ciespec2cct
The ciespec2cct function derives the Correlated Colour Temperature (CCT) T_{cp} for a given spectral power distribution (SPD) as in CIE 15:2018. Any errors in the data set or in results generated with the Lighting Toolbox are not in the liability of the CIE nor me, see licence.
Usage:
[Tcp,x,y,u,v] = ciespec2cct(lam,spec,method)
Where:
| Parameter | Description |
Tcp | Returns the Correlated Colour Temperature: Tcp |
x and y | Are the CIE 1931 x and y chromaticity coordinates. |
u and v | Are the CIE 1960 u and v chromaticity coordinates. |
lam | Defines the wavelengths, vector. |
spec | Defines the spectral power distributoin (SPD), vector or matrix. |
method | Specifies the determination method: ‘Robertson’: (default) Robertson’s calculation algorithm, formerly the only recommended algorithm by the CIE. This method is fast and quite accurate. ‘exact’: shortest distance method as described in CIE 15:2018, very accurate but comparably slow. Results may vary with different implementation methods. Both methods return NaN if the colour coordinates lie outside the meaningful interval of \Delta uv < 0.05 from the planckian locus in CIE 1960 chromaticity diagram. |
Examples
Derive Correlated Colour Temperature (CCT) of standard illuminant ‘A’:
lam = 380:780; spec = ciespec(lam,'A'); Tcp = ciespec2cct(lam,spec)
Result:
Tcp = 2856.0
Derive Correlated Colour Temperature (CCT) of standard illuminants ‘D65’ and ‘D50’ and the corresponding chromaticity coordinates:
lam = 380:780;
spec = ciespec(lam,{'D65','D50'});
[Tcp,x,y,u,v] = ciespec2cct(lam,spec)
Result:
Tcp = 6501 4999 x = 0.3127 0.3458 y = 0.3291 0.3586 u = 0.3127 0.3458 v = 0.3291 0.3586
Reference
CIE 15:2018: Colorimetry, 4th Edition. Commission Internationale de l’Eclairage (CIE), Vienna Austria, 2018, ISBN: 978-3-902842-13-8 , DOI: 10.25039/TR.015.2018. URL: https://cie.co.at/publications/colorimetry-4th-edition