Hmm…I’ll take a stab at this.
Lets create a hypothetical situation. Let say you’re lighting a person in a scene and you shine aflorescentbulb and a tungsten bulb on the person. You may be able to put a piece of paper in front of the subject’s face and white balance properly for his or her face, but then what about the areas being affected by spill from lights? You may have blotches of green(from the florescent) or orange(from the tungsten) beyond your subject since those areas may not have the same mixture of light.
Does that make sense?
Also, I think cameras may sometimes have a hard time white balancing properly when there is amixtureof color temperatures.
