Flange distance of L39 and M

[Herman Zhang]

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I want to get a L39 screw mount lens on my digital M240 and I am just wondering if the flange of the M mount is the same as the screw mount lenses. Also, does the rangefinder still works accurately if I use an adapter?

[frame-it]

 

18 minutes ago, Herman Zhang said:

I am just wondering if the flange of the M mount is the same as the screw mount lenses

M = 27.80 mm

M39 = 28.80 mm

[Ecar]

If you use a good quality, 1mm-thick adapter you will get proper RF coupling (accurate focus is a different thing as it depends on the lens calibration itself). Rayqual adapters are my personal favourites, but they are pricey. A search on the forum will yield numerous results regarding LTM to M adapters.

[dpitt]

1 hour ago, Ecar said:

If you use a good quality, 1mm-thick adapter you will get proper RF coupling (accurate focus is a different thing as it depends on the lens calibration itself). Rayqual adapters are my personal favourites, but they are pricey. A search on the forum will yield numerous results regarding LTM to M adapters.

Be sure to select adapters for the right focal length! The adapter will select the frame it brings up. So different adapters for 28/90 or 35/135 or 50/75
Also, some LTM lenses will need cutouts for the infinity lock.

[a.noctilux]

I use happily screw mount lenses on my Ms for long.

As said, some cautions to use these nice and plenty choices in different brands and periods.

First thing is good quality (*) LTM-M adapter with thickness precisely 1.0mm .

Three types is to choose from.

Cutouts is needed for some lenses with focussing lever.

 

(*) I had cheap adapters which sometimes are not possible to detach from M body, size or soft metal changed

some adapters are not exactly 1.0mm, so problems in precision

now I use only old Leitz adapters or Voigtlander ones.

[BastianK]

There is another issue, some M39 lenses have a slanted cam.
Here also the radial orientation of the lens in combination with the adapter plays a crucial role.

Had a lens like that, tried it with idk, 6 different adapters (including one of the expensive Voigtländer ones),
never was really happy with the results.

[Anbaric]

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For an M240, I would probably get a Rayqual Type III adapter or equivalent. These are compatible with 6-bit coding and infinity locks. There are three types for the framelines required by different focal lengths (35/135, 28/90, and 50/75):

https://shop.cameraquest.com/leica-screw-mount-adapters/rayqual-24/35/135-6-bit-coded-leica-screw-mount-type-iii-leica-screw-mount-lens-to-leica-m-body-adapt

[spydrxx]

I've used cheap Chinese ones, original Leica ones, and other brands. I like the Leica ones best, but usually others work just as well.