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Milo Schekkerman
Valkir1987
Netherlands
200 Posts |
 Posted - Apr 01 2016 : 12:23:28 PM
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Some of you might not yet know this, at least I think so. It is not an April fool! 
After reading three books about photo-graphical optics, visiting some web pages and the Fed book I came to a surprising conclusion. I also did some work on these Lenses.
Some claim the Fed 2.0 lens is a copy of the Leitz Summar, everything on this lens is however different. It shares some looks and double gauss type design, but that is where the similarity ends.
When you compare the optical diagram of the Fed and the Summar, you will see the lenses of the Fed have 5 flat grinded surfaces. The ones of the Summar are all round (sferical) shaped.
The Taylor Hobson f/2 shares an equal optical design of the Fed. This design has two special remarks. First, five flat surfaces are more easily and more quickly produced. Second, it only takes two kinds of quite regular optical glass to construct this lens. Compared to the Summar which uses a different one for each element.
It is very obvious for Fed to choose this kind of lens construction. The Taylor-Hobson proved to be a very good lens, performing just as good as the Summar. Easier to produce and less valuable optical glass was needed.
Another Britisch design was used for the Fed 28mm f4.5 known as the 'Ross Wide Angle'
Images where taken from 'Het Fotografisch Objectief - H.M. Dekking' and 'Photograpic Optics - Arthur Cox' and 'Camera Fed' |
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Lenny
496 Posts |
Posted - Apr 01 2016 : 3:37:08 PM
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That's interesting Milo.
7 elements with 13 round surfaces in 3 groups: Jupiter-3
6 elements with 12 round surfaces in 4 groups: Summar (Biotar, Planar)
6 elements with 10 round surfaces in 3 groups: Jupiter-8 (Sonnar)
6 elements with 7 round surfaces in 4 groups: Fed 50/2.0
6 elements with 7 round surfaces in 4 groups: Taylor-Hobson f2
4 elements with 6 round surfaces in 3 groups: Industar-22
So, if the Fed 50/2.0 was so good and so cheap to produce, why didn't they continue production after the war? The Fed should be much cheaper than the Jupiter-8 and not so much more expensive than the Industar-22. |
Edited by - Lenny on Apr 02 2016 6:11:01 PM |
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Jacques M.
France
2604 Posts |
Posted - Apr 02 2016 : 03:00:47 AM
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Fed had to recover after WW2. It took them several years. During that time, the Jupiter line was made in production, thanks to Zeiss war spoils.
More: the 2/50mm Fed lens was not coated. It was definitely a prewar lens, always interesting now by its special rendering.
Jacques. |
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Alfa2
Poland
349 Posts |
Posted - Apr 02 2016 : 03:43:03 AM
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I fully agree with Valkir1987. Great description, thanks.
Before and after WWII - there were complitely different situations in USSR regarding camera and optics production.
Before WWII there was probably cooperation with Leitz but russians could not produce such good glass as germans did. So they had to simplify their optical constructions. They wanted to produce something with aperture 2.0 so they had to simplify Summar. Even Industar 10 was not copy of Elmar 5cm.
After WWII there was complitely other reality. Russians had equipment from Carl Zeiss Jena plant and additionally it was possible to make coated lenses.
And I don't see Valkir1987 wrote Fed 2.0 had been good lens. |
Edited by - Alfa2 on Apr 02 2016 03:48:24 AM |
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Lenny
496 Posts |
Posted - Apr 02 2016 : 08:25:30 AM
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quote:
Originally posted by Jacques M.
Fed had to recover after WW2. It took them several years. During that time, the Jupiter line was made in production, thanks to Zeiss war spoils.
More: the 2/50mm Fed lens was not coated. It was definitely a prewar lens, always interesting now by its special rendering.
Jacques, but the Jupiter-8 was made for some Zorki-1 and then for all Zorki-3, much more expensive. And why not produce a new coated Fed 50/2.0 after the war. |
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Lenny
496 Posts |
Posted - Apr 02 2016 : 08:34:35 AM
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quote:
Originally posted by Alfa2
Before WWII there was probably cooperation with Leitz but russians could not produce such good glass as germans did. So they had to simplify their optical constructions. Even Industar 10 was not copy of Elmar 5cm.
And I don't see Valkir1987 wrote Fed 2.0 had been good lens.
That's interesting too. So what kind of type was Industar-10? Sad that sovietcams..com didn't finish the part of Fed 50/3.5.
