Dear Vittorio, > Can you please tell me if the XYZ values can also be negative? Yes, Device XYZ values can be negative. > For what I understood they should start from 0: > http://en.wikipedia.org/wiki/CIE_1931_color_space. What am I missing? You are missing nothing, WiKi is wrong here. Not your fault. -- Iliah Borg ib@xxxxxxxxxxx