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04-25-2015, 05:58 PM   #1
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Calibrating lens beyond fine tune?

Hello, my lens SMC Pentax-DA L 50-200mm F4-5.6 ED WR fell on the sand from an eight of 40cm, but that was enough to get the zoom ring stuck in between 100-200mm. But the main problem is that the lens can't focus. The mechanism is working correctly in AF, in the sense that it can spin back and forth without any obstruction, but it find no focus point. And actually even with manual focus I can't get to see sharp edges, the best I can do is to put the focus to infinite, but the image still looks blurry in any position of the zoom ring.
This might mean that the optical elements moved somehow? Or what else?
Apart prom trying to fine tune the lens, (that most probably is not going to help) is there a more drastic, non electronic way to calibrate it DIY?
I've tried to disassemble the lens already, more on this post, to fix the zoom ring and focus, but I couldn't spot any obvious problem, broken part, loose screw or whatever.
Any suggestion to recover the focus at least on the range 100-200mm?
Consider that I'm in Indonesia at the moment with no reliable service center, and to ship it abroad it's no option, it would cost much more than a working second hand lens.
Thank you, Davide

04-25-2015, 06:06 PM   #2
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QuoteOriginally posted by phidias81 Quote
Apart prom trying to fine tune the lens, (that most probably is not going to help) is there a more drastic, non electronic way to calibrate it DIY?
Unfortunately no. As you say fine tuning is not going to help, something is broken or misaligned inside. It needs factory service and adjustment. Not something you can do in the field. Any shops with a used lens? Maybe you can get them to take yours in trade as part payment on a different one.
04-25-2015, 08:08 PM   #3
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Only the Sigma Global Vision--Art, Contemporary, and Sports lines, although the last of these has no models available in Pentax mount--lenses have their own software for calibration and fine tuning.

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