daylight spools require only subdued light when loading; however, these are not generally used in modern sync-sound cameras, as they increase the noise level while the camera is running. Film not on daylight spools necessitates either a darkroom or a changing bag. The changing bag must be of adequate size and absolutely light-tight. It should be stored in a special case or cover to keep it spotlessly clean and dust free. (Don't let your dog sleep on it.) Any hairs, dirt, or dust in the changing bag can easily enter the magazine being loaded and from there travel to the gate. Even the tiniest of dust specks are visible on a 16mm frame because of the higher magnification of the image.
Before loading an unfamiliar magazine, practice loading it with a roll of waste film (called a dummy load) that you don't want, first in the light and then in the dark, to simulate the loading of unexposed stock.
Some magazines have their own take-up motors to wind up the film as it reenters the magazine after passing through the camera. Such motors should be tested with a waste roll before the magazine is loaded with unexposed film. Run this test with the battery to be used in filming. This test is advisable because a battery may sometimes have enough charge to run a camera with a small 100-foot internal load or an empty magazine but then fail to operate the magazine and camera when it is loaded.
Also, before loading, clean the magazine with compressed air, camera brush, and a piece of sticky paper in order to remove dust, film chips, or hair, and make sure that the rollers are moving freely. (Never wear a fuzzy or hairy sweater when cleaning camera equipment or in the darkroom.) It is a good idea to do a scratch test where you run some new film through the camera to see if the magazine or the gate is scratching the film. You examine the strip of film afterward with a light and magnifier to look for any faint abrasions in the surface of the emulsion or base. Obviously this piece of film becomes waste at this point, having been exposed to light.
After loading the magazine it is advisable to seal the lid with 1-inch camera tape. This is partly to prevent light leakage on old magazines, but mainly to prevent an accidental opening, especially if the loaded magazine is dropped. When you are loading magazines in a hurry, it is easy to confuse loaded ones and unloaded ones. Taping and labeling the loaded magazines immediately after loading will save you the annoyance of opening a supposedly empty magazine and ruining a roll of film.
It is customary to stick a piece of 1-inch white tape on the side of the magazine with the following information:
- number of that magazine
- camera roll number
- type of film stock
- emulsion and batch number
- length of the roll
- date
- title of the film
- name of the production company
This will help in the preparation of a camera report to accompany the film to the lab. Later this label is often taken right off the magazine and put onto the film can holding the exposed roll. You might also put a label on the magazine with special processing instructions, such as PUSH ONE STOP, as a reminder to everyone using the camera and to whoever later writes the camera reports and work order for the lab.
Despite the most careful cleaning and loading, even the finest camera designs will occasionally jam. The film will stop advancing somewhere along its path and the oncoming film will continue to pile up at that point, creating a "salad" of twisted and folded film. If the camera jams, remove the film from the camera interior, checking carefully to see that chips of broken film are not stuck in the gate, around the registration pin, or anywhere else. Remove the magazine to a darkroom or put it in a changing bag. You will need a spare take-up core or spool (whichever you already have in the camera) and a can with a black paper bag to unload the exposed film and rethread the magazine.
Never spool up any film with broken sprocket holes. It may jam in the processing machine in the lab and ruin a considerable amount of footage, not only yours but other customers' as well. Generally you would feel the edge of the film in the dark and snip off the part of the roll where the perforations have been broken. If you can't find the torn perf but suspect any damage inside your roll of film, write a warning clearly on the can to alert the lab technicians.
One simple procedure that helps prevent camera jams is to make sure there is no slack between the take-up roll and the sprocket roller. If there is, when the camera starts the take-up motor may snap the film taut, breaking it or causing the camera to "lose its loop" and become improperly threaded. There is usually some way of rotating the take-up roll to make it taut before you start to shoot. On the Arri SR cameras, for example, there is a button labeled "Test" that you are supposed to hit whenever you load a new magazine onto the camera. It gently engages the claw into a sprocket hole so that when you run the camera, you won't immediately damage a perf. On other cameras, you may want to manually inch the film through the movement to make sure that the loops are the correct size and that the claw is properly engaging the sprocket hole before you then trigger the camera motor.
Some magazines, instead of using a plastic core to take up the exposed film, use a metal collapsible core. Be sure not to send the roll to the lab with the collapsible core still in the center. When unloading a magazine, unclasp the collapsible core and gently lift up the roll with one hand on the inner edge and one on the outer edge. Do not let the center of the roll drop, which is called "coning" the roll and is very tedious to fix: you'd have to rewind the roll by hand in total darkness. Some magazines also have a center part that covers the spindle but holds the plastic core. Don't pull this center piece off and send it to the lab along with your film. This is very important. If you send this costly little piece to the lab, you will have trouble trying to reload the magazine without it.
Super-8 film comes in cartridges and cassettes. Not much can be done if a cassette jams, but you can help prevent jamming by making sure the cassette fits easily into the camera.
Beginners in filmmaking are quite often confused by the various aspects of camera lenses. They are intimidated by the mathematical formulas that appear in many photography books whenever lenses are under discussion. But today the filmmaker's life is easier. Readily available tables provide all the information that previously required mathematical computation. Common sense is all you need to understand lenses.
The basic function of a lens can be explained as a pinhole phenomenon. If you removed the lens from your camera and replaced it with a piece of black cardboard with a pinhole in it, you could take a picture, provided the exposure time was long enough. The picture on film would be upside down and the sides would be reversed. This is the first thing one should know about lenses: they produce images that are reversed both vertically and horizontally. The advantage of the lens over the pinhole is that while a pinhole allows only a very small amount of light to reach the film, the lens collects more light and projects it onto the film. In this way, shorter exposure times and sharper pictures are achieved.
F-stops and T-stops
The maximum amount of light a lens is capable of transmitting depends on the diameter of the lens and the focal length. By focal length we mean the distance from the optical center of the lens to the film plane when the lens is focused at infinity. The focal length divided by the diameter of the lens gives us a measure of the maximum aperture. It's quite simple. For example, a lens 1 inch in diameter with a focal length of 2 inches will pass the same amount of light as a lens 3 inches in diameter with a 6-inch focal length, because the maximum aperture, or f-stop, for both lenses is f/2 (2 4 1 5 2; and 6 4 3 5 2 also).
We can reduce the amount of light by means of an iris placed in the lens. By closing the iris we reduce the effective diameter of the lens, thus reducing the amount of light passing through the lens. Now the f-stop equals the focal length divided by the new diameter created by the iris. Therefore, if a 2-inch focal-length lens has an iris adjusted to a 1/8-inch opening, the f-stop is f/16, because 2 4 1/8 5 16. A 4-inch lens with a 1/4-inch iris opening would also be f/16, because 4 4 1/4 5 16.
So the f-stop calibration is not merely a measure of the iris opening, but instead expresses the relationship between focal length and iris.
It is important to note that the smaller the iris opening, the more times it can be divided into the focal length. Therefore, as the iris opening becomes smaller, the f-stop number becomes higher. So a lower f-stop number means more light (a larger opening), and a higher f-stop number means less light (a smaller opening).
F-stops are calibrated on the lens. They are commonly 1, 1.4, 2, 2.8, 4, 5.6, 8, 11, 16, and 22. Each higher f-stop cuts the light by exactly half. For example, f/11 allows half as much light as f/8. Conversely, f/8 allows twice as much light as f/11. If the difference is more than one stop, remember that the light doubles between each stop. So f/4 will yield eight times as much light as f/11, because f/8 is twice f/11, f/5.6 is twice f/8, and f/4 is twice f/5.6. Therefore, f/4 is eight times more light than f/11, because 2 3 2 3 2 5 8. It doubles with each step.
Some lenses have T-stops as well as f-stops. The two are almost equivalent. T-stops are more precise because they are calibrated for the individual lens. Because some light can be lost as it passes through the various elements in the lens, not every lens will produce exactly the same exposure if set to the same f-stop. So the lenses are individually tested with a light meter to determine how much light is transmitted at various settings, and the f-stop mark is adjusted on the barrel of the lens to compensate for any light loss. Since f-stops are determined by a mathematical formula and are not calculated for the individual lens, the new mark is called a T-stop. Therefore, we should consider T-stops as very accurate f-stops. When calculating the exposure or consulting the tables, f-stops and T-stops can be considered equivalent.
Lens Speed
The lowest (widest) f-stop setting will vary between lenses, depending on their focal lengths and diameters. For example, one lens may start at f/1.9 and another at f/3.5. (Often, as in these cases, the starting number is in between the usual calibrations.) Lens speed refers to the widest setting (lowest f-stop) a lens is capable of. For example, a lens that opens to 1.9 is a relatively "fast" lens, and one that opens only as far as 3.5 is a relatively "slow" lens. Because telephoto lenses are longer, their diameter will usually divide several times into their focal length, making their lowest f-stop high. Therefore, telephoto lenses tend to be slow, while wide-angle lenses tend to be fast.
Coatings
Often, some or all of the glass elements of a lens are coated with a substance that reduces glare and internal reflections that would normally make a lens less efficient. These coatings allow modern lenses to be pointed into bright lights with a minimal amount of flaring compared to older lenses with very few elements coated, if any. Coatings also help improve the speed of the lens; without the coating, some light transmission would be lost due to internal scatter.
Optimal Range
Every lens has an optimal range of f-stops that yield the sharpest image. This usually starts about two stops from the widest opening and runs to about f/11 (in other words, the middle range of f-stops are preferred). Below and above this range the lens will tend to produce slightly less sharp images. Stopping down extends the depth of field, but beyond f/11 or f/16 the maximum resolution decreases due to diffraction around the small iris opening, thereby canceling out the increase in sharpness. This is especially true of wide-angle lenses. Most professionals when shooting indoors like to set the f-stop somewhere in the optimal range (for example, f/4) and then adjust the light levels for the proper exposure. Testing is vital to determining the f-stops where the lens performs the best; occasionally you come across lenses that have been designed to look their best when shot nearly wide-open, for example.
Focusing
Apart from f-stops, nearly every lens has a calibrated ring representing focusing distances. The exceptions are some very wide-angle lenses, such as 10mm and shorter, that have a "fixed focus" -- that is, there is no need to adjust focus. With a well-adjusted reflex viewing system we can focus quickly and accurately by rotating the focus ring while looking through the lens, especially if the camera has a large, bright, and clear viewfinder image. Another method, used particularly in older cameras without reflexive viewing systems, is to measure the distance between the subject and film plane (marked on the camera by the symbol f) and set the focus ring accordingly.
The settings achieved by focusing by eye through a reflexive viewing system and by measuring and turning the focus ring may not agree. This may be due to a slight inaccuracy in the focus ring adjustment. In such cases, if the viewing system is accurate, you should depend on that rather than on the focusing calibrations.
Ideally, though, your camera, viewfinder, and lenses have been tested and adjusted so that tape measurements and the focus set by eye match each other.
Zoom Lenses
The cinematographer uses a variety of focal lengths. Older camera designs accommodated three or four lenses on a rotating plate called a turret, which allowed for quick changing between lenses. In later cameras the turret gave way to a single-lens design, the varifocal or zoom lens. It contains a variety of focal lengths and allows you to move continuously between them as you rotate the "zoom" ring of the lens. After the zoom lens was invented, the term prime lens was coined to describe an ordinary fixed focal-length lens.
The first thing to be considered when describing a zoom lens is its range -- for example, 12mm to 120mm. We can also express it as a ratio, in this case one to ten (1:10).
The Angenieux 12-120mm achieved great popularity in the 16mm film industry in the 1960s. A 10mm prime lens became its customary companion. Lenses like the Angenieux 9.5-95mm, the Zeiss 10-100mm, and the Cooke 9-50mm followed, representing a better choice to some camerapeople who were willing to sacrifice the telephoto end of the range in order to increase the wide-angle end. New zooms like the Canon 8-64mm and the Zeiss 11-110mm were also introduced to cover the larger Super-16 aperture. (See chapter 2.)
Zooming smoothly is an art. There are many mechanical aids available. Zoom lenses can come with either zoom levers, cranks, or both to allow moderately smooth zooming by hand. For very smooth zooming, though, battery-powered motors are normally used with variable speed controls. One type is operated by two buttons (in and out) or a single rocker switch with speed controlled by separate dial, although it can be modified by the pressure you exert on the rocker switch. Another type features a "joystick." The rocker switch and the joystick design allows one-touch control over both speed and direction.
Some camera operators still prefer to zoom manually by gripping and turning the zoom ring with their hand. If you use this method, you must be careful not to move other rings on the lens, such as the f-stop and focus. If you are concerned about this, you can use a small piece of tape to prevent the f-stop ring from turning.
All zoom lenses require the same focusing procedure: you open the aperture fully to reduce depth of field, zoom all the way in on the subject, and closely examine the sharpness. After focusing, it is easy to forget to return the f-stop to its proper setting. This is a very common mistake among beginners. The ability to magnify the subject by zooming in, and thus being able to see the focus very clearly, makes focusing by eye much more common when using zooms compared to when using prime lenses, where tape focusing is more common.
Many zoom lenses do not focus as closely as prime lenses. For example, the Zeiss 11-110mm will only focus as close as about 5 feet away, while a 12mm Zeiss Distagon prime lens focuses down to 8 inches. However, there are zooms that focus as close as 18 inches.
Zoom lenses by their nature have many more glass elements than do prime lenses. They are therefore more prone to flaring and losing contrast when light shines into them. They also can breathe when the focus is changed during the shot; as the glass elements move to change the focus, the focal length is altered slightly, creating a mini-zooming effect that looks like the frame is "breathing." Some zooms have been designed to minimize or eliminate that artifact. Despite these problems and their complex design, modern zoom lenses, when stopped between f/4 and f/11, are nearly as good optically as prime lenses.
Optical Attachments and Close-up Work
For close-up work, macro lenses focus as close as a few centimeters away without the use of special attachments.
Regular lenses require one of several types of attachments in order to focus more closely than they're designed to.
Extension tubes or bellows can be used to focus practically as close as the front element of the lens. They are introduced between the lens and camera body. But because extension tubes and bellows upset the normal optics, they cannot be used with optically complicated lenses, including all zooms and many wide-angle lenses. When the subject is closer than ten times the focal length of the lens, an exposure compensation is required and depends on the rate of extension.
The correction can be found in tables supplied with the devices or in the American Cinematographer Manual.
Another way to focus more closely is through the use of close-up attachments called diopters. Sometimes incorrectly referred to as filters, these are actually small single-element lenses that attach to the front of the lens in use. Their convex side faces the subject. The small arrow on the rim should point away from the camera. Diopters come in series (11, 12, 13, etc.). Each higher number allows for closer focusing. When diopters are combined, the higher number should be closest to the camera. No exposure compensation is required. Compared to extension tubes, bellows, or macro lenses, diopters are the least satisfactory as far as optical quality. Yet unlike extension tubes or bellows, diopters can be used on zoom and wide-angle lenses. And they are a relatively low-cost alternative to renting or buying a macro lens.
A split-field diopter covers only half the lens (it's basically a diopter cut in half), enabling the camera to be focused very close on one side of the frame and far away on the opposite side simultaneously. It is frequently used in commercials, where, for example, the soap package may be in the foreground with a housewife using it in the far background. The one drawback is that the fuzzy line at the split of the diopter must be hidden by lighting and composition. Also, zooming becomes difficult and panning impossible.
There are other optical attachments in current use. The magnification of a telephoto or zoom lens can be increased with a telephoto extender. For example, a 200mm lens may be made into a 400mm. Such attachments require two stops additional exposure each time the focal length is doubled. When a telephoto extender is used, the best resolution is usually obtained when the lens is stopped down (around f/11). The usual focal lengths of some zooms can also be shortened by retro-focus wide-angle attachments, and these do not require an exposure compensation. However, camerapeople usually do not like either telephoto extenders or retrofocus attachments, as they soften the picture, decreasing the resolution.
