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Correct Focus with HDV question


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#1 Janos Belik

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Posted 02 December 2008 - 12:29 PM

Hello folks,
I am having problem to achieve a good focus when I am shooting in motion (someone walking for example) Let's say that I am filming a hiker. He is hiking in front of me and I am following him, trying to maintain the same distance to maintain a focus. But I just can't achieve a good focus for entire shot. The focusing rule: zoom in, focus, zoom out to desired framing just doesn't work, even if I use fast shutter and wide angle lens. If I use auto focus, the result is even worse. (As camera and subject moves, camera is confused and shifting focus all over the place.)
Is there any trick, how to do this? The same problem is with filming birds in flight. Auto focus does not work, and I am not quick enough to keep focus with fast flying bird manually. But how do cinematographers do this? Is the secret only in their quickness? Or is there any other technique
Thank you so much,
Paul
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#2 Brian Drysdale

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Posted 02 December 2008 - 03:10 PM

Usually HDV cameras have so much depth of field that this shouldn't be a problem. It sounds like there may be a problem with the lens and perhaps the back focus may need to be set up.
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#3 Janos Belik

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Posted 02 December 2008 - 10:58 PM

Hi Brian,
thank you for your response. I am not sure what the problem is, but I have thought that back focus is usually an issue with film cameras, not video cameras.
Also, my camera was serviced by Canon lately, so I would assume that they have checked this. But anyway, I will check this possibility out.
Thanks again for your response.
Paul
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#4 Adrian Sierkowski

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Posted 03 December 2008 - 12:40 AM

Backfocus is a problem for any lensed system which is out of whack. IIRC it's something to be checked on the F900 through the day. . .so it's certainly in video . . .
It does sound as though your B/f might be out of whack. . .
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#5 alfredoparra

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Posted 03 December 2008 - 08:36 PM

could be the settings on the camera, I had kinda the same problem, do you have macro on your camera? I would reset it to the factory settings then try it again.
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#6 Mihai Bodea

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Posted 05 December 2008 - 05:48 AM

all Sony Hdv cameras have servo focus so you cannot track focus consistently (only by mistake). you should hire a focus puller.
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#7 Mike Washlesky

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Posted 05 December 2008 - 11:15 AM

Usually HDV cameras have so much depth of field that this shouldn't be a problem. It sounds like there may be a problem with the lens and perhaps the back focus may need to be set up.



Dont think there is back focus on HDV cameras. He mentions Canon serviced it, which leads me to believe its the H1, which I am pretty sure there isnt BF. And the Sony's have fixed lenses, so no BF right?
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#8 Mike Washlesky

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Posted 05 December 2008 - 11:15 AM

Usually HDV cameras have so much depth of field that this shouldn't be a problem. It sounds like there may be a problem with the lens and perhaps the back focus may need to be set up.



Dont think there is back focus on HDV cameras. He mentions Canon serviced it, which leads me to believe its the H1, which I am pretty sure there isnt BF. And the Sony's have fixed lenses, so no BF right?
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#9 grant mcphee

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Posted 05 December 2008 - 11:41 AM

These camera do have a back focus adjustment, only it's not accessible without opening them up. Connect it to a monitor, add lots of ND and open the lens up as wide as it goes, zoom into something which is easy to judge focus on (like a focus chart), focus until sharp then zoom out. If the chart looks soft at the wide end then you will have to send your camera in for a service. I had this problem with a Z1 before. If they get a whack it can sometimes knock the back-focus out and has to be sent to an engineer.
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#10 dan brockett

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Posted 05 December 2008 - 05:24 PM

I did want to add that the Canon XL-H1 does have a user adjustable back focus. I didn't even know it until another DP showed me. I hate that camera anyway. The back focus on the XL-H1, unlike a broadcast 2/3" camera, is hidden in the menu and the camera does something internally. Weird setup but at least it has it. Yes, the BF can totally be out on a fixed lens camera as well, I have encountered that a few times. It's usually when the fixed lens camera has been dropped or jarred.

Dan
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