		COLOR PHENOMENA				Page: 10. 00
Introduction	Ingredients	Spectra	Attributes	The Human Eye	Color Mixing	General Terms
Color Spaces	How to measure	Color Scales	Color Effects	After Images		Contents

	Color Scales
	X-Y-Z TRISTIMULUS on this page
	HUNTER VERSUS CIE on page 10.01
	CIE-1931 CHROMATICITY DIAGRAM on page 10.02
	CIE-1976 CHROMATICITY DIAGRAM on page 10.03

X-Y-Z TRISTIMULUS

*Standard Observer*	In 1931, the CIE originally defined the standard Observer using a 2° field of view, hence the name "2° Standard Observer"
	In 1964, the CIE defined an additional standard Observer, this time based upon a 10° field of view and this is referred to as the "10° Supplementary Standard Observer"
	The 2° standard Observer should be used for viewing angles of 1° to 4° and the 10° supplementary standard Observer should be used for viewing angles of more than 4°.

To give an idea of what a 2° field of view is like compared to a 10° field of view, at a viewing distance of an arm length a 2° field
of view would be about a 2 cm circle while a 10° field of view at the same distance would be about a 10 cm circle.

Color Matching Functions

The color matching functions are the tristimulus values of the equal energy spectrum as a function of wavelength. These functions are intended to correspond to the Sensitivity of the human Eye.
Separate sets of three color matching functions are specified for the 2° Standard Observer and the 10° Supplementary Standard Observer.

"CIE" 1931
XYZ
Tristimulus Values

or

"CIE" 1931
X₂Y₂Z₂Tristimulus Values

Tristimulus values determined based on the color matching functions
x (λ), y (λ) and z (λ) defined by CIE in 1931
and 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:

X = K ₃₈₀∫⁷⁸⁰ S (λ) x (λ) R (λ) d (λ)
Y = K ₃₈₀∫⁷⁸⁰S (λ) y (λ) R (λ) d (λ)
Z = K ₃₈₀∫⁷⁸⁰S (λ) z (λ) R (λ) d (λ)
K = 100 / { ₃₈₀∫⁷⁸⁰ S (λ) y (λ) d (λ)}

where S (λ) is the relative spectral power distribution of the illuminant;
x (λ), y (λ), z (λ) are the color matching functions for CIE-1931 2° Standard Observer
and R (λ) as the spectral reflectance of the specimen.

"CIE" 1964
X₁₀Y₁₀Z₁₀ Tristimulus Values

Tristimulus values determined based on the color matching functions
x₁₀ (λ), y₁₀ (λ) and z₁₀ (λ) defined by CIE in 1964
and 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:

X₁₀ = K ₃₈₀∫⁷⁸⁰ S (λ) x₁₀(λ) R (λ) d (λ)
Y₁₀ = K ₃₈₀∫⁷⁸⁰S (λ) y₁₀(λ) R (λ) d (λ)
Z₁₀ = K ₃₈₀∫⁷⁸⁰S (λ) z₁₀(λ) R (λ) d (λ)
K = 100 / { ₃₈₀∫⁷⁸⁰ S (λ) y₁₀(λ) d (λ)}

where S (λ) is the relative spectral power distribution of the illuminant;
x₁₀(λ), y₁₀(λ), z₁₀(λ) are the color matching functions for CIE-1964 10° Supplementary Standard Observer
and R (λ) as the spectral reflectance of the specimen.

E X P L A N A T I O N
*"2° Standard Observer"*	10-00-01
*" 10° Supplementary Standard Observer"*	10-00-02
*"CIE"*	CIE means: Commission Internationale de l'Éclairage. in English: The International Commission on Illuminant. The main international organization concerned with problems of color and color measurement.

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Last update
2010-05-18