I was really excited when I saw that the fine people at Magic Lantern had made HDR video possible on Canon DSLR cameras. Then I was greatly disappointed when I realized that that Magic Lantern still has no support for the Canon 7D. Sometimes I wonder if I should buy a second camera body for those times when a two camera shoot is better. If so I'd probably go for the T3i which is supported. That would give me access to HDR video at a pretty low price. How do they do it? Every other frame is recorded at a different ISO settings. One is darker and the other is lighter. The adjacent frames are interpolated to come up with frames that have higher dynamic range than a single ISO setting can muster. It really takes the hot sections of the frame and brings them down so detail is not lost. Check out the video below.
[vimeo 33987353 600 307]