Johannes Purkinje was a Bohemian-born Czech physiologist and pioneer of histology, best known for his observations of nerve cells (see neuron) and discovery of the Purkinje effect, that at different overall light intensities the eye is more sensitive to different colors.

 

Purkinje effect

The Purkinje effect is the tendency of the peak sensitivity of the human eye to shift toward the blue end of the spectrum at low illumination levels. It can affect visual estimates of variable stars when using comparison stars of different colors, especially if one of the stars is red.