… in a mount fitting the Leica and with thread M 39x1 …

Of the present forum membership, this might only be of importance to Howard Lewis and myself … But one day, someone may come along in search of the truth, so let’s make it easy to find:

At the end of July I demonstrated, to Howard’s satisfaction, that the original Leica thread-form was Whitworth

**LINK**

https://www.model-engineer.co.uk/forums/postings.asp?th=173961&p=5

Further information has recently come to my notice, courtesy of Zeiss Historica

**LINK**

https://www.model-engineer.co.uk/forums/postings.asp?th=174678&p=1

This letter was reprinted in the first FOLIO

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Now … as the records were destroyed, there is no direct proof that Jena used a metric equivalent : So; if anyone happens to own that specific model of lens, do please check the thread-form, and post details here.

MichaelG.

Intriguing that the mention is not of 26 tpi Whit, but 39 x 1

So, the mystery deepens.

Has anyone used thread gauges on a male genuine Leitz lens?

Possibly. Michael and i will both then be able to sleep at night

Howard

Here’s a nice geeky article about the early Sonnar: **LINK**

https://www.35mmc.com/29/04/2020/zeiss-jena-5cm-sonnars-the-magic-of-the-prewar-uncoated-sonnar-by-brian-sweeney/

‘though it does nothing to advance our knowledge of the thread-form

MichaelG.

The early lenses for precision 35 mm cameras really were advanced, for their time. The Elmar and Sonnar were far in advance of anything available at the time, setting quite a goal to reach..

Present lenses are even better. The Vario Elmar on my Panasonic FZ50 performs incredibly against the light. Just shows how much progress has been made in lenses and their coatings since the 930s.

As for enlarging lenses, a prominent photographic lecturer did not think much of my 2"Taylor Taylor Hobson Ental 2, preferring a 50 mm EL Nikkor.

Until I told him that my TTH would resolve grain at full aperture, while the El Nikkor had to be stopped down considerably so to do, on the same negative!.

Howard

I have a 35mm Sonnar as well as several other Leica screw lenses. I will attempt to measure them tomorrow.

Enlarging lenses are also "Leica Thread", a follow on from pre WW2 days when Leica made a matching enlarger for the 35mm camera so that it could use the same 50mm camera lens. I have a collection of Leica literature and will also search that for information. Leica collectors can get quite excited about the slightest known facts and I am sure the angle of the thread is well known to them.

Keith

A quick look at some of my Leica literature shows this to be a well discussed subject. The consensus seems to be that as Leica were a microscope maker and microscopes of that time used Whitworth form threads. Leica would have used what they were tooled up for and used Whitworth form.

Keith.

It is also known that early 1930s Canon (Kwanon) copies of the Leica used 39mm Metric form and would not fit a genuine Leica.

Keith.

Thanks for your confirmation, Keith

I have already convinced Howard that the Leica bodies used Whitworth-form threads … but I started this new discussion when I found the Jenoptik letter:

If the statement in it is to be believed, then they made lenses:

[quote] in a mount fitting the Leica with thread M 39x1 [/quote]

The interesting detail is of course missing, because the records were lost in the War.

So … Did they really? … and if so, to what go/no-go specification?

… or did Herr Gessinger simply get his facts wrong ?

MichaelG.

Carl Zeiss Jena,...or, in common parlance, 'East German Zeiss' made the lenses for the Pentacom 35mm SLR...the standard lens was the 58mm Biotar, if I recall and, I think used a 39x1 thread. This was later crudely copied by the Russians in the Zenith SLR which also used 39x1 and the Biotar(?) was the origin for the Helios 58mm lens.for that camera.

Have you ever referenced Leica in milton keynes.? There is a Leica Historical club who do a lot of checking through Leica MK. We often refered to them as the Leica Hysterical club.

They will have some record of Leica that they can refer to.

The Russian made Fed (Copy of the Leica 2f ) and Zorki used the 39 x 1 thread (I think that the Kiev was a copy of the Contax )

The "economy" lens was the Industar, f/2.8.

The Zenith 35 SLR used a 39 x 1 thread but the register, being a SLR was greater than the 28 mm of the Leica body.

So although "Leica thread" lenses and accessories would fit, it could then only be used for close up work.

The Periflex series, 1, 2, 3 and Gold Star used the same thread and register and provided a rangefinder which functioned with a lens of any focal length. It used the SLR technique of focussing on a small ground glass screen which was lowered onto the centre line of the lens (Manually for the 1, in-situ and automatically withdrawn for the 2 and subsequent models). The Corfield lenses were quite good.

There were also three Interplan models (A, B and C ) which accepted Exakta , Edixa/Pentax or Contax lenses, but were less popular, and short lived..

