Spatial vision
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28 terms
Terms | Definitions |
|---|---|
 Scotopic vision | Vision at the low ambient light levels typical of nighttime, mediated by rods |
| Photopic vision | Vision at the high ambient light levels typical of daylight, mediated by cone photoreceptors |
| Mesopic vision | Vision at ambient light levels intermediate between photopic and scotopic levels, typical of dusk, mediated by both rods and cones |
| Luminance grating | A laboratory stimulus used to study spatial vision; it is a striped pattern containing alternating light and dark bars, commonly with a sine wave |
| Spatial frequency | A measure of the fineness of a grating's bars, in terms of the number of grating cycles (bright-dark bar pairs) per degree of visual angle |
| Spatial contrast threshold | The minimum contrast between the lightest and darkest parts of a pattern required for it to be reliably detected by an observer; lower values indicate better performance. |
| Spatial contrast sensitivity | The reciprocal of spatial contrast threshold (1/threshold); higher values indicate better performance |
| Contrast sensitivity function | A graph of spatial contrast sensitivity to luminance gratings, plotting sensitivity as a function of grating spatial frequency. |
| Contrast ratio | The ratio between the amount of contrast in an optical images, and the contrast in the original stimulus; values near unity indicate near-perfect transference. |
| Optical transfer function | A graph of an optical system's ability to transfer luminance gratings, plotting contrast ratio as a function of grating spatial frequency. |
| Temporal contrast sensitivity | The reciprocal of the amount of contrast between the brightest and darkest phases of a flickering stimulus required for a subject to detect the flicker |
| Temporal frequency | The alternation rate of a flickering stimulus, measuring in hertz, or the number of flicker cycles (bright-dark alternations) per second |
| Temporal contrast sensitivity function | A graph of temporal contrast sensitivity as a function of flicker temporal frequency |
| Spatiotemporal contrast sensitivity | Sensitivity to combinations of spatial modulation and temporal modulation, namely luminance gratings with flickering bars. |
| Space-time plot | A polt that represents luminance variations over both space and time, with space plotted horizontally and time plotted vertically. |
| Spatiotemporal CSF | A graph of spatiotemporal contrast sensitivity, plotted sensitivity as a function of grating spatial frequency and temporal frequency. |
| Sustained channel | A channel of processing in the visual system that is most sensitive at high spatial frequencies and low temporal frequencies |
| Transient channel | A channel of processing in the visual system that is most sensitive at low spatial frequencies and high temporal frequencies |
| Threshold elevation | The contrast threshold for a test stimulus is higher following exposure to an adapting stimulus than before adaptation |
| Size after-effect | A change in the apparent spatial frequency of a test grating following exposure to an adapting grating |
| Tilt after-effect | A change in the apparent tilt of a test stimulus following the exposure to an adapting stimulus |
| Masking | A rise in the contrast threshold for a test stimulus in the presence of a second, masking stimulus. |
| Vernier acuity | An observer's acuity for detecting the direction of small spatial offsets between collinear lines or edges. |
| Hyperacuity | Acuity performance in which the observer can detect changes in the spatial location that are smaller than the distance between adjacent retinal photoreceptors. |
| Zero-crossing | A point where the value of a function such as a receptive field response changes from positive to negative |
| Peak | A point where the value of a function such as a receptive field response reaches its maximum |
| Primal sketch | A relatively primitive representation of local spatial structure in an image, produced by the initial stages of visual processing |
| Visual texture | Repetitive variation in properties such as local luminance, contrast, size, and/'or orientation to create an extended pattern |
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