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Sabine Raphael, Donald I. A. MacLeod; Minimally distinct borders in mesopic vision. Journal of Vision 2008;8(17):75. doi: 10.1167/8.17.75.
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The distinctness of the border between two adjacent fields is minimized when the fields are of equal luminance as defined by the CIE photopic standard observer (V(?)) in the photopic brightness range (Boynton, Kaiser, 1968; Wagner, Boynton 1972; Kaiser, 1971). We used minimally distinct border (MDB) matches between a constant reference and a varying comparison field under parafoveal photopic, mesopic, and scotopic conditions to assess changes in the relative contribution of rods and cones. The border criterion was compared with minimum motion settings under similar conditions (Cavanagh, MacLeod, Anstis, 1987).
A linear combination of scotopic and photopic luminance signals according to CIE V'(λ) and V(λ) functions can account for the results of both methods. There is no evidence that opponent signals or S cone responses are involved.
The criteria of minimally distinct border and minimum motion lead for one observer to similar results with a transition luminance (luminance of equal rod and cone weights) of 0.05 cd/m2. However the MDB data of the second observer show a steeper transition at a lower luminance than the minimum motion criterion would suggest. Overall the minimum motion results of the two tested observers show a good agreement over the tested luminance range while MDB matches differ strongly between observers.
A reversed Purkinje shift is observed at the highest light level tested (42 cd/m2) for MDB, shown by a decrease in sensitivity for red stimuli, which is not visible in the minimum motion data.
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KaiserP. K. (1971). Minimally distinct border as a preferred psychophysical criterion in visual heterochromatic photometry. JOSA, 61(7), 966–971
CavanaghP.MacLeodD. I. A.AnstisS. M. (1987). Equiluminance: spatial and temporal factors and the contribution of blue-sensitive cones. JOSA A, 4(8).
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