Tilt-Focus Lenses
Also called slant-focus lenses, these are an alternative to using split-field diopter attachments; they are built to pivot (bend) near the rear element, causing the focus to fall at a diagonal to the film plane. In other words, instead of only a single distance being in focus at a time, the focus falls on near objects at minimum focus at one end of the frame but on far objects at the opposite end of the frame. So you could put a row of objects on a receding diagonal to the camera and have them all fall into focus for a faux deep-focus look. The advantage over a split-field diopter is that there's no fuzzy line where the split occurs. You could do the same thing with a normal lens and a bellows attachment, but the single tilt-focus lens is a lot simpler to use.
Anamorphic Lenses
Although this primarily only concerns people shooting in 35mm, it is useful to understand what this type of lens is. The concept dates back to Dr. Henri Chretien and his invention of the Hypergonar lens, the precursor to CinemaScope in the 1950s. It involves using a single cylindrical lens element in the lens (in front or in the rear) to squeeze a horizontally wider image area onto the film, to be unsqueezed later by a matching anamorphic lens on a projector. For video transfers, the image can be unsqueezed electronically. After anamorphic lenses were introduced, the term spherical was coined to describe traditional nonanamorphic lenses.
Usually, 35mm anamorphic optics have a 2:3 squeeze (compression) factor. What this means in practical terms is that a 40mm anamorphic lens, for example, "sees" the same area horizontally that a 20mm spherical lens would, but vertically it sees what a 40mm spherical lens would. While it is possible to put an anamorphic lens on a 16mm camera, especially if it has the same PL mount (see figure 1.14) common to modern 35mm cameras, the 23 compression creates some nonstandard aspect ratios. (See chapter 2.)
Lenses with a front anamorphic element have some unique optical properties: (1) bright points of light shining into the lens will create a blue horizontal line across the frame; and (2) as objects in the background fall out of focus when racking to the foreground, the compression back there becomes greater than 2:3, making the background objects look skinnier. Out-of-focus points of light that would normally be a circular "blob" now appear to be vertical ovals in shape.
Lens Mounts
Among 16mm cameras with changeable lenses, there are four common lens mounts. The C-mount is the smallest and therefore the least strong and most sensitive. The Arri mount is stronger and positively locks into the camera. As lenses got larger and heavier, the Arri bayonet was introduced, a subsequent improvement over the regular Arri mount. A bayonet lens attaches to the camera even more securely and accurately. The regular Arri lenses will fit into either the bayonet or the regular Arri lens sockets, but a bayonet lens requires a bayonet socket and will not fit into a regular Arri mount.
But the larger and stronger Arri PL (positive lock) mount used for their 35mm cameras is now commonplace on many 16mm cameras; the main advantage is that it allows the same lenses to be used on either a 35mm or 16mm camera package.
There are many other types of mounts; Aaton, Eclair, and Cinema Products cameras have their own types of mounts, although many can be adapted to use one of the Arri mounts.
Depth of Field and Circles of Confusion
If we were to photograph only one distant point, such as a light, the lens would be in focus when it projects a point onto the film.
Because the lens can be focused for only one distance at a time, objects closer and farther away will be slightly out of focus. In figure 1.15 a second, closer light would have its image formed behind the film plane and be represented on the film as a circle. A third light, farther away, would form its image in front of the film plane and also appear on the film as a circle. These circles are called circles of confusion, and they vary in size depending on how far out of focus they are. The "confusion" is that circles smaller than 1/1000 inch in diameter confuse our eye and are seen as points in focus. This allows us to see pictures of three-dimensional objects that appear in focus.
We have a range in which objects will appear sharp. It runs between the closest and farthest objects represented as circles of confusion smaller than 1/1000 inch. This range is called depth of field (and is sometimes incorrectly called depth of focus).
The depth of field varies with the effective diameter of the lens opening and hence with the f-stop. By "effective diameter" we mean the actual size of the iris opening, not the f-stop number. If you want to change lenses without changing the depth of field, you must use the same iris opening, which will be a different f-stop. For example, an 8-inch lens shooting at f/4 has a 2-inch-diameter iris opening. If you now want to change to a 4-inch lens and retain the same depth of field, you must shoot with the same 2-inch-diameter iris, which for your 4-inch lens is f/2. This is a rare problem, and if it ever comes up, consult a depth of field chart. The above example is offered to illustrate that depth of field is dependent on the iris opening.
This chart shows the general principles that govern depth of field:
Greater depth of field Less depth of fieldWide-angle lenses Telephoto lenses
High f-stop (small Low f-stop (wide aperture)
aperture)
Subject far away from Subject close to camera
camera
Small film format Large film format (such as 35mm)
(such as Super-8)
With greater depth of field, more elements in the picture are in sharp focus. This causes the image to appear harder. There is also an impression of higher contrast. This is because when a background is out of focus, the bright highlights and the dark shadows tend to blend into a muddle of midrange values, so when they come into sharp focus, the high and low brightness values are more prominent.
Depth of field characteristics for lenses of various focal lengths, under different f-stop and focus settings, are available in many publications, including the American Cinematographer Manual (see figure 1.17 for an example). Given the focal length and f-stop and the subject-to-film-plane distance, we can determine the range of the depth of field and the dimensions of the field of view at that distance.
For each lens and f-stop the chart also gives the hyperfocal distance. This is the point of greatest depth of field. It is a precalculated figure indicating that if the given lens at the given f-stop is focused at this hyperfocal distance, everything from half this distance to infinity will be in "acceptable" focus. For example, if for a given lens and f-stop the hyperfocal distance is 20 feet, by focusing at 20 feet we would obtain everything in focus from 10 feet to infinity.
A similar principle is valuable when "splitting the focus" between two objects at different distances. They will both be equally sharp if we focus for a point not halfway between them but a third of the separation distance from the closer object. For example, two objects at 10 and 16 feet respectively would both be equally in focus if you were to focus for 12 feet. This is often referred to as the one-third-distance principle.
Depth of Focus
Not to be confused with depth of field, depth of focus refers to the distance in front of or behind the focal plane at which the film can be situated and still produce a sharp image.
Unlike depth of field, depth of focus actually decreases for wide-angle prime lenses or the wide-angle end of a zoom lens. Therefore, the distance between the back of the lens and the film plane, sometimes referred to as the back focus, becomes extremely critical. Lenses must be seated properly in their mounts. Even something like a behind-the-lens gel can be thick enough to throw the focus off on a very wide-angle lens at a wide aperture.
Focal Lengths and Perspective
Perhaps the most important physical element related to creative lens use is perspective. A lens that is "normal" for a given film gauge will reproduce reality with perspective similar to that seen by the human eye. In the case of 16mm film, a 25mm lens is normal. In Super-8, a normal lens is about 12mm, and in 35mm film, a normal lens is 50mm. Of course, what is "normal" is highly subjective; for example, humans have a wider field of view than what a 50mm lens provides on a 35mm camera, so for some filmmakers, a wider-angle lens seems to recreate human perception more naturally. Also, since the matted wide-screen projection format crops the 35mm frame to a smaller rectangle, a 35mm might be used instead of a 50mm for a "normal" perspective.
Lenses shorter than normal for a given film gauge are considered wide-angle, and those two or more times longer are telephoto.
Picture perspective is frequently misunderstood; it depends on the camera-to-subject distance and not on the lens. From the same distance, three different lenses -- wide, normal, and telephoto -- change the area of view but do not change the perspective. By using the same three lenses and changing the distances to the subject, we can retain the same field of view but with different perspectives.
One can see from figures 1.19 to 1.26 that a wide-angle lens exaggerates or elongates depth and a telephoto collapses or compresses it. For example, a person walking toward the camera will seem to approach faster with a wide-angle and slower with a telephoto. This is caused by the distance, not the lens. In a telephoto shot the person is almost always farther away than in a wide-angle shot. When similarly framed, the person walking toward the telephoto may be 25 yards away, while the person moving toward the wide-angle lens is only 5 feet away. If the wide-angle approach is redone at 25 yards, the person (very small in the frame) will move just as slowly as with the telephoto. Therefore, remember that the degree of distortion is controlled by the distance, not the lens.
This is further illustrated in figures 1.27 to 1.34 by a comparison between the effects of zooming and dollying. When you dolly, the spatial relationship between the objects in the frame -- that is, the perspective -- changes because the distances change. When you zoom, the focal length changes, yet the effect is like a gradual enlargement of one part of the frame without any change in perspective. For this reason, a zoom effect has a flat look.
To make a zoom movement appear more three-dimensional, it can be combined with a slight camera movement up, down, in, out, or to one side. A panning movement also helps, in addition to zooming past or through a foreground, such as a row of trees or a picket fence, that goes out of the picture as you zoom in. Other times a flat effect may be desired. In this case the cameraperson should make a point of avoiding foreground objects and keeping the camera rigidly framed while zooming; otherwise the flat effect will be diminished.
No lens will yield high-quality results unless it is given proper care and attention.
In all cameras, lens performance depends to a great extent on the viewing system. If prisms in this system are loose or the eyepiece is not adjusted to the operator's sight, even the most excellent lenses cannot be expected to give satisfactory results. The best way to adjust the eyepiece is to remove the lens, point the camera toward a uniformly bright area (sky, wall, etc.), and after loosening the eyepiece locking ring (if there is one), rotate the eyepiece adjustment until the grain of the ground glass or the engraved lines in the viewing system appear sharpest to your eye. Then tighten the locking ring to keep this setting from drifting. In cameras with nonremovable lenses, adjust the eyepiece while aiming at a distant object, focused at infinity and with the f-stop wide-open. The eyepiece is designed so that camera operators who wear glasses can usually adjust it for their eyesight and shoot without glasses. If not, a few eyepieces allow additional diopters to be added internally to increase the range they can be focused. If the eyepiece cannot be altered in this way, a special diopter with a rubber eyecup can be fitted over the end of the viewfinder.
As mentioned earlier, when using a reflexive viewing system, the eyepiece must be covered while the camera is running. Usually, camera operators cover it with their eye while shooting, but if they should take their eye away during the shot, or if the camera is mounted for a shot without an operator (such as on the bumper of a racing car), the eyepiece must be covered or light will enter it while the camera is running, travel through the system, and fog the film, ruining the shot. This is very important. Many cameras have some provision for closing off the eyepiece. The Arri S has a small door that swings shut across the eyepiece. Many cameras have an internal door that blacks out the viewing system when the operator turns a knob on the side of the viewer near the front of the camera. As an extra precaution, a piece of black tape might be used to cover the end of the viewfinder. A light, ghostlike apparition and an overexposed effect on the film are possible signs of light entering the viewfinder.
Lens Support Systems
Long and heavy lenses, such as 250mm or more (especially in C-mount), should rest on a lens support to prevent their length and weight from wrenching the mount out of alignment. A support will also be required for the heavier zooms, such as the Angenieux 12-240mm, and also for some of the shorter zoom lenses when they have C-mounts.
The heavier, more sensitive lenses, such as zooms, must be stored and transported in a separate case to prevent jarring the elements. They are also more sensitive to heat. If the zoom is to be stored mounted on the camera, then the case must firmly support the lens in order to avoid straining the mount.
Front rods or support rods, usually two of them, are often used to support heavier lenses, the matte box, zoom motor, and follow-focus device. Some cameras have built-in slots for front rods, either at the base or on one side of the camera. Other cameras require an adapter plate with front rod slots.
Matte Boxes
A rigid matte box or rubber sunshade is mounted in front of the lens to shade it from unwanted direct light. The matte box is usually equipped with slots to hold filters. Sometimes it will have a hinged metal flap sticking out on top to further flag off the light, called an eyebrow or sunshade extension. There may even be flaps on the left and right sides that can be attached. When longer lenses are used, sometimes a rigid cover can be added in front with a cutout rectangle just large enough to not be seen inside the picture area. This is called a hard matte and is usually labeled to identify which focal length lenses it can be used with. Again, the point is to further limit any stray light from hitting the lens or the filters.
The most common-size rectangular glass filters used are 4" 3 4", 4" 3 5" (actually 5.65"), and 6" 3 6" (actually 6.6"), so there are matte boxes made to accommodate each type. These matte boxes also have a rear holder for a round filter such as a polarizer or a diopter. Some allow you to rotate the rear element and one or more of the rectangular trays. Some of the largest matte boxes allow the filter tray section to be tilted forward or back to remove internal glass reflection problems. The filter tray slots may also be geared so that you can smoothly raise or lower the filter by turning a knob, either manually or electronically. You can use a smaller filter in a larger matte box by using an adapter tray.
Follow-Focus
Camera operators or camera assistants have a hand on the focus adjustment all the time, ready to compensate for any subject movement. If the camera-to-subject distance changes during the shot, the operator, looking through the viewing system, can readjust the focus. This is called "following" or "pulling" focus. Industry practice is to use a camera assistant, also called a focus-puller, rather than the operator to make the focus adjustments during the shot, following tape measurements and marks made on the floor during rehearsal for the actors -- and relying on experience should the actors fail to "hit their marks." A combination of fast-moving actors and a dolly or handheld camera can require a considerable amount of agility, ingenuity, and educated guessing at times on the part of the focus-puller.
The focus, zoom, and f-stop rings on most lenses have a toothed edge to allow geared devices to be attached to turn these rings without the hands having to grab the lens barrel. The most common attachment is the follow-focus unit, which allows the focus-puller to turn a knob that in turn rotates the focus ring. This knob is covered with a white plastic disk that may be marked by the focus-puller using an erasable marker to indicate specific focus points relevant to the shot. Or the focus-puller will mark the lens barrel directly, either with a white pencil or with a pen on a narrow strip of tape added around the barrel.
Stop Pulls
This is the practice of adjusting the f-stop position during the take to make an exposure change. It's often a last-resort solution to a lighting problem; for example, when moving from outdoors to indoors, there may be many stops of brightness difference to compensate for even after the interior has been lit. Since changing the f-stop in midshot usually causes an obvious shift in exposure, the camera assistant will try to make the pull when the camera is moving from one area to another, hoping the change in background will "hide" the pull.
Lens Maintenance
You can clean a dirty lens, but there's not much you can do with a scratched one. So it is wise to clean lenses carefully.
A stream of clean air, such as from an air syringe, is by far the safest way to clean a lens. Remember that canned compressed air must be used in an upright position; otherwise it may spray a gluey substance onto the lens.
A very soft brush, such as one made of camel's hair, is second on the list. It must be used only for lens cleaning. Avoid touching its bristles, as fingers are naturally greasy. Since all brushes shed, your soft lens brush should not be used on the camera, gate, or magazines: the fine, flexible hairs of a lens brush will "travel" in the camera and may end up getting wound into moving parts. A brush for camera cleaning should have stiffer bristles that are less apt to be wound into the machinery.
When using a lens brush or air, always hold the lens facing downward so that the dust does not resettle on the lens. This helps when cleaning cameras and magazines too.
Fingerprints and other stains will have to be removed with a photographic lens tissue. (Never use a silicone-coated tissue such as those sold by optometrists for cleaning eyeglasses, because it may permanently discolor the lens coating.) Before using, moisten the lens tissue with a special lens-cleaning solution. Use the solution sparingly; too much may partly dissolve the cement holding the lens elements. Do not apply the cleaning solution directly to the lens. Special solutions are available from camera shops, or you can use isopropyl alcohol (91 percent or higher). Rubbing alcohol is not recommended because it contains menthol and other ingredients that will be left on the lens by the evaporating alcohol. One excellent way to use the lens tissue is to roll it like a cigarette, break it in half, and use the fuzzy end like a brush.
Lenses should be kept clean at all times, even when stored, because fingerprints and other stains left on the lens for long periods may become imbedded in the blue coating of the lens.
One of the most sensitive parts of a lens is its mounting. For proper optical alignment with the film, the lens must be precisely locked onto the camera. Much care must be taken to make sure this mounting is not wrenched out of alignment. Repairing such damage is expensive and time-consuming and may never restore perfect mounting.
Because zoom lenses and some wide-angle lenses are of retrofocal design -- a complicated optical configuration -- they are vulnerable to even the slightest mounting inaccuracy. A retrofocal design is desirable because it permits a larger physical lens size for more expedient handling, while retaining a short focal length. For example, a 5.7mm lens is usually about 4 inches long. If it were actually only 5.7 millimeters long, it would be a very inconvenient size. In the case of zoom lenses, the increased size is necessary to accommodate the wide-angle end of the zoom range. (Retrofocal limitations prevent us from using extension tubes or bellows with zooms and some wide-angles.)
