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digital photography in available light
By mark galer
Copyright © 2006 Mark Galer and Philip Andrews
All right reserved.
Chapter One digital cameras
~ Understand the differences between various types of digital cameras.
~ Compare specifications and isolate features important to your personal workflow.
~ Appreciate the limitations of various systems and their impact on image capture and quality.
Choosing a digital camera that will meet your imaging needs (and not blow a hole in your budget) can seem as difficult and confusing as choosing a new mobile phone plan or setting your neighbors DVD recorder to record their favorite TV show in two days' time. If we focus on the key differences between the digital cameras currently available the choice can be somewhat clarified, and the range of models that will fulfil your requirements can be narrowed considerably. If you need to go shopping it can be a useful exercise to create a 'must have' list after considering the implications of the various features that digital cameras do, or do not, offer. As the numbers of makes and models of digital cameras are immense this chapter focuses its attention on a few significant cameras (significant in their respective genres) to enable direct comparisons.
Top of most people's 'things to consider' list is usually 'megapixels' – how many do I want, how many do I need? 12 or 14 megapixels is great if you like cropping your images a lot or have a constant need to cover double-page spreads in magazines at a commercial resolution or create large exhibition prints.
Many high quality 8-megapixel cameras can however create digital files that can be grown to meet these requirements if the need arises. If the ISO is kept low digital files from many cameras can be 'grown' with minimal quality loss. Choose the 'Bicubic Smoother' interpolation method in the 'Image Size' dialog box when increasing the pixel dimensions of an image to ensure maximum quality is achieved.
22-megapixel medium format capture may sound like something everyone would want to aspire to or own (and for some commercial photographers it is the only option) but you have to weigh up the implications of capturing such large files. A 22-megapixel file will place an increased burden on the hardware and software - slowing systems considerably if they do not have the performance to cope with the heavy traffic that multiple 22-megapixel files can impose. Many photographers in this period of transition from analogue to digital make the mistake of replacing like with what they perceive to be like, e.g. an analogue medium format camera such as a Hasselblad or Mamiya 645 or RZ67 with what they believe to be the equivalent digital medium format camera. It is worth noting however that the quality that can be achieved with a high end digital SLR, such as the Canon 1Ds Mark II, can match the image quality of a medium format analogue camera using a fine-grain film. A digital medium format camera, one could safely assume, is knocking on the quality door of 5 x 4 film and surpasses the quality that is available from medium format film. The price differential between a Hasselblad medium format digital camera and the Canon 1Ds Mark II is considerable and for many photographers the DSLR would outperform the Hasselblad in terms of speed and ease of handling.
The need for speed
The issue of speed can arise in many stages of a digital workflow. Many of the issues that were connected to the issue of speed that proved problematic in digital cameras only a few years ago have largely been removed from the equation. Delays between switching the camera on and being able to take your first image, achieving focus and the delay between pressing the shutter release and the camera actually capturing the image (called shutter lag) have now been mostly relegated to the digital compacts. After capturing the image the camera then has to write the file to the memory card. The issue of speed here usually only becomes problematic if the photographer is shooting in the RAW format. Camera manufacturers resolve this issue of write speed by placing a 'buffer' that can store multiple images before the camera has to write the files to the card. If an unfolding action requires the photographer to shoot bursts of images in rapid succession then the size of the buffer is an important issue if the photographer needs to capture in the RAW format. Fast shooting whilst using the camera RAW format is usually the preserve of photographers using higher quality DSLRs. If the photographer is capturing images faster than the camera can write them to the memory card the camera will be unable to capture additional images until the buffer has more available memory. If the camera is continually 'locking up' whilst the camera's processor writes the images to the card the photographer must make the choice to shoot in shorter bursts, switch to the JPEG format or upgrade to a camera with a larger buffer and faster write speed.
Note > If the camera you are looking at is not an SLR it is advised that you test the amount of shutter lag prior to making a purchase. Lag is reduced significantly in the budget digital cameras if the shutter release is already half pressed prior to capturing the image, i.e. focus and exposure are already set.
Prosumer digicams - closing the gap?
The release of three new fixed lens digital cameras (the Sony DSC-R1, Fuji s9500 and Samsung Pro 815) and the dropping prices (and sizes) of budget digital SLRs has revived a dilemma that has been growing steadily for photographic enthusiasts or 'prosumers' seeking professional quality images at an affordable price. Which camera is the right one for me? The dilemma has never been more difficult for the consumer than it is today. Sony have added further fuel to the fire with the revolutionary new R1 which is one of the most significant new digital cameras released in 2005 (together with the Canon EOS 5D DSLR and Nikon D200).
Fixed lens digital cameras are sometimes referred to as 'Digicams', 'Prosumer cameras', 'Bridge cameras' or 'EVFs' (an acronym for 'Electronic ViewFinders'). There is no traditional name because this is an entirely new breed of camera where typical examples in the genre are neither compact nor feature the mirror and pentaprism mechanisms to enable them to be called an SLR. The quality and list of professional features that these cameras boast has been growing over the last few years and the spec sheets have raised more than a few eyebrows amongst professional photographers. Although the size of these cameras has been growing (largely in response to the huge optical zooms that are integral to most of the models on offer) their price point has pretty much remained the same.
