Leica, Leitz Time Machine -- feel free to post your finding here

[wizard]

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vor 50 Minuten schrieb willeica:

It only remains to see whether the intent of the patent was carried into any production models,

The second embodiment shown and described in the patent corresponds to the production model, whereas the first embodiment does not. It is, however, quite customary to show and describe several embodiments of any any given item in a patent application, and there are several reasons for doing so. First, a patent application is usually filed early on, and often it is not clear at that point in time which variant will make it into production. Second, including more than just one embodiment in a patent application broadens the scope of protection (patent applications, if done well, should not only protect the own product, but should also prevent competitors from using alternative routes as far as possible). I should know, as I am a patent attorney by profession.

And, I have also noted myself that Leitz has touched up advertising photos to be in line with the latest model designation. That, however, in my view has nothing to do with the optical construction of any given lens. Leitz usually did not hold back on disclosing the optical structure of their lenses (they did, for example, disclose the change in optical layout of the Summilux 50 lens, too, if somewhat belatedly). If a very first version of the Summicron 50 lens with only one air space existed, why would Leitz have had any problems in disclosing that to the public? However, they consistently disclosed and advertised the two air space design from very early on. I can understand that from a collector's point of view there may be some interest in keeping the myth of some undisclosed very first version of the famous Summicron 50 alive, but unless someone presents hard evidence to prove this point, the available facts speak entirely against that myth.

Cheers,

Andy

[willeica]

13 minutes ago, wizard said:

That, however, in my view has nothing to do with the optical construction of any given lens

Of course I know that, but senses of humour and proportion are also needed  when discussing such things. It does show, however, that Leica felt that customers would not notice the external physical difference, but our feet were much more on the ground about such matters back in the early 1950s long before such items became ‘collectors’ items’. As for the ‘issue’ itself, I have already said that you are probably right and that proving otherwise would be most difficult.

William 

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[Pyrogallol]

I see the camera gained a self timer as well as a new lens.

[wizard]

vor 1 Stunde schrieb willeica:

Of course I know that, but senses of humour and proportion are also needed  when discussing such things.

Quite true, and I am sorry for not noticing the humour between the lines (I guess it would not be a problem if we were to discuss such things in person).

 

vor 7 Minuten schrieb Pyrogallol:

I see the camera gained a self timer as well as a new lens.

Ha, I didn't notice the self timer was added! The lens is actually the same, it is only the name that was changed from Summitar to Summicron, as William had correctly noted.

[luigi bertolotti]

39 minutes ago, wizard said:

 

 

Ha, I didn't notice the self timer was added! The lens is actually the same, it is only the name that was changed from Summitar to Summicron, as William had correctly noted.

... and keeping the same s/n in the 7xx.xxx ! 😁

But this question of the air space between 3rd/4th is really intriguing... usually Marco Cavina is really very precise... and he details the story precisely about the air elements...

(italian only) : http://www.marcocavina.com/articoli_fotografici/50mm_Leica_a_telemetro/00_pag.htm  

I am tempted to write him   on the matter...  (but won't dismount my Summicron 920.382 to check... 😉)

[wizard]

vor 1 Stunde schrieb luigi bertolotti:

I am tempted to write him   on the matter... 

Luigi, it would indeed be interesting to learn more from Marco Cavina on this topic, and specifically on where his information on the first optical version of the Summicron 50 lens stems from.

I have now read Marco Cavina's article in more detail, and it seem he says that the original project (of the Summicron lens) uses four radioactive lens elements and just one air lens, whereas the Summicron in its production version has two air lenses:

Il progetto originale del Summicron 5cm f/2 prevede non soltanto il doppietto anteposto al diaframma collato anzichè spaziato ad aria (come nel modello definitivo) ma utilizza ben quattro lenti in vetro all'ossido di Torio (la prima, la terza, la sesta e la settima), la cui radioattività è dichiarata apertamente, al punto che uno dei propositi messi in campo è quello di proteggere il film dal "fogging" da radiazioni applicando all'interno dei nuovi corpi macchina una lastra di vetro Flint al Piombo, 

That would mean that there may be some prototype lenses which may have had only one air lens, but that all production lenses will have two air lenses. At least this is how I understand what Marco Cavina explains.

