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d e parameters

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  • JD Smith
    How commonly do people find they need to allow non-zero d and e parameters (which change the center of the radial aberration coefficients a, b, and c) for
    Message 1 of 7 , Oct 2, 2006
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      How commonly do people find they need to allow non-zero d and e parameters
      (which change the center of the radial aberration coefficients a, b, and
      c) for rectilinear lenses? How large of a shift is typical? Does anyone
      have recommendations for good test images to assess whether d and e should
      be nonzero (standard "building at a distance"?).

      JD
    • Sacha Griffin
      100% of the time. Depends. Images that wrap 360 are good for optimizing d and e Plus, that have static features for an even spread of cp s. Sacha Griffin
      Message 2 of 7 , Oct 2, 2006
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        100% of the time.
        Depends.
        Images that wrap 360 are good for optimizing d and e
        Plus, that have static features for an even spread of cp's.

        Sacha Griffin
        Southern Digital Solutions LLC
        www.southern-digital.com
        www.seeit360.net
        www.ezphotosafe.com
        404-551-4275
        404-731-7798


        -----Original Message-----
        From: JD Smith [mailto:jdsmith@...]
        Sent: Monday, October 02, 2006 1:45 PM
        To: PanoToolsNG@yahoogroups.com
        Subject: [PanoToolsNG] d e parameters


        How commonly do people find they need to allow non-zero d and e parameters
        (which change the center of the radial aberration coefficients a, b, and
        c) for rectilinear lenses? How large of a shift is typical? Does anyone
        have recommendations for good test images to assess whether d and e should
        be nonzero (standard "building at a distance"?).

        JD



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        Yahoo! Groups Links
      • Ian Wood
        Almost always, but normally only when calibrating the lens for the first time. I ve seen figures as high as a hundred pixels, but obviously as it s a pixel
        Message 3 of 7 , Oct 2, 2006
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          Almost always, but normally only when calibrating the lens for the
          first time. I've seen figures as high as a hundred pixels, but
          obviously as it's a pixel dimension it changes with the resolution of
          the camera. Oh, and watch out for templates made with different size
          images...

          With some fisheyes such as the Sigma 8mm you may be able to get a
          starting point by putting the outer ring on, stopping down and seeing
          where the corners get cut off. Most of the time just optimise it in a
          full spherical pano.

          Ian

          On 2 Oct 2006, at 18:44, JD Smith wrote:

          >
          > How commonly do people find they need to allow non-zero d and e
          > parameters
          > (which change the center of the radial aberration coefficients a,
          > b, and
          > c) for rectilinear lenses? How large of a shift is typical? Does
          > anyone
          > have recommendations for good test images to assess whether d and e
          > should
          > be nonzero (standard "building at a distance"?).
          >
          > JD
          >
          >
          >
          > --
          >
          >
          > Yahoo! Groups Links
          >
          >
          >
          >
          >
          >
          >
          >
          >
          >
        • Erik Krause
          ... always and individual for each image. Stitching of scanned images would be much worse without. ... Not only for rectilinear lenses, for all kinds in fact.
          Message 4 of 7 , Oct 2, 2006
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            On Monday, October 02, 2006 at 10:44, JD Smith wrote:

            > How commonly do people find they need to allow non-zero d and e parameters

            always and individual for each image. Stitching of scanned images
            would be much worse without.

            > (which change the center of the radial aberration coefficients a, b, and c)
            > for rectilinear lenses?

            Not only for rectilinear lenses, for all kinds in fact. And not only
            for the center of a, b and c correction but for the complete lens
            remapping. However, they are not so much needed for longer focal
            length lenses...

            > How large of a shift is typical? Does anyone have
            > recommendations for good test images to assess whether d and e should be
            > nonzero (standard "building at a distance"?).

            I simply optimize them and the result is much better afterwards. For
            a digital camera with a fixed focal length lens optimization of per
            image d and e parameters might not be necessary. For our D70 they are
            pretty constant at about 13 and 9 pixels...

            best regards
            --
            Erik Krause
            Resources, not only for panorama creation:
            http://www.erik-krause.de/
          • JD Smith
            ... Sorry, yes I meant for non-scanned digital images. I find about 20 and 18 pixels on my D50, but it likely depends on the lens. If you allow per-image d
            Message 5 of 7 , Oct 2, 2006
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              On Mon, 02 Oct 2006 20:48:37 +0200, Erik Krause wrote:

              >> How large of a shift is typical? Does anyone have recommendations for
              >> good test images to assess whether d and e should be nonzero (standard
              >> "building at a distance"?).
              >
              > I simply optimize them and the result is much better afterwards. For a
              > digital camera with a fixed focal length lens optimization of per image d
              > and e parameters might not be necessary. For our D70 they are pretty
              > constant at about 13 and 9 pixels...

