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10-17-2011, 01:55 PM   #1
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Zoom lens won't focus to infinity - ideas?

Hey there lens repair folks...

I recently scored a 28-200mm Sakar zoom which seems to be a pretty nice lens aside from the fact that it won't focus to infinity when zoomed out to the long end. (from about 70-200mm.)

It seems I've heard on some lenses you can roll back the rubber grip on the focusing ring, loosen three screws around the barrel, and move the focusing ring a bit more toward the infinity end & re-tighten the screws to adjust the infinity "stop" point.

Any of you lens repair types know if this is true?

Thanks,
Bobbo :-)

10-17-2011, 02:47 PM   #2
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Many of the Takumar lenses that I have permit adjustment of the infinity focus by loosening three tiny screws and moving the infinity scale ring. Getting it right is trial and error and very tedious.

I've never seen a Sakar lens so not sure if the same is true there or not, but it is possible.
10-17-2011, 03:03 PM   #3
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So what's the best way to loosen the rubber grip?
10-17-2011, 07:02 PM   #4
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Something thin and long. I have a common screwdriver with a long blade that I slip under the top or bottom, push under the rest, then roll around the whole lens so it breaks the glue bond. Then I use the screwdriver to lift one edge and start sliding the grip off, again rolling around the lens.

But first, check the front element. Some Pentax zooms have the front group of lenses in a threaded carrier that screws into the front tube of the lens. On these, you can adjust infinity by screwing this carrier in or out. It's supposed to be locked in place, possibly with threadlock or a locking ring with spanner slots. If it becomes unlocked and is loose, over time it can shift and infinity focus is lost.

10-17-2011, 07:12 PM   #5
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Thanks for the info, guys! Something to try, anyway.

Bobbo :-)
10-22-2011, 07:56 AM   #6
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Same Issue with Pentax-f 70-210

Any thoughts on where the screws are located on this lens to correct the infinity issue? Thanks for any help you can provide.
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