Okay, I recently got my 5D MII back from Canon after I sent it in for warranty repair. When they did it, they reset the factory preferences. Last night I decided to use it to film my son's basketball game. I was in full Manual and mode, and, I thought, the camera's exposure was set to my specifications. The image on the screen looked fine, until I hit the record button. When I did, the image shifted and got darker.

I seem to recall it doing this when I first got the camera, but I changed something to make it not do it, and for the life of me I cannot remember what I had turned on or off to stop it.

BTW: Just out of curiosity I switched to Auto mode and it did not shift exposure level like it does in Manual.

Thanks in advance for your suggestions.

Could it be the picture setting? Have you tried all the settings?

live view settings>stills+movie>MOVIE DISPLAY (*not 'exposure simulation*)

Exposure simulation was the culprit.

I am in your debt. Many thanks.

Thanks Brian...didn't even know that existed.

you're welcome!

Just an FYI: I got a new MK3 and it was doing the same thing. Drove me nuts trying to find out why it was acting like Auto ISO was on all the time, no matter what mode I was in.

So on the MK3 there's a menu item just for Live View. If you want to engage/disengage Exposure Simulation, there's a separate menu item for that now.

I'm loving this camera... especially its low-light and audio capabilities.