Abstract

The luminance pattern presented to the eye is the product of the illumination and reflectance patterns; the spatial frequency spectrum of the luminance pattern is the convolution of the illumination and reflectance spectra. Because of the convolution, spatial frequency components of the illumination are commingled with those of the reflectance pattern, producing the potential for a variety of perceptual distortions or confusions. For example, the convolution might be expected to degrade spatial frequency discrimination, thus reducing the ability to distinguish different textures. Accurate perception requires some sort of deconvolution process which permits illumination components to be processed separately from reflectance components. One mechanism of deconvolution, which is often suggested, is an early logarithmic transform of the visual signal. Such a transform protects spatial frequency discrimination against certain kinds of multiplicative or windowing operation (such as those produced by patterns of illuminations falling on reflective surfaces) but not against others (such as the Gaussian truncation used in the laboratory). The likelihood of such a mechanism is evaluated by comparing the theoretical expectations to available data on spatial frequency discrimination.

© 1988 Optical Society of America