Kontrastsustaju

Kontrastsustaju is a term used in vision science to denote the perceptual ability to detect luminance contrast between elements of a visual scene. It describes sensitivity to differences in lightness and brightness, typically distinct from color perception, motion, or form processing, and it underpins edge detection, object recognition, and reading.

The sensitivity arises from early retinal processing and subsequent cortical analysis. Retinal photoreceptors convert luminance into signals that, via center-surround receptive fields and lateral inhibition, emphasize borders. In the cortex, gain control mechanisms and orientation-selective cells preserve contrast information across spatial frequencies, while temporal processing integrates changes in contrast over time. Overall, kontrastsustaju varies with spatial frequency, orientation, luminance level, and motion, producing a contrast sensitivity function that characterizes performance across conditions.

Measurement employs contrast definitions such as Michelson contrast for periodic patterns and Weber contrast for small targets on uniform backgrounds. The central metric is contrast sensitivity, typically graphed as a contrast sensitivity function (CSF) across spatial frequencies. Psychophysical tests use sine-wave gratings, letter charts, or real-world tasks to estimate detection thresholds and compare populations.

Clinically, kontrastsustaju declines with aging and in ocular diseases such as cataract, glaucoma, and macular degeneration, reducing readability and safe driving performance. Assessing contrast sensitivity complements standard visual acuity in diagnosing visual problems and guiding environmental design, display engineering, and accessibility standards by ensuring adequate legibility under real-world viewing conditions.

See also contrast sensitivity, Michelson contrast, Weber contrast, edge detection, visual acuity.