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So, today I dropped my ME Super. When I picked it up I realized that the focus ring of the 50mm f2 lens attached didnt turn. My question is, what could cause this? Could it be that the threads inside the lens which move the glass about are binding?

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    \$\begingroup\$ I hear that can happen if you drop the lens. \$\endgroup\$
    – dpollitt
    Commented Jan 25, 2012 at 21:37
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    \$\begingroup\$ @dpollitt, let's not be too hasty. xkcd.com/552 \$\endgroup\$
    – coneslayer
    Commented Jan 25, 2012 at 21:44
  • \$\begingroup\$ After taking the lens apart I confirmed my theory; the threads were binding. I managed to fix the lens and it works great. \$\endgroup\$ Commented Jan 26, 2012 at 3:21
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    \$\begingroup\$ @MattGiesbrecht: Awesome! Any chance you could make that an answer to your own question and mark it accepted? It might also be helpful to others in the future who have the same problem to know more about exactly how you fixed it...maybe some step-by-step instructions? \$\endgroup\$
    – jrista
    Commented Jan 26, 2012 at 3:59
  • \$\begingroup\$ The inside of the lens may have threads, gears, cams and all sorts of sliding bits. The gears and threads can get broken or jammed, the sliding bits, if dented may not smoothly slide over each other any more. Hope that's not too technical \$\endgroup\$
    – MikeW
    Commented Jan 26, 2012 at 6:10

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My problem was that the threads that move the elements were jammed. I was lucky as in this lens, a Pentax SMC-M 50mm f2, all of the glass was contained in a unit and a thread moved it back and forth or obtain focus. These threads had slipped and basically they were cross threaded. I would never try this on an autofocus lens or a zoom lens. That would be WAY to complicated. Even with a prime lens it took a lot of adjustment to get the distance scale correct and I couldn't even begin to imagine what a nightmare it would be on a zoom lens. Sorry jrista, a step by step would look like this: Disassemble Repair Reassemble Check focus Disassemble Adjust Reassemble And repeat......

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