If a zoom lens is imprecisely mounted, it may not remain in focus when zooming in or out. Incorrectly mounted wide-angle lenses will simply not be in focus.
Most Super-8 and some 16mm cameras (like the Canon Scoopic) are manufactured with a permanently mounted zoom lens. This restricts the cameraperson's choice of lenses but does mean the mounting is usually accurate.
On the screen, any camera unsteadiness becomes very obvious because the picture is being magnified many hundreds of times. To control camera steadiness, many supporting devices and techniques have been developed.
Tripods
These are the most commonly used supports. Three-legged, as their name implies, tripods basically come in three sizes: standard legs, baby legs, and "high hat." They also come in different degrees of sturdiness for cameras of different weights.
Leg lengths are individually adjustable, so the tripod can be leveled when set up on uneven ground. For older tripods with a vertical locking ring in the center of the leg, you would tighten them by always turning the top of the lock to the outside. Though incorrect, you can tighten the tripod by turning the lock the other way, but serious bending and disfiguration will damage the tripod. Furthermore, it will not be tight and may collapse, ruining the camera as well. Other tripods use a regular locking nut ("tie-down") that tightens when turned clockwise. There are also tripods that use quick-release clasps instead.
Some tripods are designed for heads with a ball-joint leveling base. They usually come in two sizes: 100mm and 150mm. There are also some smaller ball sizes normally used for video cameras that some people use for the smaller 16mm cameras. A ball-joint is very convenient and can save time by allowing the cameraperson to level just the head on top of the tripod without having to adjust the legs perfectly. This device can be dangerous, however, if it is used carelessly. There is a tendency to leave the tripod legs in a precarious imbalance and try to compensate with just the ball-joint, making the weight distribution uneven at the top of the tripod. For safety, the legs must be almost level before the final adjustment is made with the ball-joint. Heavier cameras should use the standard Mitchell flat-base instead, because the weight of the camera itself can loosen a ball-joint.
The spreader is an essential part of the tripod equipment. It locks onto the "shoes" to prevent the tripod legs from slipping. In place of a spreader, you could use camera tape, a rope, or even a piece of rug or heavy cloth. Sandbags are always useful for steadying tripods or stands. Occasionally a length of chain with a turnbuckle can also be used to secure the tripod to a platform. The spreader is needed when the tripod is on a hard surface; when outdoors on grass or dirt, you might use the tripod without the spreader, with the sharp points at the end of the tripod securely pushed into the ground. Even with a spreader, a tripod might scratch a wooden or tiled floor, so use some protective cardboard or piece of carpeting under the spreader for extra protection to the location.
In situations where baby legs are not low enough or the camera is to be mounted on, say, the top of a ladder, a high hat is practical. Often, C-clamps are used to secure the high hat in such circumstances. A number of other mounts have been developed for a variety of specialized needs, such as rigging the camera to a car.
Tripod Heads
Usually between the camera and the top of the tripod legs, although it can also be used on dollies and cranes, for example, the tripod head allows the operator to smoothly move the camera. Turning the head and camera horizontally is called panning, while turning vertically is tilting.
The tripod head must be chosen with the camera in mind. Different heads are designed to support different weights. You can take the manufacturer's suggested weight as a guide, but when selecting a head it is always a good idea to test it with the camera mounted to see how it will behave. Maneuverability and smoothness when panning and tilting are important, but equally vital is the "positive lock." Locking can be tested by tilting the camera forward so that it points below the horizon, then locking it in this position. It should remain locked. If the camera is too heavy for the head, it may overpower the lock and continue tilting down until the front of the camera is resting against the tripod leg. The weight of the camera when tilted down that far may cause an imbalance that will pull the tripod over, seriously damaging the camera.
Three basic types of tripod heads are available: friction heads, gear heads, and fluid heads. Friction heads, as their name implies, use surface resistance to smooth their movements. Most are made for still cameras and are not smooth enough for motion picture work, but there are some exceptions. Gear heads employ toothed gears and two sets of turning wheels to independently tilt and pan the camera. This takes a lot of skill to use properly but allows a tremendous degree of precision. Developed originally to handle the huge and heavy blimped cameras of the 1930s, they are still mainly used in 35mm. The weight of a camera creates inertia as it moves, something a gear head can easily overcome, making it possible to stop at an exact point after a fast pan or tilt. For most work in Super-8 and 16mm, fluid heads are the best. They use adjustable hydraulic resistance to give their movements a smooth flow. On larger productions, both a fluid and a gear head would be rented, because each is better than the other at certain types of moving shots.
Matching the two types of tripod legs, there are two types of mounts at the bottom of the heads, the Mitchell flat-base and claw-ball (ball-joint). Adapters are available for using these two systems interchangeably.
After setting up the head on the tripod, the camera is mounted by a screw that extends from the head and goes into the bottom of the camera. On some heads, a small base plate with the screw comes off the head and is separately screwed onto the camera. Then the camera, with this mounting plate attached, is locked onto the head. It's a good idea to put a piece of cloth tape on the plate near the screw to reduce any side-to-side slippage between the plate and the camera bottom. There are two sizes of screws: quarter-inch (American) and the larger three-eighths inch (German). Some cameras have two threaded holes so that they can accept either. In addition, a small and inexpensive adapter is available that will enlarge an American screw to German size. This adapter should be a standard accessory carried by all camera-people.
To make sure all the mounts are compatible, always set up the camera on the assembled tripod before leaving the equipment room or rental house. This simple practice will save you many headaches. Don't wait until you're on location to find you have different types of mounts that cannot be put together and no place to get an adapter. This applies not just to tripods but to all equipment.
Dollies
For traveling shots, several types of dollies are available. They differ in sophistication and expense.
The Chapman Super PeeWee and the J.L. Fisher 11 are good examples of hydraulic arm dollies that are small enough for location shooting but strong enough for most 16mm and 35mm cameras. There are also lightweight, portable, low-cost dollies that are basically wooden platforms with wheels underneath. For example, the skateboard dolly has small rubber skateboard wheels and will roll smoothly on standard pipe track. The doorway dolly usually has soft inflatable rubber tires underneath, useful for rolling on uneven or rough surfaces such as a sidewalk or asphalt road (its larger cousin is called a Western dolly). Shooting handheld from a wheelchair is also a popular technique for microbudget productions.
Dollies are usually run on steel or aluminum tracks, both straight and curved. Plywood sheets are sometimes laid on the floor and covered with a sheet of smooth Masonite to allow the dolly freedom to move in directions (referred to as a "dance floor" move) not possible with track. Using a wide-angle lens will help make a camera move look smoother, which can help if you have to move over a rough surface.
Occasionally an automobile is used as a dolly. In this case, bumps can be smoothed out by reducing the air pressure in the tires. When filming at a right angle to the direction of vehicle movement, the auto speed appears almost twice as fast as in reality. If necessary, running the camera at a slightly higher speed can smooth out the movement and compensate for the illusion of increased speed.
When shooting from a helicopter or moving car, antivibration devices like gyro stabilizers can be used to steady the camera.
Jib Arms and Cranes
A jib arm is essentially a miniature crane, often short enough to be mounted to a standard dolly; it allows the operator greater flexibility and speed, compared to the hydraulic boom arm of the dolly, in raising or lowering the height of the camera. However, it gets difficult to make extreme changes in height while still keeping an eye against the viewfinder, which is why it may be necessary to frame by looking at a video assist monitor instead. Cranes are usually much bigger and heavier, allowing the camera operator and the focus-puller to both sit on a platform at the end of the crane arm. Safety is absolutely essential when working with cranes; the person riding on it cannot step off the platform until the counterbalancing weight in back is adjusted. There have been so many accidents on film sets with cranes collapsing, cranes accidentally touching power lines, and so on that it is becoming more common to put the camera on a remote-controlled head at the end of the crane and operate it from the ground.
When handholding the camera, our principal concern is controlling the camera for the exact degree of steadiness we desire for the effect, whether it be smooth or jostled and vibrating.
Handheld shots can be made steadier by using most of the tricks discussed earlier, such as running the camera at a higher speed or using a wide-angle lens. Jumbled, chaotic subject action is often associated with a handheld shot, such as walking or running through a panicked crowd. Such busy activity in front of the lens will often camouflage jerky camera movements.
Steadiness is not our only consideration in handholding. Sharpness is also a problem. The 24 fps camera speed produces a 1/48-second exposure period, which is long enough to cause a relatively fast subject or camera movement to register as slightly blurred on film. Normally, this is not noticeable because each single frame is not visible long enough on the screen. However, a jerkly handheld camera will contribute to even more pronounced image blur. Thus, resolution suffers when the camera is held awkwardly.
Steady handheld work depends to a great extent on the maneuverability of the camera. Ideally, the camera operator's body and the camera should be as one, yet rough movements should be isolated from the camera. Various body mounts and rigs have been designed to transfer the camera weight from the arms and shoulders and onto the overall upper body, reducing fatigue and allowing subtler camera operating adjustments.
The highest sophistication in camera stabilizing equipment came with the invention of the Steadicam. It allows the operator to walk or run, climb stairs, or shoot from moving vehicles while keeping the camera steady. The camera becomes virtually an extension of the operator's body, allowing for vertical movement up or down of almost three feet and for panning a full 360°. The operator views the image on a video monitor while guiding with a gentle hand movement a camera that seems to be floating on air. The assistant is able to adjust the focus or f-stop by a radio-operated remote control.
The only drawback to these systems is their weight. The Steadicam system with a 16mm camera weighs approximately fifty pounds. Operators need to be physically able to move in a harness supporting the whole system; a strong back is required for this job. And since the camera is perfectly balanced at the end of the support arm, it takes tremendous skill to stop it from swaying and rocking. Keeping the horizon level during a Steadicam move is an important step in mastering this device.
Until now we have discussed ways of controlling the image recorded by the camera, covering the manipulation of focus, perspective, camera positions, and movements. There remains the time dimension. It has infinite possibilities and therefore allows for great ingenuity in its use.
Near the beginning of this chapter, we introduced time-lapse and slow-motion photography and described how they could expand or collapse time.
Some general-purpose cameras have speeds up to 75 fps available from a wild motor. This is adequate for some slow-motion purposes, but if higher speeds are necessary, there are two general types of cameras to be considered: intermittent movement and rotating prism. Intermittent cameras are the kind we have already described; they arrest each frame for the period of exposure. For this reason they are limited to a top speed of about 600 fps, but are usually slower. The rotating prism camera features a continuous film flow.
The film never stops and the prism rotates to project the image onto the passing film. Because the film does not have to stop and start for each exposure, higher speeds are possible, ranging up to 10,000 fps for 16mm film. Special scientific cameras have been designed for much higher speeds, but they are seldom of any practical use to the average filmmaker.
At high speeds many problems arise. As the exposure time becomes minimal, a great deal of light is required (and/or very fast film). There is also a reciprocity failure; at higher speeds the exposure time-f-stop relationship gradually changes so that computing the exposure may be difficult. Exposure tests are necessary. To further complicate matters, at very high speeds the reciprocity failure may be different for each layer of color in the emulsion, thus distorting the color.
Film stock for extremely high-speed photography must have "long pitch" perforations. This means the distance between the sprocket holes is slightly greater. Some can only use double-perf stock (which means they can't shoot Super-16) and require that special daylight spools be used.
In addition to slowing or speeding a movement, film can be used to remove portions of it. One term cinematographers use for the creative elimination of in-between intervals of movement is pixilation. Pixilation is much like animation in that it is often taken one or more frames at a time, but unlike animation, its subjects are frequently moving objects, like cars or people. Whereas time-lapse cinematography seeks only to speed up action, pixilation removes specific parts of the movement, modifying the apparent nature of the action. For example, an overused pixilation effect is achieved by taking a single frame every time an actor jumps up into the air. Because he is never seen except at the height of his jump, he appears to be suspended above the ground when the footage is projected at normal speed.
Another pixilation technique involves running the camera several frames at a time. Between each interval the actor walks to a different area in the field of view. The result is that he appears for a moment in each position.
Either of these pixilated effects can be achieved by shooting single frames, shooting several frames at brief intervals, or using an optical printer to print only the selected frames from normally shot footage. If the final project is for a video-only release, you can also just edit out those frames after you've transferred the footage to video; however, if for a print, you will call attention to the fact that editing was used if you cut the negative itself, which tends to produce a little jump at every splice. The creative variations on pixilation are endless and open to experimentation.
Some cameras can run backward, providing the opportunity to invert time. Reverse action can be used to make a difficult maneuver possible or to achieve an effect. In one film, a director had the camera run in reverse while filming an actor walking backward in a crowd of normally walking pedestrians. When the film was projected forward, the actor became the only person who was walking forward in a crowd of pedestrians walking backward.
Impossible actions are made possible, such as a man effortlessly jumping straight up onto the top of a wall or low roof. The actor jumps down and walks away, all backward. The action is filmed with the camera running in reverse so that when correctly projected, the actor walks to the wall and jumps straight up onto it.
Another very important use of reverse action is in making complicated maneuvers easier. The most common example is a rapid pan to a very precise framing. If shot forward, we might spend a great deal of footage before we hit just the perfect framing the director wants at the end of the shot. However, filming in reverse, we could start on that precise framing and pan away to the first, less critical angle, achieving the shot while saving time and footage.
Reverse motion is also used to make stunts safer; for example, if you need a speeding car to come to a quick stop right in front of an infant in a baby carriage, you could start the car at the near position and have it quickly drive away in reverse gear.
Not all cameras feature an ability to run backward. But reverse action can still be achieved. In 16mm or 35mm, the action can be filmed and later reversed in an optical printer; or it can be done digitally once the footage has been transferred to video. Or reverse motion can be achieved by filming with any camera held upside down. If the image is recorded upside down, we can turn the film over in the projector and show it tail-first. It will be right side up, but the action will be reversed. In the case of single-perforated film stocks, the picture will also be turned around left to right. Double-perforated stocks could be turned over, correcting the left-to-right position, but this would put the emulsion on the opposite side, causing focus problems in printing.
When using the upside-down reverse action method, the best way to deal with the left-to-right exchange is to avoid lettering or anything else that would give it away, or to shoot through a mirror. There is also the possibility of printing any necessary lettering backward. This was done for the movie Titanic; passengers had to board the ship from port side, but only the starboard side had been built by the art department, so all signs in the boarding scene were painted in mirror-image reverse and "flopped" digitally later in postproduction.
The possibilities suggested by time manipulation are endless, and we have touched on only a few. The filmmaker is limited only by his own imagination.
Having spent the first part of this chapter covering some of the basic camera features and capabilities, we now will try to bring it all into focus. Selecting a camera is similar to choosing a car. You should consider many aspects before committing your money. There is much to be said for renting rather than buying equipment, since needs vary from one filming assignment to another. There are rapid changes in camera design and there is a constant flow of new models, which would be available at rental houses. Often you can rent a much more expensive camera than you could ever afford to buy. The decision to rent or buy a camera also depends on how extensively you plan to use it. Professionals will purchase a piece of expensive equipment only when they have already been working on jobs where they've had to rent that item continuously, and therefore know that the purchase will pay for itself over a short time.
If you are preparing to shoot a short or feature-length film, it sometimes makes more sense to rent if it will be shot over a short but intense period of a few days or weeks. However, if it's going to be shot off and on over a very long period (like some documentaries), it might make more sense to own the equipment.
Many amateurs and professionals prefer to own their own cameras. In this way, if they take good care of their equipment, they can be confident about its dependability. Sometimes they will own a "standby" or "B-camera" and rent their main camera, such as an Arri, Aaton, or Panaflex.
