Originally posted by Noisychip Some camcorders even seem to have a constant 1.4 zoom lens ...
But , aside from video, AF should generally be possible in live view on newer DSLRs, right?
I mean contrast detection AF, not by flipping the mirror.
Will HSM lenses work with that?
Yes in theory it is possible, but contrast detect AF is so slow and ineffective that it would have adverse affects on the video. Nikon's new D3100 uses contract detect AF for autofocusing during video, there are no in depth reviews out yet so we have yet to see how effective it is. Nikons AF system and algorithms are generally pretty good so they might be able to pull it off, Pentax's Contrast detect (as well as their normal AF systems) are pretty miserable comparatively.
it is possible, and has been done before, but like I said the experience was so miserable that firmware updates removed the ability to use contrast detect in video, believe the T2i and the K7 pre-production review units (like the ones that DP review get) both had contrast detect AF in video but both were so terrible and inefficient that the ability was removed from the cameras firmware