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Sony XDCAM EX Pro Handhelds
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Old March 11th, 2008, 02:28 PM   #1
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infinity mark is off

I've notice that my EX lens (when I have it slipped into manual mode) seems to roll right through the real infinity focus point well before I reach the end of the focus barrel travel or even the infinity mark on the barrel.

Anyone else have the same experience? Is it normal. It would be a big problem except the color peaking is so good i can clearly see where I need to be.
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Old March 11th, 2008, 02:33 PM   #2
 
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It's normal. The mechanical stop goes beyond infinity to allow for temperature changes in the environment...the focus shifts when the temperature changes.
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Old March 11th, 2008, 02:35 PM   #3
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Sounds like a backfocus issue.

Though I don't have too much faith in those lens markings - they seem like an approximation to me. Otherwise they'd be more committal and have withness marks like a Panavision lens rather than nebulous numerals.
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Old March 11th, 2008, 03:13 PM   #4
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Bill is correct. All true pro lenses go through infinity to allow for temperature changes and the use of adapter lenses. It is not a fault.
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Old March 11th, 2008, 03:26 PM   #5
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Thanks, that's what was wondering.
I'm used to it a teeny bit but this seems more noticeable though. No back focus problem though as far as i have seen.
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Old March 11th, 2008, 04:37 PM   #6
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Quote:
Originally Posted by Leonard Levy View Post
... seems to roll right through the real infinity focus point well before I reach the end of the focus barrel travel or even the infinity mark on the barrel...

Leonard,

Bill and Alister are correct that all pro lenses, including still camera lenses go a bit past infinity to allow for any slight mechanical variations - however the problem you descibe is that the lens is focused at infinity before reaching the mark - not that the lens can go past the mark.

So that's why I think it's a (slight) backfocus issue.
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Old March 15th, 2008, 02:17 PM   #7
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Well I've discovered what my problem is . My backfocus and my infinity mark are exactly where I would expect with no filter in plsce. As soon as I roll in an ND filter my back focus completely goes to hell and my infinity focus rolls in around 30'. Very very bad news. I don't think the back focus adjustment would fix it because its OK without filter.

. Didn't notice the back focus problem till I looked on a big monitor.

Beware out there. It goes back to Sony on monday. Perhaps there is a software fix for this.

Also I've discovered lots of CA when I am fully zoomed in. very distressing.

Lenny
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Old March 15th, 2008, 04:32 PM   #8
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Perhaps somebody could try doing the backfocus calibration procedure for each of the ND filter settings. It's possible the camera stores a different set of values for each position of the ND filter wheel.

I'd try this myself but I suspect I don't have enough light to light up a back focus chart with the NDs engaged.
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Old March 15th, 2008, 05:29 PM   #9
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Bob,

You could use the back focus chart outdoors. Its pretty sunny today!
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Old March 15th, 2008, 05:48 PM   #10
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Both of my EX1s are going back to UK with backfocus and slight vignetting problems.
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