I don't know about exposure information during videos, but I do think that some kind of exposure adjustment would be essential during the event. Otherwise you would probably go completely black during totality, due to the very wide difference in lighting. I was doing a time-lapse with a wide-angle lens, for the period of totality +/- about 5 minutes on either side. I set the camera to Av mode, ISO 800 at f/5.0. At the start the shutter speed was 1/3200 sec, and during totality it was 1/15 sec. Once I finish processing it, I'll put it together and post a link.