Abstract
The mathematics of a two-stage theory for the brightness perception of impulsive functions is developed. The first stage is seen as second differencing of the spatial luminance function as imaged en the retina. The second stage is a reconstructive stage which synthesizes the outcome of the first stage into a form isomorphic with brightness perception. This two-stage process allows fo the explanation of illusions concerning the illusory propagation of brightness from points of discontinuity. A computational algorithm was presented and applied to a variety of relevant examples.