Value gives the artist the means of showing subtle changes in a form's surface-state, and it helps clarify the relative distance between forms.
Nathan GoldsteinThe inherent lightness or darkness of a form - its local-tone - is a given quality of all forms. It is affected by, but separate from, the light and dark areas that result from light falling on forms.
Nathan GoldsteinPerspective should be learned - and then forgotten. The residue - a sensitivity to perspective - helps perception, varying with each individual and determined by his responsive needs.
Nathan Goldstein