Milo wrote, "The Taylor-Hobson proved to be a very good lens, performing just as good as the Summar."
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Jacques M.
France
2604 Posts |
Posted - Apr 02 2016 : 08:49:18 AM
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quote:
Originally posted by Lenny
quote:
Originally posted by Jacques M.
Fed had to recover after WW2. It took them several years. During that time, the Jupiter line was made in production, thanks to Zeiss war spoils.
More: the 2/50mm Fed lens was not coated. It was definitely a prewar lens, always interesting now by its special rendering.
Jacques, but the Jupiter-8 was made for some Zorki-1 and then for all Zorki-3, much more expensive. And why not produce a new coated Fed 50/2.0 after the war.
Just a question of possibility. There was nothing remaining from the factory after the war. The time they recovered, the market was taken by KMZ (at least the international one). It's for the same reason that the 1/1000th shutter was abandoned, and the Fed B (with slow speeds) too. A pity.
Thanks for your diagrams, Milo! Very interesting!
Jacques. |
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Jacques M.
France
2604 Posts |
Posted - Apr 02 2016 : 09:02:57 AM
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Concerning the formula, the Industar 10 is a Tessar one, with the diaphragm between the two groups of glasses.
The Elmar has a diaphragm just behind the first glass, at least for al the prewar ones. It allows to identify the fake ones!
Jacques. |
Edited by - Jacques M. on Apr 02 2016 09:04:42 AM |
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Jacques M.
France
2604 Posts |
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Vladislav Kern
Vlad
USA
4252 Posts
My Collection
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Posted - Apr 02 2016 : 10:48:19 AM
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quote:
Originally posted by Alfa2
Before WWII there was probably cooperation with Leitz but russians could not produce such good glass as germans did. So they had to simplify their optical constructions.
I have never heard of such cooperation, mostly western designs were "borrowed" without any licensing.
Milo, this is a very nice discovery! What year was the Tylor-Hobson made?
Best regards,
Vlad |
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Milo Schekkerman
Valkir1987
Netherlands
200 Posts |
Posted - Apr 02 2016 : 12:11:37 PM
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The Taylor and Hobson was first released in 1920. (Perhaps for motion picture cameras) LTM versions appear on the Reid after the war.
I will post some references from the books about this lens tomorrow. Both have been published shortly after the war.
I also know about the Industar-10 and the Elmar. Even the elements have a different shape and dimension. |
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Alfa2
Poland
349 Posts |
Posted - Apr 02 2016 : 2:33:32 PM
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quote:
Originally posted by Lenny
That's interesting too. So what kind of type was Industar-10?
Exactly, it is how Jacques has written. All Elmars have diaphragm behind first element of the lens while all Industar 10 have diaphragm behind second one. Reason is because first element in Elmar refracts light more than first element in Industar 10. This is because russians could not produce such type of the glass which was used in first element of Elmar.
Above information I have read in monthly magazine "Fotogafia" from 50's.
quote:
Originally posted by Vlad
I have never heard of such cooperation, mostly western designs were "borrowed" without any licensing.
Now let's go to history.
After WWII within the scope of war contribution all german patents were no longer valid and one could copy their products without any limitations. Only one patent was still valid for one industry area. In motorization it was VW Beetle. In photography it was absolutely not important construction.
Above information comes from guy who worked almost 30 years in Camara Museum i Krakow.
It seems to be truth. Let's look at first Canon or Minolta camera. But russians used to copy products and than they copied not only those free patent german construction.
Little bit more history. There was strong military cooperation between Germany and USSR in 20's and first half of 30's.
Of course it is not confirmed information about cooperation Leitz - FED. That is why I have used word "probably". I have to look for this information. |
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Jacques M.
France
2604 Posts |
Posted - Apr 02 2016 : 3:07:00 PM
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Hi Vlad!
There was a bilateral cooperation between Germany and USSR, thanks to the treaty of Rapallo (1922). At least, until 1933. After, it's another story...
Though somewhere in the 30s, Makarenko himself wrote about a German delegation from Leitz coming to visit the factory and show a IIIa Leica. So, probably around 1936. Before, in the 1932/34 years, it seems really difficult to conceive and produce the Fed 1a in such a limited time, even if it is a Leica copy, just with drilling machines as past...
Between the official story and the real one, there can be miles or more... About lenses, I just thought the 2/50 Fed was a Summar copy. The track of the Taylor-Hobson is exciting!