Besides the reflex versus nonreflex viewfinder issue already covered, 16mm cameras can be loosely divided into the following categories:
MOS or non-sync-sound. These are too loud for shooting scenes while sound is being recorded; they might also not have crystal-sync motors (but many do for reasons other than shooting dialogue scenes). Often these cameras have multiple frame rate options, so they might be used to shoot non-24 fps material, in which case being loud is not a problem, since no sync-sound will be recorded anyway. Cameras in this category include the Bolex, the Bell & Howell Filmo, the Arri-S/B, the Eclair CM3, the Beaulieu R16B, the Canon Scoopic, and high-speed cameras like the Photosonics Actionmaster.
Early sync-sound ("self-blimped"). These are the first generation of quiet sync-sound cameras. Being older and cheaper, they are often someone's first sound camera purchase. These include the Arri 16BL, the Eclair NPR and ACL, the CP-16, CP-16R, and the CP-GSMO.
Modern sync-sound. These started with the release of the Arri SR and the Aaton LTR 7 in the mid 1970s and continued with the Arri SR2 and SR3, and the Aaton LTR 54, XTR, and XTRprod. Panavision also made a 16mm version of their Panaflex line called the Elaine. Recently the very small Aaton A-Minima was released.
Every couple of years, camera manufacturers bring out new designs or improvements on older models. Therefore, this book cannot hope to provide an up-to-date consumer's report on every current camera. You will have to investigate the features offered by the designs of leading manufacturers at the time you buy. In addition to providing promotional literature, equipment rental houses can often be very helpful as you make a decision.
Even the most sophisticated cameras will occasionally fail to operate properly. Usually this is caused by a rather simple malfunction. Amateur camerapeople frequently jump to conclusions, suspecting the worst, when the problem is actually some simple thing like a low battery or a bad connection. So don't panic until you've checked the obvious things first.
Most camera troubles will fall into roughly five categories:
1. The camera will not run. This could be caused by:
- dead or low battery
- broken on/off switch
- broken power cable or loose plug connections
- dirty connection between the camera body and the magazine take-up motor (applies to Arri and Beaulieu)
- buckle switch not reset (some cameras have this safety device, which automatically stops the camera if a jam occurs)
- burnt-out or otherwise damaged motor
- extremely cold weather (the camera should be winterized by changing the lubrication from oil to graphite in a camera shop before shooting in very low temperatures)
2. The projected picture is unsteady. This could be caused by:
- film loops too small or too large
- film stock that has shrunk because of improper storage
- faulty synchronization of the shutter and pulldown claw (causes a vertical blur)
- pressure plate too tight or too loose
3. The film is scratched. This could be caused by:
- dirt or emulsion buildup somewhere along the film path
- rollers stuck in the camera or the magazine
- film gate scratched or damaged
- film loops too large or too small
- film not properly threaded
4. The film is fogged. This could be caused by:
- light leak from an improperly closed camera or magazine door
- reflexive viewfinder open to light -- often because the camera operator took his or her head away from the eyepiece
- behind-the-lens filter slot that has been left open (especially on Bolex or wide-angle lenses)
- improper loading or unloading that may have exposed the film to light
- an empty lens cavity left open in the turret
5. The picture is out of focus. This is usually the fault of the camera operator or focus-puller, but it can also be caused by:
- lens not flush in the turret
- lens out of alignment
- viewfinder out of adjustment
- pressure plate not locked in correct position when the camera was loaded
Most of these troubles can be avoided by a thorough check. Before the day of shooting, all the equipment should be assembled and examined to make sure it is compatible and in working order.
Shooting a camera test is a vital step in preparation. It must be done and screened before the shooting begins so that there is ample time to deal with any problems. The main objectives of the test will be to check lens performance and picture steadiness. If two or more cameras are used, it is imperative that the frame lines be compared to make sure that footage from the two cameras can be intercut without the frame line shifting on the screen.
Lens sharpness is best checked by shooting a test chart or even a newspaper with the lens aperture wide-open (lowest f-stop). In the case of a zoom lens, the entire focal range (zoom range) must be tested.
At the same time, test the reflex viewing system and lens calibration by turning the test chart to a 45° angle.
Focus visually (or by measured distance) for a marked spot. If the viewing system or the calibrations on the lens barrel are out of alignment, the footage will be focused either closer or farther away than the marked spot.
Even the most comprehensive tests cannot eliminate human errors. Most mistakes are due to careless oversights. Camera operators have to keep track of so many small details that they are bound to eventually forget something. When they do, it will be a simple and obvious error.
The beginner is especially prone to such mistakes. Professional camerapeople develop a systemized routine of checking everything immediately before shooting. I have my own list of things to check before filming. I check that:
- tripod is level;
- gate clean;
- gate closed;
- sprockets engaged;
- footage counter reset after loading;
- forward/reverse properly set on both camera and magazine motors;
- motor speed set;
- magazine take-up taut;
- viewfinder eyepiece focused for eye;
- matte box not visible in frame;
- filter slot covered or closed;
- filter in place; and, most important, I
- check frame for composition, mike boom, set limits, etc.;
- check focus; and
- check f-stop.
The last three are the most important because they are constantly being changed during the shooting day and are therefore the most likely to be wrong when you start to shoot.
The Ditty Bag
The ditty bag contains all the small items camerapeople feel it necessary to have in their immediate reach while filming. The items may vary depending on personal choices, but most ditty bags are similar in content. Mine contains:
- American Cinematographer Manual (known as the cinematographer's bible)
- air syringe and/or can of compressed air
- orangewood sticks
- pair of fine tweezers and a dental mirror (for careful removal of film chips and hairs from inaccessible places; these are the only metal instruments used for cleaning)
- small flashlight
- camera brush made of fairly stiff hair (not camel's hair)
- lens brush made of extra-soft hair (such as camel's hair)
- lens tissue
- cotton swabs (for cleaning lenses only!)
- lens-cleaning fluid
- compact magnifying glass (cleaning aid)
- assorted screwdrivers
- needle-nose pliers
- crescent wrench
- black camera tape
- white camera tape
- gaffer's tape
- regular and grease pencils, marker pens, and ballpoints
- camera report cards (can be simple index cards)
- chalk (kept separate because of dust)
- scissors
- spare cores
- spare daylight-load spools
- 50-foot cloth measuring tape
- assortment of spare parts and adapters (e.g., quarter-inch to three-eighths-inch tripod screw adapter, a spare core center piece), depending on the type of equipment being used
- stopwatch
- contrast-viewing glasses for black-and-white and color
Apart from the ditty bag, these items might also be necessary on location or in the studio:
- spare light meter
- spare light meter battery
- spare changing bag
- spare film cans with black paper bags
- spare power and sync cables
- extension cables for mikes
- extension cables for lights
- all sorts of adapters for electrical supplies; most important, the common two-prong to grounded three-prong adapter
- spare bulbs and fuses
- spare batteries, such as for tape recorder
- spare camera battery with charger
- spare magazine take-up belts
- spare lens caps
- spare rubber eyecup
- spare supply of filters
- spare tape recorder take-up reel
- soldering iron
- voltmeter, or at least a voltage tester
- headache tablets (aspirin, etc.)
This list could go on forever. The point is that you should scale your equipment to your production, remembering that you want to be overprepared. Camera operation depends on many small details. If a camera malfunctions, all your footage may be ruined.
Lists of this sort are always of enormous value and should be made up before the day of shooting to make sure that nothing is forgotten.
Here again, as throughout this chapter, we are reminded of the great concentration and attention to detail required from the camera operator in order to maintain control in his or her work. Only after thoroughly mastering the techniques and mechanics of their craft can cinematographers develop the consistency necessary to achieve an individual stylistic approach, which is the goal of the cinematographer's art.
Copyright © 1973, 1989, 2005 by Simon & Schuster, Inc.
Product Details
| ISBN-13: | 9781439105627 |
|---|---|
| Publisher: | Touchstone |
| Publication date: | 12/01/2009 |
| Sold by: | SIMON & SCHUSTER |
| Format: | eBook |
| Pages: | 272 |
| File size: | 11 MB |
| Note: | This product may take a few minutes to download. |
About the Author
M. David Mullen, ASC, graduated from UCLA and the California Institute of the Arts graduate film program. He has photographed nearly thirty films over the past decade and has earned two IFP/Independent Spirit nominations for best cinematography.
Read an Excerpt
Chapter One: Cameras
The cinematographer's most basic tool is the motion picture camera. This piece of precision machinery comprises scores of coordinated functions, each of which demands understanding and care if the camera is to produce the best and most consistent results. The beginning cinematographer's goal should be to become thoroughly familiar and comfortable with the camera's operation, so that he or she can concentrate on the more creative aspects of cinematography.
This chapter covers many isolated bits of practical information. However, once you become familiar with camera operation, you will be able to move on to the substance of the cinematographer's craft in subsequent chapters. In the meantime, you are well advised to try to absorb each operation-oriented detail presented in this chapter, because operating a camera is all details. If any detail is neglected, the quality of the work may be impaired.
The film movement mechanism is what really distinguishes a cinema camera from a still camera. The illusion of image motion is created by a rapid succession of still photographs. To arrest every frame for the time of exposure, the principle of an intermittent mechanism was borrowed from clocks and sewing machines. Almost all general-purpose motion picture cameras employ the intermittent principle.
Intermittent mechanisms vary in design. All have a pull-down claw and pressure plate. Some have a registration pin as well. The pull-down claw engages the film perforation and moves the film down one frame. It then disengages and goes back up to pull down the next frame.While the claw is disengaged, the pressure plate holds the film steady for the period of exposure. Some cameras have a registration pin that enters the film perforation for extra steadiness while the exposure is made.
Whatever mechanism is employed requires the best materials and machining possible, which is one reason good cameras are expensive. The film gate (the part of the camera where the pressure plate, pull-down claw, and registration pin engage the film) needs a good deal of attention during cleaning and threading. The film gate is never too clean. This is the area where the exposure takes place, so any particles of dirt or hair will show on the exposed film and perhaps scratch it. In addition to miscellaneous debris such as sand, hair, and dust, sometimes a small amount of emulsion comes off the passing film and collects in the gate. It must be removed. This point is essential. On feature films, some camera assistants clean the gate after every shot. They know that one grain of sand or bit of emulsion can ruin a day's work.
The gate should first be cleaned with a rubber-bulb syringe or compressed air to blow foreign particles away. Cans of compressed air must be used in an upright position; otherwise they will spray a gluey substance into the camera. When blowing out the aperture, it is recommended that you spray from the open lens port side, with the mirror shutter cleared out of the way, through the aperture, rather than from inside the threading area into the aperture. This helps prevent blowing particles into the mirror area. An orangewood stick, available wherever cosmetics are sold, can then be used to remove any sticky emulsion buildup. There is also an ARRI plastic "skewer" for this job, bent at the end to allow you to get the inner edges of the aperture better. The gate and pressure plate should also be wiped with a clean chamois cloth — never with linen. Never use metal tools for cleaning the gate, or, for that matter, for cleaning any part of the film movement mechanism, because these may cause abrasions that in turn will scratch the passing film. Do not use Q-tips either, as these will leave lint behind.
The gate should be cleaned every time the camera is reloaded. At the same time, the surrounding camera interior and magazine should also be cleaned to ensure that no dirt will find its way to the gate while the camera is running.
The intermittent movement requires the film to be slack so that as it alternately stops and jerks ahead in one-frame advances, there will be no strain on it. Therefore, one or two sprocket rollers are provided to maintain two loops, one before and one after the gate. In some cameras (such as the Bolex and Canon Scoopic), a self-threading mechanism forms the loops automatically. In Super-8 cassettes and cartridges, the loops are already formed by the manufacturer. On manually threaded cameras, the film path showing loop size is usually marked.
Too small a loop will not absorb the jerks of the intermittent movement, resulting in picture unsteadiness, scratched film, broken perforations, and possibly a camera jam. An oversize loop may vibrate against the camera interior and also cause an unsteady picture and scratched film. Either too large or too small a loop will also contribute to camera noise.
Camera Speeds
The speed at which the intermittent movement advances the film is expressed in frames per second (fps). Each frame exposed is a single sample of a moving subject, so the higher the sampling rate, that is, the faster the frame rate, the smoother the motion will be reproduced. To reproduce movement on the screen faithfully, the film must be projected at the same speed as it was shot. Standard shooting and projection speed for 16mm and 35mm is 24 fps; standard speeds for 8mm and Super-8 are 24 fps for sound and 18 fps (or 24 fps) for silent.
If both the camera and the projector are run at the same speeds, say 24 fps, then the action will be faithfully reproduced. However, if the camera runs slower than the projector, the action will appear to move faster on the screen than it did in real life. For example, an action takes place in four seconds (real time) and it is photographed at 12 fps. That means that the four seconds of action is recorded over forty-eight frames. If it is now projected at standard sound speed of 24 fps, it will take only two seconds to project. Therefore, the action that took four seconds in real life is sped up to two seconds on the screen because the camera ran slower than the projector.
The opposite is also true. If the camera runs faster than the projector, the action will be slowed down in projection. So to obtain slow motion, speed the camera up; to obtain fast motion, slow the camera down.
This variable speed principle has several applications. Time-lapse photography can compress time and make very slow movement visible, such as the growth of a flower or the movement of clouds across the sky. Photographing slow-moving clouds at a rate of, say, one frame every three seconds will make them appear to be rushing through the screen when the film is projected at 24 fps. On the other hand, movements filmed at 36 fps or faster acquire a slow, dreamy quality at 24 fps on the screen. Such effects can be used to create a mood or analyze a movement. A very practical use of slow motion is to smooth out a jerky camera movement such as a rough traveling shot. The jolts are less prominent in slow motion.
To protect the intermittent movement, never run the camera at high speeds when it is not loaded.
When sound movies arrived in 1927, 24 fps was firmly established as the standard shooting and projection rate, although it was a frame rate occasionally used by Silent Era filmmakers. It is not actually the ideal frame rate for the recreation of motion, as it provides barely enough individual motion samples over time to create the sensation of smooth, continuous motion when played back. However, it's become the frame rate that audiences are most accustomed to seeing in movies and has become an integral part of the "film look" that many people discuss these days as they attempt to get video technology to emulate film. The main artifacts to this fairly low frame rate are strobing and flicker. Strobing is the effect of sensing that the motion is made up of too few samples and therefore does not feel continuous. One of the ramifications is that it is sometimes necessary to minimize fast movement, such as when panning the camera across a landscape; otherwise the motion seems too staccato, too jumpy. Flicker happens when the series of still images are not being flashed quickly enough for the viewer to perceive the light and image as being continuously "on." The solution generally has been for film projectors to use a twin-bladed shutter to double the number of times the same film frame is flashed before the next frame is shown. So even if the movie was shot and then projected at 24 fps, the viewer is seeing forty-eight flashes per second on the screen.
A change in camera speed will cause a change in shutter speed. In most cameras the shutter consists of a rotating disk with a 180* cutout (a half circle). As the disk rotates it closes over the aperture, stopping exposure and allowing the movement to advance the film to the next frame. Rotating further, the cutout portion allows the new frame to be exposed and then covers it again for the next pull-down. The shutter rotates constantly, and therefore the film is exposed half the time and covered the other half. So when the camera is running at 24 fps, the actual period of exposure for each frame is 1/48 second (half of 1/24). Varying the speed of the camera also changes the exposure time. For example, by slowing the movement by half, or to 12 fps, we increase the exposure period for each frame, from 1/48 to 1/24 second. Similarly, by speeding up the movement, doubling it from the normal 24 fps to 48 fps, we reduce the exposure period from 1/48 to 1/96 second. Knowing these relationships, we can adjust the f-stop to compensate for the change in exposure time when filming fast or slow motion.
A change in the speed of film movement can be useful when filming at low light levels. For example, suppose you are filming a cityscape at dusk and there is not enough light. By reducing your speed to 12 fps, you can double the exposure period for each frame, giving you an extra stop of light that may save your shot. Of course, this technique would be unacceptable if there were any pedestrians or moving cars in view; they would be unnaturally sped up if the film were projected.
Some cameras are equipped with a variable shutter. By varying the angle of the cutout we can regulate the exposure. For example, a 90° shutter opening transmits half as much light as a 180° opening. Some amateurs make fade-outs and fade-ins on their original film by using the variable shutter, assuming it can be changed smoothly while the camera is running. Professionals generally have all such effects done in the lab.
