Notan

Nōtan (濃淡) is a Japanese design concept involving the play and placement of light and dark elements as they are placed next to the other in the composition of art and imagery.

Uses
This use of light and dark translates shape and form into flat shapes on a two-dimensional surface. Nōtan is traditionally presented in paint, ink, or cut paper, but it is relevant to a host of modern-day image-making techniques, such as lithography in printmaking, and rotoscoping in animation.