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Sony VX2100 / PD170 / PDX10 Companion
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Old October 19th, 2004, 03:40 PM   #1
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Anyone have Sony adjust back focus?

I have a PD150 that I'm pretty sure isn't holding back focus. Has anyone attempted having Sony adjust theirs? If so, did they correct it? How much did they charge? How long did it take?

Thanks, Myron
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Old October 19th, 2004, 06:12 PM   #2
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Yes, Sony adjusted the back focus on my first 150. However, they were the ones that screwed it up during a warranty service.

I'd guess they will charge you the flat rate and you will get the camera cleaned, lubed and checked out.
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Old October 20th, 2004, 12:41 PM   #3
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I think I know wht back focus is, but I'm not sure. Could you define this for me and perhaps give me a procedure to see if my cameras have a problem?
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Old October 20th, 2004, 01:01 PM   #4
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The way one adjusts backfocus on a pro camera can be used to check it on any other camera.

The first thing you need is a fairly bold target. Most of the targets I've seen sort of look like a variation of the Japanese rising sun with rays eminating from the center of the circle and spreading outward. Make every other one black and leave the others white.

The set your camera up on a tripod and attach it to a large television. Focus as best you can with the lens zoomed in all the way. Now zoom all the way out and look at the image. It is smaller but should still be in focus. Repeat as necessary. Did I mention you should be in Manual Focus mode?

While you are at it, evaluate the focus as you zoom. If the image goes out of focus during the zoom (you can stop the zoom to look) then the lens is said to 'breathe' during the zoom.
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Old October 24th, 2004, 10:27 AM   #5
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<<<-- Originally posted by Mike Rehmus : While you are at it, evaluate the focus as you zoom. If the image goes out of focus during the zoom (you can stop the zoom to look) then the lens is said to 'breathe' during the zoom. -->>>

Mike, just to make sure I understand back focus correctly... ' lens breathing' say at mid zoom, is considered to be back focus? or not? I'm guessing the lens should stay in focus all through the zoom range.
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Old October 24th, 2004, 04:13 PM   #6
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Mike, if I may, I'd like to fine tune your response a bit.
In regards to the use of the back focus chart, when you zoom in full tight, you can easily see focus, as you rack focus back and forth. When you feel confident you have the lens as sharp as possible, begin zooming back and the center of the chart will begin to "shimmer", indicating you are still in max focus. When you reach the widest setting on the lens, you should still have the shimmer effect. If you lose the effect, or the picture seems soft to you, the lens is said to be out of back focus. You can reasonably duplicate the effect by focusing on something, like the bar code on a number two can. Or, a cyclone fence works well, or anything else with a fine pattern. Anything that creates a moire pattern works OK.

If the lens goes soft mid-way, but then sharpens up when it is full wide, it is said to have a "tracking" problem. Both back focus and tracking problems require factory adjustment with the cameras that don't have mechanical back focus adjustments, so a visit to the repair center would be in order. If a Canon lens with a mechanical back focus adjustment has a tracking problem, it will also need a factory correction.

A lens is said to "breathe" when there is a visible change in the object size as you change focus. It is as though you were zooming in or out a tiny bit, when in fact all you are doing is racking focus. Less expensive lenses are prone to this effect, which usually disqualifies them for use in motion pictures, or made for tv movies. Lenses that exhibit this effect usually are used on docs or eng.

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Old October 25th, 2004, 11:52 AM   #7
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Re: Anyone have Sony adjust back focus?

<<<-- Originally posted by Myron Iwankewich : I have a PD150 that I'm pretty sure isn't holding back focus. Has anyone attempted having Sony adjust theirs? If so, did they correct it? How much did they charge? How long did it take? -->>>

I have a back focus issue with my PD170. It is in the shop right now, and I do hope they can do something with it.
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Old October 25th, 2004, 01:15 PM   #8
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<<<-- Originally posted by Wayne Orr : Mike, if I may, I'd like to fine tune your response a bit.
-----------------
Glad to have it.
-------------------
A lens is said to "breathe" when there is a visible change in the object size as you change focus. It is as though you were zooming in or out a tiny bit, when in fact all you are doing is racking focus. Less expensive lenses are prone to this effect, which usually disqualifies them for use in motion pictures, or made for tv movies. Lenses that exhibit this effect usually are used on docs or eng.
----------------------

I think the 170 breaths a bit and the focus also shifts a bit throughout the zoom range. But at least it should be spot-on at the min and max. I don't know about the shimmer bit, Wayne. The 170 viewfinder doesn't have much of a peaking circuit and the analog out has none except for the normal camera setting.

I wonder if one could set the camera up for maximum sharpening
just to check the backfocus (you wouldn't normally want to do this for regular use). I'll have to try that one of these days.

---------------------------
Wayne Orr, SOC -->>>
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