The **ciespec2Y** function calculates the integrated photometric value Y of a V(\lambda) weighted spectral power distribution. 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 licence.

Y = ciespec2Y(lam,spec,k)

Where:

Parameter | Description |

`Y` | Is a scalar or vector containing the photometric value of the integrated and V(\lambda) weighted spectral power distribution(s). Also known as Tristimulus value Y. |

`lam` | Is a vector specifying the wavelength steps. |

`spec` | Is a vector or row-wise matrix containing the spectral power distribution(s). |

`k` | Is a scalar and represents the luminous efficacy K_{\text{m}}. For photopic values K_{\text{m}} equals 683.002~\frac{\mathrm{lm}}{\mathrm{W}} (default setting). |

Note: alternatively one can use the function ciespec2unit with reference ‘y’ or ciespec2xyz.

**Examples**

**Determine the photometric value from the spectral power distribution of standard illuminant ‘A’:**

lam = 360:830; spec = ciespec(lam,'A'); Y = ciespec2Y(lam,spec)

See also: ciespec

Result:

Y = 7.3689e+06

**Determine the photometric values from the spectral power distributions of standard illuminant ‘D55’ and ‘D65’:**

lam = 360:830; spec = ciespec(lam,{'D55','D65'}); Y = ciespec2Y(lam,spec)

See also: ciespec

Result:

Y = 7.1783e+06 7.2173e+06

**References**

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