Leica M mount (bayonet) technical information need.

[ejstark]

Hello friends,

 

Unfortunately I'm not the Leica user now (I'm not too rich for that

:-)) but I'm a DIY fan, so I'd like to change the Leica thread mount

on my Zorki to Leica M mount - to construct smth. like Zorki-M :-)))

(or at least make an adapter M39/Leica M, but this variant I like

less).

Anyway I've already faced to some difficulties: I couldn't find any

technical description of the Leica M mount. The patent for this mount

has expired in 1999, so I thought that it's possible to find the

necessary information in public domain. My hopes were vain :-(

So maybe you could help me and show me the ways of search... or maybe

you already have drafts, pictures, descriptions, etc. concerning Leica

M mount?

All help will be kindly appreciated!

 

Best Regards, Erick.

[roger_michel]

rather than machining a new mount from technical drawings, wouldn't it be easier to cannabilize a broken leitz/minolta CLE, CL or somesuch. even a user bessa or a rear cap for a lens might work.

[paul t]

Won't there be some problem with the lens mount/film plane difference, if you

want to mount M-mount lenses on your (originally screw-mount) Zorki? If it's to

work, I think you'll need to 'inset' the m-mount into the camera. Which will be

tricky.

[mark-j]

Leica M bayonet mounts are readily available in alternative forms if you look. One source would be Visoflex bellows adapters to mount lenses on the bellows. Extension tubes would be another. I would opt for mounting a manufactured M mount onto one of the camera's of your choice. You would need to machine off or inset the new mount 1 mm to correct for the film plane differences. Cheers.

 

Mark J.

[ejstark]

I'd like to give some explanations to make the situation clearer:

1. It's only the idea - to change the tread (screw) mount of Zorki to Leica M mount.

2. To understand that this idea is ficious in reality I must know the technical specifications of the M mount. Such information I don't have now, so why I asked for your help.

3. I DO NOT want to by already produced by their parties Screw/M-mout adapters.

4. I have (or I can get) any necessary equipment to make the M mount by myself.

[dan flanders]

I am no particular expert on Leica mounts but I have worked with adapters and am familiar with the problems involved. To adapt screw mount lenses to a M mount camera is no problem. The opposite would be extremely difficult because the mounting flange for M mount lenses is one millimeter closer to the film plane than that of the screw mount leneses. The major part of the problem is that if you mill a hole in the carcass jof the camera big enough to accomodate the M mount, you are faced with anchorage problems interfering with the shutter. A better approach would be to see if the mounting flange of the lens can be reduced the one millimeter in thickness. I have investigated this possibility because I wanted to use a Elmar C on a screw mount camera. It is possible but fraught with machining problems. I finally decided it wasn't worth the trouble so I have been devoting the saved time to devising an adapter for Kiev/Contax lenses to the Leica. Even this isn't easy but the back focus situation is in my favor. I am covering that venture in a different thread and expect to have some interesting news soon.

[ejstark]

Thank you Harry for your advices.

I've already found the confirmation of your words here: http://www.nemeng.com/leica/017e.shtml

The LTF of LTM mount (as Zorki has) is 28.80mm and LTF of the M-mount is 27.80mm.

So I think this is the main problem. :( H-m-m... let's think what we can do... I prefer not to lose hope till the end :-)

 

Anyway I'm awaiting for the "interesting news" as you mentioned in yor post.

[huw_finney]

Is not the Zorki mount quite thick, like the screw Leicas, there seems to be enough room on my IIIb to fit an M mount. I was given an M mount from extension tubes by a kind member a while ago for my Hassycron project, in the end I didn't use it. As you want to make your own would you like to borrow it to measure it up? Mail me.

[miles_s.]

Erick,

 

I have looked for this information before, without sucess. I have not found the patent you refer to (expired in 1999), but I did find U.S. 3,677,155 issued Jul. 1972, in class 396/529 (expired 1989). The patent is entitled ``LENS MOUNT'' it is by G. Bechmann of Midland, Ontario. The patent is assigned to Ernst Leitz GmbH. The patent shows a Noctilux 2nd version f/1.0. That said I don't think it will have any information you don't already know.

 

I would be interested to know the number of the patents you found.

[ejstark]

Miles,

 

I've found the following patents:

 

- No. 2,643,581 patented June 30, 1953 by US Patent Office, entitled "Bayonet union for objective parts" by Hugo Wehrenfennig (Wetzlar), assignor to Ernst Leitz G.m.b.H

 

- Patent Specification No. 695,397 issued to Ernst Leitz by UK Patent Office (London), entitled "Improvements in or relating Photographic Cameras", date of Application and filing Complete Specification: Feb.12, 1951 No.3402/51.

 

Looking on the drafts, included to these documents, I'm practically sure that they describe the M mount, but the documents and drafts describe only principles of mounting the lenses and don't contain detailed technical information: sizes, measurements of the mount, etc., what is the main negative part of them.

 

All these documents I found on the website of the European Patent Office: http://ep.espacenet.com/

 

There you can find the scanned original documents in PDF format, but these PDFs are encrypted and don't let you to print them. Also you can save to your hard-disk the copy of the current page of the PDF document only. So I got several separate PDF files (as many as pages contained in the document) instead of one full file.

 

BTW, on this site there are a lot of another patents, issued to Ernst Leitz G.m.b.H.

 

I found the patent of "Coupling for distance meters and objectives of photographic cameras", patented by O.Barnack in April 21, 1936. Patent No. 2,038,261. :-)

 

Hope this will help in your recearches. If you'll find anything interesting, please let me know, OK?

[miles_s.]

Thanks for your detailed response.

 

"[T]he documents and drafts describe only principles of mounting the lenses and don't contain detailed technical information: sizes, measurements of the mount, etc., what is the main negative part of them." It really is a negative aspect of patents. A patent will not give dimensions unless they are needed to enable the invention, or distinguish it from the prior art. The patent need only describe how to make and use the inventive concept, not how to exactly replicate the product that uses the concept.

 

Unless you find some old technical drawings you would be best to measure a sample unit. However, a patent may have a detailed drawing with out dimensions which will save you redrafting.

 

miles

PS Yup, unless you purchase a PDF from Delphion or the like, you are stuck with many single page PDF files.