When the Zenith B and E SLRs were produced, most had the 58mm, f/2 Helios, which being a copy of the Sonnar in the new mounting, to suit the 42 mm "Pentax / Edixa" register, was a very good lens

Howard

A great overview by Howard …

But I would like to clarify my underlying concern about the ‘engineering’

1. I have already demonstrated, to my own satisfaction, that a genuine L39 female thread is of Whitworth form and 26tpi
2. As Keith has confirmed, it is common knowledge that some M39x1 lens threads do not fit into the Leica body thread
3. The Jenoptik letter clearly states that some pre-War Sonnars were made with a thread “to fit the Leica” … but it also states that to be M 39x1

For all these findings to be mutually consistent, there must surely be a GO/NO-GO threshold

The questions are:

• Who, if anyone, defined it ?
• Was it a paper exercise, or a physical gauge ?
• What are the relevant numbers ?

It should be reasonably simple to work the numbers with a CAD system, but I suggest it would have been uneconomical to do so in pre-War Germany. …and why would anyone [particularly another microscope manufacturer] choose to do it ?

MichaelG.

In the hope of getting a definitive answer, I have taken Clive's advice and contacted the Leica Society.

There is a wealth of information available BUT no mention of the thread form or pitch!

The reply will be interesting.

Howard

I was a member of the Leica Historical Society for many years and have several shelves full of their literature. The consensus argument is from James Lager, an acknowledged expert on Leica History and author of several books on the subject. Google his name and you will get a lot of information.

I have tried to check several Leica screw lenses this morning and found it quite difficult as only about 4 threads are there. I t is easier to check a genuine Leica lens cap. This I have done and get a perfect fit for 26 TPI ,BSW..

Keith.

Thanks for doing that, Keith … it confirms my own findings regarding the female thread

[ and presumably the genuine Leica male thread ]

The remaining question is the one I have tried to detail

… What is required to make a nominally 1mm pitch metric thread fit “well enough”

[ I still cringe at the thought, but it seems to be a de-facto option ]

MichaelG.

Have just received this from the Leica Historical Society.Abbreviated to delete the information on microscope objectives and their tubes, making the post too large for the Forum.

Yes, the thread is definitely 26 tpi Whitworth form and it was made thus because of Leitz’s involvement with microscopes. Many threads on microscopes were Whitworth form and imperial pitches, the only one I can get a definite reference on is 0.8” x 36 tpi which is known as RMS (Royal Microscopical Society) thread used for objectives.

A thread of this size is machine-cut so messing about with thread cutting gears when you already have a lathe set up for 26 tpi just to get 1 mm is a bit pointless. The lathe would probably already have an imperial feedscrew, so you would need a 127 tooth gear for an accurate conversion to metric. Impractical and of no real benefit.

Your co-respondent can see evidence of this if he looks up catalogues of enlarger lenses from Rodenstock or Schneider-Kreuznach where the clearly state the threads (in this size) as 39 mm x 26 tpi. I think I found a Leica reference to this also but I cannot recall where.

The Soviet copies of the Leica were, as far as I know, all made with 1 mm pitch threads. They can get away with it because there are only about 3 full turns and as their production standards are somewhat relaxed, the lenses will fit a Leica. I’ve never tried a Leica lens on a Soviet camera though.

I’m not sure about the Canon copies, whether this was 1 mm or 26 tpi. If it was 1 mm and well made it will not fit a Leica camera (or vice-versa), the thread begin to bind after about one and a half turns.

I hope this helps to clarify the issue.

All the best

So now we know for sure!

Howard

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Thanks for posting this, Howard … but frankly, it is only confirmation of what I already knew

[ You will recall that I went to some considerable effort to demonstrate the thread-form for you ]

It still leaves my question unanswered though !

Elaborated in my post timestamped :   12/09/2021 10:44:27 

MichaelG.

Edited By Michael Gilligan on 14/09/2021 08:45:37

Michael, Howard,

The LHS are reading from he same Hymn sheet as me. Also if you Google "Leica L39 lens thread, you get Wikipedia giving the same, although the are incorrectly calling it M39.They give the pitch as 0.977". 0.023" difference to a 1mm pitch would definitely bind with a correctly cut thread.. I have a Russian Zorki camera and lenses,classed as a Leica copy. The 135mm focal length lens is mint,unused,so no chance of wear. I tried it on a Leica 111F body and it fits smoothly,as good as a Leica lens, so they are using 26 TPI BSW..

The whole subject is confused by both "Bibles" for collectors saying the thread is 39mm x1 mm. These are Dennis Laney " Leica Collectors Guide" and Paul-Henry van Hasbroeck, "Leica A History illustrating every Model and Acccessory"

Keith.

Edited By KEITH BEAUMONT on 14/09/2021 12:50:18

And I had always thought that van Hasbroeck was THE fount of wisdom on Leica!

You live and learn!

Howard

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Yes, Keith … and I must repeat that I read the same Hymn sheet

MY question, posed earlier in this thread, concerns Jenoptik’s statement about the pre-war Zeiss Sonnar

… May I ask you to read it carefully and tell me if there is a rational answer, as I have yet to find one.

Thanks

MichaelG.