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Canon XH Series HDV Camcorders
Canon XH G1S / G1 (with SDI), Canon XH A1S / A1 (without SDI).


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Old May 31st, 2008, 07:36 AM   #1
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Auto Focus TOO sensitive

The auto focus kept being tricked by the small led lights and the led light system from the lighting guy.
I tried manual focus and it was worse out of focus constantly.
As you can see from the pictures the grads started out of focus, then in focus, then out of focus at the bottom.
Sadly this major problem doesn't show up in the XH-A1 viewfinder. As you can see it was very dark and these teens walk fast.
Any solutions for the future?

Last edited by Greg Clark; May 10th, 2011 at 09:35 AM.
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Old May 31st, 2008, 10:05 AM   #2
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I can see how auto focus wouldn't work very well in that situation. Probably what I'd do is set a manual focus near the end of the walk, let them start soft and walk into focus. It would be difficult to follow focus by yourself. I'm assuming they all start from about the same point and walk the same direction to the same place. You could also try the focust shift--set a beginning focus and and end, then use that focust shift button. It has 3 speeds, but they're all too fast to be very useful. However, if the kids walk fast it might work.
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Old May 31st, 2008, 10:34 AM   #3
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Quote:
Originally Posted by Bill Pryor View Post
Probably what I'd do is set a manual focus near the end of the walk, let them start soft and walk into focus.
Bill thanks. This is probably my only solution if I find myself in this lighting situation in the future.
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Old May 31st, 2008, 01:17 PM   #4
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Hey guys,
Do you think that using the normal AF instead of the IAF would be better for complexly lit scenes and result in less "hunting" for fine focus. I find that my a1 often tries to find focus when the frame is already in focus and ruins my shot! Any advice would be great,
-Steve
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Old May 31st, 2008, 02:25 PM   #5
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Hi guys...........

There's a couple of things that would really help in this situation.

Firstly, the IAF "locks on" to the biggest, most contrasty thing in view, in this case, mostly the background lights.

Tighter framing would cut the amount of background out and make the people the only game in town.

The biggest help would be to have "a nother" (or even two) manning a big focusable spot (the ones they use from the balcony/ gods at theatre/ stage performances - what are they called?) and track the couples as they are walking.

Not the sort of gear you carry in your average kit bag but indispensable for this application.

Just remember that with an A1 you can't zoom AND focus at the same time, so the framing needs to be tight yet allow enough room for the targets to "grow" into the frame.


CS
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Old May 31st, 2008, 06:53 PM   #6
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Originally Posted by Chris Soucy View Post
The biggest help would be to have "a nother" (or even two) manning a big focusable spot (the ones they use from the balcony/ gods at theatre/ stage performances - what are they called?) and track the couples as they are walking.CS
Do you mean a follow spot? Yes that would have helped but I am interested in the idea by Chris Lewis to use Normal AF instead of IAF. Would the Normal AF have helped isolate the Canon so it didn't keep hunting for focus?

In the past I have used to a Panasonic DVX and it wouldn't have had this focus problem.
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Old May 31st, 2008, 07:12 PM   #7
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Dear Greg,

In my opinion, your shoot would have been tough for the normal autofocus to handle.

From looking at the image, you have a low level of light on your subjects, and then have bright LEDs in the background.

With the above, it is hard for the autofocus to focus on your dim sujects.
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Old June 1st, 2008, 07:14 AM   #8
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Quote:
Originally Posted by Chris Soucy View Post
Firstly, the IAF "locks on" to the biggest, most contrasty thing in view, in this case, mostly the background lights.
In attached fotos are the background lights out of focus too. There is only one solution for such situations - manual focus and a bigger monitor.
With onboard monitor helps b/w picture and peaking to be focused, but it will never be easy to focus moving objects in telephoto and open iris by this kind of "electronic" manual steering of optic.
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Old June 1st, 2008, 11:23 AM   #9
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It is true that the background is out of focus when the grads are out of focus and vice versa.
Manual focus at the speed that these kids walk would be impossible. I tried it and all I got was everything out of focus. I could as someone suggested frame their faces but then you miss the dress and that is everything to a teenage girl.
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Old June 1st, 2008, 01:49 PM   #10
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Is it a whole bunch of people, one set at a time, walking up the aisle that you are recording?

Your best solution might be to get the Indifocus Pro:
http://www.indifocus.com/

Put a stop at the start point and the end point of the walk.

Make several marks on the wheel that coincide with different points in the walk.

Manual focus as the people walk up, making sure your wheel mark lines up with the location of the people from your preset places.

If you don't pan or tilt the camera, you can handle the focus. If you have to pan and tilt an assistant will probably be needed for pulling the focus.

With a little practice you should be able to get perfect focus in a preplanned setup like this.

Setting the focus wheel up is a little different than working with the fixed mount lens with no stops at the end of the focus, but it is still possible to do.

Last edited by Jack Walker; June 2nd, 2008 at 12:19 AM.
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Old June 4th, 2008, 09:13 PM   #11
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I have been having real issues with both auto focus modes focusing on the wrong part of the frame (even when subject is in clear foreground and middle of frame) and I was just wondering if you guys have had any problems like that. Also, I find that the I.AF is simply unusable because it seems to always be hunting for focus, thereby making none of my shots in-focus for more than about 25 seconds!
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Old June 4th, 2008, 10:09 PM   #12
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Auto Focus

I just won't use auto focus unless it's a stationary shot and even then I don't like to use it. I suppose it's ok if you are shooting something quick without having the time to manually focus. I have had too many "vertigo" footages because of auto focus so I just don't use it. I suggest you manual focus, or manual everything. If I were you I would force myself to shoot in manual mode. It won't take long to become one with your camera. You will become a better videographer in time if you do. Once you get used to shooting in manual it will become second nature to you and the chances of shooting lousy video will be reduced dramatically. Then if you have to you can occasionally go to auto something but you won't feel good about it.
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Old June 4th, 2008, 11:34 PM   #13
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Low light and auto focus go together like oil and water. It rarely works. Try to avoid it.

Solutions: First thing I did was to begin focusing manually. As I said, auto focus doesnít work well in low light. Secondly, if you can afford it, bring a larger external monitor. That way as you manually focus, you can actually see the picture and know when you are in or out of focus. The viewfinder in these cameras is too small to check focus. And if you have nearly 50 year old eyes like mine, itís completely useless.

Good luck.
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Old June 4th, 2008, 11:53 PM   #14
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Oldest trick in the book...

Go manual,
Zoom in as far as you can go,
Find focus and remember the distance ( do not exceed that distance)
Pull out wide

Now whenever you zoom in and out as they walk, you dont even need to touch the focus because everything within that range (from your position to the focal point) will remain in focus.

It should be easier to pull this off with these small CCD cameras.
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Old June 5th, 2008, 07:30 AM   #15
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Thank You for all the ideas

I don't want to go back to my Panasonic DVX, whose auto focus was forgiving, so I will start with improving my manual focus skills with this A1.
A large monitor would definitely help with the focus and I will look into the INDIFOCUS. I will also try to get the customer to boost the lighting.
In the pictures I posted above you will notice that the kids start out in a dark area that doesn't work well for setting a manual focus start point. Any final suggestion?
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