Thanks. I think I've figured this out. This was a problem with some of the other models as well. It's a little weird but it looks like the camera remembers the last f stop setting of the last Canon lens mounted on the camera and uses that as some kind of registration for the meter system. I tested this with a few of my Canon lenses, 24-70 2.8, 50 1.4. If I have the 50 set to 5.6, then shut down the camera and swap to one of my old Nikon lenses the match needle in LiveView is way off. If I go back to the 50, set it to 1.4 then shut down, remove the lens and go back to the Nikon lens, the meter then works pretty much as expected. So what if I go from a Canon f 4.0 or 2.8 lens back to a Nikon lens you ask? The match needle metering is then messed up. I have to go from the 50 1.4 set to 1.4, shut down and then swap to the Nikon for the meter to be ok. Now I wonder if that is also the case if I'm using a Nikon F 2.0. lens. Do I first have to have a Canon f 2.0 set to f 2.0 when shutting down before going to a Nikon f 2.0 lens? What makes this so freakin' frustrating is that this stuff doesn't happen with my lesser 5D.
Aaaaaaaargh!
A.T.