Channel Mixer

The Channel Mixer does what it says—it lets you mix the channels, combining content from one or more channels and feeding it into another. We find it useful for getting grayscale images out of color ones (see “The Color of Grayscale” in Chapter 12, Essential Image Techniques), but its usefulness as a color-correction tool is less obvious.

We don’t use Channel Mixer as a global correction tool on RGB images, though we sometimes use it to make local corrections, typically to bring out highlight or shadow detail that’s only present in one channel.