AHA! Something I have experience with
Ok, so heres the deal with AF on HDSLRs, it works well on both the 7D and the 550D... the problem that arises here is that the obvious AF noise is apparent in all recordings.. plus the other part to look at is the AF point, theres no point having AF in the video if you've got autopoint select on, even when you've got single point AF there's still the problem with focusing speed and major issues of hunting.
Although i must admit, the 550D is a fantastic video piece, the 500D on the other hand is .. well.. if you want video.. go buy a cheap HD video camera.. you'll have better luck
it records in 1080 @ 20fps... a little under what I'd like to consider cinematic. the 720p is still questionable though.. due to the jello.
With Video
modes though.. during a wedding it does get quiet questionable as to being able to video and photograph a wedding single handedly. I've previously attempted at just leaving it on a tripod while i shoot.. Program
mode with AWB only works so well in this circumstance.. The best thing about dedicated videographers using HDSLR's is that they'll know to use manual in most instances, the hardest part for them is the clicking noise each scroll and turn makes, Image Stabilizer does compensate for handheld videographing, and i've seen it in action.. works wonders if you can already keep quite still.
The AF issue arises these key problem areas :
1. AF noise during video ( if you wish to leave the sound audible), USM or HSM does not help here.
2. Hunting.. AF during liveview is quite the dramatic hunter.. Even with USM lenses.
3. The freedom of one hand, what does this entail? multitasking? which would / could alter the quality of a videographer.
As a kind whisper, don't bother with Nikon video in their dslr's... Nikon's aren't made for videoing that well and the Jello effect is VERY evident in the D5000, D90 and the D300s...haven't checked out the D3s performance, but that's well out of budget for alot of us.
What I'm personally using at the moment is a nikon adaptor, with a 135mm f2.8 NIKKOR on my 7D.. it's great as a manual focus because it's so smooth and can resolve quite well considering it's age as well, so it's purely a video lens in that sense.. I'll be buying more manual focus NIKKOR lenses in the not too distant future to compensate for the lack of video lenses atm. I also use a RODE microphone..runs off a 9V battery.. which although is external.. if attached to the camera's hotshoe.. the AF noise is still audible, it's reduced heavily when removed from the hotshoe.
All in All, video in DSLR's are part of the changing times,as a happy owner of the 7D, i can say that it works well for video and has resulted to me considering against purchasing an enthusiast HD video camera. 1080p works great, and the 7D buffers like magic. thats the difference between the 7D and the 550D, CF vs. SDHC, 2 processors vs 1 processor, build quality, grip, weight, AF system. All of which come into consideration.
If you do intend on purchasing a HDSLR, please consider the following items to go along to help you in your reign :
- Hoodman Loupe or Zacuto Finder ( prefferably Zacuto branded)
- Shoulder mounting Kit available from Zacuto.. theres a few other brands that have the same sort of setup.
- External microphone ( Rode works well for me personally).
- Video Light, LED based, good catches are your 126 LED video lights that run off some camcorder batteries or 6
AA's.
- 18-135mm IS.. great lens for video.. i know it's quite blasphemous to note a EF-S lens.. but for that price you can't go wrong in the focal lengths present, the focusing ring in manual and the IS..works well as a walkaround lens.
- If you don't go for the shoulder mount, consider a handgrip that mounts to the camera via the tripod mount.
and as a bit off topic.. Trammell from Magic Lantern is currently devising a Magic Lantern Hack for the 7D to allow audio gain control, live histograms, and zebra stripes according to highlight areas.. it's been in progress for quite some time.. but soon enough it will hit the internet. Not sure if anything on the 550D will be developed as such.. but I don't doubt it one bit.
I hope this helps you in your decision as it can make a fair amount of moola, but take away alot from you to begin with, so if any other questions on video are wanted, just let me know =) I'll try to find out for you whatever you need to know as well.