Quote Originally Posted by ddi
I only have
Canon EF-S 17-85mm f/4-5.6 IS USM lens. Would that lens be of any use
for video on 7D?

Yes.


Quote Originally Posted by ddi
What lens would you recommend for video (some of it in
low light) on 7D if I can only get one lens for now?

If it's for just video, you can get better results buying old manual lenses (e.g. Nikon), because they have much better manual focus features (rotation length, dampening, etc.). But if you need still and video together, you'll get the best results from prime lenses, especially L, because they tend to have better focus rings, less breathing, etc.