"Evidence concerning the absorption of light quanta by visual pigment molecules is used to derive a theoretical relationship between the parameters of light incident on the retina and the output of the receptor cells. This relationship leads to the following prediction: when two retinal areas are illuminated, one very intensely and the other still more intensely, there will be a period of time during which the less intensely illuminated region will appear brighter than the more intensely illuminated one. Data verifying this prediction are presented. When the theoretical treatment is expanded to include certain assumptions about retinal color mechanisms, it provides an explanation of some of the changes in hue that occur when a very intense colored stimulus is viewed steadily." (PsycINFO Database Record (c) 2006 APA, all rights reserved). © 1962 American Psychological Association.

Psychophysical evidence indicates that, in the human retina, the size of the spatial-summation area decreases as illuminance increases. Such a relationship would be beneficial for the detection of spatial contrast in the presence of photon noise. We analyze an image-processing mechanism in which the area of a strictly positive point-spread function varies inversely with local illuminance while its volume remains constant. In addition to its expected effect of improving spatial resolution as illuminance increases, this mechanism also yields center-surround antagonism and all other manifestations of bandpass filtering and accounts for Ricco's law and Weber's law--including the failures of both laws as a function of test conditions. The relationship between this mechanism and lateral inhibition is analyzed.