Determining lightness from an image

A method lor the determination of lightness from image intensity is presented. For certain classes ot images, lightness corresponds to reflectance, while image intensity is the product of reflectance and illumination intensity. The method is two-dimensional and depends on the different spatial distribution of these two components of image intensity. Such a lightness-judging process is required for Land's retinex theory of color vision. A number of physical models are developed and computer simulation of the process is demonstrated. This work should be of interest to designers of image processing hardward, cognitive psychologists dealing with the human visual system and neurophysiologists concerned with the function of structures in the primate retina.