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Re: [woodandbrass] Re: Antique brass CZJ 240mm Anastigmat-Weitwinkel lens!

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  • Richard Knoppow
    ... From: Stephen Shohet To: Sent: Friday, August 17, 2012 4:46 PM Subject: [woodandbrass] Re: Antique
    Message 1 of 17 , Aug 19 3:10 PM
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      ----- Original Message -----
      From: "Stephen Shohet" <sbshohet@...>
      To: <woodandbrass@yahoogroups.com>
      Sent: Friday, August 17, 2012 4:46 PM
      Subject: [woodandbrass] Re: Antique brass CZJ 240mm
      Anastigmat-Weitwinkel lens!


      > Thank you, Richard for the PDF with patent pictures!
      > Clearly very
      > different from any bigdistant bizarre variation on a
      > Goerz-type double
      > meniscus. Steve
      >
      The story is that Von Hoegh approached Zeiss with the
      design for what became the Dagor and was turned away. He
      then went to Goerz who accepted the design and made the lens
      but swindled von Hoegh out of his royalties.
      The reason Zeiss declined the design was that Paul
      Rudolph was already working on a similar lens. von Hoegh
      shows two versions of the Dagor in his patent differing in
      the order of powers of the cemented elements. The version
      that was produced by Goerz has the positive elements on the
      outside, the opposite arrangement was used by Zeiss for one
      version of the Protar and by Watson for the Holostigmat.
      This is sometimes called a "reversed Dagor" Voigtlander
      used yet another arrangement for the Kollinear which has a
      positive element on the outside, a second positive element
      in the center, and a negative element facing the stop.
      Schneider used a reversed Dagor for the well known Angulon.
      Because the reversed Dagor is somewhat longer than the
      normal Dagor the Angulon has oversize end elements to avoid
      vignetting. The Wide Angle Dagor has equal coverage without
      the extra large elements. Note that while the Angulon has
      an enormous circle of illumination its actual coverage for a
      reasonably sharp image is only about 95 degrees about the
      same as for the W.A.Dagor. To get this coverage both lenses
      must be stopped down to about f/45.
      In fact the f/18 Zeiss Protar must also work at about
      f/45 for its maximum coverage, again about 95 degrees. The
      Schneider Angulon is slightly unsymmetrical. The purpose is
      to improve the correction for distant objects.
      I have what seems to be a prototype Angulon, its an
      awful lens. According to a friend who is a lens designer the
      original patent specifications indicate this. Some error was
      made in the design. Since a lot of Angulons were built and
      evidently had satisfactory performance it must have been
      redesigned rather early in its production. Mine has very
      serious color fringing which lenses of this type should be
      pretty much free of.


      --
      Richard Knoppow
      Los Angeles
      WB6KBL
      dickburk@...
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