Topic
Contrast (vision)
About: Contrast (vision) is a research topic. Over the lifetime, 10379 publications have been published within this topic receiving 221480 citations.
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01 Jan 1972
TL;DR: This chapter is a critical historical review of attempts to establish the spatial relationships of the structural, functional, and chemical units in the retina which correspond to such networks.
Abstract: The photoreceptor cells are transducers which absorb incident photons and transmit a proportional signal to other cells. More complex retinal functions such as the discrimination of colors and the detection of contrast and movement are accomplished by networks of many cells. This chapter is a critical historical review of attempts to establish the spatial relationships of the structural, functional, and chemical units in the retina which correspond to such networks.
170 citations
TL;DR: The data suggest that a mechanism similar to a contrast gain control acts upon MC- but not PC-pathway-cells, and confirm that use of linear modelling to describe temporal behaviour of retinal ganglion cells is appropriate for small signals.
170 citations
TL;DR: All operations are restricted so that they preserve the overall image appearance, lightness range and differences, colour ordering, and spatial details, resulting in perceptually accurate achromatic reproductions of the colour original.
Abstract: This paper presents a quick and simple method for converting complex images and video to perceptually accurate greyscale versions. We use a two-step approach first to globally assign grey values and determine colour ordering, then second, to locally enhance the greyscale to reproduce the original contrast. Our global mapping is image independent and incorporates the Helmholtz-Kohlrausch colour appearance effect for predicting differences between isoluminant colours. Our multiscale local contrast enhancement reintroduces lost discontinuities only in regions that insufficiently represent original chromatic contrast. All operations are restricted so that they preserve the overall image appearance, lightness range and differences, colour ordering, and spatial details, resulting in perceptually accurate achromatic reproductions of the colour original.
169 citations
TL;DR: Patients with the poorestPreoperative vision were as likely to regain normal function after surgery as those with the best preoperative vision and improvement in disability glare and contrast sensitivity was independent of improvement in acuity.
Abstract: • We assessed vision before and after uncomplicated extracapsular cataract extraction and intraocular lens implantation in 72 symptomatic patients with acuity equal to or better than 20/80 and no other ocular abnormality Contrast sensitivity was measured with the Pelli-Robson Letter Chart (Metropia Ltd, Cambridge, England) and disability glare was measured under daytime conditions with the Brightness Acuity Tester (Mentor OO P
168 citations
TL;DR: By measuring the discrimination of the direction thresholds as a function of contrast, a nonlinear contrast response function for the motion system is derived and appears to saturate fully at fairly low levels, in the neighborhood of 2 to 3% under the conditions examined.
Abstract: Vertical sine-wave gratings of varying spatial frequency were stepped instantaneously to the right or to the left at differing phase angles (θ). Separate paradigms measured the contrast threshold for the detection of such a step and for the discrimination of the direction of the same step. By considering the grating before and after its displacement as a rotating phasor, we made the following predictions: (1) Contrast sensitivity for the detection of a displacement should rise as sin(θ). (2) Contrast sensitivity for the discrimination of the direction of the displacement should rise as sin(θ/2). Both predictions were confirmed using a range of spatial frequencies and phase angles. From the results of additional experiments, by measuring the discrimination of the direction thresholds as a function of contrast, we derived a nonlinear contrast response function for the motion system. This function appears to saturate fully at fairly low levels, in the neighborhood of 2 to 3% under the conditions examined. Our results suggest a direct connection among the contrast sensitivity, the contrast response function, and motion-hyperacuity thresholds.
167 citations