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08-25-2015, 05:19 AM - 3 Likes   #1
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Preventing M42 adapter light leaks and dust ingress - an easy solution!

I posted a thread a couple of days ago regarding the problem of light leaks and dust ingress with M42 adapters when using lenses where the barrel is narrow at the mount (an example being the MIR-1 37mm lens I recently bought). The problem is that when using the official or third party flush M42 adapters with such lenses, the two cut-outs provided to allow easy mounting / dis-mounting of the adapter remain uncovered, allowing light and dust to enter the camera.

I've found a cheap and easy solution to this problem, which I hope others may find helpful:

I bought a rubber o-ring which has an internal diameter of 38mm and thickness of 4mm. At 38mm, it's around 5mm less than the diameter of the lens barrel. When stretched slightly, the o-ring can be rolled onto the back of the lens. After mounting the lens onto the camera, the ring can be pushed or rolled back slightly so that it sits snugly against the camera's lens mount - covering the visible areas of the M42 adapter (and, importantly, those cut-outs!) completely. The o-ring is a neat fit (which is good), so it may be necessary to go for a slightly different diameter depending on the lens, but I believe the 38mm size should stretch to fit most narrow barrel lenses. With my MIR-1, the o-ring does partially cover some of the lens barrel markings, but it's a small price to pay if I can use the lens. Obviously this won't be a weather-sealed solution, and I'd hesitate to use it in very damp or dusty environments, but I'd be quite confident to use it outdoors in reasonable conditions. Note that the electronic contacts and screw drive on the mount will remain uncovered, so you really don't want to rely on this in inclement weather!

You can find these o-rings online (I used eBay, but I'm sure they're a commonly available item).

They say a picture is worth a thousand words, so here are a few to explain what I mean:

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08-25-2015, 06:06 AM   #2
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Yeah, I use a big rubber washer on some lenses for the same reason (also provides more friction because I use it with a spring-removed adapter that says on the lens and only has a friction fit on the body). Doesn't look like you'd have room for a washer on the Mir though -- I'll have to remember the O-ring alternative. See this thread also:

https://www.pentaxforums.com/forums/58-troubleshooting-beginner-help/216718-m...s-turning.html
08-25-2015, 06:56 AM   #3
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Great idea but how do you see the aperture scale ?
08-25-2015, 08:06 AM   #4
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QuoteOriginally posted by vonBaloney Quote
Yeah, I use a big rubber washer on some lenses for the same reason (also provides more friction because I use it with a spring-removed adapter that says on the lens and only has a friction fit on the body). Doesn't look like you'd have room for a washer on the Mir though -- I'll have to remember the O-ring alternative. See this thread also:

https://www.pentaxforums.com/forums/58-troubleshooting-beginner-help/216718-m...s-turning.html
Good idea with the washer. I had thought of using some sort of wide rubber band, but if you can find a rubber washer that fits, that's ideal. And yes, I also use a spring-removed adapter! Can't be too careful

---------- Post added 08-25-2015 at 04:12 PM ----------

QuoteOriginally posted by hjoseph7 Quote
Great idea but how do you see the aperture scale ?
On the MIR-1, the aperture ring is at the front of the lens, so that's completely visible. The hyper-focal distance scale is at the back and that *is* partially obscured, but you can see enough of the markings to make out what they are. It's not perfect, but only a very minor inconvenience. See picture below. On lenses with the aperture ring at the back, the o-ring would sit behind it - I'm struggling to think of a lens where the aperture ring is flush against the mount.

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Last edited by BigMackCam; 08-25-2015 at 08:17 AM.
08-25-2015, 08:20 AM   #5
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I use my fingers to block the light. Sometimes I want to provoke the leak for artistic effect.
08-25-2015, 08:22 AM   #6
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Nice solution! I might try something like that for the Helios 44-2 and Industar 50mm
08-25-2015, 08:27 AM   #7
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QuoteOriginally posted by luftfluss Quote
I use my fingers to block the light. Sometimes I want to provoke the leak for artistic effect.
Yes, that'd work too, of course, but when carrying the camera around there's the problem of dust getting inside the camera, which is something I wanted to guard against.

I wish I had the skills to use light leaks in a way that results in artistic shots!
08-25-2015, 08:28 AM   #8
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QuoteOriginally posted by BigMackCam Quote
I'm struggling to think of a lens where the aperture ring is flush against the mount.
Very unlikely to find a lens with the aperture ring in the rear that also has light leaks -- they all have much more material around the base. It is always preset (or front aperture anyway) lenses with this problem...

08-25-2015, 09:02 AM   #9
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QuoteOriginally posted by BigMackCam Quote
Yes, that'd work too, of course, but when carrying the camera around there's the problem of dust getting inside the camera, which is something I wanted to guard against.
Fortunately for me, the couple of lenses I use which have the issue you describe are not "everyday" lenses for me. If they were, I'd probably use your O-ring solution.

QuoteQuote:
I wish I had the skills to use light leaks in a way that results in artistic shots!
Perhaps I should have used the word quirky, rather than artistic...

Helios 44-2


This is not the most severe example of the light leak - sometimes I get a large bright blob.
08-25-2015, 09:11 AM   #10
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I'll be trying this with my helios 44. Found this supplier on ebay: (item) 201405621884 but I'll ask at the local engineering shop first..
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08-25-2015, 09:14 AM   #11
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QuoteOriginally posted by luftfluss Quote
Fortunately for me, the couple of lenses I use which have the issue you describe are not "everyday" lenses for me. If they were, I'd probably use your O-ring solution.

Perhaps I should have used the word quirky, rather than artistic...
Nice - that *definitely* rates as artistic to me - what a lovely effect

---------- Post added 08-25-2015 at 05:20 PM ----------

QuoteOriginally posted by marcusBMG Quote
I'll be trying this with my helios 44. Found this supplier on ebay: (item) 201405621884 but I'll ask at the local engineering shop first..
Yes, those rings look just the ticket. In fact, I may order a bigger ring for the base of my Jupiter 21M. There's just enough play in the M42 adapter that it occasionally lets in light on the rare occasions that we get any sun!!

I'd be interested to know how you get on with the Helios 44...
08-25-2015, 03:57 PM - 1 Like   #12
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try using a square cut O-ring. Being square cut, it will set flat against your camera mount.
Many automotive stores and pretty much all bearing supply houses can make up whatever diameter You need.
08-25-2015, 04:23 PM   #13
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QuoteOriginally posted by promacjoe Quote
try using a square cut O-ring. Being square cut, it will set flat against your camera mount.
Many automotive stores and pretty much all bearing supply houses can make up whatever diameter You need.
That's an interesting idea.

One of the reasons I went for a 4mm wide o-ring was to ensure coverage of the cut-outs by the part of the o-ring that touches the adapter. The advantages are that it's off-the-shelf, very inexpensive and one stretchable ring can be used on various lenses - but your idea might work better where individual rings are cut for each lens. Thanks for the feedback!
08-25-2015, 06:21 PM   #14
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QuoteOriginally posted by luftfluss Quote
I use my fingers to block the light. Sometimes I want to provoke the leak for artistic effect.
Also good to get ghost lamps in your pictures

08-26-2015, 10:35 AM   #15
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black stretchy hairbands work really well for this purpose, you can get 'em anywhere and they are dirt cheap.
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