Okay, enough scientific stuff, let's have some fun with Photoshop.
In the following exercise, you will place two Color Samplers in the image, one for the highlight and the other for the shadow. Then you will create a Curves Adjustment Layer and correct the colors in the image using the numbers in the Info palette as your guide. Your goal in this exercise is to remove any color cast in the whites and shadows, thereby correcting the colors within the entire tonal range.
Applying Minor Curves Corrections
Open the Crew.psd image from the Examples/Chap12 folder on the companion CD. (Before your eyes are influenced by chromatic adaptation, can you see what colors need adjusting in this image?) ...