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10-06-2013, 12:40 PM   #1
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Pentax K20D & Sigma Mini-wide II 28mm 1:2.8

Hello, my name is pedro and I am new to this forum. I need some help please. I might be doing something wrong and I cant figure out what it is. I recently bought a sigma mini-wide II 28mm 1:2.8 for my K20D. When I try to mount the lens onto the camera, it gets stuck halfway when rotating it on. It takes a little bit of force to remove. I tried it twice only....the second time was to make sure that maybe I didnt seat it all the way down the first time. Am I doing something wrong? Has anyone else had this problem or something similar?? HELP!!! thank you and I really appreciate any feedback any forum member can provide me.

10-06-2013, 01:09 PM   #2
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This Sigma lens appears to be old enough to have had a C/Y (Contax/Yashica) mount option. Apparently there were a number of these made in the C/Y mount - here. The C/Y mount is very close to the K mount. Zeiss helped Pentax back in 1974/5 design and develop the K mount. The partnership broke up for whatever reason and Zeiss next went to Yashica looking for a Japanese manufacturing partner for their Contax cameras where they developed the C/Y mount (hence the name). The C/Y mount is essentially the K mount with the flanges a tad thicker, so that it's not physically compatible with the K mount. Its close but no cigar. I am thinking that the flanges are a bit thicker, and hence the lens is getting stuck half way when mounting the lens.

I really do not know of any specific way to tell the difference between the two mounts - other than comparing the thickness of the flanges on the mount. There are no stampings that I know of for C/Y mounts - Pentax mounts from third party may have PK stamped on the mounting flange. I have only had to deal with the C/Y mount when it was on a Contax lens. Due to essentially having the same registration distance, there really is no adapter that can be used.Yachica lens with the C/Y mount so as to fit on to a Pentax body.

The forum had a member - Rio Rico who was famous for using his Dremmel Tool to shave the thickness of old C/Y mount lenses down, so as to fit on Pentax bodies. Note - You would NEVER want to do this to a Contax lens since it would damage its resale value.

Hope that helps...


Last edited by interested_observer; 10-06-2013 at 01:32 PM.
10-06-2013, 02:02 PM   #3
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Interested_observer......it has been extremely helpful!!!! THANK YOU!! Seeing as to how the lens only cost me $25 shipped, I have no reservations to attempting to shave down the flanges....wonder if the k20d would still pick up and be useful even if the flanges where brought down to pentax k mount specs.
10-06-2013, 02:52 PM   #4
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Afternoon,

I see Rico really was not able to put together a step by step process in modifying a C/Y lens, but here are a few posts of his that give the general process.Here is a list sort of in terms of how to modify a lens.... (maybe not a C/Y lens, but it should be helpful)
QuoteOriginally posted by pedro730 Quote
Interested_observer......it has been extremely helpful!!!! THANK YOU!! Seeing as to how the lens only cost me $25 shipped, I have no reservations to attempting to shave down the flanges....wonder if the k20d would still pick up and be useful even if the flanges where brought down to pentax k mount specs.
Rico shot with a K20 and had no problems.... By the way, he also used and K mount extension tube to test the lens on when shaving the inside of the flanges. This way he could essentially "be inside the camera" and see how the "fitting" was going. You would want to find the shortest and least expensive extension tube possible.
hope that helps...



10-06-2013, 04:02 PM   #5
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mount id

QuoteOriginally posted by pedro730 Quote
Hello, my name is pedro and I am new to this forum. I need some help please. I might be doing something wrong and I cant figure out what it is. I recently bought a sigma mini-wide II 28mm 1:2.8 for my K20D. When I try to mount the lens onto the camera, it gets stuck halfway when rotating it on. It takes a little bit of force to remove. I tried it twice only....the second time was to make sure that maybe I didnt seat it all the way down the first time. Am I doing something wrong? Has anyone else had this problem or something similar?? HELP!!! thank you and I really appreciate any feedback any forum member can provide me.

See here to figure out your mount

SLR Lens Mount Identification Guide
10-08-2013, 09:37 PM   #6
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Excellent advice guys but honestly, im still dumbfounded by all of this. The owner claims to have used this lens on a Pentax LX and K1000. Ive uploaded some pictures of the lens itself see if that helps in helping me with my dilemma. Once again, I really appreciate everyones input on this matter. Thank you.
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10-08-2013, 10:25 PM   #7
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Any other markings on the lens?
10-08-2013, 10:59 PM   #8
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Is there a serial number on the lens? If so you might be able to call Sigma Technical Service and ask what mount it was produced with?

