Let’s try lighting Abe by placing the light on the “short side” of the face—the farther, foreshortened side.
The lighted triangle now appears on the cheek closest to the viewer. Short lighting emphasizes the cheek contour, and it can help make a face look thinner.
When short lighting is arranged so that the nose shadow merges with the shaded side of the face, many photographers call it “Rembrandt lighting.” Here’s Rembrandt’s “Lady with an Ostrich Fan,” a classic example.
As blog reader Rockhopper pointed out, some photographers use the term “Rembrandt lighting” more broadly for any three-quarter lighting, either broad or short. Rembrandt himself certainly used both broad and short lighting.
All of the arrangements we’ve seen so far are flattering and unobtrusive, good reasons why portrait painters and photographers have used them almost universally.