              Sorry, yes I meant for non-scanned digital images. I find about 20
              and 18 pixels on my D50, but it likely depends on the lens. If you allow
              per-image d and e on your D70, how much variation do you find? I could
              see that being a somewhat poorly constrained optimization direction.

              JD
            • Sacha Griffin
              You might confuse semi-advanced people with always and individual for each image. For film, yes, digital no, unless, you re using a zoom lens. For example
              Message 6 of 7 , Oct 2, 2006
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                You might confuse semi-advanced people with " always and individual for each
                image."
                For film, yes, digital no, unless, you're using a zoom lens. For example my
                28-135 has got loads of SLOP, (D & E Shift)

                "I simply optimize them and the result is much better afterwards. For
                a digital camera with a fixed focal length lens optimization of per
                image d and e parameters might not be necessary. For our D70 they are
                pretty constant at about 13 and 9 pixels..."

                However, remember everyone just because you can get your average pixel error
                down, doesn't mean your stitch is better.
                Optimization is an imaginary set of distortion points supposedly matched to
                a set of images. The "error" is the difference between your points and your
                optimization parameters combined with your image locations. You can get a
                zero error by hitting every imaginary point, but not matching your real
                images. The best stitch finds a happy medium with a spread of control
                points, and low error.

                Sacha Griffin
                Southern Digital Solutions LLC
                www.southern-digital.com
                www.seeit360.net
                www.ezphotosafe.com
                404-551-4275
                404-731-7798


                -----Original Message-----
                From: Erik Krause [mailto:erik.krause@...]
                Sent: Monday, October 02, 2006 2:49 PM
                To: PanoToolsNG@yahoogroups.com
                Subject: [PanoToolsNG] Re: d e parameters

                On Monday, October 02, 2006 at 10:44, JD Smith wrote:

                > How commonly do people find they need to allow non-zero d and e parameters

                always and individual for each image. Stitching of scanned images
                would be much worse without.

                > (which change the center of the radial aberration coefficients a, b, and
                c)
                > for rectilinear lenses?

                Not only for rectilinear lenses, for all kinds in fact. And not only
                for the center of a, b and c correction but for the complete lens
                remapping. However, they are not so much needed for longer focal
                length lenses...

                > How large of a shift is typical? Does anyone have
                > recommendations for good test images to assess whether d and e should be
                > nonzero (standard "building at a distance"?).

                I simply optimize them and the result is much better afterwards. For
                a digital camera with a fixed focal length lens optimization of per
                image d and e parameters might not be necessary. For our D70 they are
                pretty constant at about 13 and 9 pixels...

                best regards
                --
                Erik Krause
                Resources, not only for panorama creation:
                http://www.erik-krause.de/




                --


                Yahoo! Groups Links
              • Erik Krause
                ... I mean the stitch of course, not the average error (speaking of scanned images). The mentioned d and e parameters for the D70 where the result when
                Message 7 of 7 , Oct 2, 2006
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                  On Monday, October 02, 2006 at 15:14, Sacha Griffin wrote:

                  > "I simply optimize them and the result is much better afterwards. For
                  > a digital camera with a fixed focal length lens optimization of per
                  > image d and e parameters might not be necessary. For our D70 they are
                  > pretty constant at about 13 and 9 pixels..."
                  >
                  > However, remember everyone just because you can get your average pixel error
                  > down, doesn't mean your stitch is better. Optimization is an imaginary set of
                  > distortion points supposedly matched to a set of images.

                  I mean the stitch of course, not the average error (speaking of
                  scanned images). The mentioned d and e parameters for the D70 where
                  the result when creating a batch stitching template in a room paved
                  with post-it stickers. 1514 control points where evenly distributed
                  throughout all overlaps and of course I looked here more for the
                  stitching and less for the pixel error (although the pixel error *is*
                  a measure if you have enough well distributed points and you
                  repeatedly optimize and use APCLean)...

                  best regards


                  --
                  Erik Krause
                  Resources, not only for panorama creation:
                  http://www.erik-krause.de/
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