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The Pupil Goes Back To School ...

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  • stuart mcalister
    Hello All, Recently, I have been having trouble finding the optimum position for a Canon 5D with it s Sigma 8mm on a Manfrotto 303SPH. Despite the wiki page on
    Message 1 of 8 , Mar 30, 2007
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      Hello All,

      Recently, I have been having trouble finding the
      optimum position for a Canon 5D with it's Sigma 8mm on
      a Manfrotto 303SPH. Despite the wiki page on 'Pupil
      Entrance Points' stating that the ideal measurement
      for the Sigma 8mm f4, taking 6 pictures is at 47,5mm,
      another page, 'Special_issues_with_fisheye_lenses'
      goes on to say that 'Fisheye lenses and adapters do
      not have a fixed entrance pupil'.

      It then adds that theoretically, 'it is impossible to
      get a perfectly stitched panorama from a fisheye
      lens.' The proof of this is that PTGui comes up with
      the 'there may well be misalignments etc' ... when
      using a 14mm, it is more or less a perfect match.

      To find the best point, I have nudged the camera and
      the mounting plates back and forth, tweaked this,
      tweaked that and taken a multitude of test images.
      However, I've found that if I start by mounting the
      Canon 5D on the 303SPH, lens downwards, looking
      through the viewfinder and lining up the centre of the
      lens with the central point of the tripod, the end
      results are acceptable.

      Does anyone have a different sequence which they
      believe is successful?

      Regards and thanks,

      Stuart



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    • stuart mcalister
      Hello All, Recently, I have been having trouble finding the optimum position for a Canon 5D with it s Sigma 8mm on a Manfrotto 303SPH. Despite the wiki page on
      Message 2 of 8 , Mar 30, 2007
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        Hello All,

        Recently, I have been having trouble finding the
        optimum position for a Canon 5D with it's Sigma 8mm on
        a Manfrotto 303SPH. Despite the wiki page on 'Pupil
        Entrance Points' stating that the ideal measurement
        for the Sigma 8mm f4, taking 6 pictures is at 47,5mm,
        another page, 'Special_issues_with_fisheye_lenses'
        goes on to say that 'Fisheye lenses and adapters do
        not have a fixed entrance pupil'.

        It then adds that theoretically, 'it is impossible to
        get a perfectly stitched panorama from a fisheye
        lens.' The proof of this is that PTGui comes up with
        the 'there may well be misalignments etc' ... when
        using a 14mm, it is more or less a perfect match.

        To find the best point, I have nudged the camera and
        the mounting plates back and forth, tweaked this,
        tweaked that and taken a multitude of test images.
        However, I've found that if I start by mounting the
        Canon 5D on the 303SPH, lens downwards, looking
        through the viewfinder and lining up the centre of the
        lens with the central point of the tripod, the end
        results are acceptable.

        Does anyone have a different sequence which they
        believe is successful?

        Regards and thanks,

        Stuart



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      • John Houghton
        ... Stuart, A poorly positioned camera on the pano head may well result in stitching problems, but stitching problems do not necessarily mean you have a poorly
        Message 3 of 8 , Mar 31, 2007
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          --- In PanoToolsNG@yahoogroups.com, stuart mcalister
          <strtmcalister@...> wrote:
          > It then adds that theoretically, 'it is impossible to
          > get a perfectly stitched panorama from a fisheye
          > lens.' The proof of this is that PTGui comes up with
          > the 'there may well be misalignments etc'

          Stuart, A poorly positioned camera on the pano head may well result in
          stitching problems, but stitching problems do not necessarily mean you
          have a poorly positioned camera! To check the camera and head setup,
          you need to test specifically for parallax errors. Once you have
          confirmation that parallax has been eliminated, you can address any
          stitching errors that you may then get in PTGui and look for other
          causes. See:

          http://homepage.ntlworld.com/j.houghton/epcalib.htm

          John
        • stuart mcalister
          Dear John, Many thanks for getting back to me on this subject. I seem to have sorted out the problem but will certainly give your theory a good work-out. The
          Message 4 of 8 , Mar 31, 2007
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            Dear John,

            Many thanks for getting back to me on this subject. I
            seem to have sorted out the problem but will certainly
            give your theory a good work-out.

            The one remaining problem I have is that in order to
            level the 303 on the tripod, I have a heavy Gitzo ball
            joint. To keep an eye on the entire level, I have a
            small 2-way spirit level which I place on the side
            mounting plate - I watch this carefully but although
            the 303 is level, as it passes through 180 degrees,
            the entire kaboodle goes very slightly off tilt. I'm
            sure it's just a case of leveling for every shot or
            the Gitzo ball has a problem. I would have thought
            that if the Gitzo was level, as was the 303, then any
            spin would result in a level spin ...

            It seems to show up more when using the 8mm in
            confined spaces as there's more 'give' in a wider
            photographic area. Is there a chapter anywhere on
            'confined spaces'?

            Many thanks again for your time and suggestion ...

