Setting infinity focus at

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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 August 9th, 2007, 02:59 PM   #1
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Join Date: Mar 2007
Location: Fort Collins, CO
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Setting infinity focus

I was just shooting footage from a chopper at Sturgis. :-)
I ran into an issue and was wondering if anyone had a better answer.

I needed to lock the focus at infinity. On my Sony VX2100 this was simple - switch to manual focus, press the "focus at infinity" button. On the A1 I set the focus to manual then used the ring to focus at infinity. First question -

If you turn the focus ring to max distance you get a display that shows "-infinity". If you move it back just a bit the "-" symbol goes away. I discovered that the camera needs to be at "infinity" and not "-infinity" to get proper infinity focus. So . . . anyone know what "-infinity" is?

What I've decided to do is create a preset focus at infinity. Then I can use that in the same way I used the "focus at infinity" button on my VX2100.

Thoughts? Suggestions?
-- Larry Chapman
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Old August 9th, 2007, 07:40 PM   #2
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Hi Larry...........

Sounds like sheer genius to me. I've puzzled over that "- infinity" thing myself on a number of occasions. It did occur to me (briefly) that it might be something to do with infra red filters and focus points, HOWEVER as the A1 can't "see" IR (unlike the HV20) that theory got shot down in flames.

The preset idea is a corker. Can't think of a more elegant solution.

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Old August 10th, 2007, 08:43 AM   #3
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Page 37 of the NTSC manual has a note:
o Use the distance display as an estimate
The infinity symbol = Infinity focus
The infinity-minus symbol = over infinity focus.

Apparently the lens focusing element can move past what would be the infinity distance stop were there such a stop in a this servo controlled lens. So if you see the "-" symbol you have moved the focus past the infinity position.
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Old August 10th, 2007, 10:06 AM   #4
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So Canon has managed to do what even Captain Kirk never could do, go where no man has gone before, all the way to, and past, infinity.
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Old August 12th, 2007, 04:26 AM   #5
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Just zoom in all the way and focus on an infinity point, use the Peaking and maginify zoom feature on the camera to double check. Then zoom out and hey presto your shot will be in focus.

Well that's the theory anyway - :-o

From my own experience with still cameras and other video gear, not many lenses hold the focus when zooming out.
Vincent Oliver is offline   Reply

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