Amitiés. Jacques. |
Edited by - Jacques M. on Apr 02 2016 3:10:24 PM |
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Lenny
496 Posts |
Posted - Apr 02 2016 : 6:50:17 PM
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The Taylor-Hobson f2 from 1920 is just a simplified Summar from 1933. Summar is the name of the lens, the formula was called Biotar.
- First there was the Double-Gauss from 1888, 4 elements with 8 round surfaces in 4 groups.
- Developed from this Double-Gauss was the Planar from 1896, 6 elements with 12 round surfaces in 4 groups, the inner lens pairs were cemented.
- Developed from this Planar was the Taylor-Hobson from 1920, 6 elements with 7 round surfaces in 4 groups, asymmetry was added.
- Developed from this Taylor-Hobson was the Biotar from 1927, 6 elements with 12 round surfaces in 4 groups.
- After WW2 they changed the name from Biotar into Planar again.
In the wikipedia I read that the Taylor-Hobson was commercially unsuccessful.
https://en.wikipedia.org/wiki/Double-Gauss_lens
Since the Fed 50/2.0 has the same formula as the Taylor-Hobson I guess the FED 50/2 was inferior to the Summar, that might be a reason why it wasn't continued after the war. But still, the Fed 50/2.0 looks so sexy. |
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Jacques M.
France
2604 Posts |
Posted - Apr 03 2016 : 08:53:14 AM
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quote:
Originally posted by Lenny
Since the Fed 50/2.0 has the same formula as the Taylor-Hobson I guess the FED 50/2 was inferior to the Summar, that might be a reason why it wasn't continued after the war. But still, the Fed 50/2.0 looks so sexy.
I don't understand what you mean, Lenny. Once more, the Summar and the Fed 2/50 were lenses of the past, in 1950. The Summar had been replaced by the Summitar just before the war, and none of these lenses was coated at that time... If they are sought after now, it's for a question of rendering, acute and with low contrast at the same time.
As for a grading between lenses, I confess I am unable to decide which is the best, only by looking at diagrams. The quality of the camera, of mount, of the balsam, the composition of glass are certainly most important too. And concerning the real condition of the factory at the end of the war, I just remember that there were no novelty until 1955. To compare with KMZ: during these ten years, the listing of novelties would be too long...
As for the Biotar, I remember it's a lens developed by Zeiss in the thirties for prewar SLR (Exakta and Praktiflex). The Sonnar formula was too protruding for the mirror, hence the use of an evolution of the double gauss. After the war, we find again this 2/5,8cm Biotar at KMZ's (the Helios in m39 and m42 mounts) and always by Zeiss in m42 mount for the first Contax SLR.
Sorry for these explanations, a bit OT, specially to you, Milo. Now, I shut up...
Jacques. |
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Milo Schekkerman
Valkir1987
Netherlands
200 Posts |
Posted - Apr 03 2016 : 12:53:50 PM
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Thank you all for the great response. I shall translate a part from H. M. Dekking's book. And I shall try to answer most of the questions.
quote:
A typical example is the Taylor-Hobson F2 (fig 73.) which is curious for two reasons. First, the designer Lee managed to keep three of the ten surfaces flat in the final design. Which has many effords for the manufacturing and control. Second is the fact that only two types of glass where used. A work of art because in most cases the amount of elements is equal to the amount of glass types used.
One thing that must be considered too, is that optical designers where late to conclude that it had already been possible to make a succesfull double Gauss for years with existing glass types. At the time the Leica and Contax where in developtment, the focus lay on improving the Triplet and Tessar type of design. (even the Sonnar was eventually based on the three element design)
http://www.klassik-cameras.de/Biotar_en.html
Better developtment was however possible with the Double Gauss type which is still used today.
Alas I do not have the second book of Cox where the quote of commercial succes as refered in the Wikipedia article about the Taylor and Hobson is mentioned. It might not have been a succes in Photograpy but it was succesfull in the motion picture industry: http://www.cookeoptics.com/t/history.html#003
Then I remembered this: http://ussrphoto.com/forum/topic.asp?TOPIC_ID=1683
I wish I had never sold this lens. I can't compare them now... although the covering of field should be smaller.
