I want to discuss the specific technique of painting rim and edge lighting because it's one of the most reliably dramatic effects in portrait and character illustration.

Rim light: a secondary light source that hits the edge of a form from behind and to the side, creating a bright outline against the darker background. In studio photography this is often a continuous light positioned behind the subject. In painting it can be motivated by any background light source.

The effect: the rim light separates the subject from the background, creates a sense of depth and dimension, and often carries an emotional charge (golden rim light suggests heroism and warmth; cool blue rim light suggests mystery or cold environments).

The painting technique: the rim light should follow the form's edge precisely. On a sphere it follows the far side's curve. On a face it follows the jaw, cheekbone, and forehead in a thin strip that thickens over the most exposed surfaces.

The color: the rim light should be the complementary temperature to the main light. Warm main light, cool rim. Cool main light, warm rim. This temperature contrast makes the rim light read as a distinct, separate light source.