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A contrast effect is the enhancement or diminishment, relative to normal, of perception, cognition or related performance as a result of successive (immediately previous) or simultaneous exposure to a stimulus of lesser or greater value in the same dimension. (Here, normal perception, cognition or performance is that which would be obtained in ...
Contrast is a feature of visual stimuli that characterizes the difference in brightness between dark and light regions of an image. Perception of contrast is affected by the temporal frequency and spatial frequency properties of a stimulus, and the sensitivity to contrast in sine wave stimuli is characterized by the contrast sensitivity function.
The Chubb illusion is similar to another visual illusion, the contrast effect.The contrast effect is an illusion in which the perceived brightness or luminance of an identical central visual target form on a larger uniform background varies to the test subject depending on the ratio of the central form's luminance to that of its background. [4]
While being one of the most well-known contrast illusions, there are similar effects which cause two regions of identical color to appear differently depending on context: The Cornsweet illusion creates a boundary between two identically-shaded regions with a discontinuous gradient, resulting in the opposing sides appearing to be different.
In contrast, associative agnosia is a type of agnosia where perception occurs but recognition still does not occur. [1] When referring to apperceptive agnosia, visual and object agnosia are most commonly discussed; this occurs because apperceptive agnosia is most likely to present visual impairments. [ 2 ]
Seen during right ventriculography in the setting of a patent ductus arteriosus, the Goetz sign refers to the negative contrast effect seen in the pulmonary artery from non-contrast enhanced blood shunting left to right from the aorta: Gonda's sign: Viktor Gonda, Ukrainian Neuropsychiatrist, (1889–1959) neurology: pyramidal tract lesions
Mach bands can also appear when there is a discontinuity in the derivative of a gradient, a visual effect common when intensities are linearly interpolated such as in Gouraud shading. Computer image processing systems use edge-detection in a way analogous to the brain, using unsharp masking to clarify edges in photos for example.
This contrast between the light and dark creates a sharper image. (Compare unsharp masking in digital processing). This mechanism also creates the Mach band visual effect. Visual lateral inhibition is the process in which photoreceptor cells aid the brain in perceiving contrast within an image.