I also found this Fed lens test/comparison:
http://www.rangefinderforum.com/forums/showthread.php?threadid=128344
Back to Fed in Kharkov. Is there anything known about the staff responsible for the development and production of the optics? Did they develop and produces the lenses themselves, or where they designed elsewhere like Leningrad? |
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Lenny
496 Posts |
Posted - Apr 03 2016 : 2:11:24 PM
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Thanks Milo, the test with the bank note is amazing.
Is there a passport known with a Fed 50/2.0? They always mention the resolution there.
And the Jupiter-8 is disappointing, it should be more expensive to produce than the Fed 50/2.0.
I think that early in 1938 all russian lenses were calculated by GOI or calculations were checked by GOI, as we talked about this topic recently. |
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Jacques M.
France
2604 Posts |
Posted - Apr 04 2016 : 03:41:41 AM
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Amazing results in RFF! The 2/50 Fed would perform better than a Jup 8! Either they mixed the results, or the Jup was very bad. Of course, it's only a test. But I have some experience in using these two lenses, and in ordinary conditions, the Jup (8 and 3) are more contrasted than the Fed. Normal as this last one is not coated.
There is another difference between the Fed and the Summar: the diaphragm. Round hole for Fed, beautiful hexagonal one for the Summar which is said to have a slight different rendering (swirling bokeh) for that reason in some conditions. For me, the difference is very tiny...
About the exact part of Fed factory, the GOI calculated all the lenses, and checked them. The JLP is affirmative on this point. But where were these lenses produced? By whom? In Kharkov? I should be glad to know more...
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Lenny
496 Posts |
Posted - Apr 04 2016 : 05:44:44 AM
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Great explanation about the Elmar on Wikipedia.
quote:
It is sometimes thought that The Leitz Elmar 50/3.5 was a Tessar copy or clone. This is not the case. Although the lenses appear similar in layout, there is a lot more to the design and performance of a lens than simply the layout of the glass elements. The position of the stop, the optical characteristics of the glasses used for each element, the curvature of each lens surface, and the negative format which the lens is designed to cover, are all vital to the performance of the lens, and in the Leica lens these were all different from the Tessar. When the Leica was being developed Oskar Barnack tried a 50mm Tessar, but because it had been designed to cover only the 18x24mm field of a cine frame he found the coverage of the Leica 24x36mm format to be inadequate. The lens designed by Max Berek for the Leica rangefinder camera was a modified Cooke Triplet with five elements in three groups, the third group being three cemented elements, with the aperture stop in the first air space. This lens, called the Elmax, gave good coverage of the 24x36mm format and was used until improved optical glass allowed the third group to be simplified to a cemented pair and then lens was renamed the Elmar. It was not until Zeiss Ikon were developing the Contax camera to compete with the Leica that the Tessar was redesigned to cover a 24x36mm negative.
https://en.wikipedia.org/wiki/Tessar
The Fed 50/3.5 has nothing to do with the first Elmar developed from a Cooke Triplet because that Elmar was earlier in time. The Contax came out in 1932. Fed copied the Elmar Tessar. |
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Lenny
496 Posts |
Posted - Apr 04 2016 : 06:04:17 AM
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quote:
Originally posted by Jacques M.
Amazing results in RFF! The 2/50 Fed would perform better than a Jup 8! Either they mixed the results, or the Jup was very bad. Of course, it's only a test. But I have some experience in using these two lenses, and in ordinary conditions, the Jup (8 and 3) are more contrasted than the Fed. Normal as this last one is not coated.
I thought about that too Jacques, maybe those Jupiter-8 in the test were not ok. We need more tests to confirm this and comparisons at f4 too.
Still sad to me that Fed didn't produce a coated Fed 50/2 (Taylor-Hobson) after the war because it should be cheaper to produce than a Jupiter-8 (Sonnar). |
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Jacques M.
France
2604 Posts |
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Milo Schekkerman
Valkir1987
Netherlands
200 Posts |
Posted - Apr 04 2016 : 2:10:22 PM
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Let's consider too that macro and reproduction work is probably not that suitable for a Jupiter 8. Its strenghts lay elsewhere. But the results of the Fed where indeed impressive.
According the Tessar and Elmar:
The place of the aperture is not simply changed in the three element design (Industar, Tessar, Elmar because pin-cushion distorsion depends on it.
quote:
There is another difference between the Fed and the Summar: the diaphragm. Round hole for Fed, beautiful hexagonal one for the Summar which is said to have a slight different rendering (swirling bokeh) for that reason in some conditions. For me, the difference is very tiny...
