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ciecct2spec

The ciecct2spec function calculates the corresponding spectral daylight distribution for a given Correlated Colour Temperature (CCT) T_{cp} in K, according to the CIE procedure described in CIE 15:2018 Colorimetry, 4th Edition. The returned spectral range is given from 300 nm to 830 nm in 5 nm steps. 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:

[spec,lam,xd,yd] = ciecct2spec(cct,lam,Y,W)

Where:

ParameterDescription
specIs a vector containing the reconstructed spectral daylight distribution.
lamIs a vector containing the spectral wavelength: default: 300 nm – 830 nm in 5 nm steps.
xdReturns the corresponding CIE 1931 chromaticity x coordinate(s).
ydReturns the corresponding CIE 1931 chromaticity y coordinate(s).
cctSpecifies the Correlated Colour Temperature (CCT) T_{cp} in K, scalar or vector.
lam
(optional)
Is a vector defining the wavelengths. Default: 300:5:830
Y
(optional)
Defines the integral weighted target value derived from the spectral power distribution.
W
(optional)
Defines the weighting function for the integral target value (see above). Default: 'VL' for the V(\lambda) weighted photopic value.

Examples

Derive and plot the daylight’s spectral power distribution (SPD) for a CCT of 7500 K:

cct = 7500;
[spec,lam,xd,yd] = ciecct2spec(cct);
plotspec(lam,spec)
[xd,yd]

See also: plotspec

Note: plotspec only displays the visible range from 380 nm – 780 nm.

Result:

ans =

   0.2990   0.3150

Create spectral power distribution of D75 with resulting photometric value of |Y| = 10000:

lam = 380:780;
spec = ciecct2spec(7500,lam,10000);
Y = ciespec2Y(lam,spec)

See also: ciespec2Y

Result:

Y = 10000

Create spectral power distribution of ‘D65’ and ‘D5634’ with different target values and weighting functions:

lam = 360:830;
spec = ciecct2spec([6500 5634],lam,[10000 15000],{'VL','mel'});
Y = ciespec2Y(lam,spec)
mel = ciespec2unit(lam,spec,'mel')

See also: ciespec2Y, ciespec2unit

Result:

Y =

   1.0000e+04
   1.2314e+07

mel =

   1.3262e+01
   1.5000e+04

Reference

CIE 15:2018: Colorimetry, 4th Edition. Commission International de l’Éclairage (CIE), Vienna Austria, 2018, ISBN: 978-3-902842-13-8 , (DOI: 10.25039/TR.015.2018).

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