Most of us know that photos are made up of red, green and blue pixels that our eyes and brain process into the full range of colors we “see”. The great pointillist painter George Seurat broke his images down into individual dots of color. If you stand up close they are a mess, but stand back and the dots are transformed into a day in the park.
Photoshop works much the same way. We spent the last few weeks talking about layers and how they interact, but we need to dig a bit deeper. Down by the layers tab, is another tab called Channels. If you select it, you will see four different versions of your picture. An RGB composite and three greyscales called Red, Green, and Blue. By default, Photoshop displays them this way because it really contains more info. If you want to see what they really look like, just go to your Preferences, Ctrl-k or CMD-k on a Mac, => go to interface and check the show channels in color. If you select them one at a time, you will see the color information for your image.
If you click on two at a time, you will see how the colors interact to create new colors.
I don’t recommend you leave them this way, because when we start to work with them later, this view is harder to use. The grey-scales contain all the info you will need to manipulate the individual channels. Take a few different kinds of images and look at their channel info. See how much info you get from the red channel in pictures of people, the green channel in nature images and the blue channel where the sky or sea are dominant.