Have you got any spare lenses?
What kind of video camera? Be aware that if the sensor/ film is smaller than a 35mm frame (which, unless you've got a proffessional film movie camera, it will be) you won't get the same angle of view as on the camera the lens was designed for. This is the same issue as with using 35mm lenses on most digital slrs - all your lenses effectively get longer and wide angles become expensive. You can read about this issue being debated ad infinitum by idiots who can't understand it on any cmarea forum or UKC.
You're estimation of 1-2 stops light loss is probably conservative, however using a very fast lens wide open will give you very little depth of field, and focussing will be tricky. Or is that the whole point behind it?
Bring it round Feynman, I've got a safe you can break while you're at it. I've got a slection of primes from 21/3.5, 28/2.8, 35/2, 50/1.4 up to 400mm.Plus we've got Keenus' fingerboard installed in the cellar, so we can try it out.