The **ciewhitepoint** function returns the white point in CIE 1931 x and y chromaticity of any CIE standard illuminant. The function uses the reference spectra in the ciespec function and the ciespec2wp function to derive the white points.

Note: This might lead to different results compared to other calculation tools that are based on tabled values, see example of standard illuminant ‘E’.

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:

[XYZ,xyz] = ciewhitepoint('illuminant','observer')

Where:

Parameter | Description |

`XYZ` | Are the retuned tristimulus values of the standard illuminant, scaled so that Y = 1. |

`xyz` | Are the returned normalized tristimulus values scaled so that x+y+z = 1. |

`'illuminant'` | Is the given CIE standard illuminant, see table below. Several illuminants can be defined with a cell array: {‘A’,’E’,…} |

`'observer'` | Specifies the standard observer:‘xyz’ = CIE standard 2° observer (default)‘xyz10’ = CIE standard 10° observer‘rgb’ = CIE rgb |

**CIE standard illuminants:**

Illuminant | Description |

`'A'` | standard illuminant A |

`'C'` | not official standard illuminant |

`'D65'` | standard illuminant daylight 6500 K |

`'D50'` | illuminant daylight 5000 K – D65 recommended |

`'D55'` | illuminant daylight 5500 K – D65 recommended |

`'D75'` | illuminant daylight 7500 K – D65 recommended |

`'DXX'` | lluminant daylight XX00 K – not official standard |

`'DXXXX'` | illuminant daylight XXXX K – not official standard |

`'E'` | standard illuminant with equi-energy spectrum |

`'FL1'` | standard illuminant FL1: standard flourescent lamp |

`'FL2'` | standard illuminant FL2: standard flourescent lamp – recommended |

`'FL3'` | standard illuminant FL3: standard flourescent lamp |

'FL4' | standard illuminant FL4: standard flourescent lamp |

`'FL5'` | standard illuminant FL5: standard flourescent lamp |

`'FL6'` | standard illuminant FL6: standard flourescent lamp |

`'FL7'` | standard illuminant FL7: broadband flourescent lamp – recommended |

`'FL8'` | standard illuminant FL8: broadband flourescent lamp |

`'FL9'` | standard illuminant FL9: broadband flourescent lamp |

`'FL10'` | standard illuminant FL10: narrow band flourescent lamp |

`'FL11'` | standard illuminant FL11: narrow band flourescent lamp – recommended |

`'FL12'` | standard illuminant FL12: narrow band flourescent lamp |

`'FL3.1'` | standard illuminant FL3.1: standard halophosphat lamp |

`'FL3.2'` | standard illuminant FL3.2: standard halophosphat lamp |

`'FL3.3'` | standard illuminant FL3.3: standard halophosphat lamp |

`'FL3.4'` | standard illuminant FL3.4: DeLuxe type lamp |

`'FL3.5'` | standard illuminant FL3.5: DeLuxe type lamp |

`'FL3.6'` | standard illuminant FL3.6: DeLuxe type lamp |

`'FL3.7'` | standard illuminant FL3.7: three band fluorescent lamp |

`'FL3.8'` | standard illuminant FL3.8: three band fluorescent lamp |

`'FL3.9'` | standard illuminant FL3.9: three band fluorescent lamp |

`'FL3.10'` | standard illuminant FL3.10: three band fluorescent lamp |

`'FL3.11'` | standard illuminant FL3.11: three band fluorescent lamp |

`'FL3.12'` | standard illuminant FL3.12: multi band fluorescent lamp |

`'FL3.13'` | standard illuminant FL3.13: multi band fluorescent lamp |

`'FL3.14'` | standard illuminant FL3.14: multi band fluorescent lamp |

`'FL3.15'` | standard illuminant FL3.15: D65 simulator lamp |

`'HP1'` | standard illuminant HP1: standard high pressure sodium lamp |

`'HP2'` | standard illuminant HP2: colour enhanced high pressure sodium lamp |

`'HP3'` | standard illuminant HP3: standard high pressure metal halide lamp |

`'HP4'` | standard illuminant HP4: standard high pressure metal halide lamp |

`'HP5'` | standard illuminant HP5: standard high pressure metal halide lamp |

`'LED-B1'` | Phosphor-type LED |

`'LED-B2'` | Phosphor-type LED |

`'LED-B3'` | Phosphor-type LED |

`'LED-B4'` | Phosphor-type LED |

`'LED-B5'` | Phosphor-type LED |

`'LED-BH1'` | Hybrid-type LED |

`'LED-RGB1'` | RGB-type LED |

`'LED-V1'` | violet pumped phosphor-type LED |

`'LED-V2'` | violet pumped phosphor-type LED |

**Examples**

**CIE whitepoint of standard illuminant ‘A’:**

[XYZ,xyz] = ciewhitepoint('A')

Result:

XYZ = 1.0984 1.0000 0.3559 xyz = 0.4475 0.4074 0.1450

**CIE whitepoint of standard illuminant ‘A’, ‘E’ and ‘D65’:**

[XYZ,xyz] = ciewhitepoint({'A','E','D65'})

Result:

XYZ = 1.0984 1.0000 0.3559 1.0001 1.0000 1.0003 0.9505 1.0000 1.0888 xyz = 0.4475 0.4074 0.1450 0.3333 0.3333 0.3334 0.3127 0.3290 0.3582

**CIE whitepoint of standard illuminant ‘A’ for 10° standard observer:**

[XYZ,xyz] = ciewhitepoint('A','xyz10')

Result:

XYZ = 1.1114 1.0000 0.3521 xyz = 0.4511 0.4059 0.1429

**CIE whitepoint of standard illuminant ‘E’:**

[XYZ,xyz] = ciewhitepoint('E')

Result:

XYZ = 1.0001 1.0000 1.0003 xyz = 0.3333 0.3333 0.3334

Note: standard illuminant E is defined as equi-energy spectrum. This is often understood as x = y = z = \frac{1}{3}. This is a simplification, as shown below (see also CIE TR 15:2018, p. 4), and might lead to different results:

format long [XYZ,xyz] = ciewhitepoint('E') format short

Result:

XYZ = 1.000080035889627 1.000000000000000 1.000330668134761 xyz = 0.333314380777352 0.333287705799316 0.333397913423332

**Determine the tristimulus values X,Y,Z for standard illuminant ‘D65’ with an resulting e.g. illuminance of E = 15000~\textrm{lx}:**

XYZ = ciewhitepoint('D65').*15000

Result:

XYZ = 1.4257e+04 1.5000e+04 1.6332e+04

**Determine and plot the whitepoint of CIE standard illuminant ‘FL4’:**

[~,xyz] = ciewhitepoint('FL4') cie1931(xyz(1),xyz(2))

See also: plotciexy

Result:

xyz = 0.4402 0.4033 0.1565

**References:**

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

`Colorimetry - Part 2: CIE standard illuminants. Commission International de l’Éclairage (CIE), Vienna Austria, 2007.`

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