About the exact part of Fed factory, the GOI calculated all the lenses, and checked them. The JLP is affirmative on this point. But where were these lenses produced? By whom? In Kharkov? I should be glad to know more...
The Summar even has a dome shaped aperture, made to move between the sferical forms. That's why it only goes up to f12.5
The Fed swirls too when shot wide open:
Great to read the info about GOI. Fed used to have its own lens polishing workshop. But it is yet not known if they made and prepared the glass for the special optics. I would like to know more about it too.
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Jacques M.
France
2604 Posts |
Posted - Apr 04 2016 : 3:11:58 PM
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It's not a swirl, but a maelstrom...
I have never tried one of my uncoated lenses in such conditions! In the thirties, they were considered as aberrations which had to be corrected...
The movement seems different with Sonnar formula lenses. With a Sonnar 1,5/5cm or a Jup 3 wide open (or a 8,5cm or 13,5cm Sonnar or Jup), there are as many swirls as things (leaves for example) in the background, at a correct distance, of course...
PS: your Fed 2/50 is really perfectly regulated...
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Jacques M.
France
2604 Posts |
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Lenny
496 Posts |
Posted - Apr 06 2016 : 09:58:19 AM
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Of course, if you want to copy something you don't copy everything. If you have aperature blades on the shelves, you use them. They just took the design of the Taylor-Hobson formula, needed to calculate it again for the kind of glass they had available.
Thanks for the pictures Jacques, seems this Taylor-Hobson is quite expensive. And the Summar hahaha I don't want one. |
Edited by - Lenny on Apr 06 2016 10:04:25 AM |
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Vladislav Kern
Vlad
USA
4252 Posts
My Collection
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Posted - Apr 06 2016 : 10:37:35 AM
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| This is a fantastic thread! I love it when a preconceived notion is turned on its head. Marvelous job, Milo! |
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Lenny
496 Posts |
Posted - Apr 06 2016 : 11:00:45 AM
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I read in the Wikipedia that Leitz and Taylor-Hobson worked close together before the war. Leitz even built a factory in Britain. When the war started the factory was expropriated from the british government and given to Taylor-Hobson and Taylor-Hobson continued production.
I found this Summarit, the seller describes it as a Taylor-Hobson version. Could be, that even Leitz copied the Taylor-Hobson and if it does match the timeline, Fed could have copied a Leitz which was a Taylor-Hobson copy. The blades look exactly like on the Taylor-Hobson.
http://www.ussrphoto.com/UserContent/642016_Leitz Taylor-Hobson.JPG
It seems it was later in the timeline, 1950. But still, Leicaforum descibes a Summarit as Taylor-Hobson version. Maybe there was already another version earlier in the timeline.
http://www.l-camera-forum.com/leica-wiki.en/index.php/Summarit_f%3D_5_cm_1:1.5
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Edited by - Lenny on Apr 06 2016 11:43:39 AM |
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Alfa2
Poland
349 Posts |
Posted - Apr 07 2016 : 08:18:51 AM
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Yes, this is fascinating thread. I have learned a lot.
Maybe somebody can add anything interesting ?
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Jacques M.
France
2604 Posts |
Posted - Apr 07 2016 : 11:06:55 AM
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Just an addition about the Fed 4,5/28mm. This beautiful lens was probably very difficult to mount, with these six very tiny glasses in four groups... And what about the air/glass surfaces, with all these possible internal reflections...
The two main contemporaneous wide angle lenses were the Hektor 6,3/28mm (Leica) and the Tessar 8/2,8cm (mainly for Contax). The difference of aperture compared to the Fed is very impressive... We have diagrams of a Tessar and of the Fed above. The Hektor's is there:
http://www.ussrphoto.com/UserContent/742016_hektor_28_63.jpg
Jacques.
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Alfa2
Poland
349 Posts |
Posted - Apr 07 2016 : 2:03:26 PM
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Thank you, Jacques. I never thougt about the lenses this way.
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Milo Schekkerman
Valkir1987
Netherlands
200 Posts |
Posted - Apr 09 2016 : 1:53:37 PM
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Thank you all for the great response.
quote:
And what about the air/glass surfaces
Not all of them are air spaced, the two outer lenses are cemented together. (but there are a lot of remaining reflecting surfaces. I know this because my 28mm lens has a separating front element. Disassembled it once, but it takes a very skilled person in optics to repair the kit layer of such a tiny lens.
But as far as I know. The Fed 28mm is the only wide angle 35mm lens that uses this formula. Unique of its kind and construction.
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Jacques M.
France
2604 Posts |
Posted - Apr 11 2016 : 09:39:16 AM
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The cemented glasses have their bright sides: the lenses are easier to mount and have a reduced number of reflective surfaces. Six nevertheless for these two Fed lenses, plus the diaphragm which can play its part.
They have their weak points too: with age, balsam can yellow or produce haze. Summars often have that problem. My 4,5/28mm Fed too, but I won't try to disassemble it! No separation, as it seems.
When I can, I will try some photos.
Thanks for your photos in the specific forum: they are an incentive to use our old Russian lenses.
Amitiés. Jacques. |
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Milo Schekkerman
Valkir1987
Netherlands
200 Posts |
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Zoom
596 Posts |
Posted - Apr 15 2016 : 12:59:26 AM
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quote:
Originally posted by Vlad
I have never heard of such cooperation, mostly western designs were "borrowed" without any licensing.
Vlad, I'm very sorry. But this is a very primitive understanding of patent law. The lens was patented in the USSR? No? Do svidaniya! |
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Alfa2
Poland
349 Posts |
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Jacques M.
France
2604 Posts |
Posted - Apr 15 2016 : 05:17:40 AM
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Very interesting.
No number either... |
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Milo Schekkerman
Valkir1987
Netherlands
200 Posts |
Posted - Apr 15 2016 : 08:13:38 AM
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quote:
MC coating
A technique which appeared in the 60'ies. This could have been done afterwards. But what puzzles me is the larger barrel that touches the rangefinder cam. |
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Jacques M.
France
2604 Posts |
Posted - Apr 15 2016 : 08:21:35 AM
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The infinity button should be on the other side...
The lens is not well mounted.
I have somewhere a coated 2/50 Fed. The comparison could be interesting. |
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Vladislav Kern
Vlad
USA
4252 Posts
My Collection
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Posted - Apr 15 2016 : 08:25:08 AM
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quote:
Originally posted by Zoom
quote:
Originally posted by Vlad
I have never heard of such cooperation, mostly western designs were "borrowed" without any licensing.
Vlad, I'm very sorry. But this is a very primitive understanding of patent law. The lens was patented in the USSR? No? Do svidaniya!
 That's awesome! |
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Lenny
496 Posts |
Posted - Apr 15 2016 : 10:52:28 AM
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| Hello Zoom, what if the lens was patented in the USSR, would it had made any difference? |
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Milo Schekkerman
Valkir1987
Netherlands
200 Posts |
Posted - Apr 15 2016 : 3:11:00 PM
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Optical designs where easy to get in the West. Patents where very well respected and each 'house' had its own specialties. In the preface of Dekking's book he writes about the companies which where very helpfull sending him schematics and details about lens construction.
But even if you decide to 'copy' a design to a certain example, you still have to recalculate it in order to make it work with the 35mm format and camera of choice. A mount has to be designed and constructed as well. Great work for the Fed has been done on this.
The Summar of Leitz was the first succesfull double Gauss design lens with an aperture up to f2 in the Leica family. Improving the triplet led to designs like the Elmax, Elmar and Hektor. They really forgot (even Zeiss) that the Gauss design was in fact the winning concept for a standard 35mm format lens of large aperture. |
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Zoom
596 Posts |
Posted - Apr 15 2016 : 3:49:30 PM
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quote:
Originally posted by Lenny
...what if the lens was patented in the USSR, would it had made any difference?
Of course. The state guarantee the exclusive rights of the patentee. The state was tough...
quote:
Originally posted by Valkir1987
But even if you decide to 'copy' a design to a certain example, you still have to recalculate it in order to make it work.
That is quite true. |
Edited by - Zoom on Apr 15 2016 4:11:58 PM |
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Alfa2
Poland
349 Posts |
Posted - Apr 16 2016 : 06:24:47 AM
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quote:
Originally posted by Valkir1987
They really forgot (even Zeiss) that the Gauss design was in fact the winning concept for a standard 35mm format lens of large aperture.
I think they didn't forget. They had problems because they could not coat their lenses yet.
I have read interesting article in magazin "Fotografia" from 1953.
Every 1 cm of glass absorbs 2.4% of light.
