Hi again,
This website is interesting when it says the following:
"To create his greatest effects, Rembrandt ignored the usual way of painting with the light coming from outside the picture, and painted as if the source of the light was from within objects themselves. Once he started this mental origin of light, it became imperative to change the composition to show how the light he was painting could be used to best advantage."
Here is the website to read more:
http://www.guidancecom.com/alphabet/value.htm
Now this brings up a question. Why is it that dark paintings with a small light source will draw the eye more than a light painting with a small dark value on it?