Question about D800 exposure in video mode
Don't trust the LCD screen on the D800. It adjusts brightness automatically, but then stops when you hit the record button. In a shoot with the D800, a shot started well lit and moved into darkness. The exposure I saw on the LCD (even though I was using a loupe) was about two stops different from the captured footage.
Now that I know the issue, next time I use the D800 I'll disable the Auto LCD brightness, if possible.