The new Fuji s9500 now has a 9 megapixel sensor and a 10.7x optical zoom range via a twist-barrel (rather than electronic) zoom control whilst the Samsung Pro 815 has an 8 megapixel sensor and boasts a whopping 15x optical zoom spanning a colossal 28mm to 420mm zoom range (35mm equivalent). With the arrival of these impressive lenses the need to change a lens (which is obviously not possible if the lens is fixed) has been rendered a non-issue. In fact the inability to change the lens can be viewed a positive point when you consider that the 'dust on the sensor' issue* has always been a non-issue for the fixed lens digicams. The one thing you cannot describe these prosumer level digicams as, is 'compact'. The three prosumer digicams mentioned here are either about the same physical size and weight as some of the lighter DSLRs (Olympus E-500, Pentax ist and Canon EOS 350D Rebel - to name but a few) or, as is the case with the Sony R1, even heavier.
* Only Olympus have addressed the problem of dust on the sensor to date. Olympus DSLR cameras use a 'Supersonic wave filter' that vibrates the dust off the sensor when the camera is powered up.
The new Sony R1 has raised the bar in the 'tubby' stakes with the camera weighing in at a couple of grams short of a kilo. A kilo in old money is about the same as a Nikon F90/F100 SLR film camera with batteries and 50mm lens. The Sony R1 is about the same physical size as a DSLR sporting a 70-210 telephoto zoom lens - from back to front it's deep, very deep! Whilst I had this camera out on location recently some digital photographers on a photographic workshop (and shooting with a broad range of DSLRs) spied the R1 and thought I was working with a digital medium format camera! This mistake came about by the fact that the R1 looks very well endowed up top. Sony has moved the ingenious 'pop-up-and-rotate-me-in-any-direction' LCD screen to sit just behind the pop-up flash which moves forward to give adequate coverage for the wide 24mm coverage (35mm equivalent) that the Carl Zeiss lens offers. You can definitely not describe the porky R1 as 'compact'. Having said this I had both the Fuji s9500 and Sony R1 sitting comfortably in my kit bag that is normally reserved for a single DSLR system (one camera and three lenses). If you factor in the additional lenses that DSLR owners typically carry around in their kit bags then the 'kit' could still be called compact even if the prosumer digicams themselves no longer deserve or warrant this tag. With physical mass no longer a point of difference between DSLRs and prosumer digicams what exactly is it that distinguishes these two types of cameras?
Note > When comparing the weight of prosumer cameras against the specifications of a DSLR you must factor in the weight of the lens that you intend to use with the DSLR.
Choosing a system
The two major differences between the prosumer digicams and DSLRs is the size of the sensor and the type of view that we see through the viewfinder of each type of camera. The size of the sensor leads to the issue of image quality whilst the type of viewfinder image leads to an operational or handling issue. First we will look at the issue of size, i.e. does size really matter?
Sensors in the prosumer cameras have always been small, whilst in DSLRs the sensor size is comparatively much larger (more than double the dimensions and quadruple the surface area). The use of small sensors in prosumer digicams usually leads to increased levels of noise when compared to the images captured with an average DSLR camera at the same ISO - especially when comparisons are made at higher ISO settings. Larger sensor sites typically lead to less problems with noise. If money is not an issue then you can play find the noise with images captured with Canon's full size sensors found in the EOS 1Ds Mark II and new EOS 5D. The fifth generation Super CCD sensor used in the new Fuji s9500 digicam however is a marked improvement from previous sensors found in your average digicam. At ISO 80, 100 and 200 the level of noise is effectively suppressed and can match the levels of noise found in some of the budget DSLRs using CCD sensors.
If we examine the detail (zooming in to 200 or 300% on screen) from an image captured at ISO 400 on the Fuji s9500 in low light we will discover posterization and lumpy tones. These are evident as a result of in-camera processing in an attempt to suppress the noise that is inherent in files captured with the small sensors found in prosumer digicams.
This image processing makes the image look as if we are viewing the file through distorted glass. Quality is starting to be compromised. If we view a RAW file from a file that has been captured at 400 ISO without noise suppression then the smudged detail is replaced with luminance and color noise that is reminiscent of images captured with high-speed color film. Fuji, I feel, have been a little over zealous with the noise suppression in the new s9500 when the ISO moves over 200. I would personally still like to see the color noise suppressed but would have been happy to see a little luminance noise at 400 ISO rather than lose the crispness of the image in the attempt to remove all noise. There is no option for noise suppression when using the JPEG format, and switching to RAW mode in the Fuji is not a very quick affair. The RAW option is buried deep in a submenu instead of being conveniently accessed via one of the main camera switches as is the case with many other high-end cameras. I feel Fuji is underestimating the number of photographers who will want to frequently switch between JPEG snapshots and the RAW format for their personal folio images.
Note > Although the image artefacts that are starting to appear at 400 ISO, they are barely noticeable in a 4 x 6 inch print or 17 inch screen preview of the entire image.
Excerpted from digital photography in available light by mark galer Copyright © 2006 by Mark Galer and Philip Andrews. Excerpted by permission of Focal Press. All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.
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