In addition to contributing to the mood, shadows serve to effectively
highlight the contours of the face, which further defines its shape.
Some artists use a great deal of shadow—so much, in fact, that they
allow some of the facial features to become subsumed into a pool of
blackness. This can be an effective stylistic technique. Other artists
use shadows sparingly, only as accents. The manner in which you
use shadow is a matter of taste and may become a significant part of
your personal style if you choose.
It’s essential to first decide where the light source is coming from
before one begins to shade an object. The position of the light
determines the direction of the resulting shadows. Light causes
shadows. Shadows are not random events.
The face is not a flat surface. It is made up of three different planes,
and various protruding surfaces, each of which interacts with the light
in a different way. The three planes of the face are: