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Zeiss-Contax C/Y 80-200/4.0 converting to M42 mount?



I would be interested in your opinions. Especially conurus and Luis.

Would it be possible to convert a Contax/ Zeiss 80-200 zoom (the Contax/Yashica manual focus line) to M42 mount?

I do not need AF. I use only aperture priority. So the functionality available with M42 lenses would be o.k. for me. I use currently my SD14 among others with Zeiss ZS lenses (also M42 mount).

Same question would go for the C/Y 25/2.8

Thanks in advance


Well-Known Member

I own a Zeiss Planar 1.7 50mm and I wanted to convert it to M42. I found this interesting article in PBASE, a step by step about how to do the conversion.

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I got even several M42 mounts from old lenses, but at the end I didn't dare to do it because I had to cut a plastic prominence from one of the internal rings, and turned the mod undoable.
Here you can find my disassembly experience, (I have to warn that the pictures are horrible, I was under the shock of opening my beloved CZ Planar and I put not enough care to shot properly, and afterwards I haven't had courage enough to try it again).

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Basically you have to unscrew the 3 screws on the top side (once the lens upside down) and afterwards the four ones at the next level (around the crown). Be careful to not to lose the small bearing that gives the click feedback for the aperture ring. Not difficult to implement but I didn't dare at the end, so I rebuilt it back and I keep it safely for use in my Contax film camera.

I know this is valid for the Planar, not sure how to do it for the other lenses. Hope this gives you some clues.

Kind regards,


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Hi Jes

Thank you very much for the links and the info. The other conversion pictures are from Alf B. I just send him an e-mail to ask for his permission to upload them here directly. So that they do not get lost and more users can benefit of them.

I will try definitely the conversion of at least one Contax lens. Since I do use next to my SD14 also other brands, the M42 mount is for me a very important point. I then can use my converted Contax lenses at the same time on Sigma, Canon, Pentax, Sony, Olympus. So this would be really good for me.

I do not mind to make it undoable.

I have to research more about it, to be sure to be able to focus it also at infinity after the conversion.

One problem might be with low light lenses (aperture of 1.4). I am not sure whether the radius of the M42 mount is big enough for the rear element of all designs.

This was at least the argument of Zeiss for not offereing the Zeiss ZF 85, the ZF 28/2.0 and both Macros also in ZS mount. But on the other hand Alf B. converted a 85/1.4 successfull to M42 mount. Maybe the new ZS version is a different in design...

But if I would be able to convert a Contax 25, 85 and 80-200 this would be great already.

best wishes


The Contax register is 45.50mm

Olympus E System: 38.85
Sigma: 44
Canon EOS: 44
Minolta/Sony AF: 44.50
Pentax AF: 45.50
M42: 45.50
Contax/Yashica: 45.50
Nikon F: 46.50
Leica R: 47
Contax N: 48

I think ( I am not sure) the M42 register is the same as the Pentax. 45.50mm and therefore the same as the Contax register.


Well-Known Member
Yes Dirk, it's the same. That's why the Pentax M42 adapters to Pentax-k mount fit inside the K-mount and are leveled to the K mount base.