Since changing the camera speed also changes the exposure, you can compensate for a speed change in midshot (called speed ramping) by adjusting either the f-stop or the shutter to maintain the correct exposure. For example, a speed change from 24 fps to 12 fps would cause twice as much light to reach the film by the time it was running at 12 fps, so you could simultaneously close down the shutter angle from 180° to 90° as the frame changes, thus counteracting the exposure increase. However, the rendition of motion will be different when you alter the shutter angle, not just when you alter the frame rates.
Shutter movement is directly responsible for the stroboscopic effect. Take the example of the spokes of a turning wheel. Our intermittent exposures may catch each succeeding spoke in the same place in the frame, making the spinning wheel appear to be motionless. The camera may even catch each spoke in a position counterclockwise to the previous spoke captured, making the wheel look like it is running in reverse. Another variation, called skipping, results from movement past parallel lines or objects, such as the railings of a fence. They may appear to be vibrating. These effects will increase with faster movement and with a narrower shutter angle.
Exposure time controls the amount of motion blur recorded on each frame; due to the low sampling rate of 24 fps, a certain amount of blur is needed to make a moving object on one frame visually "blend" with the next frame. Too little blur and the motion seems too "sharp" and the viewer becomes more aware as to how few motion samples there really are; it no longer feels continuous but instead "steppy." Therefore, shooting at 24 fps with a closed-down shutter, like at a 45° or 90° angle, will cause faster motion to strobe heavily. This has been used as a creative effect by some filmmakers, since it adds a certain nervous, jittery energy to action scenes. The movie Saving Private Ryan is the most famous example of this technique; many of the battle scenes were shot handheld with a 45° shutter angle. It's also a useful technique when shooting spraying water or falling rain, if you want to see each droplet more clearly.
There are other reasons to use a shutter angle other than 180°, such as for filming TV screens or lights that pulse with their AC current. (See chapter 8.)
In many cameras the shutter performs a vital role in the viewing system. The front of the shutter has a mirror surface that reflects the image into the viewfinder when the shutter is closed. The great advantage of this reflex system is that all the light goes alternately to the film and to the camera operator's eye, providing the brightest image possible. The surface of the mirror shutter should be cleaned only with an air syringe or gently with compressed air; nothing should be allowed to touch it.
Other systems (such as the Bolex Reflex) use a prism between the lens and the shutter so that a certain percentage of the light is constantly diverted to the viewfinder. The disadvantage is that it reduces the amount of light going both to the viewfinder and to the film, since the beam is split. An exposure compensation is required to allow for the light "stolen" from the film by the viewing system. It is usually very slight. For example, in the Bolex Rex-5 the loss is about a third of a stop. You should consult the operator's manual for the specific camera to learn the exact compensation.
Be aware that just as the reflex camera allows light coming through the lens to reach both the film and the camera operator, it also allows light coming back through the eyepiece to reach the film. Therefore, you must keep your eye pressed against the viewfinder while filming to prevent any light-leak from fogging your image; if you are not planning on looking through the viewfinder during the take, you must seal off the eyepiece.
The viewing systems discussed so far allow the cameraperson to look through the taking lens. Many cameras of older design do not have a reflex viewfinding system. As a result, the film in the camera may not receive exactly the same image that the separate viewfinder (usually off to one side of the camera) sees. Referred to as parallax, this is especially a problem when shooting close with a wide-angle lens. However, most nonreflex cameras have an adjustment that can partly correct for parallax.
Video Assist
Also referred to as a video tap, this is a system where some of the light going to the viewfinder is also received by a tiny internal video camera; that image can then be sent to a TV monitor, either with cables or transmitted by UHF (by using an additional device). This signal can even be recorded to videotape for temporary playback on the set. The image quality of this video image is generally very poor, but it allows you to see the framing without actually looking through the viewfinder. This is mainly done so that people other than the camera operator can see the exact shot during the take. However, it is also useful when it is physically impossible to look through the camera viewfinder during the take, like when the camera is mounted on a moving vehicle, a Steadicam, or a remote-controlled crane. Occasionally the camera assistant will have a small LCD monitor mounted to the camera, which enables the assistant to see what the operator is framing. This can come in handy when shooting a scene on a telephoto or macro lens in which the operator is panning from one object to another and the focus needs to be adjusted as each object comes into view. The portable LCD screen can even be used by the operator when doing a complex dolly move, perhaps with an extreme boom up or down combined with a pan, when it may be too difficult to continually keep the eye against the viewfinder.
The film transport mechanism, the shutter, and other moving camera parts are operated by the motor. There are two basic types of motors, spring-wound and electric. Spring-wound cameras run approximately twenty to forty feet of film per wind. The advantages include a compact design and reliable performance under difficult conditions such as cold weather.
Electric motors are available in a variety of designs. The five types that are generally used are: (1) variable speed ("wild"); (2) interlocked; (3) stop frame (time-lapse); (4) constant speed; and (5) crystal speed, which is the most commonly used, especially for sync-sound production. Variable speed motors have an adjustable speed control that may range from 2 to 64 fps or more. (Above 64 fps are considered high-speed motors.) The interlocked motor synchronizes the camera with other devices, such as back or front projectors. The stop frame or time-lapse motor is usually connected with an intervalometer to allow the setting up of whatever exposure intervals are needed for time-lapse photography (such as filming the growth of plants). The constant speed motor is designed to run at a set speed, such as 24 fps, with some precision.
The most advanced type of synchronous speed motor is designed with a crystal control to regulate the speed with extreme precision. When the camera motor and the tape recorder are both equipped with crystal controls, you can film "in sync" with no cables connecting the camera to the recorder. Furthermore, several crystal control cameras can be held in sync to one or more crystal recorders, allowing for multicamera coverage with no cables to restrict the distances between them. Some crystal control motors even combine several functions, allowing the operator to change from constant speed crystal-sync to variable "wild" speeds or single frame at the touch of a switch. The best controls allow a wide variety of speeds to be shot precisely at crystal-sync, necessary for filming under certain pulsing AC light sources at high frame rates for a slow-motion shot.
Most 16mm camera motors operate on DC current supplied by batteries. Nickel-cadmium (NiCad) and nickel metal hydride (NiMH) are widely used; lithium ion batteries are becoming more common. Their life expectancy varies, depending on the conditions of use and maintenance, but on the average about five hundred cycles of recharging and discharging should be expected.
There are slow "overnight" chargers that require fourteen to sixteen hours, quick chargers that will charge batteries in half this time, and truly fast chargers that can do the job in one hour.
It is essential to familiarize yourself with the charger on hand. Some chargers will damage a battery when left to charge for longer than required. It is advisable to have at least four charged batteries on hand so that they can be rotated with enough time for slow charging.
Batteries come in three types: belt, block, and on-board. The battery belt, consisting of built-in nickel-cadmium cells, is a convenient power source for portable 16mm and 35mm cameras, especially when shooting handheld. In situations where mobility is less of an issue, longer-lasting but heavier block batteries may be used. Many modern 16mm cameras use small on-board batteries that clip onto the rear or side of the camera. All Super-8 cameras house the batteries (usually AAs) inside the camera body.
Make sure the voltage of the battery used matches what your camera motor uses. The 16mm Arri SR1 and SR2, and the Aaton XTRprod and A-Minima, for example, use a 12-volt battery, but the Arri SR3 uses a 24-volt battery (as do many 35mm cameras). Many battery belts and block batteries can be switched between 12V and 24V, or between 12V and 16V. Plug into the correct voltage connector on these batteries.
Most of the smaller 16mm cameras will house up to 100-foot loads (on metal daylight spools) inside the camera body. Modern 16mm cameras are usually equipped with film magazines capable of holding up to four hundred feet of film on a plastic core instead of a metal spool. Four hundred feet of film stock in a camera running at 24 fps will give you eleven minutes of footage. The Aaton A-Minima uses a unique 200-foot plastic spool design that must be loaded in darkness. There is an optional 1,200-foot magazine for the 16mm Panaflex Elaine and an 800-foot magazine made for the Aaton XTRprod and Arri SR3 cameras.
Having several magazines allows for a more efficient production, particularly when more than one type of film stock is used on a given day. The camera assistant loads several magazines in advance so that the magazine change will slow down the production minimally.
Remember, when considering magazines, the two decisive factors are capacity and design. The shape and placement of the magazine is sometimes important too. For most shooting situations it doesn't matter, but when you are shooting in cramped quarters, such as from the cockpit of a plane or from under a car, the bulkiness of the camera can make a difference. Here a cameraperson may want a camera with magazines that are smaller or that mount to the back rather than the top. The operator may even want to use one of the smaller cameras that only allow the 100-foot daylight spool loads.
Most magazines have to be loaded in total darkness. The smaller loads available on daylight spools require only subdued light when loading; however, these are not generally used in modern sync-sound cameras, as they increase the noise level while the camera is running. Film not on daylight spools necessitates either a darkroom or a changing bag. The changing bag must be of adequate size and absolutely light-tight. It should be stored in a special case or cover to keep it spotlessly clean and dust free. (Don't let your dog sleep on it.) Any hairs, dirt, or dust in the changing bag can easily enter the magazine being loaded and from there travel to the gate. Even the tiniest of dust specks are visible on a 16mm frame because of the higher magnification of the image.
Before loading an unfamiliar magazine, practice loading it with a roll of waste film (called a dummy load) that you don't want, first in the light and then in the dark, to simulate the loading of unexposed stock.
Some magazines have their own take-up motors to wind up the film as it reenters the magazine after passing through the camera. Such motors should be tested with a waste roll before the magazine is loaded with unexposed film. Run this test with the battery to be used in filming. This test is advisable because a battery may sometimes have enough charge to run a camera with a small 100-foot internal load or an empty magazine but then fail to operate the magazine and camera when it is loaded.
Also, before loading, clean the magazine with compressed air, camera brush, and a piece of sticky paper in order to remove dust, film chips, or hair, and make sure that the rollers are moving freely. (Never wear a fuzzy or hairy sweater when cleaning camera equipment or in the darkroom.) It is a good idea to do a scratch test where you run some new film through the camera to see if the magazine or the gate is scratching the film. You examine the strip of film afterward with a light and magnifier to look for any faint abrasions in the surface of the emulsion or base. Obviously this piece of film becomes waste at this point, having been exposed to light.
After loading the magazine it is advisable to seal the lid with 1-inch camera tape. This is partly to prevent light leakage on old magazines, but mainly to prevent an accidental opening, especially if the loaded magazine is dropped. When you are loading magazines in a hurry, it is easy to confuse loaded ones and unloaded ones. Taping and labeling the loaded magazines immediately after loading will save you the annoyance of opening a supposedly empty magazine and ruining a roll of film.
It is customary to stick a piece of 1-inch white tape on the side of the magazine with the following information:
- number of that magazine
- camera roll number
- type of film stock
- emulsion and batch number
- length of the roll
- date
- title of the film
- name of the production company
This will help in the preparation of a camera report to accompany the film to the lab. Later this label is often taken right off the magazine and put onto the film can holding the exposed roll. You might also put a label on the magazine with special processing instructions, such as PUSH ONE STOP, as a reminder to everyone using the camera and to whoever later writes the camera reports and work order for the lab.
Despite the most careful cleaning and loading, even the finest camera designs will occasionally jam. The film will stop advancing somewhere along its path and the oncoming film will continue to pile up at that point, creating a "salad" of twisted and folded film. If the camera jams, remove the film from the camera interior, checking carefully to see that chips of broken film are not stuck in the gate, around the registration pin, or anywhere else. Remove the magazine to a darkroom or put it in a changing bag. You will need a spare take-up core or spool (whichever you already have in the camera) and a can with a black paper bag to unload the exposed film and rethread the magazine.
Never spool up any film with broken sprocket holes. It may jam in the processing machine in the lab and ruin a considerable amount of footage, not only yours but other customers' as well. Generally you would feel the edge of the film in the dark and snip off the part of the roll where the perforations have been broken. If you can't find the torn perf but suspect any damage inside your roll of film, write a warning clearly on the can to alert the lab technicians.
One simple procedure that helps prevent camera jams is to make sure there is no slack between the take-up roll and the sprocket roller. If there is, when the camera starts the take-up motor may snap the film taut, breaking it or causing the camera to "lose its loop" and become improperly threaded. There is usually some way of rotating the take-up roll to make it taut before you start to shoot. On the Arri SR cameras, for example, there is a button labeled "Test" that you are supposed to hit whenever you load a new magazine onto the camera. It gently engages the claw into a sprocket hole so that when you run the camera, you won't immediately damage a perf. On other cameras, you may want to manually inch the film through the movement to make sure that the loops are the correct size and that the claw is properly engaging the sprocket hole before you then trigger the camera motor.
Some magazines, instead of using a plastic core to take up the exposed film, use a metal collapsible core. Be sure not to send the roll to the lab with the collapsible core still in the center. When unloading a magazine, unclasp the collapsible core and gently lift up the roll with one hand on the inner edge and one on the outer edge. Do not let the center of the roll drop, which is called "coning" the roll and is very tedious to fix: you'd have to rewind the roll by hand in total darkness. Some magazines also have a center part that covers the spindle but holds the plastic core. Don't pull this center piece off and send it to the lab along with your film. This is very important. If you send this costly little piece to the lab, you will have trouble trying to reload the magazine without it.
Super-8 film comes in cartridges and cassettes. Not much can be done if a cassette jams, but you can help prevent jamming by making sure the cassette fits easily into the camera.
Beginners in filmmaking are quite often confused by the various aspects of camera lenses. They are intimidated by the mathematical formulas that appear in many photography books whenever lenses are under discussion. But today the filmmaker's life is easier. Readily available tables provide all the information that previously required mathematical computation. Common sense is all you need to understand lenses.
The basic function of a lens can be explained as a pinhole phenomenon. If you removed the lens from your camera and replaced it with a piece of black cardboard with a pinhole in it, you could take a picture, provided the exposure time was long enough. The picture on film would be upside down and the sides would be reversed. This is the first thing one should know about lenses: they produce images that are reversed both vertically and horizontally. The advantage of the lens over the pinhole is that while a pinhole allows only a very small amount of light to reach the film, the lens collects more light and projects it onto the film. In this way, shorter exposure times and sharper pictures are achieved.
F-stops and T-stops
The maximum amount of light a lens is capable of transmitting depends on the diameter of the lens and the focal length. By focal length we mean the distance from the optical center of the lens to the film plane when the lens is focused at infinity. The focal length divided by the diameter of the lens gives us a measure of the maximum aperture. It's quite simple. For example, a lens 1 inch in diameter with a focal length of 2 inches will pass the same amount of light as a lens 3 inches in diameter with a 6-inch focal length, because the maximum aperture, or f-stop, for both lenses is f/2 (2 4 1 5 2; and 6 4 3 5 2 also).
We can reduce the amount of light by means of an iris placed in the lens. By closing the iris we reduce the effective diameter of the lens, thus reducing the amount of light passing through the lens. Now the f-stop equals the focal length divided by the new diameter created by the iris. Therefore, if a 2-inch focal-length lens has an iris adjusted to a 1/8-inch opening, the f-stop is f/16, because 2 4 1/8 5 16. A 4-inch lens with a 1/4-inch iris opening would also be f/16, because 4 4 1/4 5 16.
So the f-stop calibration is not merely a measure of the iris opening, but instead expresses the relationship between focal length and iris.
It is important to note that the smaller the iris opening, the more times it can be divided into the focal length. Therefore, as the iris opening becomes smaller, the f-stop number becomes higher. So a lower f-stop number means more light (a larger opening), and a higher f-stop number means less light (a smaller opening).
F-stops are calibrated on the lens. They are commonly 1, 1.4, 2, 2.8, 4, 5.6, 8, 11, 16, and 22. Each higher f-stop cuts the light by exactly half. For example, f/11 allows half as much light as f/8. Conversely, f/8 allows twice as much light as f/11. If the difference is more than one stop, remember that the light doubles between each stop. So f/4 will yield eight times as much light as f/11, because f/8 is twice f/11, f/5.6 is twice f/8, and f/4 is twice f/5.6. Therefore, f/4 is eight times more light than f/11, because 2 3 2 3 2 5 8. It doubles with each step.
