I am having great difficulty shooting moving things (i.e.my 15 month old baby girl) because once video starts recording, the focus is fixed and any movement of the subject away from the focal plane means a blurred/OOF subject. It's driving me nuts. I am currently looking for a camera that can track autofocus on the subject while (she) moves. I thought the Panasonic GH2 could do that but was disappointed to find it does it only AF tracking in stills mode, not video. The only camera I found so far that can track AF while shooting video is the Panasonic G2. Are there any others? (Current gear is m4/3 Olympus EPL1 with pancake 20mm f/1.7 lens but open to other brands)
Camera with AF tracking in video mode?
- Thread starter electron
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After scouring the internet, I found it! The Olympus E-PL1. The camera I already have does AF tracking in video.:bsmilie:Note to self: m.u.s.t. r.e.a.d. m.a.n.u.a.l.
The only thing i had to do was change to 'C-AF-TR' mode and it followed focus on the subject in VIDEO mode. It's a bit slow but the good news is I don't have to buy a new camera. yay!
inyouheart
New Member
Sounds like a happy guy who found his love one. Good luck! 
I believe the new sony alpha 55 can do that, thanks to the new translucent mirror.
http://www.dpreview.com/reviews/sonyslta55/
http://www.dpreview.com/reviews/sonyslta55/
There's 2 kinds of AF mode that DSLRs use. One is phase detection, which is the very fast AF which a DSLR uses when u operate it using the viewfinder, and the other is called contrast detection AF, the slower AF that is being used with live view and video modes. This is the reason u will notice a significant increase in focusing speed when u use viewfinders, as contrast detection needs to do a "front focus, back focus" in order to lock on, unlike phase detection which can directly focus lock on a subject.
All DSLRs in the market right now uses contrast AF when in video mode as well as in live view mode (except Sony and Olympus DSLRs, which use phase detection AF in live views), thus u will notice that video AF is slow and will have the tenancy to hunt, as well as front-back focus often when they need to refocus (irritating as hell right when doing video recording. I HATE that). Thats why most people switch to manual focusing when they take video, cause of the slow AF and the focusing issue.
However, Sony has released 2 DSLRs, the A33 and A55, and these 2 cameras are the only DSLRs in the world which offers phase detection autofocus in video mode (even olympus DSLRs can only phase AF in live view, they still contrast AF in video). As such, the A33 and A55 has the fastest live view as well as autofocusing in video mode (and without the front back focus thingy of contrast AF).
Here's some examples:
Continuous AF in video, tracking moving cars
http://www.youtube.com/watch?v=_qoVCBFnQzY
You will notice that, due to phase AF, there is no hunting when the subject moves and the camera refocuses.
AF speed:
http://www.youtube.com/watch?v=b9nLcv6hLsQ
This video is to show the AF refocusing speed when the camera needs to quickly refocus.
Do note that the lenses used in the above 2 videos are non motorised lenses, thus their AF speed is not that fast (not the fault of the camera, its the lenses). Sony has motorised lenses (termed SSM), and those lenses are MUCH faster than their normal lenses.
Also, the A33 and A55 are Sony's entry level DSLRs. Sony will be coming out with their semi pro DSLRs later this year, and its AF speed (in video and in photo shooting) will be even faster than the entry level A33/A55.
You can compare it against the D3100's video mode, which uses contrast detection (and this is one of the fastest contrast detection AF in video in the market right now)
http://www.youtube.com/watch?v=0pOJ1eikUeQ
You'll notice that everytime the D3100 needs to refocus, the front back focusing hunting occurs. Also, most times the camera needs to stop moving for a little while, before the camera will try to focus. And whats worse is the "rubberband effect" (look at 1:28 - 1:30min, at the fences, when the camera is moving).
The front back focusing of contrast detection is very annoying in video...
PS: Sony NEX uses contrast detection AF. Only A33 and A55 has phase detection.
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