How do I provide illumination information when performing ''xyz2srgb'' conversion with the MAKECFORM function?

I have computed the XYZ values with 3 different illuminants, that is, by using the same reflectance spectrum but with 3 different illuminants: A, EE and D65. I obtain very different colors when I translate the values to the corresponding sRGB values. I expect the color to be more or less the same e.g. as with tungsten and day light illumination.

Answer 1

[MathWorks Support Team]

The XYZ to sRGB conversion in the Image Processing Toolbox is based on ICC color profiles. Such profiles assume D50 illumination. Therefore XYZ values should be adapted to D50 illumination before conversion. A VonKries or linear Bradford adaptation could be used but the Toolbox does not yet provide this functionality.

More information on Chromatic Adaptation can be found at the following URL:

http://www.brucelindbloom.com/index.html?Eqn_ChromAdapt.html

[KAE]

I would suggest that documentation for all color transformation functions (makecform, xyz2rgb, etc.) indicate that a D50 illuminant and 2 degree observer (I believe) is assumed. Otherwise the user could easily miss their assumption of other illuminants and observers like D65/10.