Some lenses have T-stops as well as f-stops. The two are almost equivalent. T-stops are more precise because they are calibrated for the individual lens. Because some light can be lost as it passes through the various elements in the lens, not every lens will produce exactly the same exposure if set to the same f-stop. So the lenses are individually tested with a light meter to determine how much light is transmitted at various settings, and the f-stop mark is adjusted on the barrel of the lens to compensate for any light loss. Since f-stops are determined by a mathematical formula and are not calculated for the individual lens, the new mark is called a T-stop. Therefore, we should consider T-stops as very accurate f-stops. When calculating the exposure or consulting the tables, f-stops and T-stops can be considered equivalent.
Lens Speed
The lowest (widest) f-stop setting will vary between lenses, depending on their focal lengths and diameters. For example, one lens may start at f/1.9 and another at f/3.5. (Often, as in these cases, the starting number is in between the usual calibrations.) Lens speed refers to the widest setting (lowest f-stop) a lens is capable of. For example, a lens that opens to 1.9 is a relatively "fast" lens, and one that opens only as far as 3.5 is a relatively "slow" lens. Because telephoto lenses are longer, their diameter will usually divide several times into their focal length, making their lowest f-stop high. Therefore, telephoto lenses tend to be slow, while wide-angle lenses tend to be fast.
Coatings
Often, some or all of the glass elements of a lens are coated with a substance that reduces glare and internal reflections that would normally make a lens less efficient. These coatings allow modern lenses to be pointed into bright lights with a minimal amount of flaring compared to older lenses with very few elements coated, if any. Coatings also help improve the speed of the lens; without the coating, some light transmission would be lost due to internal scatter.
Optimal Range
Every lens has an optimal range of f-stops that yield the sharpest image. This usually starts about two stops from the widest opening and runs to about f/11 (in other words, the middle range of f-stops are preferred). Below and above this range the lens will tend to produce slightly less sharp images. Stopping down extends the depth of field, but beyond f/11 or f/16 the maximum resolution decreases due to diffraction around the small iris opening, thereby canceling out the increase in sharpness. This is especially true of wide-angle lenses. Most professionals when shooting indoors like to set the f-stop somewhere in the optimal range (for example, f/4) and then adjust the light levels for the proper exposure. Testing is vital to determining the f-stops where the lens performs the best; occasionally you come across lenses that have been designed to look their best when shot nearly wide-open, for example.
Focusing
Apart from f-stops, nearly every lens has a calibrated ring representing focusing distances. The exceptions are some very wide-angle lenses, such as 10mm and shorter, that have a "fixed focus" — that is, there is no need to adjust focus. With a well-adjusted reflex viewing system we can focus quickly and accurately by rotating the focus ring while looking through the lens, especially if the camera has a large, bright, and clear viewfinder image. Another method, used particularly in older cameras without reflexive viewing systems, is to measure the distance between the subject and film plane (marked on the camera by the symbol f) and set the focus ring accordingly.
The settings achieved by focusing by eye through a reflexive viewing system and by measuring and turning the focus ring may not agree. This may be due to a slight inaccuracy in the focus ring adjustment. In such cases, if the viewing system is accurate, you should depend on that rather than on the focusing calibrations.
Ideally, though, your camera, viewfinder, and lenses have been tested and adjusted so that tape measurements and the focus set by eye match each other.
Zoom Lenses
The cinematographer uses a variety of focal lengths. Older camera designs accommodated three or four lenses on a rotating plate called a turret, which allowed for quick changing between lenses. In later cameras the turret gave way to a single-lens design, the varifocal or zoom lens. It contains a variety of focal lengths and allows you to move continuously between them as you rotate the "zoom" ring of the lens. After the zoom lens was invented, the term prime lens was coined to describe an ordinary fixed focal-length lens.
The first thing to be considered when describing a zoom lens is its range — for example, 12mm to 120mm. We can also express it as a ratio, in this case one to ten (1:10).
The Angenieux 12-120mm achieved great popularity in the 16mm film industry in the 1960s. A 10mm prime lens became its customary companion. Lenses like the Angenieux 9.5-95mm, the Zeiss 10-100mm, and the Cooke 9-50mm followed, representing a better choice to some camerapeople who were willing to sacrifice the telephoto end of the range in order to increase the wide-angle end. New zooms like the Canon 8-64mm and the Zeiss 11-110mm were also introduced to cover the larger Super-16 aperture. (See chapter 2.)
Zooming smoothly is an art. There are many mechanical aids available. Zoom lenses can come with either zoom levers, cranks, or both to allow moderately smooth zooming by hand. For very smooth zooming, though, battery-powered motors are normally used with variable speed controls. One type is operated by two buttons (in and out) or a single rocker switch with speed controlled by separate dial, although it can be modified by the pressure you exert on the rocker switch. Another type features a "joystick." The rocker switch and the joystick design allows one-touch control over both speed and direction.
Some camera operators still prefer to zoom manually by gripping and turning the zoom ring with their hand. If you use this method, you must be careful not to move other rings on the lens, such as the f-stop and focus. If you are concerned about this, you can use a small piece of tape to prevent the f-stop ring from turning.
All zoom lenses require the same focusing procedure: you open the aperture fully to reduce depth of field, zoom all the way in on the subject, and closely examine the sharpness. After focusing, it is easy to forget to return the f-stop to its proper setting. This is a very common mistake among beginners. The ability to magnify the subject by zooming in, and thus being able to see the focus very clearly, makes focusing by eye much more common when using zooms compared to when using prime lenses, where tape focusing is more common.
Many zoom lenses do not focus as closely as prime lenses. For example, the Zeiss 11-110mm will only focus as close as about 5 feet away, while a 12mm Zeiss Distagon prime lens focuses down to 8 inches. However, there are zooms that focus as close as 18 inches.
Zoom lenses by their nature have many more glass elements than do prime lenses. They are therefore more prone to flaring and losing contrast when light shines into them. They also can breathe when the focus is changed during the shot; as the glass elements move to change the focus, the focal length is altered slightly, creating a mini-zooming effect that looks like the frame is "breathing." Some zooms have been designed to minimize or eliminate that artifact. Despite these problems and their complex design, modern zoom lenses, when stopped between f/4 and f/11, are nearly as good optically as prime lenses.
Optical Attachments and Close-up Work
For close-up work, macro lenses focus as close as a few centimeters away without the use of special attachments.
Regular lenses require one of several types of attachments in order to focus more closely than they're designed to.
Extension tubes or bellows can be used to focus practically as close as the front element of the lens. They are introduced between the lens and camera body. But because extension tubes and bellows upset the normal optics, they cannot be used with optically complicated lenses, including all zooms and many wide-angle lenses. When the subject is closer than ten times the focal length of the lens, an exposure compensation is required and depends on the rate of extension.
The correction can be found in tables supplied with the devices or in the American Cinematographer Manual.
Another way to focus more closely is through the use of close-up attachments called diopters. Sometimes incorrectly referred to as filters, these are actually small single-element lenses that attach to the front of the lens in use. Their convex side faces the subject. The small arrow on the rim should point away from the camera. Diopters come in series (11, 12, 13, etc.). Each higher number allows for closer focusing. When diopters are combined, the higher number should be closest to the camera. No exposure compensation is required. Compared to extension tubes, bellows, or macro lenses, diopters are the least satisfactory as far as optical quality. Yet unlike extension tubes or bellows, diopters can be used on zoom and wide-angle lenses. And they are a relatively low-cost alternative to renting or buying a macro lens.
A split-field diopter covers only half the lens (it's basically a diopter cut in half), enabling the camera to be focused very close on one side of the frame and far away on the opposite side simultaneously. It is frequently used in commercials, where, for example, the soap package may be in the foreground with a housewife using it in the far background. The one drawback is that the fuzzy line at the split of the diopter must be hidden by lighting and composition. Also, zooming becomes difficult and panning impossible.
There are other optical attachments in current use. The magnification of a telephoto or zoom lens can be increased with a telephoto extender. For example, a 200mm lens may be made into a 400mm. Such attachments require two stops additional exposure each time the focal length is doubled. When a telephoto extender is used, the best resolution is usually obtained when the lens is stopped down (around f/11). The usual focal lengths of some zooms can also be shortened by retro-focus wide-angle attachments, and these do not require an exposure compensation. However, camerapeople usually do not like either telephoto extenders or retrofocus attachments, as they soften the picture, decreasing the resolution.
Tilt-Focus Lenses
Also called slant-focus lenses, these are an alternative to using split-field diopter attachments; they are built to pivot (bend) near the rear element, causing the focus to fall at a diagonal to the film plane. In other words, instead of only a single distance being in focus at a time, the focus falls on near objects at minimum focus at one end of the frame but on far objects at the opposite end of the frame. So you could put a row of objects on a receding diagonal to the camera and have them all fall into focus for a faux deep-focus look. The advantage over a split-field diopter is that there's no fuzzy line where the split occurs. You could do the same thing with a normal lens and a bellows attachment, but the single tilt-focus lens is a lot simpler to use.
Anamorphic Lenses
Although this primarily only concerns people shooting in 35mm, it is useful to understand what this type of lens is. The concept dates back to Dr. Henri Chretien and his invention of the Hypergonar lens, the precursor to CinemaScope in the 1950s. It involves using a single cylindrical lens element in the lens (in front or in the rear) to squeeze a horizontally wider image area onto the film, to be unsqueezed later by a matching anamorphic lens on a projector. For video transfers, the image can be unsqueezed electronically. After anamorphic lenses were introduced, the term spherical was coined to describe traditional nonanamorphic lenses.
Usually, 35mm anamorphic optics have a 2:3 squeeze (compression) factor. What this means in practical terms is that a 40mm anamorphic lens, for example, "sees" the same area horizontally that a 20mm spherical lens would, but vertically it sees what a 40mm spherical lens would. While it is possible to put an anamorphic lens on a 16mm camera, especially if it has the same PL mount (see figure 1.14) common to modern 35mm cameras, the 23 compression creates some nonstandard aspect ratios. (See chapter 2.)
Lenses with a front anamorphic element have some unique optical properties: (1) bright points of light shining into the lens will create a blue horizontal line across the frame; and (2) as objects in the background fall out of focus when racking to the foreground, the compression back there becomes greater than 2:3, making the background objects look skinnier. Out-of-focus points of light that would normally be a circular "blob" now appear to be vertical ovals in shape.
Lens Mounts
Among 16mm cameras with changeable lenses, there are four common lens mounts. The C-mount is the smallest and therefore the least strong and most sensitive. The Arri mount is stronger and positively locks into the camera. As lenses got larger and heavier, the Arri bayonet was introduced, a subsequent improvement over the regular Arri mount. A bayonet lens attaches to the camera even more securely and accurately. The regular Arri lenses will fit into either the bayonet or the regular Arri lens sockets, but a bayonet lens requires a bayonet socket and will not fit into a regular Arri mount.
But the larger and stronger Arri PL (positive lock) mount used for their 35mm cameras is now commonplace on many 16mm cameras; the main advantage is that it allows the same lenses to be used on either a 35mm or 16mm camera package.
There are many other types of mounts; Aaton, Eclair, and Cinema Products cameras have their own types of mounts, although many can be adapted to use one of the Arri mounts.
Depth of Field and Circles of Confusion
If we were to photograph only one distant point, such as a light, the lens would be in focus when it projects a point onto the film.
Because the lens can be focused for only one distance at a time, objects closer and farther away will be slightly out of focus. In figure 1.15 a second, closer light would have its image formed behind the film plane and be represented on the film as a circle. A third light, farther away, would form its image in front of the film plane and also appear on the film as a circle. These circles are called circles of confusion, and they vary in size depending on how far out of focus they are. The "confusion" is that circles smaller than 1/1000 inch in diameter confuse our eye and are seen as points in focus. This allows us to see pictures of three-dimensional objects that appear in focus.
We have a range in which objects will appear sharp. It runs between the closest and farthest objects represented as circles of confusion smaller than 1/1000 inch. This range is called depth of field (and is sometimes incorrectly called depth of focus).
The depth of field varies with the effective diameter of the lens opening and hence with the f-stop. By "effective diameter" we mean the actual size of the iris opening, not the f-stop number. If you want to change lenses without changing the depth of field, you must use the same iris opening, which will be a different f-stop. For example, an 8-inch lens shooting at f/4 has a 2-inch-diameter iris opening. If you now want to change to a 4-inch lens and retain the same depth of field, you must shoot with the same 2-inch-diameter iris, which for your 4-inch lens is f/2. This is a rare problem, and if it ever comes up, consult a depth of field chart. The above example is offered to illustrate that depth of field is dependent on the iris opening.
This chart shows the general principles that govern depth of field:
Greater depth of field Less depth of fieldWide-angle lenses Telephoto lenses
High f-stop (small Low f-stop (wide aperture)
aperture)
Subject far away from Subject close to camera
camera
Small film format Large film format (such as 35mm)
(such as Super-8)
With greater depth of field, more elements in the picture are in sharp focus. This causes the image to appear harder. There is also an impression of higher contrast. This is because when a background is out of focus, the bright highlights and the dark shadows tend to blend into a muddle of midrange values, so when they come into sharp focus, the high and low brightness values are more prominent.
Depth of field characteristics for lenses of various focal lengths, under different f-stop and focus settings, are available in many publications, including the American Cinematographer Manual (see figure 1.17 for an example). Given the focal length and f-stop and the subject-to-film-plane distance, we can determine the range of the depth of field and the dimensions of the field of view at that distance.
For each lens and f-stop the chart also gives the hyperfocal distance. This is the point of greatest depth of field. It is a precalculated figure indicating that if the given lens at the given f-stop is focused at this hyperfocal distance, everything from half this distance to infinity will be in "acceptable" focus. For example, if for a given lens and f-stop the hyperfocal distance is 20 feet, by focusing at 20 feet we would obtain everything in focus from 10 feet to infinity.
A similar principle is valuable when "splitting the focus" between two objects at different distances. They will both be equally sharp if we focus for a point not halfway between them but a third of the separation distance from the closer object. For example, two objects at 10 and 16 feet respectively would both be equally in focus if you were to focus for 12 feet. This is often referred to as the one-third-distance principle.
Depth of Focus
Not to be confused with depth of field, depth of focus refers to the distance in front of or behind the focal plane at which the film can be situated and still produce a sharp image.
Unlike depth of field, depth of focus actually decreases for wide-angle prime lenses or the wide-angle end of a zoom lens. Therefore, the distance between the back of the lens and the film plane, sometimes referred to as the back focus, becomes extremely critical. Lenses must be seated properly in their mounts. Even something like a behind-the-lens gel can be thick enough to throw the focus off on a very wide-angle lens at a wide aperture.
Focal Lengths and Perspective
Perhaps the most important physical element related to creative lens use is perspective. A lens that is "normal" for a given film gauge will reproduce reality with perspective similar to that seen by the human eye. In the case of 16mm film, a 25mm lens is normal. In Super-8, a normal lens is about 12mm, and in 35mm film, a normal lens is 50mm. Of course, what is "normal" is highly subjective; for example, humans have a wider field of view than what a 50mm lens provides on a 35mm camera, so for some filmmakers, a wider-angle lens seems to recreate human perception more naturally. Also, since the matted wide-screen projection format crops the 35mm frame to a smaller rectangle, a 35mm might be used instead of a 50mm for a "normal" perspective.
Lenses shorter than normal for a given film gauge are considered wide-angle, and those two or more times longer are telephoto.
Picture perspective is frequently misunderstood; it depends on the camera-to-subject distance and not on the lens. From the same distance, three different lenses — wide, normal, and telephoto — change the area of view but do not change the perspective. By using the same three lenses and changing the distances to the subject, we can retain the same field of view but with different perspectives.