            Regards,

            Stuart


            --- John Houghton <j.houghton@...> wrote:

            > --- In PanoToolsNG@yahoogroups.com, stuart mcalister
            >
            > <strtmcalister@...> wrote:
            > > It then adds that theoretically, 'it is impossible
            > to
            > > get a perfectly stitched panorama from a fisheye
            > > lens.' The proof of this is that PTGui comes up
            > with
            > > the 'there may well be misalignments etc'
            >
            > Stuart, A poorly positioned camera on the pano head
            > may well result in
            > stitching problems, but stitching problems do not
            > necessarily mean you
            > have a poorly positioned camera! To check the
            > camera and head setup,
            > you need to test specifically for parallax errors.
            > Once you have
            > confirmation that parallax has been eliminated, you
            > can address any
            > stitching errors that you may then get in PTGui and
            > look for other
            > causes. See:
            >
            > http://homepage.ntlworld.com/j.houghton/epcalib.htm
            >
            > John
            >
            >




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          • John Houghton
            ... Stuart, If you have set up the head so that the entrance pupil is aligned with the axis of rotation of the head to eliminate parallax, then you should have
            Message 5 of 8 , Mar 31, 2007
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              --- In PanoToolsNG@yahoogroups.com, stuart mcalister
              <strtmcalister@...> wrote:
              >
              > I'm sure it's just a case of leveling for every shot or
              > the Gitzo ball has a problem. I would have thought
              > that if the Gitzo was level, as was the 303, then any
              > spin would result in a level spin ...

              Stuart, If you have set up the head so that the entrance pupil is
              aligned with the axis of rotation of the head to eliminate parallax,
              then you should have no problems stitching a panorama shot in a
              confined area. The levelling of the head will have no bearing on the
              stitching quality. If the axis of rotation is not precisely vertical,
              it is usually a very simple task to accurately level the panorama using
              t1 points on vertical edges in PTGui: no more than two minutes work at
              most.

              John
            • Serge Maandag (yahoo)
              ... It s true that with a fisheye the NPP depends of the angle at which light enters the lens surface. I wrote a page about that:
              Message 6 of 8 , Mar 31, 2007
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                > It then adds that theoretically, 'it is impossible to
                > get a perfectly stitched panorama from a fisheye
                > lens.' The proof of this is that PTGui comes up with
                > the 'there may well be misalignments etc' ... when
                > using a 14mm, it is more or less a perfect match.

                It's true that with a fisheye the NPP depends of the angle at which light
                enters the lens surface. I wrote a page about that:
                http://pano.maandag.com/index.php?id=57

                But it shouldn't give you unstitchable results if you are a few mm off the
                NPP.
                Be sure to optimize horizontal and vertical shift though. That usually
                makes a lot of difference.

                And as for the moving NPP: it moves forward and backward. So if you shoot
                in a confined space, it might help to optimize individual FoV for each
                image. Be sure to have lots of control points, though.

                Serge.
              • stuart mcalister
                Serge, Many thanks ... I ll give your paper a read. Regards, Stuart ... ___________________________________________________________ The all-new Yahoo! Mail
                Message 7 of 8 , Mar 31, 2007
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                  Serge,

                  Many thanks ... I'll give your paper a read.

                  Regards,

                  Stuart
                  --- "Serge Maandag (yahoo)" <yahoo@...> wrote:

                  > > It then adds that theoretically, 'it is impossible
                  > to
                  > > get a perfectly stitched panorama from a fisheye
                  > > lens.' The proof of this is that PTGui comes up
                  > with
                  > > the 'there may well be misalignments etc' ... when
                  > > using a 14mm, it is more or less a perfect match.
                  >
                  > It's true that with a fisheye the NPP depends of the
                  > angle at which light
                  > enters the lens surface. I wrote a page about that:
                  > http://pano.maandag.com/index.php?id=57
                  >
                  > But it shouldn't give you unstitchable results if
                  > you are a few mm off the
                  > NPP.
                  > Be sure to optimize horizontal and vertical shift
                  > though. That usually
                  > makes a lot of difference.
                  >
                  > And as for the moving NPP: it moves forward and
                  > backward. So if you shoot
                  > in a confined space, it might help to optimize
                  > individual FoV for each
                  > image. Be sure to have lots of control points,
                  > though.
                  >
                  > Serge.
                  >




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                • Erik Krause
                  ... Usually (as a beginner) one pays far too much attention to the NPP and less or none to other causes of stitching errors. The NPP plays a role *only* if
                  Message 8 of 8 , Mar 31, 2007
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                    On Saturday, March 31, 2007 at 13:41, Serge Maandag (yahoo) wrote:

                    > It's true that with a fisheye the NPP depends of the angle at which light
                    > enters the lens surface. I wrote a page about that:
                    > http://pano.maandag.com/index.php?id=57
                    >
                    > But it shouldn't give you unstitchable results if you are a few mm off the
                    > NPP. Be sure to optimize horizontal and vertical shift though. That usually
                    > makes a lot of difference.

                    Usually (as a beginner) one pays far too much attention to the NPP
                    and less or none to other causes of stitching errors. The NPP plays a
                    role *only* if there are subjects at different distances in the
                    overlap region, and they probably are evident only if the distance
                    between near and far subjects is relatively large.

                    The usual causes of stitching errors are:
                    - not allowed to optimze all necessary parameters for a task.
                    - wrongly or not calibrated lens
                    - too few control points for the amount of parameters to optimize
                    (see: http://wiki.panotools.org/Perspective_correction )
                    - sideways or up-down displacement of the rotation axis.


                    best regards

                    --
                    Copyright (c) 2007 Erik Krause
                    Verbatim copying and distribution strictly forbidden
                    except those allowed in wiki.panotools.org/User_Guidelines
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