Helmholtz–Kohlrausch effect
Encyclopedia
The Helmholtz–Kohlrausch effect (after Hermann von Helmholtz
and Rudolf Kohlrausch
) is an entoptic phenomenon
wherein the intense saturation
of spectral hue
is perceived as part of the color's
luminance
. This brightness increase by saturation, which grows stronger as saturation increases, might better be called chromatic luminance, since "white" or achromatic luminance is the standard of comparison. It appears in both self-luminous and surface colors, although it is most pronounced in spectral lights.
Hermann von Helmholtz
Hermann Ludwig Ferdinand von Helmholtz was a German physician and physicist who made significant contributions to several widely varied areas of modern science...
and Rudolf Kohlrausch
Rudolf Kohlrausch
Rudolf Hermann Arndt Kohlrausch was a German physicist.-Biography:He was a native of Göttingen, the son of educator Heinrich Friedrich Theodor Kohlrausch...
) is an entoptic phenomenon
Entoptic phenomenon
Entoptic phenomena are visual effects whose source is within the eye itself. In Helmholtz's words:...
wherein the intense saturation
Saturation
Saturation or saturated may refer to:- Meteorology :* Dew point, which is a temperature that occurs when atmospheric humidity reaches 100% and the air is saturated with moisture- Physics :...
of spectral hue
Hue
Hue is one of the main properties of a color, defined technically , as "the degree to which a stimulus can be describedas similar to or different from stimuli that are described as red, green, blue, and yellow,"...
is perceived as part of the color's
Color
Color or colour is the visual perceptual property corresponding in humans to the categories called red, green, blue and others. Color derives from the spectrum of light interacting in the eye with the spectral sensitivities of the light receptors...
luminance
Luminance
Luminance is a photometric measure of the luminous intensity per unit area of light travelling in a given direction. It describes the amount of light that passes through or is emitted from a particular area, and falls within a given solid angle. The SI unit for luminance is candela per square...
. This brightness increase by saturation, which grows stronger as saturation increases, might better be called chromatic luminance, since "white" or achromatic luminance is the standard of comparison. It appears in both self-luminous and surface colors, although it is most pronounced in spectral lights.