Measurement and modeling of adaptation to noise in images

— Webster has proposed “that adaptation increases the salience of novel stimuli by partially discounting the ambient background.” This is an excellent, concise, description of the purpose and function of chromatic adaptation in image-reproduction applications. However, Webster was not limiting this proposal to just chromatic adaptation, but rather using it as a general description for all forms of perceptual adaptation. Demonstrations of adaptation to other properties of image displays such as motion, blur, and spatial frequency led the authors to ponder the question of whether observers might adapt to the noise structure in images to enhance the novel stimuli — the systematic image content. This phenomenon, noise adaptation in images, was easily demonstrated, but apparently has not been carefully studied in the past. Psychophysical measurements of noise adaptation in color image perception is described and mathematical prediction of the effect is explored. The results illustrate the hypothesized pattern-dependent adaptation and its prediction through adaptation of a 2-D contrast-sensitivity function in an image-appearance-model-based difference metric.