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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Patent•
31 Oct 2007
TL;DR: In this article, a selective light wavelength filter was used to improve contrast sensitivity of the ophthalmic system, wherein the selective filter provided improved contrast sensitivity for ophthalmics.
Abstract: The present invention relates to ophthalmic systems comprising a selective light wavelength filter, wherein said selective filter provides improved contrast sensitivity.
184 citations
TL;DR: Two different visual displays that induce blindsight in normal observers are reported and it is shown that conscious experience remains defective at presentation times much longer than the onset of visual sensitivity.
Abstract: Some patients with lesions in visual cortex lack conscious visual experience but, when tested, exhibit a significant ability, termed 'blindsight', to discriminate visual stimuli. Here we report two different visual displays that induce blindsight in normal observers. Using an objective measure, we show that conscious experience remains defective at presentation times much longer (1 s) than the onset of visual sensitivity (˜60 ms). To obtain this effect, we generate a contrast between visual textures and then conceal the contrast by superimposing 'complementary' textures. Complementarity can involve either opposite motion or binocular rivalry and orthogonal orientation. In both cases, observers locate the texture contrast reliably but do not, by either subjective or objective measures, consciously experience it. Taken together with present knowledge of the visual cortical site(s) at which opposite motion and rivalrous orientation interact, this observation bears upon the functional anatomy of conscious visual experience.
184 citations
Journal Article•
TL;DR: Visual function in patients with glaucoma, as measured by contrast sensitivity, does improve after beta-blocker therapy and the CSV-1000 contrast sensitivity test is a clinically reliable tool for monitoring these changes.
Abstract: Purpose. To determine the relationship between changes in contrast sensitivity, if any, after glaucoma therapy and the test-retest reliability of the CSV-1000 contrast sensitivity test. Methods. Patients with primary open angle glaucoma (N = 16) were retrospectively evaluated to determine changes in visual function, as measured by contrast sensitivity, after beta-blocker therapy. A control group (N = 24) of normally sighted patients was tested and retested on contrast sensitivity. For the control group, the coefficients of repeatability (95% confidence interval for test-retest variability [COR]) were calculated for each spatial frequency. The CORs were compared to the changes in vision found after therapy in the patients with glaucoma. Results. The group with glaucoma showed a significant improvement (P < .01) in contrast sensitivity at all spatial frequencies. The test-retest variance for normals, as measured by the COR, was smaller than the mean differences in contrast sensitivity before and after therapy at all spatial frequencies, expect 18 cyc/deg. Conclusions. Visual function in patients with glaucoma, as measured by contrast sensitivity, does improve after beta-blocker therapy. Further, the CSV-1000 is a clinically reliable tool for monitoring these changes. Invest Ophthalmol Vis Sci. 1994;35:3357—3361.
183 citations
TL;DR: It is suggested that contrast acts as a pictorial depth cue simulating the optical effects of aerial perspective, and is an effective depth cue in the absence of any other depth information.
183 citations
TL;DR: In this paper, a digital set of 29 hyperspectral images of natural scenes was acquired and its spatial frequency content analyzed in terms of chrominance and luminance defined according to existing models of the human cone responses and visual signal processing.
Abstract: The spatial filtering applied by the human visual system appears to be low pass for chromatic stimuli and band pass for luminance stimuli. Here we explore whether this observed difference in contrast sensitivity reflects a real difference in the components of chrominance and luminance in natural scenes. For this purpose a digital set of 29 hyperspectral images of natural scenes was acquired and its spatial frequency content analyzed in terms of chrominance and luminance defined according to existing models of the human cone responses and visual signal processing. The statistical 1/f amplitude spatial-frequency distribution is confirmed for a variety of chromatic conditions across the visible spectrum. Our analysis suggests that natural scenes are relatively rich in high-spatial-frequency chrominance information that does not appear to be transmitted by the human visual system. This result is unlikely to have arisen from errors in the original measurements. Several reasons may combine to explain a failure to transmit high-spatial-frequency chrominance: (a) its minor importance for primate visual tasks, (b) its removal by filtering applied to compensate for chromatic aberration of the eye's optics, and (c) a biological bottleneck blocking its transmission. In addition, we graphically compare the ratios of luminance to chrominance measured by our hyperspectral camera and those measured psychophysically over an equivalent spatial-frequency range.
181 citations