title: The scotopic visibility curve and cone intrusion.
abstract: The scotopic visibility curves of two observers have been measured by determining their absolute thresholds for monochromatic lights and by direct comparison matching just above the threshold, in a 10 degree field with its centre 15 degrees above the fixation point. The results were all similar to the CIE scotopic curve. However, the threshold results in the long-wave part of the spectrum could be considerably modified by subliminal red and green lights. This is consistent with Drum's observations of sub-additivity at threshold. Above threshold, supra-additivity was obtained. A scotopic curve is evidently a non-linear combination of rod and cone responses which varies with the conditions of observation.
mesh_terms: D003116:Color; D003623:Dark Adaptation; D006801:Humans; D010783:Photometry; D010786:Photoreceptor Cells / Q000502:physiology*; D012684:Sensory Thresholds / Q000502:physiology; D014796:Visual Perception / Q000502:physiology*