Differences in apparent contrast in yellow and white light

The purpose of this study was to investigate suprathreshold contrast perception in white and yellow light. The contrast of black-on-white letters was adjusted to match the perceived contrast of yellow-on-yellow letters presented simultaneously on a video display, At lower contrasts (7-15%), the apparent contrast of yellow letters was slightly enhanced compared black-on-white letters (mean enhancement = 23%), but this effect diminished with increasing contrast. The slight enhancement in yellow light was independent of letter size, and could not be explained by luminance differences between yellow and white displays. This effect may relate to the subjective improvement often reported when wearing yellow (blue-blocking) lenses.