What is this pin on a Zeiss Jena 180mm Sonnar?

I just received this medium format Pentacon 6 lens which I intend to use on a Pentacon Six camera, but also want to mount it on a Cannon 5d Mk II with an adapter. Problem is, it has a pin sticking out in the back (besides the aperture control pin), which is preventing the lens from attaching to the EOS adapter. This pin doesn't sink in at all, but pulls out a little bit, but not all the way out. What is this extra pin for? Can this just be trimmed off? I have an exact same lens which only has the aperture control pin, not this additional pin. Here is an image of the two lenses. One on the left is the strange one...........

 

These P6 lenses were often used with a converter tube for Praktica/Pentax M42 screw-thread use with semi-auto aperture control. The pin may have been inserted to prevent the adapter twisting - just a guess.

 

I have a copy of the 180mm Jena 'Olympia' Sonnar, and I've seen and handled quite a few more. I also have a few other Zeiss Jena and Meyer P6 lenses. This is the first time I've seen such an additional pin, and my inclination would be to pull it from the lens, since it serves no useful purpose.

 

I'd say it was an amateur modification anyway, from what I can see in your picture.

 

And two Olympia Sonnars? That's a bit greedy!:p

Edited February 6, 2019 by rodeo_joe|1

Remove the three screws that retain the ring the aperture pin passes through. My hunch is that odd pin will come off with the ring and there will be no role that it plays in normal lens use.

The pin changes height when you turn the aperture ring. It transfers that information to the adapters for 35mm cameras.

 

Instead of cutting it off, I would try to remove it in a reversible manner.

The pin changes height when you turn the aperture ring. It transfers that information to the adapters for 35mm cameras.

 

Instead of cutting it off, I would try to remove it in a reversible manner.

 

Yes, it indeed changes height as the aperture ring is turned. I think it would be wise to take it to a camera repair shop and let them do it professionally. It's hard to tell how this pin is assembled deep inside the flange. The lens is too pristine for me to mess with. Tom Chow, do you know which 35mm cameras need this pin to communicate with? I was intending to mount it on a Canon EOS camera, which doesn't seem to need it as there is no provision to accept this pin.

Thanks

The pin changes height when you turn the aperture ring. It transfers that information to the adapters for 35mm cameras.

Yes, it seems there was an adapter from Pentacon Six to Pentacon Super that retained the automatic diaphragm and also allowed full aperture metering. Here's a picture (not mine):

 

Carl Zeiss Jena Sonnar 2,8/180 (links) und Sonnar 4/300 (Mitte) mit Pentacon-six-Anschluss (mit Zusatzstößel) sowie Sonnar 2,8/180 (rechts)… | Pentacon | Pinterest

 

https://i.pinimg.com/736x/f5/ab/2e/f5ab2e89b661ac6c6c6287d993163b48.jpg

The pin changes height when you turn the aperture ring. It transfers that information to the adapters for 35mm cameras.

Are you sure about that Tom?

 

I have a factory-made P6 to M42 Praktica/Pentax adapter, and there's no facility for transfer of aperture information. And Praktica/Pentax lenses had no aperture coupling to the camera body anyway.

 

It's also difficult to see how the linear motion of a pin could be converted back to the usual rotary action of an aperture ring. Even if the camera accepted such information. So I'll be fascinated to know what camera such an adapter might be for.

 

Edit. OK the response came in while I was typing.

 

A Pentacon Super eh! All six owners of one must have been overjoyed at that innovation!

Its interesting that the lens on the right also had the pin at one time. You can see the hole it protruded through and it looks like its been "worked" over time by the pin. If you can't just remove the three screws and the pin mechanism, then yes take it to someone who can do this for you.

Yes, an M42 mount with open aperture metering. It did not last long, and later non-zebra lenses did not have that pin. I think the Pentax M42 ES version was a better design though.

 

I don't have that adapter, but I do have a P6 to Exakta external bayonet that has a spot for the pin, but there is no aperture information transferred on that mount.

Edited February 7, 2019 by tom_chow

I borrowed a Pentacon 6 to EOS adapter from a friend, an inexpensive Chinese product he says, and it fit on this lens like a glove. The wall to the side of the adapter is thin enough that it misses the protruding pin by a mm at most and makes it work. I think the particular adapter was designed with this pin in mind. Whew!!

 

While I don't think this zebra lens is the Olympia version (they were silvery metallic, AFAIK, and would be great to have), these zebra versions are well respected, and even with a single coating it renders good color and contrast. I have seen many of these zebra variety without the pin, including another one of mine. Yes, I did get a little greedy and ended up with two :-P