From light absorbing piont of view 2 cemented lenses can be treaten like 1 lens. The most "dangerous" are surfaces between air and glass.
Two surfaces of a lens (air/glass/air) absorbs 10% of light.
This is the reason why they could not use Planar which was calculated in 1896, but Tessar from 1902 had less surfaces where air and glass met.
There are 2 intersting tables regarding light absobring. If somebody is interested in it I will place them here.
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Edited by - Alfa2 on Apr 16 2016 06:28:52 AM |
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Lenny
496 Posts |
Posted - Apr 16 2016 : 08:57:05 AM
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quote:
Originally posted by Alfa2
There are 2 intersting tables regarding light absobring. If somebody is interested in it I will place them here.
Sure Alfa, please post them, it's interesting. |
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Jacques M.
France
2604 Posts |
Posted - Apr 16 2016 : 12:13:57 PM
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Here is my coated Fed lens, beside a regular one:
We already discussed about it.
Jacques. |
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Alfa2
Poland
349 Posts |
Posted - Apr 16 2016 : 12:55:42 PM
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First table. I think it is clear for all. Of course it refers to not coated lenses only.
Jacques, very interesting coated FED 2/50 but there is too less photo. We cannot see e.g if rear lens is coalted too.
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Jacques M.
France
2604 Posts |
Posted - Apr 16 2016 : 3:05:47 PM
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Thanks to this first table, Alfa.
Generally speaking, I think that Sonnars were easier to cement. For example:
http://www.ussrphoto.com/UserContent/1642016_Sonnar 1,5-5cm formula.jpg
Seven lenses in three groups, 4 surfaces air/glass only. In the thirties/fifties, these Sonnars were better than Leica lenses. The Leitz Summicron (2/50mm, double gauss evolution) made up lost time, which was partially due to the poor resistance of the front glass of Summars and Summitars...
Zeiss produces now Planars (evolution of the "double-gauss")as well as Sonnars, for Leica M and others. Of course, things are different now...
Concerning my "coated" Fed 2/50mm, it's only the first lens which is coated.
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Milo Schekkerman
Valkir1987
Netherlands
200 Posts |
Posted - Apr 16 2016 : 3:22:30 PM
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quote:
I think they didn't forget. They had problems because they could not coat their lenses yet.
I have read interesting article in magazin "Fotografia" from 1953.
Every 1 cm of glass absorbs 2.4% of light.
From light absorbing piont of view 2 cemented lenses can be treaten like 1 lens. The most "dangerous" are surfaces between air and glass.
Two surfaces of a lens (air/glass/air) absorbs 10% of light.
This is the reason why they could not use Planar which was calculated in 1896, but Tessar from 1902 had less surfaces where air and glass met.
There are 2 intersting tables regarding light absobring. If somebody is interested in it I will place them here.
Coatings reduce the reflection and increase the contrast and sharpness. It is certainly true that designs with many air glass surfaces finally got their succes after lens coating was possible.
Zeiss even tried to develop glass with a refraction and dispersion close to that of air. This led to the 'Herar'. Only a few of them where produced.
But the focus for 35mm photography remained improving the triplet base. I doubt the main reason for this is the need of coating the surfaces.
Gauss designs where used in 35mm format mirror reflex camera's (Exakta) and motion picture camera's with beam splitters. A Gauss leaves more room behind the lens for mirrors and prisms in 35mm format. Retro focus lenses where yet to be developed.
Improving the triplet led to the Zeiss Sonnar, but such lens can only be used on a rangefinder. (it has only one reflective surface less than the Biotar) More than 1000 pages of optical calculations where needed to design the Sonnar. It really took more time in the computerless age.
Paradoxes and misconceptions have delayed the development of optics for ages. Isaak Newton for example was convinced of the fact that it was optically impossible to correct the shifting of colors with lenses. As a result telescopes where only built with mirrors. Film used to be sensitive only for blue and violet. It was not needed to correct colors for photography. But in field optics and microscopes, color correction was needed.
Only one Sonnar type lens appeared for the SLR, known as the Takumar 58mm.
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xalmaz
Russia
37 Posts
My Collection
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Posted - Apr 17 2016 : 09:27:52 AM
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Dear Milo,
Seems, Jupiter11/Jupiter21/Jupiter6 are not Sonnars now? They was on SLR. Rear distance of Sonnars just below focus length, no more.
http://xalmaz.narod.ru |
Edited by - xalmaz on Apr 17 2016 09:28:28 AM |
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Lenny
496 Posts |
Posted - Apr 17 2016 : 11:15:34 AM
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quote:
Originally posted by xalmaz
Seems, Jupiter11/Jupiter21/Jupiter6 are not Sonnars now?