One can see from figures 1.19 to 1.26 that a wide-angle lens exaggerates or elongates depth and a telephoto collapses or compresses it. For example, a person walking toward the camera will seem to approach faster with a wide-angle and slower with a telephoto. This is caused by the distance, not the lens. In a telephoto shot the person is almost always farther away than in a wide-angle shot. When similarly framed, the person walking toward the telephoto may be 25 yards away, while the person moving toward the wide-angle lens is only 5 feet away. If the wide-angle approach is redone at 25 yards, the person (very small in the frame) will move just as slowly as with the telephoto. Therefore, remember that the degree of distortion is controlled by the distance, not the lens.
This is further illustrated in figures 1.27 to 1.34 by a comparison between the effects of zooming and dollying. When you dolly, the spatial relationship between the objects in the frame — that is, the perspective — changes because the distances change. When you zoom, the focal length changes, yet the effect is like a gradual enlargement of one part of the frame without any change in perspective. For this reason, a zoom effect has a flat look.
To make a zoom movement appear more three-dimensional, it can be combined with a slight camera movement up, down, in, out, or to one side. A panning movement also helps, in addition to zooming past or through a foreground, such as a row of trees or a picket fence, that goes out of the picture as you zoom in. Other times a flat effect may be desired. In this case the cameraperson should make a point of avoiding foreground objects and keeping the camera rigidly framed while zooming; otherwise the flat effect will be diminished.
No lens will yield high-quality results unless it is given proper care and attention.
In all cameras, lens performance depends to a great extent on the viewing system. If prisms in this system are loose or the eyepiece is not adjusted to the operator's sight, even the most excellent lenses cannot be expected to give satisfactory results. The best way to adjust the eyepiece is to remove the lens, point the camera toward a uniformly bright area (sky, wall, etc.), and after loosening the eyepiece locking ring (if there is one), rotate the eyepiece adjustment until the grain of the ground glass or the engraved lines in the viewing system appear sharpest to your eye. Then tighten the locking ring to keep this setting from drifting. In cameras with nonremovable lenses, adjust the eyepiece while aiming at a distant object, focused at infinity and with the f-stop wide-open. The eyepiece is designed so that camera operators who wear glasses can usually adjust it for their eyesight and shoot without glasses. If not, a few eyepieces allow additional diopters to be added internally to increase the range they can be focused. If the eyepiece cannot be altered in this way, a special diopter with a rubber eyecup can be fitted over the end of the viewfinder.
As mentioned earlier, when using a reflexive viewing system, the eyepiece must be covered while the camera is running. Usually, camera operators cover it with their eye while shooting, but if they should take their eye away during the shot, or if the camera is mounted for a shot without an operator (such as on the bumper of a racing car), the eyepiece must be covered or light will enter it while the camera is running, travel through the system, and fog the film, ruining the shot. This is very important. Many cameras have some provision for closing off the eyepiece. The Arri S has a small door that swings shut across the eyepiece. Many cameras have an internal door that blacks out the viewing system when the operator turns a knob on the side of the viewer near the front of the camera. As an extra precaution, a piece of black tape might be used to cover the end of the viewfinder. A light, ghostlike apparition and an overexposed effect on the film are possible signs of light entering the viewfinder.
Lens Support Systems
Long and heavy lenses, such as 250mm or more (especially in C-mount), should rest on a lens support to prevent their length and weight from wrenching the mount out of alignment. A support will also be required for the heavier zooms, such as the Angenieux 12-240mm, and also for some of the shorter zoom lenses when they have C-mounts.
The heavier, more sensitive lenses, such as zooms, must be stored and transported in a separate case to prevent jarring the elements. They are also more sensitive to heat. If the zoom is to be stored mounted on the camera, then the case must firmly support the lens in order to avoid straining the mount.
Front rods or support rods, usually two of them, are often used to support heavier lenses, the matte box, zoom motor, and follow-focus device. Some cameras have built-in slots for front rods, either at the base or on one side of the camera. Other cameras require an adapter plate with front rod slots.
Matte Boxes
A rigid matte box or rubber sunshade is mounted in front of the lens to shade it from unwanted direct light. The matte box is usually equipped with slots to hold filters. Sometimes it will have a hinged metal flap sticking out on top to further flag off the light, called an eyebrow or sunshade extension. There may even be flaps on the left and right sides that can be attached. When longer lenses are used, sometimes a rigid cover can be added in front with a cutout rectangle just large enough to not be seen inside the picture area. This is called a hard matte and is usually labeled to identify which focal length lenses it can be used with. Again, the point is to further limit any stray light from hitting the lens or the filters.
The most common-size rectangular glass filters used are 4" 3 4", 4" 3 5" (actually 5.65"), and 6" 3 6" (actually 6.6"), so there are matte boxes made to accommodate each type. These matte boxes also have a rear holder for a round filter such as a polarizer or a diopter. Some allow you to rotate the rear element and one or more of the rectangular trays. Some of the largest matte boxes allow the filter tray section to be tilted forward or back to remove internal glass reflection problems. The filter tray slots may also be geared so that you can smoothly raise or lower the filter by turning a knob, either manually or electronically. You can use a smaller filter in a larger matte box by using an adapter tray.
Follow-Focus
Camera operators or camera assistants have a hand on the focus adjustment all the time, ready to compensate for any subject movement. If the camera-to-subject distance changes during the shot, the operator, looking through the viewing system, can readjust the focus. This is called "following" or "pulling" focus. Industry practice is to use a camera assistant, also called a focus-puller, rather than the operator to make the focus adjustments during the shot, following tape measurements and marks made on the floor during rehearsal for the actors — and relying on experience should the actors fail to "hit their marks." A combination of fast-moving actors and a dolly or handheld camera can require a considerable amount of agility, ingenuity, and educated guessing at times on the part of the focus-puller.
The focus, zoom, and f-stop rings on most lenses have a toothed edge to allow geared devices to be attached to turn these rings without the hands having to grab the lens barrel. The most common attachment is the follow-focus unit, which allows the focus-puller to turn a knob that in turn rotates the focus ring. This knob is covered with a white plastic disk that may be marked by the focus-puller using an erasable marker to indicate specific focus points relevant to the shot. Or the focus-puller will mark the lens barrel directly, either with a white pencil or with a pen on a narrow strip of tape added around the barrel.
Stop Pulls
This is the practice of adjusting the f-stop position during the take to make an exposure change. It's often a last-resort solution to a lighting problem; for example, when moving from outdoors to indoors, there may be many stops of brightness difference to compensate for even after the interior has been lit. Since changing the f-stop in midshot usually causes an obvious shift in exposure, the camera assistant will try to make the pull when the camera is moving from one area to another, hoping the change in background will "hide" the pull.
Lens Maintenance
You can clean a dirty lens, but there's not much you can do with a scratched one. So it is wise to clean lenses carefully.
A stream of clean air, such as from an air syringe, is by far the safest way to clean a lens. Remember that canned compressed air must be used in an upright position; otherwise it may spray a gluey substance onto the lens.
A very soft brush, such as one made of camel's hair, is second on the list. It must be used only for lens cleaning. Avoid touching its bristles, as fingers are naturally greasy. Since all brushes shed, your soft lens brush should not be used on the camera, gate, or magazines: the fine, flexible hairs of a lens brush will "travel" in the camera and may end up getting wound into moving parts. A brush for camera cleaning should have stiffer bristles that are less apt to be wound into the machinery.
When using a lens brush or air, always hold the lens facing downward so that the dust does not resettle on the lens. This helps when cleaning cameras and magazines too.
Fingerprints and other stains will have to be removed with a photographic lens tissue. (Never use a silicone-coated tissue such as those sold by optometrists for cleaning eyeglasses, because it may permanently discolor the lens coating.) Before using, moisten the lens tissue with a special lens-cleaning solution. Use the solution sparingly; too much may partly dissolve the cement holding the lens elements. Do not apply the cleaning solution directly to the lens. Special solutions are available from camera shops, or you can use isopropyl alc ohol (91 percent or higher). Rubbing alcohol is not recommended because it contains menthol and other ingredients that will be left on the lens by the evaporating alcohol. One excellent way to use the lens tissue is to roll it like a cigarette, break it in half, and use the fuzzy end like a brush.
Lenses should be kept clean at all times, even when stored, because fingerprints and other stains left on the lens for long periods may become imbedded in the blue coating of the lens.
One of the most sensitive parts of a lens is its mounting. For proper optical alignment with the film, the lens must be precisely locked onto the camera. Much care must be taken to make sure this mounting is not wrenched out of alignment. Repairing such damage is expensive and time-consuming and may never restore perfect mounting.
Because zoom lenses and some wide-angle lenses are of retrofocal design — a complicated optical configuration — they are vulnerable to even the slightest mounting inaccuracy. A retrofocal design is desirable because it permits a larger physical lens size for more expedient handling, while retaining a short focal length. For example, a 5.7mm lens is usually about 4 inches long. If it were actually only 5.7 millimeters long, it would be a very inconvenient size. In the case of zoom lenses, the increased size is necessary to accommodate the wide-angle end of the zoom range. (Retrofocal limitations prevent us from using extension tubes or bellows with zooms and some wide-angles.)
If a zoom lens is imprecisely mounted, it may not remain in focus when zooming in or out. Incorrectly mounted wide-angle lenses will simply not be in focus.
Most Super-8 and some 16mm cameras (like the Canon Scoopic) are manufactured with a permanently mounted zoom lens. This restricts the cameraperson's choice of lenses but does mean the mounting is usually accurate.
On the screen, any camera unsteadiness becomes very obvious because the picture is being magnified many hundreds of times. To control camera steadiness, many supporting devices and techniques have been developed.
Tripods
These are the most commonly used supports. Three-legged, as their name implies, tripods basically come in three sizes: standard legs, baby legs, and "high hat." They also come in different degrees of sturdiness for cameras of different weights.
Leg lengths are individually adjustable, so the tripod can be leveled when set up on uneven ground. For older tripods with a vertical locking ring in the center of the leg, you would tighten them by always turning the top of the lock to the outside. Though incorrect, you can tighten the tripod by turning the lock the other way, but serious bending and disfiguration will damage the tripod. Furthermore, it will not be tight and may collapse, ruining the camera as well. Other tripods use a regular locking nut ("tie-down") that tightens when turned clockwise. There are also tripods that use quick-release clasps instead.
Some tripods are designed for heads with a ball-joint leveling base. They usually come in two sizes: 100mm and 150mm. There are also some smaller ball sizes normally used for video cameras that some people use for the smaller 16mm cameras. A ball-joint is very convenient and can save time by allowing the cameraperson to level just the head on top of the tripod without having to adjust the legs perfectly. This device can be dangerous, however, if it is used carelessly. There is a tendency to leave the tripod legs in a precarious imbalance and try to compensate with just the ball-joint, making the weight distribution uneven at the top of the tripod. For safety, the legs must be almost level before the final adjustment is made with the ball-joint. Heavier cameras should use the standard Mitchell flat-base instead, because the weight of the camera itself can loosen a ball-joint.
The spreader is an essential part of the tripod equipment. It locks onto the "shoes" to prevent the tripod legs from slipping. In place of a spreader, you could use camera tape, a rope, or even a piece of rug or heavy cloth. Sandbags are always useful for steadying tripods or stands. Occasionally a length of chain with a turnbuckle can also be used to secure the tripod to a platform. The spreader is needed when the tripod is on a hard surface; when outdoors on grass or dirt, you might use the tripod without the spreader, with the sharp points at the end of the tripod securely pushed into the ground. Even with a spreader, a tripod might scratch a wooden or tiled floor, so use some protective cardboard or piece of carpeting under the spreader for extra protection to the location.
In situations where baby legs are not low enough or the camera is to be mounted on, say, the top of a ladder, a high hat is practical. Often, C-clamps are used to secure the high hat in such circumstances. A number of other mounts have been developed for a variety of specialized needs, such as rigging the camera to a car.
Tripod Heads
Usually between the camera and the top of the tripod legs, although it can also be used on dollies and cranes, for example, the tripod head allows the operator to smoothly move the camera. Turning the head and camera horizontally is called panning, while turning vertically is tilting.
The tripod head must be chosen with the camera in mind. Different heads are designed to support different weights. You can take the manufacturer's suggested weight as a guide, but when selecting a head it is always a good idea to test it with the camera mounted to see how it will behave. Maneuverability and smoothness when panning and tilting are important, but equally vital is the "positive lock." Locking can be tested by tilting the camera forward so that it points below the horizon, then locking it in this position. It should remain locked. If the camera is too heavy for the head, it may overpower the lock and continue tilting down until the front of the camera is resting against the tripod leg. The weight of the camera when tilted down that far may cause an imbalance that will pull the tripod over, seriously damaging the camera.
Three basic types of tripod heads are available: friction heads, gear heads, and fluid heads. Friction heads, as their name implies, use surface resistance to smooth their movements. Most are made for still cameras and are not smooth enough for motion picture work, but there are some exceptions. Gear heads employ toothed gears and two sets of turning wheels to independently tilt and pan the camera. This takes a lot of skill to use properly but allows a tremendous degree of precision. Developed originally to handle the huge and heavy blimped cameras of the 1930s, they are still mainly used in 35mm. The weight of a camera creates inertia as it moves, something a gear head can easily overcome, making it possible to stop at an exact point after a fast pan or tilt. For most work in Super-8 and 16mm, fluid heads are the best. They use adjustable hydraulic resistance to give their movements a smooth flow. On larger productions, both a fluid and a gear head would be rented, because each is better than the other at certain types of moving shots.
Matching the two types of tripod legs, there are two types of mounts at the bottom of the heads, the Mitchell flat-base and claw-ball (ball-joint). Adapters are available for using these two systems interchangeably.
After setting up the head on the tripod, the camera is mounted by a screw that extends from the head and goes into the bottom of the camera. On some heads, a small base plate with the screw comes off the head and is separately screwed onto the camera. Then the camera, with this mounting plate attached, is locked onto the head. It's a good idea to put a piece of cloth tape on the plate near the screw to reduce any side-to-side slippage between the plate and the camera bottom. There are two sizes of screws: quarter-inch (American) and the larger three-eighths inch (German). Some cameras have two threaded holes so that they can accept either. In addition, a small and inexpensive adapter is available that will enlarge an American screw to German size. This adapter should be a standard accessory carried by all camera-people.
To make sure all the mounts are compatible, always set up the camera on the assembled tripod before leaving the equipment room or rental house. This simple practice will save you many headaches. Don't wait until you're on location to find you have different types of mounts that cannot be put together and no place to get an adapter. This applies not just to tripods but to all equipment.
Dollies
For traveling shots, several types of dollies are available. They differ in sophistication and expense.
The Chapman Super PeeWee and the J.L. Fisher 11 are good examples of hydraulic arm dollies that are small enough for location shooting but strong enough for most 16mm and 35mm cameras. There are also lightweight, portable, low-cost dollies that are basically wooden platforms with wheels underneath. For example, the skateboard dolly has small rubber skateboard wheels and will roll smoothly on standard pipe track. The doorway dolly usually has soft inflatable rubber tires underneath, useful for rolling on uneven or rough surfaces such as a sidewalk or asphalt road (its larger cousin is called a Western dolly). Shooting handheld from a wheelchair is also a popular technique for microbudget productions.
Dollies are usually run on steel or aluminum tracks, both straight and curved. Plywood sheets are sometimes laid on the floor and covered with a sheet of smooth Masonite to allow the dolly freedom to move in directions (referred to as a "dance floor" move) not possible with track. Using a wide-angle lens will help make a camera move look smoother, which can help if you have to move over a rough surface.
Occasionally an automobile is used as a dolly. In this case, bumps can be smoothed out by reducing the air pressure in the tires. When filming at a right angle to the direction of vehicle movement, the auto speed appears almost twice as fast as in reality. If necessary, running the camera at a slightly higher speed can smooth out the movement and compensate for the illusion of increased speed.
When shooting from a helicopter or moving car, antivibration devices like gyro stabilizers can be used to steady the camera.
