Amedeo Contax to Leica M Adapter - External Bayonet Lens Issue

[quilts]

I recently purchased one of the Amedeo internal/external mount Contax to Leica M adapters and am able to mount my 50mm f1.5 Sonnar using the internal mount without issue. However, I'm also trying to mount a Contax Sonnar 135mm f4 using the external mount and can seemingly get it to mount, but the rangefinder is not coupled. With the adapter removed from the camera I can see that the cam built into the adapter is not moving at all when rotating the focusing tab on the lens. Both lens and adapter are set to infinity when mounting. The red dot is centered on the top and the tab on the lens clicks into place.



I don't have a Contax RF body, but I also tested mounting the 135mm Sonnar on a Nikon S2 I have and it goes on and couples to the rangefinder just fine so I believe I ruled out any specific lens issue. I spoke with @Sonnar Brian and he shared that the longest of the three "protrusions" from the Contax lens needs to line up with the long slot in the Amedeo adapter to allow the cam to drop into place. So I believe I will need to file either the longest lens cam or file the slot in the adapter slightly to fit. It was hard to capture, but see the photo below to show the cam not quite dropping into the adapter slot. It's catching on the right hand side slightly.





I don't intend to use this lens on a Contax RF body, so my first inclination is to file down the lens cam slightly rather than mess with the adapter. But wanted to ask the general forum if that sounds like a good plan or if there is some other issue I may be missing?

 

[Cascadilla]

That adapter costs a lot more than a Zeiss 135 f/4 for Contax in decent condition. If I were you I'd be inclined to do a little surgery on the lens to see if you can get it to work properly on the adapter since you're not interested in using it on a Contax.

 

[quilts]

That adapter costs a lot more than a Zeiss 135 f/4 for Contax in decent condition. If I were you I'd be inclined to do a little surgery on the lens to see if you can get it to work properly on the adapter since you're not interested in using it on a Contax.

That was my thought as well. Before doing so, I figured I'd poll the forum and see if there were any unintended pitfalls I'd encounter by going that route.

 

[jc031699]

Sometimes those fins just need to be slightly bent to engage properly with the focus mechanism. Also if you read up on it, placing the camera focus at 3m and the lens focus at infinity before mounting can help the focus cam snap into place more easily. Part of the process of this happening is rotating the lens focus relative to the lens focus cam after the external bayonet is secured and locked. You can look in the back of the adapter and see that happening.