TABLE OF CONTENTS | Note | Luminance is proportional to intensity. For an introduction to the terms brightness, intensity, luminance, and lightness, see page 11. |
In photography, video, and computer graphics, the gamma symbol, y, represents a numerical parameter that describes the nonlinearity of luminance reproduction. Gamma is a mysterious and confusing subject, because it involves concepts from four disciplines: physics, perception, photography, and video. This chapter explains 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.
| Note | Electro-optical transfer function (EOTF) refers to the transfer function of the device that converts from the electrical domain of video into light - a display. |
This chapter focuses on electronic reproduction of images, using video and computer graphics techniques and equipment. I deal mainly with the reproduction of luminance, or, as a photographer would say, tone scale. Achieving good tone reproduction is one important step toward achieving good color reproduction. (Other issues specific to color reproduction were presented in the previous chapter, Color science for video.)
A cathode-ray tube (CRT) is inherently nonlinear: The luminance produced at the screen of a CRT is a nonlinear function of its voltage input. From a strictly physical point of view, gamma correction in video and computer graphics can be thought of as the process of compensating for this nonlinearity in order to achieve correct reproduction of...
