Chapter 5 - Brightness perception and encoding curves

Abstract

In this chapter we discuss brightness perception, the relationship between the intensity of the light (a physical magnitude) and how bright it appears to us (a psychological magnitude). It has been known for a long time that this relationship is not linear, that brightness isn't simply proportional to light intensity. But we'll see that determining the brightness perception function is a challenging and controversial problem: results depend on how the experiment is conducted, what type of image stimulus are used and what tasks are the observers asked to perform. Furthermore, brightness perception depends on the viewing conditions, including image background, surround, peak luminance and dynamic range of the display, and, to make things even harder, it also depends on the distribution of values of the image itself. This is a very important topic for imaging technologies, which require a good brightness perception model in order to encode image information efficiently and without introducing visible artifacts.