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Re: d e parameters

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  • 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 1 of 7 , Oct 2, 2006
      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 2 of 7 , Oct 2, 2006
        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/




        --


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      • 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 3 of 7 , Oct 2, 2006
          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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