You might consider going to/calling an old camera shop or thrift shop / goodwill and see if they have an old Pentax film camera and test the lens on it.

I have a number of old K, M and A lenses (going back to 1975) in the K mount, that I have had no problems with in the slightest. This is somewhat baffling.



10-09-2013, 07:51 AM   #9
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The only other markings are the numbers on the aperature ring and the serial # of 4307766....as far as I can tell there are no other markings on it
10-09-2013, 09:43 AM   #10
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I have to say the mount looks identical to the mount on my sigma mini-wide. (I have the same lens). I was going to suggest that this might have been made for sigmas shortlived range of film slr's which used a mount that was ALMOST identical to PK. But I don't think that's the case. My best suggestion at this point is to really scrutinise the mount and see if there is in fact a wee dent or distortion which is causing the problem

best of luck
10-09-2013, 09:51 AM   #11
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QuoteOriginally posted by marcusBMG Quote
I was going to suggest that this might have been made for sigmas shortlived range of film slr's which used a mount that was ALMOST identical to PK. But I don't think that's the case.
It's close, but this can't be SA-mount. The Sigma SA-mount bayonet is almost identical to K-mount (slightly larger, which would explain the OP's symptoms), but the electronics are copied from Canon's EF mount. If this was an SA lens, you'd see little copper squares inside the mount, instead of the little round contacts around the rim. There'd be no aperture lever, either.

By the way, Sigma's SLR line continued into the digital age. I have one.
10-09-2013, 10:05 AM   #12
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QuoteOriginally posted by scratchpaddy Quote
It's close, but this can't be SA-mount. The Sigma SA-mount bayonet is almost identical to K-mount (slightly larger, which would explain the OP's symptoms), but the electronics are copied from Canon's EF mount. If this was an SA lens, you'd see little copper squares inside the mount, instead of the little round contacts around the rim. There'd be no aperture lever, either.

By the way, Sigma's SLR line continued into the digital age. I have one.

Thats pretty much what I half remembered but didn't check... thank you. Doesn't help the OP tho'
10-10-2013, 07:49 AM   #13
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Hi, I am the seller of the lens and hope I can make the case more clear.

This is the original ebay selling address:
Sigma Mini Wide II 28mm F 2 8 Lens 28 2 8 Pentax PK Mount | eBay

I am a pentax user from 2004 starting with a set of takumars and I have just sold out my Pentax LX and three lens I used with it. This 28mm is one of them. After Pedro told me he has some problems on fitting the lens to his K20D and telling me the lens in not PK mount but a CY mount, I was confused as I have used it on my LX for some time already. So I did a research on the difference of the two versions of the sigma lens. My seems to be identical to all others PK version.



I am not sure if it works on Pentax DSLR as this is really old lens. And I did not find other clue either. Hope Pedro can be helped and I also wish to know the answer.

Regards,
Yitao
10-13-2013, 09:11 AM   #14
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Yitao,
The lens you sold is K-mount and is a variant that has the Ricoh "P" pin in addition to the Pentax "A" contacts. This was a common configuration in the late 1980s and is the most likely cause of the rough/tight mount experience. The good news is that the pin appears to be the "safe" ball-type that is less likely to bind on the drive coupling for Pentax AF bodies.

To the OP...I would suggest that you not attempt to shave or modify the mount lugs unless you are keen on ruining the lens. The "shaving" in the other comment is part of the process of modifying a C/Y lens to accept a replacement K-mount.


Steve

Last edited by stevebrot; 10-13-2013 at 09:21 AM.
10-13-2013, 10:16 AM   #15
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Morning,

With the additional background on the lens, I certainly would not shave the mounts in that it is a PK mount. I only suggested that is may be a C/Y mount in that they too start off mounting and then binding about half way on due to the lug thickness difference. I do wish that all the sellers were as forthcoming and helpful as yliu410 has been.

All of that being said - I do not have a clue as to why you are having problems mounting the lens. You could go the macro extension tube route. For $8 (free shipping), these have the camera mount, and you can "mount" the lens on them and see from the inside what may be going on - given that they exhibit the same mounting problem as the camera body itself.
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