the most obvious problem, in practical terms is this:
you set the white balance on your subject, and the shadows will have an obvious color cast. if you move your camera or your subject, the color will change.
you can use that effect to positive ends creativly….
for example….
you place a ct (yellow/orange) gell in front of your camera lens and set a custom white balance to compensate. you then place that same ct gel on your main light and light your subject. (or place the gel on the light and set color balance at the subject)your subject will be color corrected and everything else will be tinted (guess what color? hint: opposite color on a color wheel). now suppose you have one or two more lights the same as your main light (stronger ct gels), which you use to rimlight your subject (they’ll wind up having a color cast because of your white balance setting).
using the above technique will yeild the following:
a normal colored subject, with yellowish (warm) rimlighting against a blueish (cool)background effectivly using color to seperate and pull forward your subject from it’s cooler (pushed back) background.
cool colors appear to recede and warm colors appear to come forward.
