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To investigate how patients with macular scotomas use residual functional retinal areas to inspect visual detail, a scanning laser ophthalmoscope (SLO) was used to map the retinal locations of scotomas and areas used to fixate. Three patients with dense macular scotomas of at least 20 months duration and with no explicit low vision training were tested. SLO(More)
Changes of annulus luminance in traditional disk-and-annulus patterns are perceptually ambiguous; they could be either reflectance or illuminance changes. In more complicated patterns, apparent reflectances are less ambiguous, letting us place test and standard patches on surrounds perceived to be different grays. Our subjects matched the apparent amounts(More)
An achromatic surface in a complex scene has both an apparent reflectance attribute (lightness) and an overall intensitive attribute (brightness). We studied changes of these two attributes as a function of changes in illumination level and pattern complexity. Subjects observed simultaneously two arrays of simulated achromatic surfaces with identical(More)
Changes of annulus luminance in traditional disk-and-annulus patterns can be perceived to be either reflectance or illuminance changes. In the present experiments, we examined the effect of varying annulus reflectance. In Experiment 1, we placed test and standard patch-and-surround patterns in identical Mondrian patchworks. Only the luminance of the test(More)
Models of the spatial response of human vision are important for applied work, but the available contrast sensitivity function (CSF) data vary widely due to the diverse spatiotemporal stimuli used over the years. To assist selection, this paper: (1) reports measurements of the effects on the CSF of varying the spatial and temporal windows of grating(More)
At mesopic mean luminances, a fixed luminance contrast produces less brightness contrast than it does at photopic luminances. This suggests that lightnesses of surfaces might also be altered at low luminances. I measured lightness, brightness, and brightness contrast in CRT simulations of achromatic paper patchworks. The illuminance of the standard pattern(More)
We have measured the ability of observers to estimate the contrast ratio (maximum white luminance / minimum black or gray) of various displays and to assess luminous discrimination over the tonescale of the display. This was done using only the computer itself and easily-distributed devices such as neutral density filters. The ultimate goal of this work is(More)
Three experiments were conducted in an attempt to replicate and clarify Gilchrist's (1977, 1980) experiments on the effects of depth information on judgments of achromatic surface color. Gilchrist found that coplanarity, and not retinal adjacency, was the dominant factor in determining achromatic color matches. Because such matches can be made on the basis(More)