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: A reanalysis of published data shows that the development of the spatial contrast sensitivity function can be described satisfactorily by the simultaneous vertical and horizontal scaling of a template function whose shape on a log-log axis does not change during development.
Abstract: The development of spatial contrast sensitivity in human and monkey infants reveals changes in the properties of underlying contrast-detection mechanisms in the visual system. A reanalysis of published data shows that the development of the spatial contrast sensitivity function can be described satisfactorily by the simultaneous vertical and horizontal scaling of a template function whose shape on a log–log axis does not change during development. Because individuals differ in the point to which contrast sensitivity has developed at any particular time, the use of group-averaged data as a basis for estimating the course of the developmental process has two undesirable results. First, it provides estimates of spatial contrast sensitivity during development that do not reflect any individual’s sensitivity. Second, it incorrectly suggests that the shape of the spatial contrast sensitivity function changes during development.
138 citations
TL;DR: Visual contrast sensitivity to sinusoidal gratings of five spatial frequencies was measured in 15 patients with Alzheimer's disease and in eight control subjects; the 15th patient was unique: she had an impairment in object and face recognition so severe that she could not recognize her husband visually.
Abstract: • Visual contrast sensitivity to sinusoidal gratings of five spatial frequencies was measured in 15 patients with Alzheimer's disease and in eight control subjects. Contrast sensitivity thresholds were elevated at all frequencies in 14 patients compared with control subjects. The 15th patient was unique: she had an impairment in object and face recognition so severe that she could not recognize her husband visually. Her sensitivity to low and intermediate frequencies was markedly reduced in relation to that of other patients, whereas her sensitivity to the highest frequency tested equaled theirs. These observations emphasize the importance of low spatial frequency information for visual object and face recognition.
137 citations
TL;DR: Although significant hue discrimination and contrast sensitivity deficits were observed in both groups of diabetic patients, contrast sensitivity was abnormal more frequently than hue discrimination, and the hue discrimination deficits, but not the contrast sensitivity abnormalities, were correlated with the patients' hemoglobin A1 level.
137 citations
TL;DR: It is suggested that Alzheimer's disease affects later central visual functions more than early relatively peripheral ones.
Abstract: Visual functions of patients with senile dementia of the Alzheimer type were compared with those of young people and age-matched controls. Visual acuity and spatial frequency contrast sensitivity did not differ significantly between Alzheimer patients and normal elderly subjects, although both were impaired in comparison with young subjects. Alzheimer patients required more time than ageing controls to identify letters and were susceptible to the interfering effects of a backward pattern mask on letter recognition over a longer interval. The spatial extent over which the pattern mask was effective, as well as the time interval over which a homogeneous mask interfered with letter recognition, were equivalent in normal old people and Alzheimer patients. In all the masking tasks, young people performed better than the old. It is suggested that Alzheimer's disease affects later central visual functions more than early relatively peripheral ones.
136 citations
12 May 1997
TL;DR: In this paper a method is presented that makes use of both camera-based depth information and the luminance image to determine corresponding point sets on the partial surfaces using an optical flow approach.
Abstract: Textured surface models of three-dimensional objects are gaining importance in computer graphics applications. These models often have to be merged from several overlapping partial models which have to be registered (i.e. the relative transformation between the partial models has to be determined) prior to the merging process. In this paper a method is presented that makes use of both camera-based depth information (e.g. from stereo) and the luminance image. The luminance information is exploited to determine corresponding point sets on the partial surfaces using an optical flow approach. Quaternions are then employed to determine the transformation between the partial models which minimizes the sum of the 3-D Euclidian distances between the corresponding point sets. In order to find corresponding points on the partial surfaces luminance information is linearized. The procedure is iterated until convergence is reached. In contrast to only using depth information, employing luminance speeds up convergence and reduces remaining degrees of freedom (e.g. when registering sphere-like shapes).
136 citations