Visual phase resolution for gray-scale textures

Abstract

We compared the effects of two different phase-filter operations (quantization and randomization) on the discriminability of gray-scale textures. The resulting discrimination scores were found to be the same, provided the filter operations had been normalized with respect to the mean absolute difference in phase. This enabled us to show that the phase information of gray-scale textures could be compressed to only 16 phase states-a value that was twice as high as previously suggested. We found it difficult to decide whether the observers based their decisions on Fourier phase or on luminance profile cues, which prompted us to further analyze the results in terms of the percent bit modulation of the phase-filtered images. The latter measure of space-domain differences captured human performance equally well; therefore, our results are not supportive of the notion that the visual system encodes spatial phase information per se. © 1988 Psychonomic Society, Inc.