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  1. #1

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    Don't Trust Everything You Read On The Internet, or: 2 Myths of the Biogon Lens

    These stuff are known to many people in this forum, but I didn't find any concise summary, so here goes. Note that I am not a lens designer, I just like to look at pretty pictures, so if there are errors in this post, my apology in advance.

    It is often said that the Biogon lens is a "near symmetrical" design. Plus, a well known blogger wrote "..the Mamiya (7) 43mm is a copy of the better, original 10 element Biogon..." this quote by Ken Rockwell has been repeated many times, usually leaving off the end of his sentence: "...first used in the 75mm f/4.5 lens for view cameras."

    So first of all, is the Biogon a "near-symmetrical" design? Here's the Biogon diagram from the 1954 patent application. You can see Mr. Bertele signature:


    I am not a lens designer, and while the two halves look sort of similar in overall profile, one has to squint a lot to say that the halves are symmetrical. Certainly, I highly doubt the lens would image correctly if you swap the halves, which would be IMHO, a test for a true symmetrical design.

    Here are two examples of symmetrical design:
    1) The Schneider Super Angulon large format lens


    2) and the famous Dagor ("Double Anastigmatic Goerz"), also a large format lens


    They are very symmetrical.

    How about Mr. Rockwell's claim that the Mamiya 7 43mm is a better copy of the original 75mm Biogon? I can't find a separate lens diagram that shows the 75mm Biogon, but according to the Zeiss document, the initial batches of postwar-Biogon (21mm, 38mm, 53mm and 75mm) were designed at the same period, with no indication that they use different lens formulations. Here's the Biogon 38mm lens diagram:



    Which to my eyes, look just like the diagram in the patent. I would say that any negative statement about the Biogon 38mm being a simplified copy is not supported by facts.

    And the Mamiya 43mm lens diagram? As far as I know, there is no 43mm lens diagram on the web anywhere. However, I did own the lens once and have the instruction manual, which conveniently, has the lens diagrams:



    Certainly not an exact copy of the one in the patent. May be the 75mm Biogon is different and closer to the Mamiya 43mm lens? Anyone knows definitively?

    For further references, here's Schneider designed Leica 21mm Super Angulon:


    and the modern 21mm ZM "Biogon" lens, which does not look at all like a Biogon:


    I have the 25mm ZM which I believe has the same profile. The 35mm Biogon C ZM also does not look at all like the Biogon, so it is clear that Zeiss is now using the word Biogon as a brand, rather than a design.

    This is actually not the first time they changed what is a Biogon. Apparently there was a Biogon design, also done by Mr. Bertele, prior to WWII. However, when he designed the new series of lens during the post-war period, Zeiss opted to reuse the name. This is why I used the phrase "postwar-Biogon" above.

    Regardless, while the Biogon is not symmetrical and probably not even near-symmetrical, even in 2015, the Biogon design in the form of the Hasselblad SWC various incarnations, is still one of the best lens and produces amazing images.
    // My name is Richard Man, I can't get APUG to change my username :-)
    // I am a Hybrid Photographer, using 4x5, Hasselblad, Leica etc. with digital post-processing workflow.
    http://richardmanphoto.com http://facebook.com/richardmanphoto

  2. #2
    Mustafa Umut Sarac's Avatar
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    I tried to read many scientific papers on lens design and read that Biogon latest have 450 lp/mm compared to Leitz lenses from 1950s to 1980s have 250 lp/mm resolution.

    After 15 years of reading , I found most noticable difference bebtween lenses are nonlinear glass characteristics ad three dimensional transfer function which two are responsible about sfumato effect.

    I look to a Leica photograph and search in hundreds of drawings , paintings , gravures , photogravures , half toning effects , color mixing characteristics of hand colored bw postcards which they are printed with 11 to 16 or more lithographs or I am reading all the paint , ink , layer characteristics of the paintings to their thickness change referencing value etc etc.

    Three dimensional transfer function is a very complex and artisan originated business to design a lens.

    It is responsible to convert a original reference 3d dimensional volume and light grade change in to a photograph.

    Volume change on subject and light change on subject requires different calculations and different results on the film.

    First-
    - you decide how many parts would be divided on the subject for volume change
    - you find differantial equations to explain above.
    - than you find another equations to convert xyz in to xy.

    Photographers always forgot to understand , the source image is three dimensional and photographers have no idea about lens designers work to calculate the volume and light change.

    They are photographers and bigger portion have no idea about 3d sculptures or art movements. So when someone talks about relief effect , they laugh.
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  3. #3

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    a symmetrical lens design is for doing 1:1 reproduction which is common sense if you think about it. Anything close to symmetrical lens will likely perform best at close focussing distances. So portraits and product photography. Landscapes on the other hand which require focussing at hyperfocal distance would benefit from other designs. Don't know what they are called though.

  4. #4

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    didjiman wrote:

    I am not a lens designer, and while the two halves look sort of similar in overall profile, one has to squint a lot to say that the halves are symmetrical. Certainly, I highly doubt the lens would image correctly if you swap the halves, which would be IMHO, a test for a true symmetrical design.
    I have nothing against didjeridoos but I have to disagree with you. I once bought twenty 38/4.5 Biogons. Steve Grimes put one in a proper #0 for me, I still have one "in case of need" in its original AGI F.135 shutter, and the others are long sold. The lens forms a perfectly good image when reversed but of course it gives better image quality at magnifications above 1:1 than at lower magnifications.

