`Gamma' and its disguises: The nonlinear mappings of intensity in perception, CRTs, film, and video

Abstract

In photography, video and computer graphics, the gamma symbol γ represents a numerical parameter that describes the nonlinearity of intensity reproduction. Gamma is a mysterious and confusing subject, because it involves concepts from four disciplines: physics, perception, photography, and video. In this note I will explain how gamma is related to each of these disciplines. Having a good understanding of the theory and practice of gamma will enable you to get good results when you create, process, and display pictures. This note focuses on electronic reproduction of images, using video and computer graphics techniques and equipment. However, the discussions of perception and photography may be of general interest as well. This note deals mainly with the reproduction of intensity, or as a photographer would say, tone scale. This is one important step to achieving good color reproduction, but issues specific to color are covered elsewhere.