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| minimal angle of resolution (MAR) |
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Definition
| smallest visual angle between two points that can be reliably distinguished as separated in visual space |
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| line of sight, projects from fovea to fixation point |
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| number of linear millimeters in the crotex allotted to a given linear degree of visual space |
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| translationally invariant |
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Definition
| because the magnification factor falls off with eccentricity, and the minimal angle of resolution increases at teh same rate, so...the product of MAR and M(magnification factor) is relatively constant. doesn't always hold for eccentricites less than 2.5 degrees. |
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Term
| equivalent cortical distance |
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Definition
| minimum angle of resolution x magnification factor. therefore the neural machinery involved in the determinatin of the MAR is the same size everywhere in the cortex, MAR varies in the outside world because the mapping from retina to cortex is distorted |
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| gradation in brightness that is continuous |
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| one complete cycle of light and dark |
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| 1/period...usually expressed in visual angles |
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| measure of the difference in brightness between the light and dark bars. usually a percentage or fraction |
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| contrast sensitivity function |
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Definition
| the range of sensitivities of a subject to a variety of spatial frequencies |
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| the highest frequency that can be detected: for humans about 60 cycles/degree |
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| the ability of a system to reliably detect and and characterize the spatial frequency of a stimulus is reliant upon the frequency of sampling and the ability of teh retin ato respond to the frequencies present in the scene |
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| infrequent sampling confuses higher frequencies with lower ones |
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| highest frequency that can be defined unambiguously is one that is sampled twice in each cycle |
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| 1/(2x) x being the distance of one period. this is the frequency of sampling needed to unambiguously know the frequency of the wave. based entirely on the spacing of the photoreceptors |
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| optics of our eyes function as this - allow low frequencies to go through but blur very high frequencies |
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