Edited September 14, 2021 by wizard
addition of text

[luigi bertolotti]

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Yes, and that's the reason for I think to write him... given that you understand Italian 😎, give a look at his timeline :

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(evidenced in red the relevant infos on this matter) ; in brief, for non Italian readers his assertions are :

1950 : prototypes marked Summitar* :  1st glass couple air-spaced, 2nd unspaced (as for 1st embodiement of the Patent)

1951 : first items marked Summicron , same Thorium glass and same schema of Summitar*  (implying : only one "air lens")

1952 : new Leitz LaK9 glass, optical redesign with air spacing 3rd/4th elements as for 2nd embodiement of the Patent, starting around 993.00.  (btw, residual Thoriumimpurity  in Lanthanium of LaK9 glass, resulting in residual radioactivity)

What is partially unclear is :

- looks that the Summicrons surely "one air element", according to him, can be very few (920.001 to 920.072) :

- looks that the Summicron surely "two air elements", according to him, are  all the items from 993.000

What about the ones in the middle as mine ? (they ought to be, note, some thousands) One or two air spaces ?

 

Edited September 14, 2021 by luigi bertolotti

[Erato]

FYR.

https://translate.google.com/translate?hl=&sl=it&tl=en&u=http%3A%2F%2Fwww.marcocavina.com%2Farticoli_fotografici%2FLeitz_Summitar_star_radioactive_glass%2F00_pag.htm

=====Beginning of the quote=====

In the current state of historical reconstructions, it has always been believed that the rare Summitar * (star) prototypes produced 
in 1951 were in all respects optically identical to the subsequent Summicron of 1953, of which they constituted 
evaluation pre-series: vice versa, these objectives adopted the intermediate scheme present in the project just 
discussed, however, the problem of radioactive thorium glass remained unsolved, which had not been possible to screen 
either with a rear flat-parallel glass or with the adoption of the seventh lead-flint glass lens.

In the meantime, the aforementioned LaK9 glass with lanthanum oxide was produced at the Wetzlar glassworks, with 
excellent optical characteristics, perfectly superimposable to those of the previous thorium glass (refractive index 
nD = 1.694 - Abbe number 54.7) but devoid of radioactive elements; the designers quickly 
worked on the "intermediate" Summitar scheme, eliminating the previous refractive glasses and replacing them with the LaK9 type; perhaps in 
search of a certain economy in scale (lanthanum glass was very expensive at the time), it was decided to replace the last 
objective lens with a more conventional glass, the BaF10 type, cheaper and equipped with an index of refraction
slightly lower and equal to 1.6734; since all the glasses were slightly revised, the final correction of the 
aberrations required the air spacing of the second front doublet as well, thus bringing to six groups of 
air-spaced lenses against the four of the original Summitar and the five of the intermediate star evolution, however, 
the adoption of anti-reflective treatments avoided any problems: the first Summicron was born, launched in 1953 and 
destined for immediate worldwide success, the dean of a legendary dynasty whose fame is still solid 
today. 

The presence of some Summicrons of the first hour (freshman at the turn of the million) with front lens yellowed by
radioactivity does not constitute a contradiction: at the time the complex methodology for refining lanthanum from other 
elements with which it was linked, such as yttrium, cerium and thorium (contained in the original Monazite as thorium oxide in a quantity 
equal to 12%), was absolutely not reliable and certain batches of rare earths sent to glass factories were contaminated with it; the 
Summicron front lens was in LaK9 and some examples have this feature.

=====End of the quote=====

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[luigi bertolotti]

Marco Cavina has just written me, answering to my question on the matter :  in brief, he says that :

.- The fact that the "very first" Summicrons had only one "air lens" (3rd/4th el. glued) was reported to him by ErwinPuts, several years ago

-  But the number of such Summicrons idetical to Summitar *,  is uncertain... he does not remember if the number he reported (920.001 to 922.072) came also from Puts or from another people.

-  He never checked personally one of such early lenses.

(by my side, I'm quite hesitant to try to dismount my 920.382... 🙄 even if could I find good  I instructions... maybe would be tempted...)

