Thanks for your answer ! Clarification : - each missing RGB LUT value resulting in 256x256 missing colors I mean that if for instance the R value 244 is missing in the output LUT, then 256x256 colors will never be reached (all 244xGxB triples) - "Effective LUT entry depth seems to be 12 bits" I use DVI and can't figure how the software determines this value . Is there a documentation about graphics cards output ? ( human readable ? ;-) ) _________________________________________________________________ Your E-mail and More On-the-Go. Get Windows Live Hotmail Free. https://signup.live.com/signup.aspx?id=60969