Quantization Effects in Digital Imaging Systems

Colors and tones in CEPS and other digital imaging systems do not vary continuously, but in small, discrete steps, because of the limited precision with which the relevant quantities are represented internally. The resulting quantization effects, such as banding, contouring, and noise, can be objectionable to the viewer under certain circumstances. A conceptual analysis of these effects is developed, within the context of non-linear color-reproduction processes and human visual response. The advantage of employing perceptually uniform variables is made explicit. The analysis results in general techniques for minimizing objectionable quantization effects and determining the digital precision required at various points within a system. Typical applications are presented for soft-copy (i.e. monitor display) and hard-copy proofing.