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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TL;DR: There was a highly significant difference between the scores from different optometrists for all three charts, with older observers tending to exhibit lower contrast sensitivity, and this sensitivity deficit was most pronounced at higher spatial frequencies.
57 citations
TL;DR: It is suggested that contour alignment alters visual processing in rats, despite their lack of orientation columns in the visual cortex, in the first report that the arrangement of visual features relative to each other affects visual behavior in rats.
Abstract: We measure rats' ability to detect an oriented visual target grating located between two flanking stimuli ("flankers"). Flankers varied in contrast, orientation, angular position, and sign. Rats are impaired at detecting visual targets with collinear flankers, compared to configurations where flankers differ from the target in orientation or angular position. In particular, rats are more likely to miss the target when flankers are collinear. The same impairment is found even when the flanker luminance was sign-reversed relative to the target. These findings suggest that contour alignment alters visual processing in rats, despite their lack of orientation columns in visual cortex. This is the first report that the arrangement of visual features relative to each other affects visual behavior in rats. To provide a conceptual framework for our findings, we relate our stimuli to a contrast normalization model of early visual processing. We suggest a pattern-sensitive generalization of the model which could account for a collinear deficit. These experiments were performed using a novel method for automated high-throughput training and testing of visual behavior in rodents.
57 citations
TL;DR: An excellent performance in terms maximum entropy preservation, better contrast enhancement and the best visual appearance of low contrast medical images has been achieved.
57 citations
04 Oct 1998
TL;DR: The model is shown to accurately fit psychophysical contrast sensitivity data as well as intra- and inter-channel contrast masking data from several different psychophysical experiments.
Abstract: This paper presents a comprehensive distortion metric for digital color images. It is based on a normalization model of the human visual system that incorporates color perception. The model is shown to accurately fit psychophysical contrast sensitivity data as well as intra- and inter-channel contrast masking data from several different psychophysical experiments. The output of the metric is compared with subjective data for natural images.
57 citations
TL;DR: This study points out the importance of using simple clinical test charts and further underscores the idea that there is a primary visual deficit in Ad, and finds reduction in contrast sensitivity at all spatial frequencies when compared to the elderly normal.
Abstract: Contrast sensitivity has been shown to be affected in Alzheimer's disease (Ad). We investigated low contrast acuity and contrast sensitivity using clinical test charts in this patient population. Additionally, we tested patients with vascular dementia (vd) and mixed dementia (md), (Alzheimer' with vascular dementia). Contrast sensitivity was assessed using the Vistech VCTS 6500 test chart. Low contrast acuity was measured using the Regan charts at four contrast levels (96%, 50%, 25% and 11%). The patient population consisted of 19 Ad patients, 9 vd patients and 10 md patients. Reduction in acuity was found with contrast level in all cases. Regression lines were fit to the data and statistical analysis was performed. We did not find a statistically significant difference between the Ad and vd or md groups. We did, however, find a difference between the vd and md groups. We did find reduction in contrast sensitivity at all spatial frequencies when compared to the elderly normal. Correspondingly, we found a significant difference in acuity when compared with normal data at the four contrast levels tested. Acuity is reduced with contrast in all patient groups. Our contrast sensitivity results are similar to those reported in the literature. This study points out the importance of using simple clinical test charts and further underscores the idea that there is a primary visual deficit in Ad.
57 citations