I posted an
introduction to understanding channels, and there's also a
discussion thread. Feel free to post questions there and I'll jump in.
Also search for articles on using the Apply Image, Calculations, and Channel Mixer commands.
It's also important to have an understanding of Blend Modes.
Meanwhile, here's a quick example of using channels to restore an image:
anetteoriginal.jpg
In this picture not only is there a color cast, but there are yellow stains on the brides face.
The first thing I did was look at the individual channels and noticed that the stains were only visible in the Blue channel, but the Green channel looked pretty good. So I created a Channel Mixer Adjustment layer and used it to replace the Blue channel with the Green.
channelMixer.jpg
Then I created a Curves Adjustment layer and did some basic color correction.
anetteoriginal_G23.jpg
The stains and color cast are gone and it took less than a minute. This is not necessarily the final image, but I'm in much better shape for further restoration.
Regards,
Michael