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Illuminant file

Illuminants or light sources are used in colorimetric analysis or color comparison of the software. For some users it might be necessary to create or use custom illuminants.

To create a custom illuminant file, please use the following file format:

Illuminant files are ASCII text files, which usually have the file extension *.ill. An application like notepad.exe delivered with MS-Windows might be used to create or edit illuminant files.

Illuminant file format

The illuminant file format is described in the following:

Header block

A header block might be added optionally containing information about the illuminant using comment lines.

Comment lines start with a # character. These lines will be ignored during import.

Main data block

The main data block contains the self reflectance values for the particular wavelengths.

Each line starts with the reflectance value, followed by one or more spaces. In the same line the wavelength is given separated by // characters.


123.12345678   //123

Reflectance values might contains as many decimals as required or none. Wavelengths must be given without any decimals as integer numbers.

The wavelength range must at least cover values from 380-780 nm!

Illuminant file example



# Custom Illuminant File


# CIE Standard Illuminant A relative spectral power distribution 300 nm - 830 nm at 5 nm intervals

# Source A

# S(Lamda) Lamda

0.930483 //300

1.128210 //305

1.357690 //310

1.622190 //315

1.925080 //320

2.269800 //325

2.659810 //330

3.098610 //335

3.589680 //340

4.136480 //345




254.314000 //810

256.221000 //815

258.071000 //820

259.865000 //825

261.602000 //830