Patent ID: 7227586

Claim:
A method of processing an N-component color signal from a color signal source so as to eliminate dependency on color temperature and/or intensity variation by using a mathematical algorithm derived from the source sensitivities to different wavelengths of light in a signal processing computer supplied with the color signal, to provide new values for the components making-up the color signal which are independent of the color temperature of the light illuminating, or deemed to illuminate, the subject described by the color signal, wherein the N components, such as RGB signals of a 3 component color signal, define an image of an illuminated colored subject, the processing serving to produce modified signal components defining an image of the same subject as if illuminated under light of different color temperature, comprising the steps of: (1) generating the N-(RGB etc.) components of a color signal corresponding to an illumination of the subject using illumination of color temperature T 1 ; (2) forming the N log values (R′ G′ B′ etc.) of the N-RGB etc. components of the color signal so obtained; and (3) computing the N log values (R*, G*, B* etc.) of the N-RGB etc. components of the color signal for a different illumination color temperature T 2 using the equation: ( R*G*B* . . . )=( R′G′B′ . . . )+ X ( u,v,w, . . . ) where X is proportional to (T1–T2) and u, v, w, etc. are constants that depend only on the spectral sensitivities of the signal source and Planck's equation defining black body illumination.