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: In this article, a new index FCI is proposed for estimating the effect of feeling of contrast quantitatively under any light sources, which is derived using a simple transformation of the gamut area, constituted by a specially selected four-color combination in CIE LAB color space.
Abstract: “Visual clarity” or “feeling of contrast” of object colors under illumination is affected significantly by changing color-rendering property of light source used. Though the feeling of contrast is considered one of the most important characteristics on color-rendering properties of light sources, it cannot be estimated adequately by using the present Ra method. The new index FCI is proposed for estimating the effect of feeling of contrast quantitatively under any light sources. The FCI is derived using a simple transformation of the gamut area, which is constituted by a specially selected four-color combination in CIE LAB color space. The FCI correlates well with the illuminance ratio for equal feeling of contrast (or equal visual clarity) on various light sources reported so far. Using the FCI together with the present CIE Ra, the color-rendering capability of a light source can be well clarified. © 2007 Wiley Periodicals, Inc. Col Res Appl, 32, 361–371, 2007
136 citations
TL;DR: This work demonstrates that this local contrast can be characterized in terms of a log-normal distribution and shows that the two defining parameters of this model can in turn be expressed in Terms of the minimum speckle size and the extent of the local neighborhood.
Abstract: In describing the first-order properties of laser speckle under polarized illumination conditions, it is almost an article of faith that the contrast is unity. In many processing schemes, however, the contrast defined as the quotient of the standard deviation and the mean is calculated over a localized spatial region. In such cases, this local contrast displays a distribution of values that can depart substantially from unity. Properties of this distribution depend on details of the data acquisition and on the size of the local neighborhood over which the contrast is calculated. We demonstrate that this local contrast can be characterized in terms of a log-normal distribution. Further, we show that the two defining parameters of this model can in turn be expressed in terms of the minimum speckle size and the extent of the local neighborhood. Performance of the model is illustrated with some typical optical coherence tomography data.
136 citations
TL;DR: An overview of the visual problems likely to be encountered in Parkinson's disease and the pattern electroretinogram (PERG) is useful in evaluating retinal dopamine mechanisms and in monitoring dopamine therapies in PD.
Abstract: Parkinson's disease (PD) is a common disorder of middle-aged and elderly people in which degeneration of the extrapyramidal motor system causes significant movement problems. In some patients, however, there are additional disturbances in sensory systems including loss of the sense of smell and auditory and/or visual problems. This paper is a general overview of the visual problems likely to be encountered in PD. Changes in vision in PD may result from alterations in visual acuity, contrast sensitivity, colour discrimination, pupil reactivity, eye movements, motion perception, visual field sensitivity, and visual processing speeds. Slower visual processing speeds can also lead to a decline in visual perception especially for rapidly changing visual stimuli. In addition, there may be disturbances of visuospatial orientation, facial recognition problems, and chronic visual hallucinations. Some of the treatments used in PD may also have adverse ocular reactions. The pattern electroretinogram (PERG) is useful in evaluating retinal dopamine mechanisms and in monitoring dopamine therapies in PD. If visual problems are present, they can have an important effect on the quality of life of the patient, which can be improved by accurate diagnosis and where possible, correction of such defects.
136 citations
TL;DR: It is possible to offer a plausible explanation of some of these phenomena by invoking the existence in the human visual system of broad-band, phase-sensitive channels, as well as of narrow-band channels.
136 citations
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TL;DR: So dominant are contours in their visual perception that it seems almost instinctive for us to draw first the outlines of any object that the authors attempt to portray, and line drawings are found in some of the oldest evidence of how man interprets what he sees.
Abstract: "WHEN a dog bites a man, that is not news . . . But if a man bites a dog, that is news," so wrote John B. Bogart, City Editor of The Sun in New York many years ago. The relation between contour and contrast is similar. It is not news, but old and common knowledge that it is the contrast, or difference, in the brightness or color of two adjacent areas that causes the appearance of a contour between them. And so dominant are contours in our visual perception that it seems almost instinctive for us to draw first the outlines of any object that we attempt to portray. Instinctive or not, the practice is at least as old as the most ancient evidence of how man interprets what he sees -"line drawings" are found in some of the oldest
136 citations