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The Bezold–Brücke shift or luminance-on-hue effect is a change in hue perception as the luminance (light intensity) of a
color Color (or colour in English in the Commonwealth of Nations, Commonwealth English; American and British English spelling differences#-our, -or, see spelling differences) is the visual perception based on the electromagnetic spectrum. Though co ...
changes. As intensity increases, the apparent hue of stimuli of a constant spectral distribution shifts towards
blue Blue is one of the three primary colours in the RYB color model, RYB colour model (traditional colour theory), as well as in the RGB color model, RGB (additive) colour model. It lies between Violet (color), violet and cyan on the optical spe ...
, if its
dominant wavelength In color science, the dominant wavelength is a method of approximating a color's hue. Along with purity, it makes up one half of the Helmholtz coordinates. The dominant wavelength of a given color is defined to be the wavelength of monochromatic ...
is below around 500 nm; or yellow, if its dominant wavelength is above 500 nm. As intensity is decreased, apparent hue shifts towards red or
green Green is the color between cyan and yellow on the visible spectrum. It is evoked by light which has a dominant wavelength of roughly 495570 nm. In subtractive color systems, used in painting and color printing, it is created by a com ...
. The effect was noted in 1866 by physiologist Ernst Wilhelm von Brücke, and experimental investigations by physicist and meteorologist
Wilhelm von Bezold Johann Friedrich Wilhelm von Bezold (June 21, 1837 – February 17, 1907) was a German physicist and meteorologist born in Munich, Kingdom of Bavaria. He is best known for discovering the Bezold effect and the Bezold–Brücke shift. Bezol ...
were published in 1873. It was re-investigated more thoroughly by Donald McL. Purdy in 1931. Stimuli of certain wavelengths ("invariant hues") retain their apparent hue despite changes in luminance; these have similar but not quite the same wavelengths as the
unique hues Unique hue is a term used in perceptual psychology of color vision and generally applied to the purest hues of blue, green, yellow and red. The proponents of the opponent process theory believe that these hues cannot be described as a mixture of ...
red, yellow, blue, and green. A similar hue shift, the Abney effect, occurs when a visual stimulus is mixed with white light. Both the Abney effect and the Bezold–Brücke shift apply not only to colors in isolation, but also to surface colors: for example, due to the Bezold–Brücke shift, the highlights and shadows of an object can appear to have different hues. The shift in the hue is also accompanied by the changes in the perceived saturation. As the brightness of the color stimuli increases, their color strength also increases to a maximum point and then decreases again; in such a way that it is still wavelength specific. This can, to an extent, be considered as an inverse of the
Helmholtz–Kohlrausch effect The Helmholtz–Kohlrausch effect (named after Hermann von Helmholtz and V. A. Kohlrausch) is a perceptual phenomenon wherein the intense saturation of spectral hue is perceived as part of the color's luminance. This brightness increase by sat ...
. In the case of the Helmholtz–Kohlrausch effect, the partially desaturated stimulus is seen to be brighter than fully saturated or achromatic stimulus.


See also

*
Opponent process The opponent process is a color theory that states that the human visual system interprets information about color by processing signals from photoreceptor cells in an antagonistic manner. The opponent-process theory suggests that there are thre ...
* Purkinje shift * Abney effect


Bibliography

* W. von Bezold: ''Die Farbenlehre in Hinblick auf Kunst und Kunstgewerbe''. Braunschweig 1874
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* "Über das Gesetz der Farbenmischung und die physiologischen Grundfarben", ''Annalen der Physiologischen Chemie'', 1873, 226: 221–247. *


References

Color appearance phenomena {{color-stub