Bezold–Brücke shift

Under the Bezold - bridge phenomenon is defined as the change of the color perception as a function of the adaptation level is within the range of the day sight. Is named the phenomenon after Wilhelm von Bezold and Ernst Wilhelm von bridge.

The phenomenon

The color discrimination, more precisely the color discrimination, in the human eye is dependent on the luminance. At very low luminance a color stimulus between 380 nm and 480 nm causes a color stimulus of blue violet, between 480 nm and 570 nm is a green perception, and between 570 nm to long-wave limit of visibility at 760 nm red is perceived. With increasing luminance, the distinction is better, at about 0.0015 cd / cm ² to 1 cd / cm ² to 160 spectral hues plus 30 purple tones can be distinguished. The distinction is improved with further increase in luminance at a high density but increases again. In the glare area are only a whitish yellow and a whitish blue violet perceive. Some subject can also only perceive a bright light. This phenomenon is referred to as the Bezold - Abneysches phenomenon. The background of this dependence is different in the light sensitivity of rods ( scotopic or night vision) and also color charming receptive cones (eye) justified ( photopic or tags marriages).

Number of theoretically possible colors

To estimate the number of possible " foreseeable " colors are the saturation and the brightness observed. The number of perceptible saturation levels for the normal observer in turn depends on the color, for example, given as " wavelength same color " and is located in the green zone at its highest. The number is roughly 4 to 25 In the brightness can be a few hundred steps specify. The number of theoretically possible colors arises as to several hundred thousand. However, real about 10,000 to tens of thousands in hue, saturation and brightness distinguishable color nuances are possible, but they are still dependent on other factors, such as ambient light, psychological bias, the waking state, coloristic exercise.

For Italian mosaic workers 30,000 distinct shades are called.

Source and Literature

• Karl hat, Foitzik Leonhard, Wolfgang Krug, Günter Schreiber: Brockhaus ABC of optics. F.A.Brockhaus VEB Verlag, Leipzig 1961.