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:

Parameter | Description |

`spec` | Is a vector containing the reconstructed spectral daylight distribution. |

`lam` | Is a vector containing the spectral wavelength: default: 300 nm – 830 nm in 5 nm steps. |

`xd` | Returns the corresponding CIE 1931 chromaticity x coordinate(s). |

`yd` | Returns the corresponding CIE 1931 chromaticity y coordinate(s). |

`cct` | Specifies the Correlated Colour Temperature (CCT) T_{cp} in K, scalar or vector. |

`lam` | 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 = 0.2991 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 1.2318e+07 mel = 1.3259e+01 1.5000e+04

**Reference**

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