Monday, June 18, 2007
Working Within Color Spaces
Myth: Color space has the most important effect on color
Do you use Adobe RGB?
Is sRGB a pro format? Should pros really start using ColorMatch RGB? Or is there some other new color space permutation that will give even better results? The problem with this discussion on color space is that it assumes the digital camera has captured the correct colors in the first place and that all you need is the right color space to get the most from those colors. Digital cameras don't quite work that way, unfortunately.
Digital cameras “interpret” the colors of the world differently than how we see them. This isn't news to anyone who shot slide film in the past, of course. Digital cameras do have biases in the way they see colors, just like slide film, but there's something more that needs to be considered. Typically, you'll find that, overall, a camera deals with colors in a consistent way, yet when it comes to specific colors, image color capture may be deficient. It isn't just interpretation, but an actual deficiency in the way that color is seen by the sensor and its associated circuits and algorithms.
You can often see this in outdoor shots. Less-saturated blue skies captured by some cameras pick up an odd gray-blue color that wasn't in the real scene, and a number of cameras have trouble getting greens right in foliage.
Product photographers know this phenomenon all too well. The whole studio setup has great colors, except for that very specific color on the client's product. It doesn't matter if you shoot sRGB, Adobe RGB or anything else, that color just doesn't want to register properly with the sensor in your camera.
So what's a photographer to do? I shouldn't present the problem without offering some sort of solution. There are several, actually. First, it's helpful to just recognize this problem, so you can look for it and work to compensate, if needed. In some situations, frankly, this isn't really going to affect the final result, so obsessing over color capture doesn't offer any benefits.
But there are situations where deficiency in color capture can cause problems. You may find that one RAW conversion program works better with your subjects and your cameras than others. Every RAW conversion program uses its own interpretation of how to assemble the colors captured by the sensor (it has to take the color information coming from the Bayer pattern on the sensor and create colors for the image). Adobe Camera Raw, for example, doesn't create world-neutral colors, but colors that are definitely Adobe's interpretations.
Some RAW converters give you some control over color channels, and that can help. In Camera Raw, for example, there's a tab labeled “Calibration” (a name that doesn't do it justice).
There, you can affect the red, blue and green components of the photograph individually, including both hue and saturation. This can be useful when you need colors to separate and certain colors to match.
You can also spend a little time with Photoshop's Color Range tool to select a color for special adjustment. Using the individual colors of Hue/Saturation will also work.
I've found the Contrast: Color Range tool of Nik Color Efex Pro (www.niksoftware.com) to be helpful. It allows you to affect very specific colors by the use of a slider going across the color spectrum. It works best on a separate layer, so I can better control where and how much the effect occurs.
Recently, I learned of another useful color tool, DCF Full Spectrum (www.tribecalabs.com). I haven't used it a lot yet, but it seems to have good potential for dealing with the shortcomings of digital cameras and colors. Tribeca Labs has analyzed many digital camera images in order to create software that would compensate for their color weaknesses.
When you have color challenges from sensor color weaknesses, color space wars are the least of your worries. The client doesn't care whether you shot Adobe RGB or can work in ColorMatch RGB if the colors aren't exactly right. Relying on the “right” color space can give you a false sense of security that colors are also “right.”