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Re: [PanoToolsNG] Re: The Pupil Goes Back To School ...

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  • 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 1 of 8 , Mar 31, 2007
      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 2 of 8 , Mar 31, 2007
        --- 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 3 of 8 , Mar 31, 2007
          > 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 4 of 8 , Mar 31, 2007
            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 5 of 8 , Mar 31, 2007
              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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