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11-19-2010, 06:52 PM   #1
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Lens repair - M 50mm f/1.4

I've got this lens, and the optics are in pristine condition. Sadly, the focus ring is stiff and won't focus correctly at infinity. I believe the focus ring got misaligned relative to the focus indicator, and won't go past infinity. For 10 meters and under it focuses fine, all the way down to 0.45 meters.

Anyone with experience disassembling this or a similar lens (M 50mm, A 50mm)? Any idea on how hard is it to disassembly and realign this one?

I'll attempt this tomorrow and would appreciate pointers. Thanks.

11-19-2010, 07:10 PM   #2
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1) Unscrew the front retaining ring with a piece of rubber.
2) Remove 3 tiny screws and the filter mount.
3) Loose 3 tiny screws inside slightly, readjust the focus ring then tight them again. Threadlock all screws afterward.
11-19-2010, 07:21 PM   #3
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Original Poster
QuoteOriginally posted by wlachan Quote
1) Unscrew the front retaining ring with a piece of rubber.
2) Remove 3 tiny screws and the filter mount.
3) Loose 3 tiny screws inside slightly, readjust the focus ring then tight them again. Threadlock all screws afterward.
Thanks.

At 1), do you mean the ring that contains the model name and serial number? I'll have to improvise some tool to unscrew that. What do you use?
11-19-2010, 07:33 PM   #4
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That's the ring. Just wear a rubber glove and turn it anti-clockwise will do.

11-19-2010, 08:22 PM   #5
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QuoteOriginally posted by wlachan Quote
That's the ring. Just wear a rubber glove and turn it anti-clockwise will do.
Either you have stronger fingers, or this ring is very tight

The ring is too thin, I can barely get friction enough to unscrew it. I'll have to come up with something else, like a rubber cup to push against and turn with the palm of the hand.
11-19-2010, 10:25 PM   #6
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That will do as well if the cup is strong enough. Something like this is the appropriate tool if all else failed.

49mm 49 Lens Repair Tool / Filter Wrench Scratch Free! on eBay.ca (item 370250594192 end time 18-Dec-10 20:58:49 EST)
11-19-2010, 11:30 PM   #7
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I've heard of folks using:
1. An eraser
2. A chair foot rubber thingy (what's this called?)
3. Rubber drain stop

Just about anything rubber that'll fit in there would probably work.
Make sure the filter threads are clean and undamaged. It'll be really difficult to get the ring out if they're dirt or dented.
11-19-2010, 11:42 PM   #8
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QuoteOriginally posted by Kryosphinx Quote
I've heard of folks using:
1. An eraser
2. A chair foot rubber thingy (what's this called?)
3. Rubber drain stop

Just about anything rubber that'll fit in there would probably work.
Make sure the filter threads are clean and undamaged. It'll be really difficult to get the ring out if they're dirt or dented.

A crutch tip is what I used. $3 at Walmart for a pair.
Lofstrand Crutch Tips (ADULT CRUTCHES) 7/8 - Canes Galore - Custom

11-20-2010, 01:45 AM   #9
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QuoteOriginally posted by hcarvalhoalves Quote
I'll have to improvise some tool to unscrew that. What do you use?
Best cheap tool: duc tape roll; use one with the right size and it should work quite well.

Last edited by Manel Brand; 01-08-2011 at 05:11 AM.
12-10-2010, 12:12 AM   #10
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Thank you!!!!

This article just saved my (50mm 1.4) life!!!

The filter ring has been loose on my lens as long as I've owned it (about 6 years). I never thought much of it as I only paid $20 for it and it's not in the greatest shape. Recently it's become my most used lens and my favorite look. Tonight I picked up the camera and heard something rattle...there was a tiny screw in between the front lens element and the filter!

Panicked, I thought the worst. "It'll cost a fortune to fix!" "Might as well start looking for a new one :-(" Then I googled, found this article, followed the instructions and now my lens is in MUCH better shape. All three of the little screws holding on the filter ring were loose but are now in nice and tight.

Thank you PentaxForums!
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