Ok, I understand how it does it.
So how should I should I meter it so white is near 0 or may be 5% (at least keep something hehe).
I think that if I shoot in RAW, I could modify this more easily in GIMP or photoshop, white the white balance functions.
But if I want to do it on the camera ? I do a white balance on grey instead ?
Should I get a grey chart ?