http://cyrilleberger.blogspot.com/2007/10/pigments-color-conversion-system.html
But I want Krita 2(.0) to be a reliable, high quality, extra, super, cool, (put here any other positive term) High-Dynamic Range imaging application. And thanks to the introduction, during the last few week, of the Color Conversion System (CCS), it’s now possible to have reliable color conversion between two High-Dynamic Range color spaces. And that’s cool, because one of the main task in the High-Dynamic Range work flow is to convert to Low-Dynamic Range (a process called tonemapping), but most algorithms to accomplish that task use the XYZ color space, while most images are in RGB, that means that the image first need to be converted to XYZ (and now you understand why it is interesting to keep the High-Dynamic Range information).