Adapt Contax Stereotar C lens to M mount?

[jaques]

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I have recently come across a Zeiss Stereotar C lens for Contax cameras. It is an expensive and rare lens- and looks very much like the even more expensive and rare Leica Stereo lens.

 

I would sell the lens as I don't have any contax cameras- but I was wondering if it would be possible to mount it on one of my M cameras?

 

I have seen some Contax to Leica adaptors- I have no experience with Contax and am wondering if there is any obvious reason this won't work? I am not sure if if the Stereotar is even the same contax mount as these adaptors? The rear of the steroetar lens looks as if part of the camera slots into the lens bayonet rather than the other way around as with m mount. The adaptor rings look liek they are for a different mount.

 

 

Adapters: Classic Contax RF to Leica Screw

Amedeo Muscelli's Contax-to-Leica Adapter

 

The Stereotar lens has a little window that may block the RF window on an M camera- but it also looks like it may line up correctly and allow a view through.

 

It has a prism that goes on the front- on mine there is a crack at one edge of one of the front pieces of glass. I am not sure how much this may affect the images- or if it would be possible to replace that element?

 

attached sterotar image is from: Zeiss IKON Stereotar.C 1:3.5 f=35mm (35mm f/3.5) lens - MIR Image Library

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[giordano]

This could get complicated. Probably it will fit. Things to watch out for:

 

The septum between the two lenses protrudes a very long way into the body, almost touching the body casting above and below the film gate. Probably there's a little more space inside a film M than in a Contax, but be careful.

 

When the Stereotar is mounted, to get the best stereo effect the line joining the two lens axes has to be exactly parallel with the line of the film. On a Contax body the outer bayonet mount achieved that automatically. If you're using a Contax-to-LTM adapter plus an LTM-to-M adapter, you could end up with the Stereotar distinctly tilted. With the Muscelli Contax-to-M adapter things should line up correctly given the care Mr Muscelli generally seems to take.

 

Even if the Stereotar's rangefinder prism happens to line up with the M rangefinder window you won't be able to use it for reliable focusing because of the different base lengths and magnifications of the M and Contax finders.

[jaques]

Thanks for the reply. I was worried about the septum going too far into the body. However it looks like with the adapter in place it should only be one CM or less.... having said that I I think I will try it on an m2 before I try it on an m9.

 

Concerning the focus- don't these rings take the differing base lengths of the rangefinders into consideration? They say they are fully rangefinder coupled? It looks to me like the little window is just glass- not a lens- and that all it does is allow light through to the RF? Of course this could be entirely wrong. Does anyone know if Muscelli is still making these rings? I couldn't find a direct source for them. There are some cheaper ones on ebay now- coming out of hong kong. In the images they look to be well made, but the Muscelli ones look to be very fine indeed.

[giordano]

Concerning the focus- don't these rings take the differing base lengths of the rangefinders into consideration? They say they are fully rangefinder coupled?

 

The Contax-to-Leica adapters you've mentioned are rangefinder-coupled. That is, they convert the Contax rangefinder coupling (rotation of the lens or focusing ring through about 180 degrees between infinity and 1m) to the Leica one (linear movement of about 4mm between infinity and 1m.

It looks to me like the little window is just glass- not a lens- and that all it does is allow light through to the RF? Of course this could be entirely wrong.

It is. The Stereotars don't use the normal Contax rangefinder coupling (doing so would have made them much more complicated and expensive). Before you mount them, you have to set the focusing mount on the Contax body to infinity.

 

The Stereotar you show is the postwar f/3.5 one, where the little window contains a prism (or two counter-rotating prisms, I don't know which) that are linked to the Stereotar's internal focusing mount. If you mount the f/3.5 Stereotar on a Contax IIa or IIIa, the little window comes exactly in front of the rangefinder window. When you turn the knurled wheel around the little window, the prism(s) move, the Stereotar's internal focusing mount moves, and you have proper coupled-rangefinder focusing even though the rangefinder in the Contax body is locked on infinity.

 

That's why coupled focusing of the Stereotar depends crucially not only on the position of the rangefinder window but also on the rangefinder base and magnification - and hence why there's a negligible chance of it working on an M.

Does anyone know if Muscelli is still making these rings? I couldn't find a direct source for them. There are some cheaper ones on ebay now- coming out of hong kong. In the images they look to be well made, but the Muscelli ones look to be very fine indeed.

 

I don't know whether Muscelli is still at work. As for the Chinese adapters:

 

a) The ones I've seen appear to be Contax-to-LTM, which could mean the Stereotar will end up tilted relative to the axis of the film as I warned in my first post.

 

Some of the Ebay listings don't distinguish between Contax-to-LTM and Nikon rangefinder-to-LTM. Since the Contax and Nikon mounts are superficially identical but not 100% compatible, this would usually be a cause for concern - but it won't affect the Stereotar.

[jaques]

Thanks once again for the detailed response Giordano. I emailed Muscelli and he asked to be sent pictures of the lens so I will see what he says. It does seem highly unlikely that it will work out. I will keep trying though- even if I can only achieve manual focusing- as I would love to able to take stereo pairs on the M9... perhaps Muscelli could make me a specal ring just for this lens.... hope springs eternal.

[jaques]

There was a bit of a delay in the mail- but I finally managed to get an adaptor ring from Mr Muscelli- excellent service.

 

The ring is nicely made- and mounts smoothly to my Leica bodies.

 

And the great news is: the Stereotar seems to mount perfectly and looks to be horizontal- by eye.

 

So far I have not mounted it on the M9- there is a septum divider - it is protrudes... almost exactly 20mm from the rear of the bayonet flange. It looks by eye- like it will mount an an M8 or M9 with a few mm to spare before the shutter is destroyed but I am too scared to try:rolleyes:. I am considering removing the septum and replacing it with a shorter one.

 

It mounts fine on my M3.

 

The RF window doesn't line up- so this can only ever be a manual focus lens on a leica which is a shame... But if I can make it work on an M9 I will be satisfied with my folly:

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