Real world lighting is a great way to experiment. Another factor is your initial enviroment. Daylight(consider source direction), incandescent(source, direction & distance) which will be softer and the new energy saver bulbs have yellow and pink hues. Flourescent, harsh white and sometimes different enviromental hues added to these also. (consider the same variables). Even when I'm not trying, I find myself noticing light factors as to how it would look in an image.

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Ockham's razor- It's that simple