I have already worked on this picture, I found in some tutorials some little tips for that,
with changing the 2 gamma values with 1, i have a nice look,
But i have no idea of the real look on projection, you understand my worry.
If i work too bright or to dark, that will be a problem after.
I need something more precise if there is a way 
I will look for more and wish i could do some test with the lab before
Thanks to your help.
Jaz