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07-26-2013, 06:39 AM   #1
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SMC Tak 50 1.4 jams on Sony NEX 6. Please help.

Hi, all,

This is my first post on Pentax Forums. I'm a Minolta SLR/Sony DSLR/Sony NEX shooter. But I've taken to adapting legacy lenses on my NEX 6. Which leads me to my question.

I'm trying to use the Pentax M42 SMC 50 mm 1.4 (last version) on a Sony NEX 6, with either the Rainbow Imaging M42/NEX adapter or the Fotodiox one. My problem is that when zoomed to infinity (or near infinity), the lens' zooming action starts to bind up and the aperture ring gets really hard to turn, almost impossible. This happened first on the RI adapter, so I bought the Fotodiox one. But the problem persisted.

When unmounted, the zoom and aperture rings work fine. Easy to turn and no binding at all. Plus my other Pentax Tak lenses work perfectly (a 28 3.5, a 35 3.5 , and a 55 1.2) on either adapter.

So why is this happening? I'm assuming the rear element is bumping against something as I zoom out. But why does this affect the aperture ring, too. there something I can do about it short of returning the lens? Is there a different adapter to try?

Thanks, legacy Tak experts, for your guidance.

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07-26-2013, 06:58 AM   #2

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I'd say the rear elements bend something in the adapter, which in turn blocks the aperture ring, when you focus to infinity. Try mouting and using the lens on the adapter without the camera attached, maybe you'll see what's happening.
07-26-2013, 07:15 AM   #3
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With zooming you mean focusing, right?
07-26-2013, 07:23 AM   #4
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Mea culpa

Yes, of course. I meant "focusing," as this is a prime lens. Not enough coffee this morning!

Thank you.

07-26-2013, 07:25 AM   #5
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QuoteOriginally posted by Giklab Quote
I'd say the rear elements bend something in the adapter, which in turn blocks the aperture ring, when you focus to infinity. Try mouting and using the lens on the adapter without the camera attached, maybe you'll see what's happening.
OK, thanks, I'll try that.
07-26-2013, 08:10 AM   #6
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that;s really odd. I've never had a problem with any Taks on the NEX. An M42 adapter should be a very simple extension. Giklab's idea is right, try it with the adapter off camera. I'd be interested to hear the conclusion.
07-26-2013, 01:12 PM   #7
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It is because of the way the Tak 50/1.4 is constructed; a protruding rear. I've only experienced problems with the Nex adapters, but the lens works fine on Sony/Minolta SLRs and Pentax SLRs. Your best bet is to use the 50/1.4 on an SLR, or to get a Tak 55mm for your Nex...
07-26-2013, 03:34 PM   #8
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Same happened with me on my Sony Nex F3, with Sony M42 Adapter.

I also have a PK/Nex adapter. I put my original Pentax M42 adapter (for PK DSLR's) into the Sony PK and it worked fine....

Phil P

07-27-2013, 11:37 AM   #9
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Problem Solved

Hi, again.

After further research and posting on the Sony NEX Forum on DPReview, I discovered the cause of my problem. Apparently with this lens, the aperture ring lug (the small rectangular piece at the rear element) can bump against the adapter flange if the flange is too wide (which mine was). So as you focus to infinity, the lug hits the flange and freezes up the aperture ring. I'm told some adapters are designed to prevent this problem. But since I already had two M42 adapters in house, I opted for another solution: remove material from the flange at the location of conflict (about 2 o'clock). Filing took about 10 minuues and totally solved the issue. The lens works perfectly now. I just need to test its IQ to see if I like it.

Anyway, thanks all for helping out a Takumar newbie and first-time visitor to this forum. You are all very kind. Have a great weekend!
07-27-2013, 07:57 PM   #10
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QuoteOriginally posted by harrylew Quote
The lens works perfectly now.
The question now being...does the lens work perfectly on the cameras it was designed to work with (Spotmatic models with open aperture metering)? When time come to sell the lens, be sure to explicitly state that nature of your mod. Believe it or not, those cameras are relatively common and actively being used by film photographers including several users on this site. An upgrade to the f/1.4 lens only to discover that the lens has been "fixed" does not make for a good purchase experience. Ditto for collector purchases.


(...surgical fixes on vintage/rare/valuable Pentax lenses to accommodate mounting to other systems is not a popular action around these parts, though your modification is less likely to attract lightning bolts and flames than the common practice of "neutering" FA Limited and Pentax-K 50/1.2 lenses so that they don't interfere with the mirror on Canon FF dSLRs.)

Last edited by stevebrot; 07-27-2013 at 08:04 PM.
07-27-2013, 08:08 PM   #11
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I think he filed down the flange on the adapter, not the lug on the lens.

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