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Contrast sensitivity is typically expressed as the reciprocal of the threshold contrast for detection of a given pattern (i.e., 1 ÷ contrast threshold). [15] Using the results of a contrast sensitivity exam, a contrast sensitivity curve can be plotted, with spatial frequency on the horizontal, and contrast threshold on the vertical axis.
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.
Log-log plot of spatial contrast sensitivity functions for luminance and chromatic contrast [improve caption] The neurological conversion of color from LMS color space to the opponent process is believed to take place mostly in the lateral geniculate nucleus (LGN) of the thalamus, though it may also take place in the retina bipolar cells.
It is especially vital to assess a child's contrast sensitivity at a young age in order to determine the distance and accuracy with the child can distinguish facial features. A very popular test designed specifically for this reason is the "Hiding Heidi Low Contrast Face Pictures" test (which the LEA Vision Test System produces a version of.)
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For many sensory modalities, over a wide range of stimulus magnitudes sufficiently far from the upper and lower limits of perception, the 'JND' is a fixed proportion of the reference sensory level, and so the ratio of the JND/reference is roughly constant (that is the JND is a constant proportion/percentage of the reference level).
Cones, in contrast, while having much lower intensity sensitivity, have much better time resolution than rods do. For both rod- and cone-mediated vision, the fusion frequency increases as a function of illumination intensity, until it reaches a plateau corresponding to the maximal time resolution for each type of vision.
Contrast (or more precisely Michelson-contrast) is defined as the difference in luminance between two stimulus areas, divided by the sum of luminance of the two. Contrast sensitivity is the inverse of the smallest contrast that can be detected; a contrast sensitivity of 100 means that the smallest (Michelson-) contrast that can be detected is 1%.