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Old March 19th, 2013, 04:13 AM   #1
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HM600 Auto Focus

Just wondering what other peoples thoughts are on the HM600/HM650s auto focus?

I just finished a 5 day shoot with my HM600, and I've come to the conclusion that the auto focus is terrible. I was shooting a pretty fast paced sports event, and auto focus would have been handy.

My main issue is that the focus hunts back and forth constantly. Even once the camera finds focus, after a few seconds it will start rapidly "pulsing" between different focus points, making the footage unusable. I've also noticed the focus drifting when set manually. I.e. I framed up and focused on something during the event, and a few minutes later the focus had shifted. This is while using a fixed aperture. Is this even possible?

I used to use the auto focus on my Canon XA10 a lot, and I trusted it completely. 99% of the time it worked perfectly.

I don't trust the HM600s auto focus at all, to the extent that I won't ever use it. This is a pretty big deal for me due to the kinds of sports events that I shoot. I did notice that JVC listed "auto focus improvements" in the latest firmware update. Hopefully they will continue improving it.

However I will say that this is my only complaint about the camera. In ever other aspect it's absolutely fantastic.

Last edited by Jody Arnott; March 19th, 2013 at 05:05 AM.
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Old March 19th, 2013, 07:14 AM   #2
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Re: HM600 Auto Focus

Hi Jody

It might just be the big zoom with the current sensors that cause the issue. A lot of guys (including me) had much the same problem on the Panasonic AC-130/160 and that has 1/3" chips and a 23X zoom ...the technical explanation was something about the physical size of the zoom that prevented auto focus to be reliable. I really needed a decent AF at weddings so both my cameras were on-sold ...I read numerous posts from a guy that filed horses running in a narrow paddock and he just couldn't get it right. Have you tried switching the camera between 2 objects on a reasonably big zoom?? Rod Pike from New Zealand had major issues with his 160 and it would actually freeze up now and again...He ended up getting the servo zoom replaced ... Maybe chat with Rod about the issue he might be able to shed some light on the subject?

Chris
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Old March 19th, 2013, 08:10 PM   #3
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Re: HM600 Auto Focus

Quote:
Originally Posted by Jody Arnott View Post
Just wondering what other peoples thoughts are on the HM600/HM650s auto focus?
I understand this is a limitation due to a combination of lens size, lens length, weight and economics.

As Chris said, there has been a huge amount of discussion and complaining about the AF on the Panasonic AG130/160, which have a very similar lens.

This is one of the most in-depth threads o the subject. It may help with your understanding.
AC130: Video footage of the Auto Focus in action - Page 18

As a test, you should find the AF works much better if you keep the zoom under 12x.

The nearest camera to these I've used recently was a Canon XH-A1s. It has a 20x zoom and the AF was quite unreliable at the tele end of the zoom. At 12x or under, it behaved much like other cameras.

The other thing to consider, when comparing it to a smaller chip camera is that there is less DOF so focus is more critical, and most importantly, the part of the lens that needs to move fro a focus operation is at least 3 time heavier.
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Old March 24th, 2013, 06:04 PM   #4
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Re: HM600 Auto Focus

Quote:
Originally Posted by Chris Harding View Post
Hi Jody

...I read numerous posts from a guy that filed horses running in a narrow paddock and he just couldn't get it right. Have you tried switching the camera between 2 objects on a reasonably big zoom?? Rod Pike from New Zealand had major issues with his 160 and it would actually freeze up now and again...He ended up getting the servo zoom replaced ... Maybe chat with Rod about the issue he might be able to shed some light on the subject?

Chris
Hi Jody/ Chris,

Rod here,- as Chris stated my panasonic 160a lens/servo assembly was deemed faulty and was replaced under warranty. It would indeed completely lock up occasionally. But I never had the pulsing/breathing issue on the 160A, I believe this was fixed with the 160A launch,(although Panny never said so, but that is my guess) but there were many reports of 130s and 160s pulsing on auto.

My 160A is now fine and I love it more and more. However as Chris and Mike point out, this is a long lens and mine is not instant by any means, but will lock on in around one second or up to three seconds if light or contrast is wanting.. I think it is the price you pay for a long optic which screws down DOF at extremes and restricts light with a diminishing aperture.
Cheers
Rod
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