frudawski

# ciespec2xyz

The ciespec2xyz function calculates the normalized CIE 1931 colour coordinates x,y,z, also known as normalized Tristimulus values, for a given spectral power distribution (SPD). Any errors in the data set or in results generated from the reference data or the Lighting Toolbox are not in the liability of the CIE nor me, see license.

Usage:

[xyz,x,y,z,XYZ] = ciespec2xyz(lam,spec,observer)

Where:

Note: For several input spectra use a row-wise matrix.

Note: For the determination of Tristimulus values XYZ one can also use the ciespec2unit function with reference ’xyz’.

Examples

Determine the normalized Tristimulus values for standard illuminant ‘D65’:

lam = 360:830;
spec = ciespec(lam,'D65');
xyz = ciespec2xyz(lam,spec)

Result:

xyz =

0.3127    0.3290    0.3582

Determine the normalized x and y component of the Tristimulus values for standard illuminant ‘D65’:

lam = 360:830;
spec = ciespec(lam,'D65');
[~,x,y] = ciespec2xyz(lam,spec)
plotciexy(x,y)

Result:

x = 0.3127
y = 0.3290

Determine the normalized x and y component of the Tristimulus values for standard illuminants ‘A’ and ‘D65’:

lam = 360:830;
spec = ciespec(lam,{'A','D65'});
[~,x,y] = ciespec2xyz(lam,spec)

Result:

x =
0.4475
0.3127

y =
0.4074
0.3290

Determine the Tristimulus values for standard illuminants ‘A’ and ‘D65’:

lam = 360:830;
spec = ciespec(lam,{'A','D65'});
[~,~,~,~,XYZ] = ciespec2xyz(lam,spec)

Result:

XYZ =

8.0942e+06   7.3689e+06   2.6226e+06
6.8599e+06   7.2173e+06   7.8584e+06

Note: The same results can be achieved with the ciespec2unit function:

lam = 360:830;
spec = ciespec(lam,{'A','D65'});
XYZ = ciespec2unit(lam,spec,'xyz')

Result:

XYZ =

8.0942e+06   7.3689e+06   2.6226e+06
6.8599e+06   7.2173e+06   7.8584e+06

Reference

ISO/CIE 11664-1:2019(E): Colorimetry - Part 1: CIE standard colorimetric observers. Commission International de l’Éclairage (CIE), Vienna Austria, 2019.