Nikkor external-mount lenses on Leica w/adapter?

[ssmc]

Hi all,

I hope I can phrase the following question in a way that makes sense. I have an S3 2000 and I later bought an Amedeo S-LTM adapter so I could use the excellent 50/1.4 Nikkor on a Leica body. First, this is my understanding:


- since the Nikkor 50mm is an internal-mount lens, all the focusing is accomplished by / dependent on the adapter

- the Amedeo adapter has the helicoids cut to mimic the appropriate travel of a Leica RF (3.1380mm from 0.9m -> infinity if I have the numbers right)

So my first question is this: will external-mount Nikon (or CV S-mount) lenses, with the focusing helicoids in the lens, focus correctly on a Leica with an adapter (which does nothing except position the lens at the correct distance from the film plane)? Not just at infinity, but at all distances?

Second (less important) question - does anyone know the true "design" focal length of the 50mm Nikkors? I know the Leicas are supposed to be 51.6mm...

I am thinking of grabbing a CV 35/2.5 and maybe a 50/1.5 while they're still available but it sure would be cool if they would also work on a Leica.

Thanks in advance for any input/experience on this!

Scott

 

[Phil_F_NM]

Yes they will work (for the most part, with some caveats.)
I used external mount Nikkors on my M9 and M4 with an Amedeo adapter just fine.

There are a few issues though:
You might find a lens that has a rear element shroud that is wide enough to contact the cam follower in the Leica body which at best can only give you the wrong focus and at worse knock your RF out of calibration. You can test this by opening the back of your film M, trip the shutter on bulb and lock it open with a release. Then stick on the Amedeo adapter then mount the lens. You'll be able to look from the back to see if the rear of the lens contacts the cam follower in the camera.

The other issue is that you won't see the framelines of your external mount lens since the Amedeo adapter is set to key up the 50mm frames in the Leica VF. Not to worry, you probably have a frameline preview that works and can use that while composing or use an external.

There is a list here on RFF about which lenses definitely work and which ones definitely don't work. There are cases where one lens will work and another in the same focal length, of the same design wont. My 2.8cm Nikkor works fine without contacting the cam follower but some have experienced improper focus due to the rear element retaining ring/shroud.

The 3.5cm f/1.8 absolutely doesn't work at all. The f/2.5 and f/3.5 versions do just fine though. The 13.5cm and 10.5cm lenses work fine. I have both. The 8.5cm lenses supposedly work but I have never tested one. The CV 21mm f/4 does not work at all for the same reason as the 3.5cm f/1.8

As for focusing, the true rate of the lens' focusing on an external mount lens is controlled by the slope of the helicals. This motion is imparted upon the Amedeo adapter by the spring loaded coupler at the back of all Nikon and Contax mount RF lenses.

The nominal focal length of Nikon RFs is 51.6mm just like Leica.

Hope this helps.

Phil Forrest

 

[jonmanjiro]

http://www.rangefinderforum.com/forums/showthread.php?t=79631

 

[ssmc]

Thanks for the info - I was not aware of how the focusing actually worked on external-mount lenses - and for the link, I dunno how I missed finding that!

Bummer about the CV 35/2.5 though!

Happy holidays!
Scott 🙂