I am asking out of curiosity. I bought a DSLR to take pictures, not video. I bought an HD camcorder to take video and not pictures. Both excel for their purpose. Neither one can come close to doing the job of the other.
I did take a small video with my T1i and couldn't stand even trying it. AF is horrible, video is questionable at best. I took the same video with my HV20 and it is astounding. I can understand people only wanting one device. However, I think it will be a long while before a DSLR can be as good as a camcorder for video. They would have to create a specific "video lens" to manage for the speed of autofocus necessary.
For me, I'll stick with two separate devices.
I used to think the same way. I had a DSLR and a pretty good Sony Handycam. I had a couple of point-and-shoot cameras that took HD videos as well, hence I thought what the heck - my DSLR is for pics, not for vids.
That was until I bought my Canon 7D. So my response to why I use it for videos - IT ROCKS!
A lot of people complain about the auto-focus, etc in using the video capability of a DSLR. First off, using my 7D I can record videos at ISO1600 and they appear crisp and clean. Now imagine if you use a lens that has a really wide aperture (I use my 50mm f/1.4 USM) for videos, at ISO1600 and shutter speed of 1/30 - there is hardly any scenery that you cannot capture, including lowlight. Bump it up to ISO3200 and noise increases but the overall video quality still is very good.
On auto-focus, the reason you would like to buy a lens with FTM (full-time manual focus) is because you would like to adjust the focus manually while you record videos using the 7D (or 550D for that matter). But it is not true the screen is dark; that only means you have not selected the right ISO, aperture and shutter speed. Or perhaps the lens you are using is not the kind that is ideal for lowlight.
My 7D at 24fps full 1080 HD video produces cinema-quality videos. And oh by the way, it does take awesome stills! So that is another reason I became a convert - I do not really need to carry a separate device anymore, and that is sort of liberating.
Try connecting your Canon DSLR with HD video capability on an HDTV and see for yourself. Or simply play it over your PC that uses a monitor that is at least 19 inch big.
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Noogy
'Photography is my therapy.'
Canon EOS 7D, Canon EOS 400D, Canon D10, Lumix TZ5, Kodak V1253