Jib Arms and Cranes
A jib arm is essentially a miniature crane, often short enough to be mounted to a standard dolly; it allows the operator greater flexibility and speed, compared to the hydraulic boom arm of the dolly, in raising or lowering the height of the camera. However, it gets difficult to make extreme changes in height while still keeping an eye against the viewfinder, which is why it may be necessary to frame by looking at a video assist monitor instead. Cranes are usually much bigger and heavier, allowing the camera operator and the focus-puller to both sit on a platform at the end of the crane arm. Safety is absolutely essential when working with cranes; the person riding on it cannot step off the platform until the counterbalancing weight in back is adjusted. There have been so many accidents on film sets with cranes collapsing, cranes accidentally touching power lines, and so on that it is becoming more common to put the camera on a remote-controlled head at the end of the crane and operate it from the ground.
When handholding the camera, our principal concern is controlling the camera for the exact degree of steadiness we desire for the effect, whether it be smooth or jostled and vibrating.
Handheld shots can be made steadier by using most of the tricks discussed earlier, such as running the camera at a higher speed or using a wide-angle lens. Jumbled, chaotic subject action is often associated with a handheld shot, such as walking or running through a panicked crowd. Such busy activity in front of the lens will often camouflage jerky camera movements.
Steadiness is not our only consideration in handholding. Sharpness is also a problem. The 24 fps camera speed produces a 1/48-second exposure period, which is long enough to cause a relatively fast subject or camera movement to register as slightly blurred on film. Normally, this is not noticeable because each single frame is not visible long enough on the screen. However, a jerkly handheld camera will contribute to even more pronounced image blur. Thus, resolution suffers when the camera is held awkwardly.
Steady handheld work depends to a great extent on the maneuverability of the camera. Ideally, the camera operator's body and the camera should be as one, yet rough movements should be isolated from the camera. Various body mounts and rigs have been designed to transfer the camera weight from the arms and shoulders and onto the overall upper body, reducing fatigue and allowing subtler camera operating adjustments.
The highest sophistication in camera stabilizing equipment came with the invention of the Steadicam. It allows the operator to walk or run, climb stairs, or shoot from moving vehicles while keeping the camera steady. The camera becomes virtually an extension of the operator's body, allowing for vertical movement up or down of almost three feet and for panning a full 360°. The operator views the image on a video monitor while guiding with a gentle hand movement a camera that seems to be floating on air. The assistant is able to adjust the focus or f-stop by a radio-operated remote control.
The only drawback to these systems is their weight. The Steadicam system with a 16mm camera weighs approximately fifty pounds. Operators need to be physically able to move in a harness supporting the whole system; a strong back is required for this job. And since the camera is perfectly balanced at the end of the support arm, it takes tremendous skill to stop it from swaying and rocking. Keeping the horizon level during a Steadicam move is an important step in mastering this device.
Until now we have discussed ways of controlling the image recorded by the camera, covering the manipulation of focus, perspective, camera positions, and movements. There remains the time dimension. It has infinite possibilities and therefore allows for great ingenuity in its use.
Near the beginning of this chapter, we introduced time-lapse and slow-motion photography and described how they could expand or collapse time.
Some general-purpose cameras have speeds up to 75 fps available from a wild motor. This is adequate for some slow-motion purposes, but if higher speeds are necessary, there are two general types of cameras to be considered: intermittent movement and rotating prism. Intermittent cameras are the kind we have already described; they arrest each frame for the period of exposure. For this reason they are limited to a top speed of about 600 fps, but are usually slower. The rotating prism camera features a continuous film flow.
The film never stops and the prism rotates to project the image onto the passing film. Because the film does not have to stop and start for each exposure, higher speeds are possible, ranging up to 10,000 fps for 16mm film. Special scientific cameras have been designed for much higher speeds, but they are seldom of any practical use to the average filmmaker.
At high speeds many problems arise. As the exposure time becomes minimal, a great deal of light is required (and/or very fast film). There is also a reciprocity failure; at higher speeds the exposure time-f-stop relationship gradually changes so that computing the exposure may be difficult. Exposure tests are necessary. To further complicate matters, at very high speeds the reciprocity failure may be different for each layer of color in the emulsion, thus distorting the color.
Film stock for extremely high-speed photography must have "long pitch" perforations. This means the distance between the sprocket holes is slightly greater. Some can only use double-perf stock (which means they can't shoot Super-16) and require that special daylight spools be used.
In addition to slowing or speeding a movement, film can be used to remove portions of it. One term cinematographers use for the creative elimination of in-between intervals of movement is pixilation. Pixilation is much like animation in that it is often taken one or more frames at a time, but unlike animation, its subjects are frequently moving objects, like cars or people. Whereas time-lapse cinematography seeks only to speed up action, pixilation removes specific parts of the movement, modifying the apparent nature of the action. For example, an overused pixilation effect is achieved by taking a single frame every time an actor jumps up into the air. Because he is never seen except at the height of his jump, he appears to be suspended above the ground when the footage is projected at normal speed.
Another pixilation technique involves running the camera several frames at a time. Between each interval the actor walks to a different area in the field of view. The result is that he appears for a moment in each position.
Either of these pixilated effects can be achieved by shooting single frames, shooting several frames at brief intervals, or using an optical printer to print only the selected frames from normally shot footage. If the final project is for a video-only release, you can also just edit out those frames after you've transferred the footage to video; however, if for a print, you will call attention to the fact that editing was used if you cut the negative itself, which tends to produce a little jump at every splice. The creative variations on pixilation are endless and open to experimentation.
Some cameras can run backward, providing the opportunity to invert time. Reverse action can be used to make a difficult maneuver possible or to achieve an effect. In one film, a director had the camera run in reverse while filming an actor walking backward in a crowd of normally walking pedestrians. When the film was projected forward, the actor became the only person who was walking forward in a crowd of pedestrians walking backward.
Impossible actions are made possible, such as a man effortlessly jumping straight up onto the top of a wall or low roof. The actor jumps down and walks away, all backward. The action is filmed with the camera running in reverse so that when correctly projected, the actor walks to the wall and jumps straight up onto it.
Another very important use of reverse action is in making complicated maneuvers easier. The most common example is a rapid pan to a very precise framing. If shot forward, we might spend a great deal of footage before we hit just the perfect framing the director wants at the end of the shot. However, filming in reverse, we could start on that precise framing and pan away to the first, less critical angle, achieving the shot while saving time and footage.
Reverse motion is also used to make stunts safer; for example, if you need a speeding car to come to a quick stop right in front of an infant in a baby carriage, you could start the car at the near position and have it quickly drive away in reverse gear.
Not all cameras feature an ability to run backward. But reverse action can still be achieved. In 16mm or 35mm, the action can be filmed and later reversed in an optical printer; or it can be done digitally once the footage has been transferred to video. Or reverse motion can be achieved by filming with any camera held upside down. If the image is recorded upside down, we can turn the film over in the projector and show it tail-first. It will be right side up, but the action will be reversed. In the case of single-perforated film stocks, the picture will also be turned around left to right. Double-perforated stocks could be turned over, correcting the left-to-right position, but this would put the emulsion on the opposite side, causing focus problems in printing.
When using the upside-down reverse action method, the best way to deal with the left-to-right exchange is to avoid lettering or anything else that would give it away, or to shoot through a mirror. There is also the possibility of printing any necessary lettering backward. This was done for the movie Titanic; passengers had to board the ship from port side, but only the starboard side had been built by the art department, so all signs in the boarding scene were painted in mirror-image reverse and "flopped" digitally later in postproduction.
The possibilities suggested by time manipulation are endless, and we have touched on only a few. The filmmaker is limited only by his own imagination.
Having spent the first part of this chapter covering some of the basic camera features and capabilities, we now will try to bring it all into focus. Selecting a camera is similar to choosing a car. You should consider many aspects before committing your money. There is much to be said for renting rather than buying equipment, since needs vary from one filming assignment to another. There are rapid changes in camera design and there is a constant flow of new models, which would be available at rental houses. Often you can rent a much more expensive camera than you could ever afford to buy. The decision to rent or buy a camera also depends on how extensively you plan to use it. Professionals will purchase a piece of expensive equipment only when they have already been working on jobs where they've had to rent that item continuously, and therefore know that the purchase will pay for itself over a short time.
If you are preparing to shoot a short or feature-length film, it sometimes makes more sense to rent if it will be shot over a short but intense period of a few days or weeks. However, if it's going to be shot off and on over a very long period (like some documentaries), it might make more sense to own the equipment.
Many amateurs and professionals prefer to own their own cameras. In this way, if they take good care of their equipment, they can be confident about its dependability. Sometimes they will own a "standby" or "B-camera" and rent their main camera, such as an Arri, Aaton, or Panaflex.
Besides the reflex versus nonreflex viewfinder issue already covered, 16mm cameras can be loosely divided into the following categories:
MOS or non-sync-sound. These are too loud for shooting scenes while sound is being recorded; they might also not have crystal-sync motors (but many do for reasons other than shooting dialogue scenes). Often these cameras have multiple frame rate options, so they might be used to shoot non-24 fps material, in which case being loud is not a problem, since no sync-sound will be recorded anyway. Cameras in this category include the Bolex, the Bell & Howell Filmo, the Arri-S/B, the Eclair CM3, the Beaulieu R16B, the Canon Scoopic, and high-speed cameras like the Photosonics Actionmaster.
Early sync-sound ("self-blimped"). These are the first generation of quiet sync-sound cameras. Being older and cheaper, they are often someone's first sound camera purchase. These include the Arri 16BL, the Eclair NPR and ACL, the CP-16, CP-16R, and the CP-GSMO.
Modern sync-sound. These started with the release of the Arri SR and the Aaton LTR 7 in the mid 1970s and continued with the Arri SR2 and SR3, and the Aaton LTR 54, XTR, and XTRprod. Panavision also made a 16mm version of their Panaflex line called the Elaine. Recently the very small Aaton A-Minima was released.
Every couple of years, camera manufacturers bring out new designs or improvements on older models. Therefore, this book cannot hope to provide an up-to-date consumer's report on every current camera. You will have to investigate the features offered by the designs of leading manufacturers at the time you buy. In addition to providing promotional literature, equipment rental houses can often be very helpful as you make a decision.
Even the most sophisticated cameras will occasionally fail to operate properly. Usually this is caused by a rather simple malfunction. Amateur camerapeople frequently jump to conclusions, suspecting the worst, when the problem is actually some simple thing like a low battery or a bad connection. So don't panic until you've checked the obvious things first.
Most camera troubles will fall into roughly five categories:
1. The camera will not run. This could be caused by:
- dead or low battery
- broken on/off switch
- broken power cable or loose plug connections
- dirty connection between the camera body and the magazine take-up motor (applies to Arri and Beaulieu)
- buckle switch not reset (some cameras have this safety device, which automatically stops the camera if a jam occurs)
- burnt-out or otherwise damaged motor
- extremely cold weather (the camera should be winterized by changing the lubrication from oil to graphite in a camera shop before shooting in very low temperatures)
2. The projected picture is unsteady. This could be caused by:
- film loops too small or too large
- film stock that has shrunk because of improper storage
- faulty synchronization of the shutter and pulldown claw (causes a vertical blur)
- pressure plate too tight or too loose
3. The film is scratched. This could be caused by:
- dirt or emulsion buildup somewhere along the film path
- rollers stuck in the camera or the magazine
- film gate scratched or damaged
- film loops too large or too small
- film not properly threaded
4. The film is fogged. This could be caused by:
- light leak from an improperly closed camera or magazine door
- reflexive viewfinder open to light — often because the camera operator took his or her head away from the eyepiece
- behind-the-lens filter slot that has been left open (especially on Bolex or wide-angle lenses)
- improper loading or unloading that may have exposed the film to light
- an empty lens cavity left open in the turret
5. The picture is out of focus. This is usually the fault of the camera operator or focus-puller, but it can also be caused by:
- lens not flush in the turret
- lens out of alignment
- viewfinder out of adjustment
- pressure plate not locked in correct position when the camera was loaded
Most of these troubles can be avoided by a thorough check. Before the day of shooting, all the equipment should be assembled and examined to make sure it is compatible and in working order.
Shooting a camera test is a vital step in preparation. It must be done and screened before the shooting begins so that there is ample time to deal with any problems. The main objectives of the test will be to check lens performance and picture steadiness. If two or more cameras are used, it is imperative that the frame lines be compared to make sure that footage from the two cameras can be intercut without the frame line shifting on the screen.
Lens sharpness is best checked by shooting a test chart or even a newspaper with the lens aperture wide-open (lowest f-stop). In the case of a zoom lens, the entire focal range (zoom range) must be tested.
At the same time, test the reflex viewing system and lens calibration by turning the test chart to a 45° angle.
Focus visually (or by measured distance) for a marked spot. If the viewing system or the calibrations on the lens barrel are out of alignment, the footage will be focused either closer or farther away than the marked spot.
Even the most comprehensive tests cannot eliminate human errors. Most mistakes are due to careless oversights. Camera operators have to keep track of so many small details that they are bound to eventually forget something. When they do, it will be a simple and obvious error.
The beginner is especially prone to such mistakes. Professional camerapeople develop a systemized routine of checking everything immediately before shooting. I have my own list of things to check before filming. I check that:
- tripod is level;
- gate clean;
- gate closed;
- sprockets engaged;
- footage counter reset after loading;
- forward/reverse properly set on both camera and magazine motors;
- motor speed set;
- magazine take-up taut;
- viewfinder eyepiece focused for eye;
- matte box not visible in frame;
- filter slot covered or closed;
- filter in place; and, most important, I
- check frame for composition, mike boom, set limits, etc.;
- check focus; and
- check f-stop.
The last three are the most important because they are constantly being changed during the shooting day and are therefore the most likely to be wrong when you start to shoot.
The Ditty Bag
The ditty bag contains all the small items camerapeople feel it necessary to have in their immediate reach while filming. The items may vary depending on personal choices, but most ditty bags are similar in content. Mine contains:
- American Cinematographer Manual (known as the cinematographer's bible)
- air syringe and/or can of compressed air
- orangewood sticks
- pair of fine tweezers and a dental mirror (for careful removal of film chips and hairs from inaccessible places; these are the only metal instruments used for cleaning)
- small flashlight
- camera brush made of fairly stiff hair (not camel's hair)
- lens brush made of extra-soft hair (such as camel's hair)
- lens tissue
- cotton swabs (for cleaning lenses only!)
- lens-cleaning fluid
- compact magnifying glass (cleaning aid)
- assorted screwdrivers
- needle-nose pliers
- crescent wrench
- black camera tape
- white camera tape
- gaffer's tape
- regular and grease pencils, marker pens, and ballpoints
- camera report cards (can be simple index cards)
- chalk (kept separate because of dust)
- scissors
- spare cores
- spare daylight-load spools
- 50-foot cloth measuring tape
- assortment of spare parts and adapters (e.g., quarter-inch to three-eighths-inch tripod screw adapter, a spare core center piece), depending on the type of equipment being used
- stopwatch
- contrast-viewing glasses for black-and-white and color
Apart from the ditty bag, these items might also be necessary on location or in the studio:
- spare light meter
- spare light meter battery
- spare changing bag
- spare film cans with black paper bags
- spare power and sync cables
- extension cables for mikes
- extension cables for lights
- all sorts of adapters for electrical supplies; most important, the common two-prong to grounded three-prong adapter
- spare bulbs and fuses
- spare batteries, such as for tape recorder
- spare camera battery with charger
- spare magazine take-up belts
- spare lens caps
- spare rubber eyecup
- spare supply of filters
- spare tape recorder take-up reel
- soldering iron
- voltmeter, or at least a voltage tester
- headache tablets (aspirin, etc.)
This list could go on forever. The point is that you should scale your equipment to your production, remembering that you want to be overprepared. Camera operation depends on many small details. If a camera malfunctions, all your footage may be ruined.
Lists of this sort are always of enormous value and should be made up before the day of shooting to make sure that nothing is forgotten.
Here again, as throughout this chapter, we are reminded of the great concentration and attention to detail required from the camera operator in order to maintain control in his or her work. Only after thoroughly mastering the techniques and mechanics of their craft can cinematographers develop the consistency necessary to achieve an individual stylistic approach, which is the goal of the cinematographer's art.
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