 

[jpattison]

On 9/27/2021 at 11:02 AM, luigi bertolotti said:

(by my side, I'm quite hesitant to try to dismount my 920.382... 🙄 even if could I find good  I instructions... maybe would be tempted...)

 

Luigi, 

Why not stand it (front element down) on an unexposed section of film in a totally light tight box for a few days?

If it fogs the film, will this prove it to have the Thorium oxide front element ? 

Compare with a LaK9 front element Summicron if you can.

Just a thought, John

Edited September 30, 2021 by jpattison

[rfaspen]

If only we were near each other...I have multiple Geiger counters.  We could test, and even measure the amount of emissions (if any).

Do you know any geologists or bioengineering researchers?  They might have a Geiger counter to lend.

[luigi bertolotti]

6 hours ago, jpattison said:

Luigi, 

Why not stand it (front element down) on an unexposed section of film in a totally light tight box for a few days?

If it fogs the film, will this prove it to have the Thorium oxide front element ? 

Compare with a LaK9 front element Summicron if you can.

Just a thought, John

The problem is that my goal would be not to check the radioctivity (it is - checked years ago, and color is also typical) , but to verify if the 3rd/4th element are glued or separated... and I think it's a verification you can make only dismounting the top part of the lens (you can - rather easily - unscrew it, revealing the diaphragm mechanism, but this top component should in turn be disassembled and this is a delicate operation)

 

[rfaspen]

6 minutes ago, luigi bertolotti said:

The problem is that my goal would be not to check the radioctivity (it is - checked years ago, and color is also typical) , but to verify if the 3rd/4th element are glued or separated... and I think it's a verification you can make only dismounting the top part of the lens (you can - rather easily - unscrew it, revealing the diaphragm mechanism, but this top component should in turn be disassembled and this is a delicate operation)

 

Of course.  I'm a bit sheepish because I read intently the preceding posts.  Should have known.

I can't think of a way to check those front elements without disassembly.  We used to check for the number of element surfaces by counting the reflections of a light source as the lens is held at a tilt angle.  That idea probably won't help here.

[luigi bertolotti]

1 hour ago, rfaspen said:

Of course.  I'm a bit sheepish because I read intently the preceding posts.  Should have known.

I can't think of a way to check those front elements without disassembly.  We used to check for the number of element surfaces by counting the reflections of a light source as the lens is held at a tilt angle.  That idea probably won't help here.

That's an idea, thanks 😉 The supposed air space (if present) is probably very thin... but I'll try...

[luigi bertolotti]

I tried the test with reflection light... but can't say if it's trustable (had not a proper little single lamp)... but in the occasion, I dismounted the top lenshead of both my Summicron collapsible (920.382 and 1.043,366 - this one is surely with 3rd/4th element separated by the "air lens") : what is evident is that the two components are different :

(older at right)

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920.382 has clearly a more "compact" optical cell... does this mean that 3rd/4th are glued, according to first embodiement of the patent and like Summitar * ? I don't know, but think that can be...

Btw, both have the usual  "factory hand scratchings"... of obscure meaning (1.043.366 has "66"... last digits... but 920.382 has a "77" - not visible in the picture...)

 

[rfaspen]

That is very suggestive.  The plot thickens...☺️

[luigi bertolotti]

Many in this forum do have Summicrons retractable... and dismounting the top is easy...ather pics are welcome 😎

[alan mcfall]

Here is 920218, hand engraved "87" and also + 9.      Trying to find 920109 which I have somewhere.

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[alan mcfall]

920838, hand engraved 88 and -7,  rear element looks same as 920218, still not sure if there is a gap between elements 3 and 4. Glass is oh so yellow, but need to use a Geiger counter to be sure.  921255 is also the same with engraving 579.

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Edited October 3, 2021 by alan mcfall
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[luigi bertolotti]

Thanks Alan : your 920.xxx s  look like mine, with those 2 distinct features that are definitely different in the 1.043.366 I depicted above (left) : the 2mm height can be not so precise (raw caliper) but is surely less than the 1.043.366 which is around 2,8-3 mm.

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