XH-A1 focus slips? at DVinfo.net

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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 December 2nd, 2009, 04:16 AM   #1
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XH-A1 focus slips?

i have noticed this a few times:
set interview with non moving subject, camera on tripod, zoom in to face and focus, zoom out. then off with a HV30 on a merlin for alternate perspectives, and when back to XH-A1 i zoom in to the face to check focus and notice the focus is off.
anyone notice something similar? i would think the focus, once set manually should NOT change!
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Old December 2nd, 2009, 06:11 AM   #2
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I think when you zoom out you lose a tiny tad of focus same when you zoom in again. Try focusing back at the framed shot, use peaking. HTH Cheers.
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Old December 2nd, 2009, 08:33 AM   #3
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I lose focus all the time

I shoot High School theater.

I understand when the lights change the camera might lose focus, but when I just follow an actor it happens too. Or zoom in or out.

I haven't figured out exactly when it does it and it doesn't happen all the time. It is very annoying. It seems to happen about 4-5 times per show

Thank goodness I have a fixed view second camera, so I can cut to that shot when it does happen.

Howard
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Old December 2nd, 2009, 04:50 PM   #4
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Losing Focus on the XH-A1

I don't know why it happens but I lose focus quite often after zooming in , focus, and zoom out again. I just don't trust this kind of focusing any more, with this camera. It never happens when I am using my DV500 or GYX2B cameras. That's the one thing I just don't like about this camera. I know it doesn't make sense but it happens to me all the time. So I just focus at the zoom level I wish to shoot at (critical focus?) and all is well.
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Old December 2nd, 2009, 10:28 PM   #5
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I've shot many hours with my A1 in everything from bright snowscapes to dimly lit race tracks and I've never seen this problem.

If the light is variable and you do not manually change the focus what may be happening is that the depth of field changes. It will narrow as light goes down and your iris opens. A trick I learned is to focus with as much ND filter as you can handle and open the iris up to more than 6. Focus with those settings and lock it in. Then, set ND filters, shutter speed and iris as appropriate. The depth of field will still widen and narrow, but it will do so in front of and behind the plane you focused on. This trick should help you set the plane where you want it.
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Old December 3rd, 2009, 01:10 AM   #6
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i'm a big fan of the slow zoom into someone's face as they talk about intense subjects, so if i do my focus at the wide end, it is unlikely to be crisp at the zoom end...
Tripp: i will give that technique a try. it seems that it would initially give you the shallowest depth of field for a more precise focus, and then you widen it with less ND and by closing the iris. is that right? (there should be a stupid rhyme to remember what the iris does to depth of field, ala 'righty tighty...'!)
also, i'm wondering why the iris would open by itself as light diminishes if in manual mode?
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Old December 3rd, 2009, 07:29 AM   #7
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The iris should not move on manual. You didn't mention that the camera was on full manual so I left open the possibility that the iris could be in an auto mode. It's something I do for both the locked off and moving cameras when shooting day-to-night motor racing.

This technique wasn't something anyone taught me. I sussed it out on my own for reasons I cannot remember anymore.

After thinking about your situation a bit more, there could be some gremlins causing the camera to shift focus on its own since the focus is adjusted by servo. You might give the camera a full reset by pressing the reset button. That might clear up any wonky code in memory. A faulty LANC controller could cause it as well. If your camera is still under warranty you might pursue this with Canon. This problem should not happen. If it was a widespread problem there would have been a large hue and cry from the user community.
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