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Sunday, May 1, 2005

The Craft of RAW

Use RAW to make good photos better, not bad photos okay

Look at any color—if it's darker, it has more black and less chroma, or color information; if it's lighter, then it has more white and also less chroma. The same thing happens whether you expose film or digital. Dark colors have less color in them to reveal; light colors also have less color in them.

As you process a RAW file, the result is that underexposure or overexposure can mean you don't have the tones or colors you really wanted. At best, this will mean more work for you in processing your photos. You'll move one control to where the image looks good, but to correct problems, you need to make a counter-adjustment with another control. That may throw off color, so you need to make another counter-adjustment. Now, the first control looks off, so you have to go back and tweak it again. You think you have it all right, make the conversion and then find the file still doesn't look right, so you have to start over again. It can become a major workflow problem.

At the worst, problem exposures in RAW will mean you never can get the colors that were originally in the scene. Sure, you can intensify this using saturation controls, but that means more work, typically harsher tonal gradations and almost always more noise.

Noise is a problem. Digital camera manufacturers have put a lot of effort into noise reduction, and they keep getting better—as long as exposure is correct for the scene. Problems with exposure result in increased processing of an image, which will enhance and reveal noise that you don't want in the picture. Noise is strongly affected by both the type and size of sensor in the camera, the ISO setting used and the exposure. You can choose the ISO setting, you can't change the sensor, and you definitely can affect exposure.

Underexposure has a great potential for adding unwanted noise in any digital image. It's true that you can limit the noise in the image in processing, to a degree, and by using noise-reduction software. This isn't a simple fix, however, and there are trade-offs.

The first is a workflow issue. For a variety of reasons, you might not see the noise until later in the process. It can be especially noticeable in a larger print. When you go back to the image, you'll see it there, but it just doesn't always pop out at you on the computer monitor. Now you'll have to reprocess the image and print again.

The second trade-off is that removing noise can affect details in a photo. Noise is a very fine detail in an image, in a sense. If you remove it, then other fine details may be affected as well. Over-processing a photo to control noise can make it look very unnatural, with odd-looking tonal and color transitions. You're much better off minimizing noise initially by shooting at the right exposure and limiting your use of higher ISO settings (you should test your camera's ISO settings to see what it does and what's acceptable).

RAW came into the market with such hype that many photographers thought it could do miracles. One of the most common misconceptions I hear is that RAW is so adaptable that you don't have to be as concerned about exposure or color since you can fix it in the computer later. Such thinking shortchanges RAW, creates more computer work (which can be frustrating) and can give you less than the best tonalities and color.

The key: shoot it right in the first place. If you have any doubts, try another exposure. Another misconception is that RAW never requires bracketing. In a difficult lighting situation, bracketing can be helpful.

RAW has amazing capabilities. Just remember that its full possibilities are enabled only when the image is thoughtfully exposed and captured by the sensor initially. RAW makes a good exposure better; it only means a lot of work with a poor exposure.

Editor Rob Sheppard's latest book is the PCPhoto Digital Zoom Camera Handbook, a guide to advanced digital cameras. He's leading a photo tour to Peru again this summer; visit the Palm Beach Photographic Centre website at www.workshop.org.



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