80 C HAP TER 02. LIGHT AND COLOR Many display programs perform incomplete gamma correction, that is, the image is corrected such that the displayed material is left intentionally nonlinear. Often, a gamma value of 2.2 is used. The effect of incomplete gamma correction is that contrast is boosted, which viewers tend to prefer [83]. In addition, display devices reflect some of their environment, which reduces contrast. Partial gamma correction may help regain some of this loss of contrast [350]. One of the main advantages of using a gamma encoding is that it reduces visible noise and quantization artifacts by mimicking the human contrast sensitivity curve. 8 However, gamma correction and gamma encoding are separate issues, as explained next. 2.11 BRIGHTNESS ENCODING Digital color encoding requires quantization, and errors are inevitable during this process. In the case of a quantized color space, it is preferable for reasons of per- ceptual uniformity to establish a nonlinear relationship between color values and the intensity or luminance. The goal is to keep errors below the visible threshold as