Purkinje effect

[13] Similarly, airplane cockpits use red lights so pilots can read their instruments and maps while maintaining night vision to see outside the aircraft.

[14] The animal subjects do not perceive red lights and thus experience darkness (the active period for nocturnal animals), but the human researchers, who have one kind of cone (the "L cone") that is sensitive to long wavelengths, are able to read instruments or perform procedures that would be impractical even with fully dark adapted (but low acuity) scotopic vision.

Purkyně noticed that his favorite flowers appeared bright red on a sunny afternoon, while at dawn they looked very dark.

He reasoned that the eye has not one but two systems adapted to see colors, one for bright overall light intensity, and the other for dusk and dawn.

Purkyně wrote in his Neue Beiträge:[16][17] Objectively, the degree of illumination has a great influence on the intensity of color quality.

Nuances of red, which otherwise burn brightest in daylight, namely carmine, cinnabar and orange, show themselves as darkest for quite a while, in contrast to their average brightness.