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Tuesday, October 27, 2009

Color Space In Black-And-White

What is a color space, which options are best to use, and how can you make your own custom profiles to get the most out of your chosen color space?

This Article Features Photo Zoom

The subject of color space in digital photography seems to attract lots of controversy and very little consensus, which is unfortunate considering just how important your choice of color space is when it comes to producing the best photographic images. Understanding what a color space is and how to choose the best one for your specific needs will help ensure you’re making the most of your image-optimization workflow.

What Is A Color Space?
A color space is a definition of the range of colors available to you as you’re working with an image. If a color isn’t available in the current color space, you can’t use that color in your image. You can think of a color space as being akin to a painter’s palette, with only the colors in that palette available for the image that’s being created on the canvas.

One key fact that’s often misunderstood is that a color space doesn’t define how many colors are available, but rather the range of possible colors. The number of colors possible in a digital image depends on the bit-depth of that image. For example, an 8-bit-per-channel RGB image can contain over 16.7 million possible colors (16,777,216 colors, to be exact); a 16-bit-per-channel image can contain over 281 trillion possible colors (at least in theory). The color space is responsible for defining the specific range of possible colors. So, do you have over 16.7 million shades of red, or do those colors encompass the full visible spectrum?

Adobe RGB Color Space	sRGB Color Space	ProPhoto RGB Color Space
CIExyz diagrams show the difference between various color space gamuts. At a glance, ProPhoto RGB seems superior, but be aware that some of the colors in that gamut don’t actually exist in the visible spectrum—you might choose a color space with no real advantage.

Clearly, you can have a great many colors to choose from when working on your images. But which specific colors actually will be available? That depends on the color space you choose, since each color space defines a unique range of colors that will be available to you. It’s important to use a color space that encompasses all of the colors you’ll be able to produce in print as well as on your monitor display. Otherwise, you could be unnecessarily preventing yourself from utilizing some colors that you would have been able to print, for example.

It’s possible to use any ICC color profile as a color space, but generally, you’ll want to use a working space profile to define the range of colors available for your images. A working space profile is an ICC color profile specifically designed to define a range of colors available for use, rather than as a definition of the output properties for a given device (such as a printer or monitor display).