Please help me understand the versions of "M39" mo

connloyalist · Joined: 22 Jul 2020 Posts: 345 Location: the Netherlands

Hi All,

I would appreciate some help in understanding the variations of the "M39" mount. My current understanding is that there are (at least?) two different versions:

1. Leica Screw Mount (LSM) / Leica Thread Mount (LTM) / L39 / Leica M39. These are all the same thing and according to Wikipedia is M39 x 26 TPI Whitworth, about 0.977mm. This has a flange distance of 28.8mm for rangefinder camera's.

2. "Soviet" M39 with a 1 mm DIN thread and a 45.2mm flange distance for an SLR.

Wikipedia also lists:

3. Canon J mount, M39 x 24 TPI.

I am assuming that you cannot tell the difference between a Leica M39 and a Soviet M39 by looking at a lens. So the classification would have to be made based on manufacturer? Anything of Soviet or East German origin would be for a 45.2mm flange distance and everything from a West German company would be for the 28.8mm flange distance?

Regards, C.

iangreenhalgh1 · Expire: 2014-01-07

The vast majority of Soviet M39 lenses are 28.8mm for rangefinders. The only Soviet M39 lenses with the longer flange focal distance are for the early Zenit SLRs and the one you will see most often is the Helios 44.

sergtum · Joined: 14 Nov 2016 Posts: 735

iangreenhalgh1 · Expire: 2014-01-07

Alright then, the vast majority of Soviet M39 lenses imported into Western Europe are with 28.8mm FFD for rangefinders.

The I-22 and I-50 are found in both M39 variants, so your list is confusing.

D1N0 · Joined: 07 Aug 2012 Posts: 2536

The Industar 50 for m39 SLR look like the industar 50-2 for m42. The ones for rangefinder/Ltm don't

DConvert · Joined: 12 Jun 2010 Posts: 921 Location: Essex UK

Most M39 (actually M39 at 26tpi) lenses are either:

SLR - Zenit S/ZM39 (flange distance 45.2)
Rangefinder - Leica screw/LTM/L39 (flange distance 28. Cool

or enlarger lenses of no fixed flange distance

but there are quite a few more with the same threads yet different flange distances:

The Industar 69 from the Chaika half frame rangefinder with flange distance around 28mm (definitely shorter than LTM but easily modified to LTM)
Leitz viscoflex I has flange distance 40
Paxette series II has flange distance 44 (one source claims 45.7)
Kilarscope has flange distance 78.8
Kilarflex has flange distance 92.3

Going to other thread patterns while still M39:
Copal #1 lenses have a M39x0.75 mounting thread
Canon S lenses are mainly LTM, but the earliest are supposedly M39x1 the difference is tiny so this could be a measuring error.
Canon J lenses are reported as M39 at 24tpi

I've got the first 4 listed here all the others are just info collected from the web over the years Smile

iangreenhalgh1 · Expire: 2014-01-07

I think Copal/Compur #1 is 40mm, but I'm not sure without checking, I do know you can't screw an M39 lens into one.

calvin83 · Joined: 12 Apr 2009 Posts: 7576 Location: Hong Kong

Don't forget the Braun M39 lenses wit 44mm flange distance

connloyalist · Joined: 22 Jul 2020 Posts: 345 Location: the Netherlands

Reading the above replies I get the impression that M39 is the most varied size there is.

Would it be fair to say that as a rule of thumb (!), Russian lenses could be either 28.8mm or 45.2mm, and with some exceptions as noted most other lenses are probably 28.8mm but you can't be sure until you try?

It just occurred to me that I inherited an EXA to M39 and an M39 to EXA adapter with a lens I bought a while back. At least I assume it is M39 because it is too small for M42. I am assuming this is M39 at 45.2mm. The M39 (lens) to EXA (camera) looks like it could be correct for 45.2mm (haven't measured it). I don't see how you would go from EXA lens to M39 camera at 45.2mm while retaining infinity focus. These two adapters do fit each other both ways around.

Regards, C.

DConvert · Joined: 12 Jun 2010 Posts: 921 Location: Essex UK

DConvert · Joined: 12 Jun 2010 Posts: 921 Location: Essex UK

jamaeolus · Expire: 2015-08-20

connloyalist · Joined: 22 Jul 2020 Posts: 345 Location: the Netherlands

BurstMox · Expire: 2016-08-02

DConvert · Joined: 12 Jun 2010 Posts: 921 Location: Essex UK

Lightshow · Joined: 04 Nov 2011 Posts: 3666 Location: Calgary

M39 is only a diameter of thread measurement, its actually a bit too vague IMO, like calling AR, SR, EF , F, etc "Bayonet Mount" but sadly that's the mess we're given to deal with from manufacturers that didn't consider how things would change in the future with regard to adapting lenses from every conceivable mount made and the confusion it will unleash on the novice adapter enthusiast, thankfully there are resources such as this wonderful site full of wonderful sharing/helpful people to help lift the fog of confusion and make adapting as painless as it can be.
Like Dog

sergtum · Joined: 14 Nov 2016 Posts: 735

D1N0 · Joined: 07 Aug 2012 Posts: 2536

But Why is the 21m so much heavier than the 21 and 21A. Respectively 980,690 and 740grams. Did they put in a bigger hunk of glass?

BurstMox · Expire: 2016-08-02

D1N0 · Joined: 07 Aug 2012 Posts: 2536

titrisol70 · Joined: 14 Dec 2021 Posts: 183 Location: State of Denial

I have a Zorki4 that came with a Jupiter 8, camera never worked right and was boxed
A few weeks back I received a Leica IIIf (Elmar 50/3.5) from a friend and I brought the J8 back from the box with the idea to use it.
Len fit well in the camera. However, the cam that moves the RF wheel is of different lengths, and thus the RF doesnt work with both lenses

At infinity I have 7.83mm in the Elmar but only 7.76mm on the J8.
Elmar (10ft) 3.05m 6.68mm J8 3m 6.60

I managed to bring the Zorki4 to open in B mode (at least) and got the same results.
While in a ground glass both were focusing correctly, the RF was out of whack for the Elmar.

In conclusion the cam lenghts are not standard in the FSU lenses, and basically you have to calibrate your camera RF per lens

philslizzy · Joined: 07 Aug 2012 Posts: 4745 Location: Cheshire, England

OK in flange focal distance order you have these common 39mm standards that cause confusion:

Soviet Chaika. The lenses have a 27.5 mm focal distance (the 28mm f2.8 will fit a Leica but it wont focus, or cover the frame)

The LTM (Leica thread mount) is British standard, 39mm by 26 turns per inch and a flange focal of 28.8mm

Soviet rangefinder lenses are M39, to all intents and purposes the same as LTM. (Although the RF coupling isn't precisely the same, I've never experienced issues.)

B39 (AKA M39) for Braun Paxette. 44mm FFD

ZM39 Soviet Zenit, with an FFD of 45.2mm (NOT 45.46 as reported elsewhere)

Some Leitz and other lenses may have an LTM screw designed for the PLOOT or Visoflex 1 (62.5mm FFD),

Kilarscope (78.8mm FFD) and Kilarflex (92.3mm FFD) though those tend to be 400mm or over lenses.

Then there are enlarging lenses. Standard M39 or LTM screw fit, but no fixed back focus

The Chinese Great Wall, which just had the one lens FFD unknown but likely to be > 60mm

To my knowledge the early Canon Hansa models used a bayonet mount (invented by Nikon) then changed to LTM. I'm not aware of a different screw thread.

visualopsins · Expire: 2025-04-11

philslizzy!