Purkinje effect

The Purkinje effect is the shift in human visual sensitivity toward shorter wavelengths as illumination decreases, making blue-green objects appear relatively brighter than red ones.

Rods (retina): Retinal photoreceptors specialized for vision at low light levels, with high sensitivity and no color discrimination. Their short-wavelength sensitivity drives the shift as dim conditions recruit rod vision.
Visible spectrum: The range of electromagnetic wavelengths detectable by human vision, approximately 380 to 700 nanometers. The effect compares the eye's responses across this range of wavelengths.
Jan Evangelista Purkyně: A Czech anatomist and physiologist whose work included early observations of changes in vision under different illumination. His observations of flowers in daylight and twilight gave the phenomenon its name.
Purkinje shift: The measurable displacement of peak visual spectral sensitivity from longer to shorter wavelengths as illumination decreases. This name emphasizes the sensitivity-curve displacement behind the broader Purkinje effect.
Color constancy: The tendency to perceive an object's surface color as relatively stable under changing illumination. Unlike color constancy, the Purkinje effect concerns changing relative brightness across wavelengths.
Cones (retina): Retinal photoreceptors that support color vision and high-acuity sight in brighter conditions. Their longer-wavelength sensitivity dominates before falling illumination shifts vision toward rods.
Luminance: A photometric measure of light intensity weighted by human visual sensitivity. Decreasing luminance moves vision toward the rod-dominated conditions that produce the effect.
Photometry: The measurement of light weighted according to the sensitivity of human vision. Photometric measurements quantify the brightness shift across wavelengths and illumination levels.
Mesopic photometry: The measurement of light at intermediate levels where rod and cone sensitivities both contribute. It accounts for the changing spectral sensitivity that standard daylight photometry misses.
Simultaneous contrast: A change in perceived color or brightness caused by the surrounding visual context. It depends on neighboring stimuli, whereas the Purkinje effect tracks illumination level.

Linked from 4 pages