DURATION OF SCOTOPIC CONTRAST HUES

STABELL, U. & STABELL, B. Duration of scotopic contrast hues. Scand. J. Psychol. , 1971, 12, 106–112.–It is generally accepted that following intense and prolonged bleaching, regeneration of cone pigments in man takes a few minutes to reach completion. The results show that the scotopic hue may remain visible for more than one hour. Hence, it is suggested that light signals and not bleaching signals produce the scotopic contrast hues.     

NIGHT VISION AS CHROMATIC VISION

Assuming that night vision is an exclusive function of the rods, and that it is colorless, the duplicity theory states that rod vision is achromatic vision. Studies relevant to color in night vision are reviewed. It is concluded that color may be observed well below the breakpoint of the dark adaptation curve, and that the duplicity theory therefore needs revision.     

RODS AS COLOR RECEPTORS IN PHOTOPIC VISION

Comparing a foveal and an extra-foveal field during dark adaptation, transition from chromatic to achromatic vision at intensity levels above the cone plateau started around the break of the dark adaptation curve. Pre-stimulating the two fields in a dark-adapted state with deep red, and test-stimulating when returning sensitivity had reached absolute threshold of the dark-adapted eye, with green filters at intensities above the specific threshold, the fields matched as to hue and saturation. It appears that rod and cone activities are integrated and function as a synchronized unit during the initial recovery phase of dark adaptation.     

COLOR THRESHOLD MEASUREMENTS IN SCOTOPIC VISION

The absolute and the color threshold in scotopic vision generally coincide during dark adaptation, indicating that color-threshold intensity is a measure of the concentration of rhodopsin, and that different modes of rhodopsin regeneration are reflected in the measurements of the color threshold.