Influence of variations in edge blur on minimally distinct border judgments: a theoretical and empirical investigation.

Minimally distinct border (MDB) settings were made for white-chromatic borders that varied from 1 to 32 arcmin in the space constant of Gaussian blur. The spectral characteristics, additivity, and variability of the MDB judgments remained essentially unchanged across all degrees of edge blur up to and including a space constant of 8 arcmin. For space constants of 16 and 32 arcmin, the variability of the settings increased dramatically, but no consistent trends toward changes in spectral characteristics or additivity were found. Predictions of visual response to edge blur were derived from Wilson and Gelb's six-channel model of spatial vision [J. Opt. Soc. Am. A 1, 124 (1984)]. The fits of these calculations to the data suggest that either a single low- to mid-spatial-frequency-tuned channel mediates MDB judgments over a wide range of variations of edge blur or else the channels that jointly mediate these judgments are importantly similar in their chromatic characteristics.