Tristimulus values

Tristimulus values

• The amounts of the three primary colors needed to form any particular color are called the tristimulus values, denoted by X, Y, Z (or any other three symbols).
• For any color with spectrum $S(λ)$

$X = ∫S(λ)x(λ)dλ$, $Y = ∫S(λ)y(λ)dλ$, $Z = ∫S(λ)z(λ)dλ$

• Trichromatic (or chromaticity) coefficients
  $x=\frac{X}{X+Y+Z}$, $y=\frac{Y}{X+Y+Z}$, $z=\frac{Z}{X+Y+Z}$

• Only two chromaticity coefficients are necessary to specify the chrominance of a light.
  $x+y+z=1$