Frederick A. A. Kingdom

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Contrast thresholds for stereoscopic depth identification (crossed or uncrossed) were measured as a function of disparity by use of isoluminant (red-green) and isochromatic (yellow-black) 0.5 cycles/deg Gabor patches. For the purposes of comparison, stimulus contrasts were scaled by their respective detection thresholds. The Gabor patches could be either(More)
We have measured the sensitivity of the human visual system to sinusoidal modulations of orientation in micropattern-based textured stimuli. The result is the orientation modulation function, or OMF, which describes this sensitivity as a function of the spatial frequency of orientation modulation. We found that the OMF was bandpass with peak sensitivity at(More)
Michelson's contrast, C, is an excellent metric for contrast in images with periodic luminance profiles, such as gratings, but is not suitable for images consisting of isolated stimulus elements, eg single bars; other metrics have been devised for such stimuli. But what metric should be used for random-dot images such as are commonly used in stereograms and(More)
We present an algorithm for separating the shading and reflectance images of photographed natural scenes. The algorithm exploits the constraint that in natural scenes chromatic and luminance variations that are co-aligned mainly arise from changes in surface reflectance, whereas near-pure luminance variations mainly arise from shading and shadows. The novel(More)
Contrast thresholds for stereoscopic depth identification (crossed or uncrossed) were measured as a function of disparity using isoluminant (red-green) and isochromatic (yellow-black) 0.5 c/deg Gabor patches. For the purposes of comparison stimulus contrasts were scaled by their respective detection thresholds. The detection thresholds employed were(More)
This paper presents a summary of experimental findings, theoretical models and unresolved issues regarding border effects on brightness, of which the Cornsweet illusion (Cornsweet, 1970 Visual Perception. Academic Press: New York) is the best-known example. It is argued that no current theoretical model completely accounts for the wide variety of effects(More)
Two distinct paradigms have characterized most previous studies of texture perception: one has dealt with texture segregation, the other with the processing of texture gradients. Typically, studies of texture segregation have used stimuli with abrupt textural variations, whereas studies of texture gradient processing have used stimuli with smooth textural(More)
Previous measurements of contrast discrimination threshold, delta C, as a function of pedestal contrast, C, for sine-wave gratings have shown a power law relationship between delta C and C at suprathreshold levels of C. However, these studies have rarely used contrasts greater than 50%. Whittle (1986), using incremental and decremental patches, found that(More)