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08-29-2011, 11:54 AM   #1
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Damaged Filter Ring ON F50/1.7

I just picked up a Pentax-F 50mm 1.7 for $40. It has a dent on the filter ring. i wonder any one here know whether the ring can be replaced.

08-29-2011, 12:11 PM   #2
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I may be totally wrong here (and I'll likely be quickly corrected) but judging from my similar lenses, I'll guess that replacement is not really feasible. What I've done to finesse such situations is 1) use a hammer and wooden dowel to tap out the dent as much as possible, with a little assistance from pliers as needed, and 2) remove the glass from a UV filter and jam that onto the lens thread. Then at least I have a good thread for hoods, filters, whatever.
08-29-2011, 12:25 PM   #3
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I Thought the F50 f1.7 was a Plastic bodied lens (like the FA50). How does it have a Dented filter ring? I would expect it to be Cracked rather than dented.

08-29-2011, 04:56 PM   #4
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The filter ring is made of soft plastics, that's why it can be easily dented. It was mounted on a chunky film body SF1. The ring can be easily removed by removing 3 screws. There are 2 methods to repair it: 1. custom maching a new ring using aluminum alloy; 2. grind away the threaded part of the ring. Remove glass from a 49mm filter, remove the bottom thread and glue this metal ring on the plastic ring. The latter is easy for any one to do. I'll look into the first one and ask machine shop to make several metal rings. I am sure there is demand for it.

08-29-2011, 08:14 PM   #5
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RioRico's approach works nicely in my experience; un-dent the existing ring and screw in a glassless uv filter or step-up ring.

If the existing ring can easily be removed you might take it off and soften the dented region in boiling water before reshaping.

Once the existing ring is backed up by a metal ring it won't be so susceptible to future damage.
08-29-2011, 08:17 PM   #6
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QuoteOriginally posted by violini Quote
I just picked up a Pentax-F 50mm 1.7 for $40. It has a dent on the filter ring. i wonder any one here know whether the ring can be replaced.
Great buy! The fix will be easy & you saved quite a bit on a good lens!
08-30-2011, 07:20 AM   #7
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This particular lens (f50/1.7) has a plastic filter thread, so repairing the dent may end up breaking it more.
However, the good news is that it is easy to remove. First, set the focus to the closest point (0.5m or so).
Look at the large plastic element which contains the filter threads right beside the focus ring. You will see three screws.

The large plastic element comes out once you remove the three screws.

You can now try to repair/glue the dent without any danger to the glass, and mount either a UV or a hollowed out 49mm filter ring to enforce it once you fix it. You can also transplant that part from a donor lens or order it from Pentax if they still stock it.

As a drastic alternative, you can shave the filter threads with sandpaper (200,400,600,1200) until it is gone and sanded to a smooth finish. This way will guarantee you will not have another broken filter ring on this lens ever again

Keep in mind that you will need an alternate lens cap if you choose the above surgery.

QuoteOriginally posted by violini Quote
I just picked up a Pentax-F 50mm 1.7 for $40. It has a dent on the filter ring. i wonder any one here know whether the ring can be replaced.
08-30-2011, 07:38 PM   #8
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Dented filter ring repairs/tools

Discussions on the Manual Focus forum too.

General instructions

H2

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