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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14 Dec 2008
TL;DR: Quantitatively evaluate contrast flow level selectivity noted during fluoroscopically guided lumbosacral transforaminal epidural steroid injections to identify the minimum injectate volume at which LS-TFESIs may still be considered "selective" with no injectate extending to either the adjacent levels or to the contralateral side.
58 citations
TL;DR: It is found that under poorly attended conditions targets can be detected only when the target contrast exceeds the surround contrast (contrast popout) or when thetarget orientation differs from the surround orientation by more than 10-15 degrees (orientation popout).
58 citations
TL;DR: The analysis of influence of polarity on legibility showed that, generally, dark backgrounds lead to better results for colors with greatest luminance contrast, and that more than 90-year-old Le Courier legibility table is not appropriate for integrative color computer displays.
58 citations
TL;DR: A psychophysical experiment was performed in which images of natural scenes under two successive daylights were presented on a computer-controlled high-resolution color monitor and receptor-based rather than colorimetric properties of the images provided a good fit to the effects of scene and of illuminant change on color constancy.
Abstract: To what extent do observers' judgments of surface color with natural scenes depend on global image statistics? To address this question, a psychophysical experiment was performed in which images of natural scenes under two successive daylights were presented on a computer-controlled high-resolution color monitor. Observers reported whether there was a change in reflectance of a test surface in the scene. The scenes were obtained with a hyperspectral imaging system and included variously trees, shrubs, grasses, ferns, flowers, rocks, and buildings. Discrimination performance, quantified on a scale of 0 to 1 with a color-constancy index, varied from 0.69 to 0.97 over 21 scenes and two illuminant changes, from a correlated color temperature of 25,000 K to 6700 K and from 4000 K to 6700 K. The best account of these effects was provided by receptor-based rather than colorimetric properties of the images. Thus, in a linear regression, 43% of the variance in constancy index was explained by the log of the mean relative deviation in spatial cone-excitation ratios evaluated globally across the two images of a scene. A further 20% was explained by including the mean chroma of the first image and its difference from that of the second image and a further 7% by the mean difference in hue. Together, all four global color properties accounted for 70% of the variance and provided a good fit to the effects of scene and of illuminant change on color constancy, and, additionally, of changing test-surface position. By contrast, a spatial-frequency analysis of the images showed that the gradient of the luminance amplitude spectrum accounted for only 5% of the variance.
57 citations
TL;DR: For gratings with constant relative area contrast sensitivity functions were similar in shape and had the same maximum sensitivity but were shifted horizontally towards lower illuminances with decreasing spatial frequency but when replotted as a function of retinal illuminance divided by spatial frequency squared fell on a common curve.
57 citations