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RAW Workflow from Capture to Archives
A complete digital photographer's guide to raw imaging
By Philip Andrews Yvonne J. Butler Joe Farace
Copyright © 2006 Philip Andrews, Yvonne J. Butler and Joe Farace
All right reserved.
Chapter One Raw School 101
It's a new day in photography. The earth-shattering change brought on by the availability of instant feedback on the digital camera's LCD, or directly on computer monitor through tethered or wireless camera-to-computer capture, with histogram and capture information displayed, has changed the way we work and play in the realm of photography. Many, if not most of us, have ditched the chemicals and transformed our film darkrooms into digital darkrooms. We're showing our clients or family and friends our work on various devices or as a quick print, right after it's produced and we're printing our own masterpieces or transmitting the image files directly to our imaging bureau. What is the next step in this ongoing digital development? Well, now many of us are embracing the advantages of 'raw' capture and building the new skills necessary to process and enhance our raw files in order to bring them closer to perfection or, at the very least, our liking.
Unless you have been sleeping, or is that hibernating, under a rock for the last few months you will already know that 'shooting raw' is the latest hot topic for digital photographers the world over. More and more mid to high level SLR and compact cameras provide the option for switching from the traditional capture formats of JPEG and TIFF to raw. This capture format change gives photographers even more control over the digital photos they create by taking back a bunch of processing steps that until now have been handled by the camera, and placing them firmly in the hands of the shooter. By providing access to the image data early on in the processing workflow, photographers have more creativity options and better quality control with their pictures but, as with most things, along with this new found flexibility comes increased responsibility. Over the next few chapters we will take a close look at what it means to shoot, process and output raw files, and also get a sneak preview of the new wave of 'complete raw workflow' enhancement tools and techniques that are now entering the market. But before we get to ahead of ourselves let's start at the beginning with some details on the format itself.
What is raw?
To get a handle on what this file format is, and how it can help you make better pictures, we need to start by looking at the capture part of the digital photography process. All single shot digital cameras (except those using the Foveon chip) contain a sensor that is made up of a grid, or matrix, of light sensitive sites. Each site responds proportionately to the amount of light that hits its surface. By recording and analyzing each of these responses a tone is attributed to each sensor position in the grid. In this way a digital picture can be created from the range of scene brightnesses that are focused through the lens onto the sensor's surface. Fantastic though this is, this process only results in a monochrome (black, white and gray) picture as the Charge Coupled Device (CCD) or Complementary Metal Oxide Semiconductor (CMOS) sensors by themselves cannot record the color of the light, only the amount of light hitting the sensor site.
So how do our cameras create a color photo using mono sensors? Well, to produce a digital color photograph a small filter is added to each of the sensor sites. In most cameras these filters are a mixture of the three primary colors red, green and blue, and are laid out in a special design called a Bayer pattern. It contains 25% red filters, 25% blue and 50% green, with the high percentage of green present in order to simulate the human eye's sensitivity to this part of the visible spectrum. Adding a color filter to each sensor site means that they respond to both the color and brightness of portions of the scene. Using this system the various elements of a color scene are recorded as a matrix or pattern of red, green and blue pixels of varying brightnesses. If you greatly magnify one of these images you will see the three-color matrix that was created at the time of capture.
The unprocessed sensor data saved at this point is referred to as a raw file. It contains information about the brightness and color of the scene, but in a form that can't be readily edited or enhanced with standard photo software. Until the current influx of raw-enabled digital cameras and software, photographers were blissfully unaware of the existence of such files, as the images that they received from their cameras were already converted from the raw state to the much more familiar (and usable) JPEG or TIFF form. This conversion occurs as an integral part of the capture process, where the raw data coming from the sensor is used to create a full color image. Special algorithms are employed to change the Bayer-patterned data to a standard RGB form; in the process the extra details for a non-red sites, for instance, are created using the information from the surrounding red, green and blue sites. This process is called interpolation, and though it seems like a lot of 'smoke and mirrors' it works extremely well on most cameras.
So when you opt to save your images in JPEG or TIFF formats, this capture and interpolation process happens internally in the camera each time you push the shutter button. Selecting raw as your preferred capture format stops the camera from processing the color separated (primary) sensor data from the sensor, and simply saves this data to your memory card. This means that the full description of what the camera 'saw' is saved in the image file and is available to you for use in the production of quality images.
When selecting raw for image quality, the digital camera stores only the raw image and EXIF or metadata (camera type, lens and focal length used, aperture, shutter, and more). Any camera presets and parameter settings you make, such as contrast, saturation, sharpness, and color tone (found in the Parameters menu on the Canon EOS 20D, for example), do not affect the data recorded for the image. They do, however, become the defaulted values during raw conversion, until you elect to change all or some of them. Only ISO speed, shutter speed and aperture setting are processed by the camera at the time of capture.
