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Katharina Foote, Steven Buck; Rod Hue Biases for Foveal Stimuli on CRT Displays. Invest. Ophthalmol. Vis. Sci. 2013;54(15):3023. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Signals from rod photoreceptors bias (shift) the hues determined by cone photoreceptors for extrafoveal mesopic stimuli - creating green, blue, and red rod hue biases at long, middle, and short wavelengths, respectively. The fovea contains far fewer rods and S cones but may not be immune to rod hue biases. Here, we determine which biases are found for foveal stimuli presented on a CRT display.
On a CRT display, a 1-s duration test disk of 0.5°, 1.0°, or 2.0° diameter alternated with a 3-s duration array of 0.25° fixation dots placed 4° from fixation, all on a black background. Seven observers adjusted the hue of the test disk around the RGB phosphor mixture triangle, to yield each of the 4 unique hues, Ured, Ugreen, Ublue, and Uyellow. Light levels ranged from 0.05 - 0.17 (CIE2°) or 0.08 - 0.03 (CIE10°) cd/m2.
1°-2°-diameter foveal test disks (a) produced rod green bias at Uyellow for most observers, (b) favored rod green bias at Ublue over the rod red biases shown in prior extrafoveal studies, and (c) produced less consistent rod hue biases at Ured and Ugreen. 0.5°-diameter foveal test disks produced no consistent rod hue biases across observers. Remaining rod hue biases tended to be small but some observers showed larger idiosyncratic effects for a specific unique hue.
1°-2°-diameter foveal disks on a CRT display produced relatively strong rod green bias, mediated by rod interaction with L & M cones, presumably in midget/parvo pathways. In contrast, these foveal stimuli disadvantaged rod influence mediated by S cones, presumably in small-bistratified/konio pathways, producing only weak/inconsistent rod red bias at Ublue and rod blue bias at Ured and Ugreen. 0.5°diameter disks disadvantaged all rod hue biases, but with individually idiosyncratic exceptions for some observers.
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