The tools of Fourier analysis can be used to explain visual phenomena of spatial brightness interaction provided that attention is confined to small perturbations of spatially uniform fields. A perturbation approach is outlined here, and a transfer function is presented which is appropriate for small perturbations. The transfer function was obtained from human subjects with psychophysical methods, for the case of briefly flashed, achromatic fields at photopic levels of illumination. For the frequency range of 0.005 to 0.15 cycles per minute of arc, the transfer function is roughly proportional to spatial frequency, thus reflecting, in large part, nonoptical properties of the system. A simple mechanism of lateral inhibition could underlie this transfer function.
MICHAEL DAVIDSON, "Perturbation Approach to Spatial Brightness Interaction in Human Vision," J. Opt. Soc. Am. 58, 1300-1308 (1968)