Chiaroscuro

use of strong contrasts between light and dark, usually bold contrasts affecting a whole composition in art

Chiaroscuro in art is the use of strong contrasts between light and dark.

Giovanni Baglione. Sacred and Profane Love. 1602–1603, showing dramatic compositional chiaroscuro

This is usually done to make the composition a lot more dramatic. It is also a technical term used by art historians and artists for the contrast of light. It gives a sense of volume when modelling three-dimensional (or 3D) figures. Similar effects used in photography and cinematography are also called chiaroscuro.