Newbie question...on continuous focus.

[Jeff Hinson]

Why is it a DSLR (video mode) cannot continuously focus like a camcorder ?...say XA10 and GH2.

Is there a DSLR (video mode) that can do this as good as a camcorder...Im not aware of any.

Just curious.

Jeff

[Don Palomaki]

DSLR is designd as a still camera that can take video as a bonus. It could be designed to allow continuous focus if the maker wanted to do so.

Because a DSLR has a much larger sensor than most camcorders, it has shallower depth of field, and continuous accurate auto focus may become more difficult. The greater DOF of a typical 1/3" camcorder sensor is more forgiving of slight focus errors.

[Jeff Hinson]

Thanks Don...

I really didn't think about the "size" of the sensor...but yes, I can see where it would be easier/cheaper to continuous focus on a smaller sensor. I think I would go all DSLR if I could get one with large sensor and continuous focus as good as a camcorder....but would probably be way over my budget.

I use the XA10 and GH2 they work just fine.

Thanks for your reply
Jeff

[Don Litten]

Actually, some can Jeff.
The GH2 has continuous AF. It is slow and inaccurate, at least on mine, but Works on something like a pole cam. I forget which lens it works with because I hardly use the stock lenses, but it's either the 20mm pancake or 14-XX

There is a difference between DLR's and Camcorders. That's why I have both. Use the right tool because neither does it all.

[Jeff Hinson]

@Don Litten...

Yes, I know, I have a GH2 and XA10 ...the XA10 for auto focus accuracy.
I was just curious if a DSLR was available. It must be hard to engineer, or it would already be on the market. I prefer to shoot with the low profile DSLRs.

Thanks,
Jeff

[D.J. Ammons]

The new Canon T4i has continuous autofocus in video mode if you use the new STM lenses. However the youtube reviews I have seen of it show it is very, very slow to focus and nothing like you need in a run and gun situation such as a wedding reception.

I was all set to get the T4i but now will probably get the XA10 instead. Still would like the T4i but it moves down he priority list.

[Don Litten]

That's one of the things that keeps me from pulling the trigger on an AF-100.
The autofocus is very good on my XA10 and I would have to sell it.

[Noa Put]

the af100 and the xa10 are 2 totally different camera's that serve different purposes, it's like my t2i and my sony cx730, the Sony is the best "crashcam" I have in my arsenal, it's ready in a sec and if needed can handle r&g situations MUCH better then my T2I can. The T2i only gets used in controlled situations.

The main advantage I can think of with any large sensor camera is shallow dof, it's very nice for creative shots but hell if you want to follow someone giving a speech in a dark venue and your at F2.0 or f1.4, especially if that person moves around. Now I just use my Sony as it can almost match my dslr in low light and don' t have to worry about pulling focus, I just lock the focus before I start recording and I only have to concentrate on holding that person right in frame.

If you want good autofocus I wouldn't buy a dslr.

[Don Litten]

Yes and no, Noa

I have 3 DSLR's and 5 camcorders, 2 are getting dated now. The GH2's are far and away the best at just about everything, except autofocus.

The AF100 was supposed to bridge the gap but isn't doing a very good job.

The XA10 has the best autofocus of the DSLR's. I sold my 7D which had autofocus if you wanted to stretch the definition some..

[Paul R Johnson]

Autofocus on a camera with limited depth of field sounds like a non-feature. How would you control what it focussed on? WIth a narrow depth of field there could easily be very large percentages of the frame soft, so the camera would have to lock onto perhaps a specific part of the field, giving you control of which bit you want, then the camera would have to go in and out of focus a few times to make it sharp. This means you can't move, because then the sharp point will also have moved. It seems unlikely that auto focus on a DSLR would be very useful to me?

[D.J. Ammons]

The Canon T4i's continuous autofocus has face recognition I believe whereyou can indicate the face you want to keep in focus. It just takes it awhile to do that!

[Don Litten]

The GH2 does too DJ and it does a fairly good job as long as you have good light. The lower the light the slower the focus though.

[Chris Barcellos]

I have a Sony VG20, which is a large sensor camera. It does a fairly decent job of auto focusing in lit situations. Getting into shadows and darkness is a problem for most autofocus rigs, no matter what the camera.