Filter model for lightness and brightness on different backgrounds

A filter model is proposed to account for the effects of background luminance on perceived brightness or lightness of a target area. Special attention is focused on a crispening effect describable as a local increase of the rate of change of brightness with target luminance, as target luminance passes through the level of background luminance. The model is based on the assumption of competition, in the form of mutual-shunting-feedback inhibition, between target and surround.