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08-22-2015, 09:26 AM   #1
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MIR-1 + M42 adapter - preventing dust ingress / light leaks?

So I just acquired a really nice "Grand Prix Brussels" MIR-1. I'm really pleased with it - the condition is even better than expected - yet it's caused me to re-visit an unresolved issue. When attached to the camera using my usual flush-fitting M42 adapter, the rear of the lens doesn't cover the adapter removal cut-outs, allowing dust and light to enter the camera. As I tend to switch lenses frequently, it's not too practical for me to use electrician's tape to cover the cut-outs, so I'm wondering if anyone has come up with an elegant solution for this? I'm considering buying some rubber o-rings (similar to the one below) to fit around the neck of the lens and roll back against the mount - what do you think?

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08-22-2015, 11:06 AM   #2
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I'm thinking the o-ring will be the best bet; I have this problem with my Helios 44 and, If I recall, my TAIR-3 to a lesser extent.

Side note, that looks like an amazingly clean copy. Holy shoot.
08-22-2015, 11:45 AM   #3
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I have the same thing with my helios 44 (original silver 13 blade version). O ring sounds good - where do you get one?
08-22-2015, 11:55 AM   #4
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QuoteOriginally posted by marcusBMG Quote
I have the same thing with my helios 44 (original silver 13 blade version). O ring sounds good - where do you get one?
I'm just looking on eBay UK right now... will post what I find here shortly

---------- Post added 08-22-2015 at 08:02 PM ----------

Right, got it!

I'm not sure if it's OK to post links here, so... in ebay uk, search for "38mm x 4mm rubber o-ring"...

My thinking is, a ring with 38mm inside diameter should stretch and would be a good, neat fit around the neck of the lens, and at 4mm thick it should easily cover the cut-outs... Looks like there are plenty of other diameter / thickness options available from other sellers.

08-22-2015, 12:04 PM   #5
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Could you slip something like this on the lens before screwing it onto the adapter?

2pcs Black Rubber Grommet Hole Plug Electrical Cable Wire Gasket 30mmx42mm | eBay
08-22-2015, 12:07 PM   #6
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You could cut a flange from an aluminum beverage can. Since the OEM adapter sits recessed in the bayonet mount it shouldn't throw off infinity focus.

eBay is the best place get small quantities of O-rings in just about any size. You might be able to find some place local that sells on the Internet and you can just buy a small quantity over the counter. They usually have minimum quantities if you order through the web.
08-22-2015, 12:09 PM   #7
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QuoteOriginally posted by UncleVanya Quote
Could you slip something like this on the lens before screwing it onto the adapter?

2pcs Black Rubber Grommet Hole Plug Electrical Cable Wire Gasket 30mmx42mm | eBay
Possibly, though that looks pretty thick! My idea with the o-ring is the same - roll it onto the back of the lens, fit the lens into the adapter then roll the o-ring into place against the mount...

---------- Post added 08-22-2015 at 09:05 PM ----------

Well, I've ordered a 38mm internal diameter x 4mm thick o-ring. Should arrive Tuesday, so I'll give it a try and post the results here
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