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02-26-2013, 09:16 AM   #1
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M42 Adapter - Lenses turning

Hello!

I just got my original Pentax M42 Adapter and put my Schneider Kreuznach 360mm on it.
When it's on the camera it is not sitting 100% tight. The Lens is turning a bit to the left or right, depending on how in which direction you are focusing.

Is that normal?
Thank you in advance

02-26-2013, 09:44 AM   #2
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With the Pentax adapter I put the adapter into the camera and then screw the lens into the adapter. This should seat the lens snugly against the camera mount. The Pentax adapter is just ever so slightly recessed in the mount so that when the lens tightens against the mount it pulls everything tight. If it is not tightening up like that check to see what it is stopping against.

Note that different lenses will end up in a different position and not always with the aperture scale facing up. Just turn until it is tight.

Does that help?
02-26-2013, 09:46 AM   #3
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I'm not familiar with that lens, but the only such problems I've had with the adapter were with lenses where the rear surface was narrow enough that it came tight against the adapter but not the K-mount flange. (Happens with some very early Takumar.) I notice the Pentax M42 adapter fits very slightly below the K-mount flange, so that the lenses normally tighten against the body flange. If the back of the lens fits within the body flange it will feel loose. (I wouldn't think a 360mm would!)
02-26-2013, 11:38 AM   #4
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Thanks for your replys.

I checked now again and it seems to be the adapter itself that is sitting loose.
I turn it until it locks, but even locked it goes a bit to the left and right.
It's the adapter itself that is not sitting tight.

02-26-2013, 11:45 AM   #5
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QuoteOriginally posted by Szenario Quote
Thanks for your replys.

I checked now again and it seems to be the adapter itself that is sitting loose.
I turn it until it locks, but even locked it goes a bit to the left and right.
It's the adapter itself that is not sitting tight.
The original adapter should be a bit loose what you put it into the mount but lock when you put a lens in it. I've read about some Russian lenses being too small of diameter in the mount so it never gets really tight and maybe it's the same with your lens?
02-26-2013, 11:52 AM   #6
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QuoteOriginally posted by VisualDarkness Quote
The original adapter should be a bit loose what you put it into the mount but lock when you put a lens in it. I've read about some Russian lenses being too small of diameter in the mount so it never gets really tight and maybe it's the same with your lens?
I don't know. But I have some trouble putting the adapter inside the mount. I have to fight a bit until it will sink in. Unfortunately I don't have another M42 lens to test. I guess there is now solution to this.
I can move the adapter itself with my fingers when putting inside and locked and it's exact the same range of movement when the lens is on.
02-26-2013, 11:56 AM   #7
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QuoteOriginally posted by VisualDarkness Quote
The original adapter should be a bit loose what you put it into the mount but lock when you put a lens in it. I've read about some Russian lenses being too small of diameter in the mount so it never gets really tight and maybe it's the same with your lens?
Yes, that's right -- the genuine adapters are designed to be slightly loose. On lenses where the mount tapers in too much so there is no "base" to the lens on the outer mount, it will be wobbly. My Meyer-Optik 135 & 200 are like this -- I rig them up with a generic adapter (spring removed) and a big rubber washer put on at an angle to give them some friction when mounted. If you use the non-infinity adapters with the flange on the outer mount it will be much more solid, but you will lose infinity focus...
03-02-2013, 02:01 AM   #8
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Mount adapter to lens and then lens to the camera. That will take care of the fiddly business of putting the adapter into the mount opening. As for looseness, the above comments are correct. The Pentax-brand adapter should be slightly loose with a few degrees of play when mounted alone to the camera. This is by design. When a lens is mounted the back flange of the lens should engage the surface of the body's mount flange to provide proper registration to the sensor plane. It should also "snug up" the adapter onto its bayonet "ears".

As mentioned above, there are a number of vintage and FSU (former Soviet Union) lenses that have an unusually narrow back flange. The result is that the lens wobbles somewhat. vonBaloney's solution is one of the best I have read though care should be taken to make sure that there is no stand-off between the lens back and the K-mount flange on the camera.


Steve

(...lucky to be relatively wobble free with my adapted lenses...)

03-02-2013, 11:07 AM - 1 Like   #9
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QuoteOriginally posted by stevebrot Quote
Mount adapter to lens and then lens to the camera. That will take care of the fiddly business of putting the adapter into the mount opening. As for looseness, the above comments are correct. The Pentax-brand adapter should be slightly loose with a few degrees of play when mounted alone to the camera. This is by design. When a lens is mounted the back flange of the lens should engage the surface of the body's mount flange to provide proper registration to the sensor plane. It should also "snug up" the adapter onto its bayonet "ears".

As mentioned above, there are a number of vintage and FSU (former Soviet Union) lenses that have an unusually narrow back flange. The result is that the lens wobbles somewhat. vonBaloney's solution is one of the best I have read though care should be taken to make sure that there is no stand-off between the lens back and the K-mount flange on the camera.


Steve

(...lucky to be relatively wobble free with my adapted lenses...)
While my solution "works" in that in provides good friction (but no lock since I've removed the spring from the generic adapter), I'm not totally sold on the wisdom of it because basically what you end up with is a rubber washer sliding across all your electrical contacts and other mount parts, possibly rubbing off tiny bits of the washer into your contacts. So, at your own risk an all that. Also, once the washer has been on there a while and stretches out (it is basically too small at first and you force it up and hold it on with the adapter), you can't adjust it all and must be careful not to flip it backwards off the mount (or it will just fall off) -- you'll never get back your good fit and friction once it is all stretched out. A fancier version of what I've done would glue something on there permanently, but with my version if something goes wrong I can rip it off in seconds and I'm back to plain m42. If you don't mind losing infinity, the non-infinity adapters are a much easier solution to gain a solid mount.

Here is a picture of what my Meyer/Pentacons look like with the washer mount, along with a washer I haven't used yet. (Good to have a spare.) You see how the washer rests at an angle on the tapered part of the lens with inner edge down to provide the extra friction. You know I also just remembered that with these tapered mounts if you don't have the washer there, there is actually a light leak from where the spring was in the m42 adapter. So you need it for that too.
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