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Report on Circular Fisheye lens for APS-C Format

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  • Roger D. Williams
    The August issue of Asahi Camera magazine (no relation to Asahi Pentax) carries a report on the MADOKA 180 lens. This is made by the Yasuhara company, which
    Message 1 of 4 , Aug 3, 2012
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      The August issue of Asahi Camera magazine (no relation to Asahi
      Pentax) carries a report on the MADOKA 180 lens.

      This is made by the Yasuhara company, which caused a stir a decade or so
      ago producing a range-finder camera for film. More recently, it has been
      concentrating on lens design. The camera had its fans but was quirky
      and turned out to have unacceptable defects.

      The latest product, of which manufacturing prototypes have just been
      released, is a 7.3mm lens giving a circular fisheye image that just fills
      the minor axis of the APS-C format.

      It is being released initially with the Sony E mount for NEX cameras,
      which should interest several people on this list. 4/3 mount versions
      are promised. It was claimed to be the only full-circle fisheye lens
      available for the NEX cameras. It does not have contacts to link with
      NEX electronics.

      The article was written by someone who isn't very familiar with fisheye
      lens and doesn't even mention their application to stitched panoramas.
      So what's new! (sigh). However, it does commend Yasuhara for the lens's
      manual focus ring, which "should enable sharply focused items too close
      to the lens to rely on the high depth of focus using pan-focus settings."
      Its "singular freedom from flare and ghosts" was also praised, in view of
      the fact that its very wide field of view necessarily means that light from
      a complete hemisphere is going to get scattered around and between the
      glass elements.

      The front surface of the lens is not very bulbous, and is protected from
      fingering by being recessed slightly within a raised rim. It is small and
      light, 61 x 43mm and 200g, and (the writer says) has image quality that
      is sharp and contrasty and largely independent of aperture settings.

      The maximum aperture is f/4 which makes it a little darker than the
      Samyang, but  is very attractively listed at 22,000 yen (280 US$)
      Software that will "correct the huge distortion" is being developed,
      and will be limited to a 140-degree rectilinear FOV. Talk about
      reinventing the wheel!! But it WILL enable MADOKA to serve as a
      very, VERY wide-angle lens, which may expand demand a little. I
      used the Zenitar 16mm FSU fisheye in this way for years.

      The sample pictures are too small to be sure, but there seems to be
      neither visible ghosting nor flare. The 140-degree rectilinear image
      looks quite unusable, though, as you might expect.

      I sometimes get asked to purchase products available only, or early,
      in Japan, for people abroad, but I was recently cautioned that accepting
      money for purchases made on behalf of people in other countries
      laughably counts as "money laundering," and the Japanese authorities
      are anxious to make prosecutions. So sorry, folks... Can't help.

      Roger W.

      --
      Business: www.adex-japan.com
      Pleasure: www.usefilm.com/member/roger
      Panorama: Rogerama on photosynth.net
    • Michel Thoby
      Hi Roger, ... Thanks a lot for translating and sharing this info with us. IMO some untold facts could be added to the article written by the Yasuhara
      Message 2 of 4 , Aug 4, 2012
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        Hi Roger,

        Le 4 août 2012 à 06:49, Roger D. Williams a écrit :

        The August issue of Asahi Camera magazine (no relation to Asahi
        Pentax) carries a report on the MADOKA 180 lens.
        (....)
        The article was written by someone who isn't very familiar with fisheye
        lens and doesn't even mention their application to stitched panoramas.
        (...)
        Software that will "correct the huge distortion" is being developed, and will be limited to a 140-degree rectilinear FOV.
        (....)

        Roger W.

        Thanks a lot for translating and sharing this info with us. 

        IMO some untold facts could be added to the article written by the Yasuhara company...
        FYI There had been several discussions about it rolling lately on the Panoguide forum:

        This lens is very special as it's AFAIK the first  commercial fisheye lens with Orthographic projection that can be mounted on a commercial (APS-c or larger) camera. Orthographic could be approximately described as the "opposite" to Stereographic for fisheye lens.
        Because of this rare projection, there is a huge compression near the edge of the circular image and the FoV is absolutely restricted: a sole row of image in portrait mode cannot give an VFoV strictly equal to180 degrees because some few pixels shall always be missing before this ultimate limit.
        Theoretically, a full HFoV 360 degrees panorama can be got from only three shots around. But from few early intricate experiments (with real and synthetic images, all having the same fisheye orthographic radial mapping), I have concluded that it is unwise to do so. Four images around are OK though.
        Hints:
        1) The Optimizer function of current leading panorama stitching programs become (more often than not) unstable when valid Control Points very near the image circular boundary are manually placed and "forced" by the user.
        2) The 360 x 180 output panorama is good elsewhere but it is very distorted (and of a poor quality) near and around the Nadir" or around the Zenith" (or both): there is a small star-like blurry pattern surrounding the "empty" circular black hole(s).
        So, and in short: 
        Cropping the circular image might be implicitly required for panographic purpose too! If not done, the so-called "huge distortion" cannot be perfectly corrected (whatever the software is).
        Pitch above or below the horizontal (by, say, ten or fifteen degree) is recommended and it shall be required to shoot one (of more) supplementary image to fill (or to patch) the empty hole at the pole(s) in order to get a full spherical pano.