    Mustafa Umut Sarac, who prefers to be addressed as Umut, wrote:
    I tried to read many scientific papers on lens design and read that Biogon latest have 450 lp/mm compared to Leitz lenses from 1950s to 1980s have 250 lp/mm resolution.
    This is a lovely example of the confusion between design type and trade name. Ludwig Bertele designed and patented two quite different lenses that Zeiss sold as Bigons. The first is an f/2.8 Sonnar derivative sold mainly for Contax rangefinder cameras (see U.S. patent 2,084,309), the second is an f/4.5 Aviogon derivative sold for press and view cameras (see U.S. patent 2,721,499). There was also an f/5.6 version for repro cameras. Two designs, one trade name. All they have in common is the trade name.

    Quite recently Zeiss resurrected the Biogon trade name to cover lenses that have nothing in common with the design types Bertele patented or with each other. Many more designs, still one trade name. Because of this it is impossible to speak generally about "Biogons." We have be very clear about which one we mean.

  5. #5
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    Dr. Hubert Nasse, senior scientist at Zeiss and chief optical designer wrote in Camera Lens News 41 (2011) published by Zeiss Carl Zeiss AG Camera Lens Division:

    "In 1946 the first patent for a new kind of symmetrical wide-angle lens was applied for by the Russian lens designer Michail Rusinov. It looked as if two retrofocus lenses had been combined with the rear elements together and thus had a symmetrical arrangement of positive refractive powers close to the aperture, surrounded at the front and back by strongly negative menisci.
    As of 1951, Ludwig Bertele carried this idea further and designed the legendary Biogon on behalf of Zeiss..."
    ---

    Quote Originally Posted by Dan Fromm View Post
    didjiman wrote:

    I have nothing against didjeridoos but I have to disagree with you. I once bought twenty 38/4.5 Biogons. Steve Grimes put one in a proper #0 for me, I still have one "in case of need" in its original AGI F.135 shutter, and the others are long sold. The lens forms a perfectly good image when reversed but of course it gives better image quality at magnifications above 1:1 than at lower magnifications.

    Mustafa Umut Sarac, who prefers to be addressed as Umut, wrote:


    This is a lovely example of the confusion between design type and trade name. Ludwig Bertele designed and patented two quite different lenses that Zeiss sold as Bigons. The first is an f/2.8 Sonnar derivative sold mainly for Contax rangefinder cameras (see U.S. patent 2,084,309), the second is an f/4.5 Aviogon derivative sold for press and view cameras (see U.S. patent 2,721,499). There was also an f/5.6 version for repro cameras. Two designs, one trade name. All they have in common is the trade name.

    Quite recently Zeiss resurrected the Biogon trade name to cover lenses that have nothing in common with the design types Bertele patented or with each other. Many more designs, still one trade name. Because of this it is impossible to speak generally about "Biogons." We have be very clear about which one we mean.
    Regards,
    Georg

  6. #6

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    Quote Originally Posted by snapguy View Post
    And...your point is.....?
    Just saying.

  7. #7

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    Quote Originally Posted by Dan Fromm View Post
    I have nothing against didjeridoos but I have to disagree with you. I once bought twenty 38/4.5 Biogons. Steve Grimes put one in a proper #0 for me, I still have one "in case of need" in its original AGI F.135 shutter, and the others are long sold. The lens forms a perfectly good image when reversed but of course it gives better image quality at magnifications above 1:1 than at lower magnifications.
    I stand corrected. Thanks Dan for correcting my mere speculation. The Biogon design still looks less than symmetrical though, wouldn't you agree?
    // My name is Richard Man, I can't get APUG to change my username :-)
    // I am a Hybrid Photographer, using 4x5, Hasselblad, Leica etc. with digital post-processing workflow.
    http://richardmanphoto.com http://facebook.com/richardmanphoto

  8. #8

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    didijman, the f/4.5 Biogon looks as symmetrical to me as a man with two ears on one side of his head and one on the other. It certainly isn't perfectly symmetrical.

    That said, Brian Caldwell, a very capable lens designer, has argued (my words here, not his) that f/4.5 Biogons rely on symmetry for some of their corrections. You and he don't have quite the same understanding of symmetry.

  9. #9
    Nodda Duma's Avatar
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    Don't Trust Everything You Read On The Internet, or: 2 Myths of the Biogon Lens

    From a design point, the Biogon would be symmetric because the odd aberrations in the first half are canceled by the odd aberrations in the second half (odd aberrations including coma, distortion, and lateral color). Kind of like a freebie. When this happens, we call the design symmetric....even if the front and rear halves are physically slightly different. It then becomes much easier to correct the remaining aberrations. Hence why the fastest lenses are usually double gauss.

    The physical difference in layout is because the lens is designed for infinite conjugate..a fancy term for correction at infinite focus. But it is still considered symmetrical due to negation of aberrations before and after the central stop.

    Contrast to something like a telephoto or Petzval, where the aberrations are corrected individually in each group (Petzval), or just beat down by lens shape, use of achromats, and other tricks in the bag (telephoto).


    Btw, older designs are perfectly symmetrical because it was easier / faster for the designer to only work with one half of the design to correct the even aberrations. Once that was done he copies it on the other side of the stop and automatically eliminates odd aberrations without the necessity of further hand calculations. With computer aided design, you aren't limited by that and can get a bit more performance out by letting it depart from physical symmetry as a final design step. That actually works really well.


    Back to modern Biogons: I would guess the designer used an earlier Biogon as the starting point for a redesign, mentioned that fact in front of the wrong person (ie a marketing person), and they ran with it. I'd bet money that's what happened.

    Cheers,
    Jason
    Last edited by Nodda Duma; 04-23-2015 at 08:39 PM. Click to view previous post history.

  10. #10

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    Jason, thank you! Great to hear from someone who knows these stuff.
    // My name is Richard Man, I can't get APUG to change my username :-)
    // I am a Hybrid Photographer, using 4x5, Hasselblad, Leica etc. with digital post-processing workflow.
    http://richardmanphoto.com http://facebook.com/richardmanphoto

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