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Open Access Publications from the University of California

Intensity-dependent spatial summation

  • Author(s): Cornsweet, TN
  • Yellott, JI
  • et al.

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. © 1995 Optical Society of America.

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