The standard of value adopted by a painter, is light. The value of any color depends upon the amount of light reflected from it. Thus, if you look at a man dressed in black, you will notice that the black upon the shoulder, or the chest, or whatever part receives the greatest quantity of light, will seem less black than those parts which receive less light. And it may be only in the hollows or shaded parts that the black looks really black. Well, each one of these separate degrees of black represents to the painter a separate value of black.