Luminance Requirements for Hue Identification in Small Targets

Abstract

Foveal luminance thresholds for identification of red (642 nm), yellow (584 nm), green (521 nm), and blue (468 nm) were determined by the method of constant stimuli for a range of small stimulus sizes and for two exposure durations. The luminances necessary for chromatic and absolute thresholds were also specified. The luminance required for chromatic threshold was found to be lowest for the 642-nm stimulus and highest for the 468-nm stimulus; the threshold for correct hue identification was found to be inversely related to wavelength. The ratios of the luminance necessary for hue perception to the absolute threshold ranged from 1.14 for the 642-nm stimulus to 1.51 for the 584-nm stimulus. The ratio of the luminance required for correct hue identification to the absolute threshold ranged from 1.32 for the 642-nm stimulus to 3.33 for the 521-nm stimulus. More reliable responses and fewer confusions in the hue identification were associated with the 642-nm stimulus than with the other wavelengths. The identification thresholds of this study are compared with the detection thresholds for similar targets.