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We have studied the ability of observers to discriminate between suprathreshold vertical sinusoidal spatial-frequency gratings on the basis of spatial frequency. The results show that spatial-frequency discrimination is not a smooth function of spatial frequency but instead appears regularly segmented. Similar results were also obtained in an experiment in(More)
We measure the center-to-center spacings and disorder in spacings between all pairs of cones in a strip of primate retina extending from the foveal center to approximately 5.75 deg of retinal eccentricity along the temporal horizontal meridian. The strip is partitioned into windows, and the positions of the cone centers in each lattice window are digitized(More)
We test the hypothesis that the diameters of foveal and near-foveal rods and cones for one well-studied human photoreceptor mosaic and one well-studied monkey photoreceptor mosaic (Macaca fascicularis) are scaled relative to focal length. We conclude that this hypothesis is not supported. Rather than being scaled proportionally, the sizes of the rods and(More)
We test three specific models of how the human visual system computes a just-noticeable-difference (jnd) in spatial separation. The strategies employed by these three models range from strictly local to global, and use a new discrimination task that measures the precision with which displacements of random dots in random dot arrays can be detected. Fits of(More)
Quantitative analysis of a primate photoreceptor lattice shows that the foveal lattice is a highly regular hexagonal structure with a positional correlation length of at least 130 photoreceptors. This result indicates that the photoreceptor lattice is not sufficiently disordered to prevent aliasing in the fovea, but rather could provide the metric with(More)
A two-frequency two-response paradigm was employed. The stimulus on any trial was a compound grating containing two sinusoidal components of different spatial frequencies where the contrast in one or both components could be zero. The observer gave two responses each indicating confidence that one of the two components had been presented with contrast(More)
In a recent study of spatial-frequency discrimination [J. Opt. Soc. Am. 72, 1367 (1982)], we reported evidence for the quantization of position in the human visual system with the fundamental unit of quantization being the photoreceptor spacing for spatial frequencies greater than 2 cycles per degree (c/deg). In this paper we extend our measurements to(More)
Vernier acuity (delta v) as a function of two-dot separation (s) was measured at five retinal locations between the foveal center and 2.0 deg of eccentricity. We compare these results with average cone spacing at each of the corresponding retinal eccentricities and find that the angular dot separations at which the delta v versus s function intersects the(More)
Recently we reported that hyperacuity thresholds for separation-discrimination tasks were not smooth functions of spatial variables but rather were regularly segmented with sharp transitions between the segments. In this study we have measured the orientation dependence of two tasks involving visual hyperacuity, the discrimination of spatial frequencies and(More)