An extra processing step
Sounds great, doesn't it? All the quality of an information rich image file to play with, but what is the catch? Well, for the most part raw files have to be processed before they can be used in a standard image editing application like Photoshop. It is true that brand new applications, like Adobe's Lightroom and Apple's Aperture, can enhance raw files without first converting them, but for the most part serious editing can only take place on a converted raw file. So to access the full power of these digital negatives you will need to employ a special raw converter. These programs come as either stand alone pieces of software, or as a dedicated feature in your favorite editing package. Some can process files from capture devices of several manufacturers, others are restricted for use with single camera models only. They range from very expensive, fully featured, professional workhorses to free bundled utilities supplied with raw-enabled cameras.
Designed specifically to allow you to take the unprocessed raw data directly from your camera's sensor, and convert it into a usable image file, these editors also provide access to other image characteristics that would otherwise be locked into the file format. Variables such as color space, white balance mode, image sharpness and tonal compensation (contrast and brightness) can all be accessed, edited and enhanced as part of the conversion process.
Behold the new negative
So to put it simply, a raw file is a digital photo file format that contains the unprocessed image data from a digital camera's sensor. Cameras with raw file support save the white balance, saturation, contrast, color, tone and sharpness settings for the file as tags (or place markers) but do not process them at the time of recording. The same settings for JPEG (and TIFF) files are processed in-camera and cannot be undone, if you will, in the digital darkroom. With raw capture you have full control over your raw file's destiny. Capturing what you see in raw mode is the closest you can get to producing pure, unadulterated image data that will be ready for your creative control and interpretation.
A raw file is often called a digital negative for two or more reasons. First, raw files may be processed and converted multiple times without ever damaging the original image data. Second, the photographer is required to process and convert the digital negative in the digital darkroom post-capture, in a way similar to working with a negative in a traditional film darkroom. You always have the negative, whether digital or film, to reinterpret at a later date.
Why bother with raw? Why not just stick to JPEG?
OK, I know what you are thinking. Shooting in raw means more processing work for the photographer. So why bother? Why not just stick to JPEG? Well the answer is twofold – better image quality and more creative control.
Not too long ago when asked why I would ever choose raw over JPEG, I often said, 'I shoot raw for the creative control I have over the images'. I've given this broad answer much thought and now think that it does not say quite enough about the power of raw. It's not just about creative control. It's also about quality control and assurance, if you will – not to sound too much like a Ford or General Motors executive or anything. When we tell our camera not to go ahead and process our files in-camera and make the decision to become the processing lab ourselves, we decide we want full creative control over working with our images to make them color correct, void of artifacts and defects (which are inherent in JPEG files), and great images overall and we expect to assure our clients and/or ourselves what we have produced is of top quality. That's creative control, quality control, and quality assurance all rolled into one!
When we shoot raw instead of JPEG (or TIFF) we have as much control over image quality as we want and we can make creative changes to our raw file within the raw converter (or conversion process) well before we even get to the enhancement stage using imaging software. The camera sets markers for the selections we make at capture and we can move (adjust) the markers for exposure, white balance, and more during conversion. This is not the case for JPEG files as they are processed in-camera and after download we take what we get (a fully processed file) and go from there. We have to try our best to recover detail or fix a problem in Photoshop or other imaging software, often using up precious time and creating more frustration than the image is worth to us. With raw capture, if your exposure and white balance are off just a little or, heaven forbid, even way off, you have the advantage of being able to correct and adjust your initial capture settings with a fair amount of success. With JPEG capture, if the exposure and white balance, for example, are a little askew you're stuck, baby! Throw it away!!
When only the best will do!
Just as many photographers pride themselves in only shooting in manual mode, or boast about using the Levels or Curves features in Photoshop, rather than the Auto options, quality conscious shooters eagerly jump at the opportunity that raw capture affords by allowing them to get their hands on their photos early on in the processing chain. The conversion options provided by the camera at the time of capture, good though they may be, still provide an automatic-only approach to this important step. In contrast, armed with the top quality raw editing software that is now available and a raw-enabled camera, the desktop photographer can make careful and considered judgments about the many variables that impact on the picture conversion, providing customized picture-by-picture solutions never possible in the camera.
One of the real advantages of enhancing your photos during raw conversion is the changes are being applied to the full 12- or 14 -bit image rather than the limited color space of the 8-bit JPEG image. The changes are made to the file at the same time as the primary image data is being interpolated to form the full color picture. Editing after the file is processed (saved by the camera in 8-bit versions of the JPEG and TIFF format) means that you will be applying the changes to a picture with fewer tones and colors. And we all know the benefits, or should do, that such high bit editing provides.
Excerpted from RAW Workflow from Capture to Archives by Philip Andrews Yvonne J. Butler Joe Farace Copyright © 2006 by Philip Andrews, Yvonne J. Butler and Joe Farace. 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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