Consistent shadow values for painters

Abstract

A simple visual aid is presented, that can be produced in black-and-white on a piece of paper. A painter can use this aid to insure the consistency of shadow values in a painting. Consistency is necessary when an object with multiple colours, such as a shirt with red and white stripes, is seen in both light and shadow. All the values (the values of white in light, red in light, white in shadow, and red in shadow) must be correctly related to each other to make the painting convincing. Consistent values can be found by drawing a few lines on the visual aid. The scientific derivation of the visual aid is described. Finally, an application is suggested, that could heighten Adelson’s “checkerblock” illusions.