It appears that the Rebel T4i w/ 18-135mm IS STM lens does continuos autofocus in video mode.

Canon U.S.A. : Consumer & Home Office : EOS Rebel T4i 18-135mm IS STM Lens Kit (http://www.usa.canon.com/cusa/consumer/products/cameras/slr_cameras/eos_rebel_t4i_18_135mm_is_stm_lens_kit)

I wish my 60D did that. :(

And the video autofocus is silent too. Just like my 18 month old GH2 ;-)

Ugh....I kind of thought the whole point behind the dslr revolution was that the filmmaker finally had such precise control over the focus (the whole shallow depth of field thing). Why else would they have put up with the dslr's inherent shortcomings, if not for that creative control of focus?

If you have a dslr in autofocus mode surely you'd be better off with a regular camcorder? As soon as you hand control back to the camera what is the dslr actually bringing to the table? Canon understood this when they designed the C300 (with no autofocus whatsoever).

I'm surprised this is actually a selling point now.

Simon,

Because now you still have all the creative control you want over manual focus PLUS you don't need a low-end camcorder and you can take great photos too.

There are times when it is good to have autofocus. On a steadicam when you are moving toward or away from the subject. It's impossible to manual focus in that situation without some ridiculously expensive wireless follow focus system.

Secondly, there are times when you might want to flip it to auto just to check focus. The screens on the DSLR simply are not high rez enough to be completely confident in focusing. If you are recording you can't zoom in to check focus.

Thirdly, I bought two GH2's for the only reason that they autofocus. I can give them to non-professionals to grab shots here or there. I'd never give any non-pro a camera that you have to manual focus.

In otherwords, having autofocus capabilities is very handy. Would I use it a lot. No, but I'd rather have it available than not available.

Brett,

I'd just like to mention that sometimes you need autofocus when you just have no opportunity to manual focus. The classic example is in sports, when you literally have only enough time to notice the action, point the camera and press the button. Blink and you miss the shot.

There are times when recording video when I could use a very-rapid autofocus.

Richard

So if you had the aperture set to something like f1.4 and the camera was placed on a glidecam, could you then walk backwards while a subject was walking towards you?

Would the camera continue to focus on the subjects face? That would be great for weddings.

is it phase detect or contrast autofocus? most AF on live view systems is of the inferior type, constantly hunting in medium to low light or low contrast areas.

also hopefully the metering system is better than the T2i's; AF and metering are the two areas i dislike about the T2i's. With speedlites they are horrid.

From what I've read, the t4i uses phase detection and contrast autofocus in the center of the screen and relies more on just contrast autofocus towards the edge of the screen. There is a example online, however its not using one of the STM lenses that is was designed for. I cant wait to see a video with autofocus in full action, it doesn't have to be perfect, it just has to be usable. If so, I will order 1 to replace my old t2i to go with my t3i & 5d.

if it is half as competent as the XHA1 AF system, i will likely buy one. assuming magic lantern works on the T4i's as well. that with the 2 T2i's i already possess should prove a decent setup for now.

...Would the camera continue to focus on the subjects face? That would be great for weddings.

The GH2 has face-recognition autofocus that is great for fast action in video mode (e.g., sports, kids) - don't know if the T4i has that.

The autofocus didn't seem that impressive when they reviewed it on DRTV.
They do tend to monkey about rather than doing real testing though.
(Autofocus tests at 11:00-11:17 and 12:22-12:40)
Canon 650D / T4i Hands-on Review - YouTube

I was all ready to purchase a T4i for my Wedding & Event Videography work but the examples of the auto focus I found on Youtube so far have discouraged me.

My plan was to use the T4i for creative pre wedding video shots on my glidetrack, etc and then for video of the reception. From the samples I saw on Youtube there is no way the auto focus would be usable filming a reception. Obviously would not need it for most of the glidetrack pre wedding shots but to justify this vs a Canon XA10 I need the auto focus to be excellent. We have two Sony V1's for our main cameras and a Canon HV20 for our B roll (backup fixed center cam)

I was going to say, just because it has continuous auto focus doesn't mean it's any good.
The Nikon D3100s full auto was indisputably crushed by the most basic handi cam. If you desperately want auto focus you still have to go get a Vixia or something.

There are times when it is good to have autofocus. On a steadicam when you are moving toward or away from the subject. It's impossible to manual focus in that situation without some ridiculously expensive wireless follow focus system.

I couldn't agree more... I have the t3i on a merlin steadicam which is great when there is a lot of lighting because I can close the f-stop and have a large depth of field, however, when at reception where there is little light, I need more light and open the f-stop, the focusing is impossible when using a steadicam. I'll look for other reviews of the t4i and autofocus in low light, when I get mine, I will post some video.

Wedding Videographers in Long Island (http://www.whitediamondvideo.com)