I spoke in the first part of this tutorial about the mystique surrounding masks in the computer graphics world, but the fear and lack of understanding about channels seems to be greater than with masks. We are going to put that to rest once and for all right here. Channels are simply the view of an image separated into color components. If you are working with images for the Web, you will be working in RGB mode, or Red, Green and Blue. These three colors are used to produce the images you see on your screen.
Channels simply take the image and divide the information on a color basis.
See the sample at the left of a photo, plus the channels that make up this image. Channels are represented as grayscale images. To help understand how the channels work, I have included a comparative view of the color channels. In the left column, the channels are represented as grayscale images, the default and recommended setting. I am also not recommending that you change your preferences for showing the color channels in color.