Purkinje Effect

The shift of a human eye’s peak luminance sensitivity (peak of the Luminosity Function) of the eye to shift toward the blue end of the color spectrum at low illumination levels. This is because the Scotopic Luminosity Function peaks at Rhodopsin’s Peak Sensitivity (~500nm), whereas the Photopic Luminosity Function peaks at ~555nm. As the light intensity decreases and the Photopic and Scotopic visual systems are working in parallel (Mesopic visual system), the peak of the Luminosity Function decreases towards 500nm.

Colors in Mesopic vision therefore have a tendency to be distorted in luminance, where the reds get dimmer and the greens get brighter. This is the Purkinje Effect.