The von Kries coefficient law in color adaptation describes the relationship between the illuminant and the human visual system sensitivity.
[1][2][3] The law accounts for the approximate color constancy in the human visual system.
The von Kries coefficient law compensates for the illumination change using a purely diagonal scaling of the cone absorptions.
A German physicist and physician, Helmholtz asserted that “the nervous substance in question is less sensitive to reacting light falling on it than the rest of the retina that was not previously stimulated”.
Helmholtz, along with Thomas Young, proposed the trichromatic theory, or the Young–Helmholtz theory, that stated that the retina contains three types of cones, which respond to light of three different wavelengths, corresponding to red, green, or blue.
Many researchers, including Eileen Wassof (1959), Burnham et al. (1957), and Macadam [12] rejected his law as being insufficiently accurate.
α, β, and γ are the von Kries coefficients corresponding to the reduction in sensitivity of the three cone mechanisms due to chromatic adaptation.
are cone responses for the test illuminants, then Using these to solve for the coefficients, we get: α
Wirth, in research done from 1900 to 1903, demonstrated through his studies that the law can be considered “nearly valid for reacting lights that are not too weak”.
[8] The theory on sensitivity and reacting light was also evaluated and emphasized by Wright in 1934 studies, where he stated, “Now suppose R’, G’, and B’ are hypothetical stimuli that produce responses along A, B, and C,… three independent set of fibers to the brain.
Then a reduction in sensitivity produced by light adaptation will, for a test colour that stimulates A alone, produce an intensity depression of R’ but no colour change; similarly if B or C are stimulated alone.” The von Kries coefficient law has also been known to be an inaccurate predictor of asymmetric matching experiments.
Therefore, any discrepancies in calculations are due to the visual system behaving in accordance with newer models Further research by Brian Wandell on Wassof's findings revealed that when objects analyzed by the coefficient law are in the same context, the rates of cone absorption as realized by the law match up with experimental values.
However, when the two objects are seen under different illuminants, the cone absorptions do not correlate with the true values.
Color appearance is an interpretation of the physical properties of the objects in the image.
For example, many chromatic adaptation platforms (CATs) are based on the von Kries coefficient law.
It has been used in applications ranging from psychophysical work by researchers such as Takasari, Judd, and Pearson; it has also been used in electrophysiological experiments.
Alternatives to the von Kries coefficient law, while they have been brought up and studied (for example, Jameson and Hurvich's induced opponent response chromatic adaptation theory), have never reached the level of prevalence found by the simplicity of the von Kries coefficient law.
Nearly all commercial digital cameras use the von Kries coefficient law to model the variation and chromatic adaptation.
from two radiant spectra can be matched by appropriate choice of diagonal adaptation matrices D1 and D2:[12] where
This leads to the von Kries transform for chromatic adaptation in LMS color space (responses of long-, medium-, and short-wavelength cone response space):