Jupiter-11 is a Tessar type, 4 elements in 3 groups. Don't understand why it got the Jupiter name because this formula is so easy and aperature 4.0 is definitely not like the sun (Sonnar). Other Jupiters are much more complicated. But a 135mm lens in the same type like the Jupiter-9 might have been so expensive that nobody could afford it. |
Edited by - Lenny on Apr 17 2016 11:17:45 AM |
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Jacques M.
France
2604 Posts |
Posted - Apr 17 2016 : 11:33:36 AM
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I just think that Milo talked of the "normal" 50mm lenses.
It's right, for example, that Zeiss could not use their Sonnars on the Contax S, because a question of register. Hence the solution of the Biotar.
Some lenses had to be "cut" to adapt to a new register. For example, the Sonnar 13,5cm (Jup 11), but not the 8,5cm (Jup 9). And the Industar 22, "cut" to be put on the first Zenit...
I was surprised when I discovered that Canon had abandoned their Sonnars (the 1,5/5cm for example) to put double Gauss type lenses (the 1,4/50mm). Probably a question of normalization with their rangefinder and SLR cameras.
Some lenses were difficultly mounted on rangefinders: the 2,8/3,5cm (Jup 12) is the extreme type, with its protruding back. Some Bessas don't accept it...
Jacques. |
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Milo Schekkerman
Valkir1987
Netherlands
200 Posts |
Posted - Apr 17 2016 : 3:04:55 PM
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quote:
I just think that Milo talked of the "normal" 50mm lenses.
True! Forgot to tell about that. The Jupiter 11, 9 and 6 are all true Sonnars. (which derived from the Triplet) The Zeiss Triotar is a 135mm f4 Triplet, and even a Tessar exists.
The Jupiter 12 is the only non Sonnar in this row. The Jupiter 12 is a Biogon making things complicated. It should have been named Helios instead.
Sonnar, Triplet and Tessar: Three group design.
Helios: Double Gauss, 4 group design with 6 element.
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Milo Schekkerman
Valkir1987
Netherlands
200 Posts |
Posted - Apr 18 2016 : 08:12:15 AM
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I also forgot to tell, that the resolving power of a lens doest not increase when a coating is applied. It will improve contrast and therefore also countour sharpness.
When optical glass ages, a natural coating will form as a result of contact with air. If you are lucky and the balsam layers remain intact, the lens will improve in performance. |
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Alfa2
Poland
349 Posts |
Posted - Apr 18 2016 : 1:21:46 PM
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Milo, thank you for your explanation. It is very interesting. I did not know some facts you have written.
But why performances on not coated Xenon/Summarit 1.5/50 were so week (only 5 groups of elements) while performances of coated lenses with more groups of elements were/are OK ?
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Edited by - Alfa2 on Apr 18 2016 3:01:11 PM |
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Alfa2
Poland
349 Posts |
Posted - Apr 18 2016 : 1:36:22 PM
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Coating strongly reduces reflections and stray light.
And pls read what is written e.g. here
http://www.klassik-cameras.de/Biotar_en.html
"Ib) SONNAR family
Ernemann was merged 1926 into ZEISS-IKON and Bertele founds himself a lens designer in Jena. Already in 1924 he succeed in scaling down the Ernostar f/2 integrating a cemented group consisting of three elements (triplet). At Zeiss he managed to connect the third and fourth element, and therefore reduced the total of optical groups to three and effetively reduced objectionable reflections and stray light. Within a year he afford to enhance the aperture of that lens about virtually one f/stop to f/1.5 by means of replacing the last element with a cemented group of two.
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With the advancement in coating technique it is possible today to arrange glass elements isolated rather than to combine them into a group without getting objectionable reflections and stray light. Secondly fabrication of cemented triplets were, and are, more expensive than with isolated elements. At least the short back-focus length makes the Sonnar compact in build but not usable for most SLR cameras because the moving mirror requires more space. These facts - not performance considerations - caused the extinction of "true" Sonnars since 1960."
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Edited by - Alfa2 on Apr 19 2016 12:09:19 PM |
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Topic |
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Prewar Fed Optics (once more)
