Rod hue biases produced on CRT displays

摘要

Studies of rod hue biases (RHBs) using Maxwellian-view displays have shown that rod stimulation can shift the balance of hues at mesopic light levels. We investigated the prevalence of RHBs on CRT displays, which present broader-band stimuli against dark-grey veiling backgrounds, typically without control of observer pupil size. Observers saw a 4?°-diameter stimulus centered 7?° from fixation on a conventional CRT. Observers adjusted stimulus hue to each of the 4 unique hues, following the perimeter of the triangle formed by the 3 phosphors, at equal photopic luminance. Rod influence was estimated from chromaticity differences measured under dark-adapted (rod maximum) and cone-plateau (rod minimum) conditions. The CRT produced all 3 previously-identified RHBs, which affected all 4 unique hues at low mesopic light levels. Effects occurred at 2.6 cd/m2 for some observers but never at 26 cd/m2. At optimal light levels below 0.5 cd/m2, rods (1) enhanced green vs. red at unique yellow, (2) enhanced blue vs. yellow at both unique green and unique red, and (3) enhanced red vs. green at unique blue. Effect magnitudes varied considerably among observers and could be reduced or eliminated by using smaller foveal stimuli.