Color stimulus function
As color stimulus function .phi .lambda is the spectral distribution of the color stimulus , respectively. She surrenders
- for body colors from the multiplication of the incident illuminating radiation S λ by the "remaining" ( remitted ) portion β λ , which is referred to as the degree of remission :
- φ λ = S λ * β λ
- for transparent bodies from the multiplication of the incident illumination radiation by the portion τ λ that passes through , which is referred to as the degree of transmission :
- φ λ = S λ * τ λ .
On the other hand, a distinction must be made between the radiance factor, also designated by β (λ), another variable from light measurement technology .
The f to the formula elements λ set-index λ is to illustrate that it is spectral function values of the individual wavelengths is λ. The relationships are based on the Lambert-Beer law , which strictly only applies to monochromatic light, i.e. in terms of measurement technology at a narrow interval at the point λ.
When changing from one (illuminating) type of light to a type of light with a different spectral distribution or similar influences - e.g. when viewing with colored glasses - there is a color distortion , a change in the color stimulus function. This falsification (change in color stimulus) can be noticed, for example, in the dark when a (suitable) colored surface is illuminated at regular intervals by the light of the traffic lights - i.e. alternately in red, yellow, green.
In order to show the influence of the width of wavelength sections (here 10 nm to 100 nm) on color rendering , rectangular spectra of different widths in the diagram were subjected to a calculation of the color stimulus function.
literature
Manfred Richter: Introduction to colorimetry . Walter de Gruyter, Berlin / New York 1976