        Michel


      • Roger D Williams
        Good additional information, Michel! ... By the way, the article was written by a supposedly impartial journalist on the Asahi Camera staff, not by Yasuhara s
        Message 3 of 4 , Aug 4, 2012
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          Good additional information, Michel!

          On Aug 4, 2012, at 6:27 PM, Michel Thoby <thobymichel@...> wrote:

          Hi Roger,

          Le 4 août 2012 à 06:49, Roger D. Williams a écrit :

          The August issue of Asahi Camera magazine (no relation to Asahi
          Pentax) carries a report on the MADOKA 180 lens.
          (....)
          The article was written by someone who isn't very familiar with fisheye
          lens and doesn't even mention their application to stitched panoramas.
          (...)
          Software that will "correct the huge distortion" is being developed, and will be limited to a 140-degree rectilinear FOV.
          (....)

          Roger W.

          Thanks a lot for translating and sharing this info with us. 

          IMO some untold facts could be added to the article written by the Yasuhara company...
          FYI There had been several discussions about it rolling lately on the Panoguide forum:

          By the way, the article was written by a supposedly impartial journalist on the Asahi Camera staff, not by Yasuhara's people. Mind you, they generally never write anything critical about the products they review...

          This lens is very special as it's AFAIK the first  commercial fisheye lens with Orthographic projection that can be mounted on a commercial (APS-c or larger) camera. Orthographic could be approximately described as the "opposite" to Stereographic for fisheye lens.
          Because of this rare projection, there is a huge compression near the edge of the circular image and the FoV is absolutely restricted: a sole row of image in portrait mode cannot give an VFoV strictly equal to180 degrees because some few pixels shall always be missing before this ultimate limit.
          Theoretically, a full HFoV 360 degrees panorama can be got from only three shots around. But from few early intricate experiments (with real and synthetic images, all having the same fisheye orthographic radial mapping), I have concluded that it is unwise to do so. Four images around are OK though.
          Hints:
          1) The Optimizer function of current leading panorama stitching programs become (more often than not) unstable when valid Control Points very near the image circular boundary are manually placed and "forced" by the user.
          2) The 360 x 180 output panorama is good elsewhere but it is very distorted (and of a poor quality) near and around the Nadir" or around the Zenith" (or both): there is a small star-like blurry pattern surrounding the "empty" circular black hole(s).
          So, and in short: 
          Cropping the circular image might be implicitly required for panographic purpose too! If not done, the so-called "huge distortion" cannot be perfectly corrected (whatever the software is).
          Pitch above or below the horizontal (by, say, ten or fifteen degree) is recommended and it shall be required to shoot one (of more) supplementary image to fill (or to patch) the empty hole at the pole(s) in order to get a full spherical 

          That all makes good sense. Looks as if I could get back to four shots at right angles on a hand-held monopod if they are all pointed slightly down to cover the nadir area provided I take one pointing up to fill in the zenith. Sounds good. Of course I would need a Sony NEX! I doubt if a Pentax mount could be made due to the very different geometry. Unfortunately I find the NEX line completely uncongenial and I cannot imagine buying one.

          Roger W.
        • prague
          Hi Michel, ... Is this because the 3rd degree polynomial lens model used by panotools is not sufficient to model this kind of projection? Maybe Tom Sharpless
          Message 4 of 4 , Aug 5, 2012
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            Hi Michel,

            --- In PanoToolsNG@yahoogroups.com, Michel Thoby <thobymichel@...> wrote:
            >
            > 1) The Optimizer function of current leading panorama stitching programs become (more >often than not) unstable when valid Control Points very near the image circular boundary are >manually placed and "forced" by the user.

            Is this because the 3rd degree polynomial lens model used by panotools is not sufficient to model this kind of projection?

            Maybe Tom Sharpless could also comment, I know he's working on lens correction software with a different type of lens model...?


            Jeffrey
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