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03-18-2008, 05:26 PM   #1
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Mamiya/Sekor M42 lenses

I've been looking for a vintage prime long distance lens for quite some time, so finally I bought a very mint Mamiya/Sekor 300mm 1:5.6 today.

This evening, I screwed the lens onto a genuine Pentax M42 adapter on my K10D.
After a few (great) shots (the lens quality is truely fabulous) I had some trouble getting the lens back off.

When it finally did come off, i noticed a tiny metal pin of about half a mm at the buttom of the lens, outside the screwmount (so it's not the apture pin).
Is this some kind of 'communication' contact or something else?

Does anybody have this same experience with Mamiya lenses or know what i can do about this little problem?






Last edited by frederik9111; 03-19-2008 at 01:21 PM.
03-18-2008, 06:28 PM   #2
Ole
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Could you post a picture of the mount? Could be that the pin found it's way into the AF shaft as the infameous Rikoh K-mount lenses do.
03-19-2008, 03:27 AM   #3
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Mistery pin

(I'll provide picture later today, I'm at my office now)

That could be it! Is this a fixable problem?
I'ld hate to send this lens to the back of my lens closet.

QuoteOriginally posted by Ole Quote
Could you post a picture of the mount? Could be that the pin found it's way into the AF shaft as the infameous Rikoh K-mount lenses do.
03-19-2008, 08:12 AM   #4
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Sorry to hear that.

I have had Mamiya DSX slr since 70:s because it was my first brand new camera. I have bougth some additional lenses (actually many) to it for nostalgic reasons. So the system is familiar to me.

Unfortunately as far as I know, you cannot use Mamiya SX lenses in Pentax K cameras.

I tried to modify one 50mm lens (I had two of them). I removed the aperture info pin and used Dremel to grind the corner flange away. It didnt help. Aperture ring contacts to K/42 adapter and it dont move when lens is attached. And you should anyway use glue or something to stuck the autoaperture pin into closed position....

03-19-2008, 08:19 AM   #5
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QuoteOriginally posted by frederik9111 Quote
I've been looking for a vintage prime long distance lens for quite some time, so finally I bought a very mint Mamiya/Sekor 300mm 1:5.6 today.

This evening, I screwed the lens onto a genuine Pentax M42 adapter on my K10D.
After a few (great) shots (the lens quality is truely fabulous) I had some trouble getting the lens back off.
QuoteOriginally posted by frederik9111 Quote
When it finally did come off, i noticed a tiny metal pin of about half a mm at the buttom of the lens, outside the screwmount (so it's not the apture pin).
Is this some kind of 'communication' contact or something else?
This pin is used to tell the body the aperture setting.

QuoteOriginally posted by frederik9111 Quote
Does anybody have this same experience with Mamiya lenses or know what i can do about this little problem?
Nothing, read my other post.

How it was possible to you to use the aperture ring? normally this pin and the flange in the outer rim of the aperture ring touch to the mount and stucks the aperture ring.... and the actual aperture does not work either, because it is operated by the aperture pin. SX lenses do not have auto/manual switch for aperture. And original K/M42-adapters do not have an flange for this pin to push it to closed position.
03-19-2008, 01:22 PM   #6
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Mamiya screwmounts

Pictures added!

I've drawn a red circle round the mistery pin. Does this ring a bell?

The seller guaranteed me that this lens should be perfectly compatible with a Pentax DSLR with adapter ring. So this wasn't correct?
Any other information about this lens is still welcome!


Thx! Frederik

Last edited by frederik9111; 03-19-2008 at 01:27 PM.
03-19-2008, 02:42 PM   #7
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QuoteOriginally posted by frederik9111 Quote
Pictures added!

I've drawn a red circle round the mistery pin. Does this ring a bell?
It is a pin which tells to the Mamiya DSX body which aperture is selected for open aperture exposure measurement. Very similar system as late Pentax m42 bodies had. Mamiya had also simlar lockking device as later bayonet mounts have. You can see the hole of this mechanisn in the opposite side of the mount than the pin is.

QuoteOriginally posted by frederik9111 Quote
The seller guaranteed me that this lens should be perfectly compatible with a Pentax DSLR with adapter ring. So this wasn't correct?
Any other information about this lens is still welcome!
No it wasnt.

Mamiya lenses and DSX / SX system:
Mamiya MSX and DSX 35mm Cameras
03-19-2008, 06:44 PM   #8
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You probably have to remove that pin in order to safely use the lens on your Pentax K mount camera.

03-23-2008, 02:42 PM   #9
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Mamiya screwmounts

Extra tips or info is still welcome!
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