Color & Light Knowledge

Measuring Instruments

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Tristimulus values determined based on the color matching functions , and defined in 1931 by CIE; also referred to as 2° XYZ tristimulus values. They are suitable for a viewing angle of 4° or less and are defined for reflecting objects by the following formulas:
	where S(λ): Relative spectral power distribution of the illuminant , , : Color-matching functions for CIE 2° Standard Observer (1931) R(λ): Spectral reflectance of specimen
Tristimulus values determined based on the color matching functions , and defined in 1964 by CIE; also referred to as 10° XYZ tristimulus values. They are suitable for a viewing angle of more than 4° and are defined for reflecting objects by the following formulas:
	where S(λ): Relative spectral power distribution of the illuminant , , : Color-matching functions for CIE 10° Supplementary Standard Observer (1964) R(λ): Spectral reflectance of specimen

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