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Re: panotools lens distortion coefficients from other programs

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  • Erik Krause
    ... Panotools and related programs use exponents 1,2,3 and 4 while Brown uses 0, 2, 4 and 6. You would need to fit a panotools-style correction curve to a
    Message 1 of 2 , Oct 10, 2011
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      Am 10.10.2011 15:59, schrieb Fanotec:
      > Many photogrammetric programs use Brown's distortion model for lens
      > distortion correction.
      > they have good facility to calculate the coefficients accurately and
      > automatically.
      > eg
      > http://www.agisoft.ru/products/lens/
      > http://downloads.agisoft.ru/lens/doc/en/lens.pdf
      >
      > I wonder if any one can relate the coefficients used in panotools to Brown's
      > model.

      Panotools and related programs use exponents 1,2,3 and 4 while Brown
      uses 0, 2, 4 and 6. You would need to fit a panotools-style correction
      curve to a Brown one. No idea whether this is easily possible. Panotools
      doesn't support tangential distortion, which the Brown model does.

      -> http://wiki.panotools.org/Lens_correction_model

      As a test one could use excel to create points with the Brown model and
      then fit a respective polynomial to get the panotools values.

      However, Agisoft use a LCD screen as calibration target, which implies
      that they don't focus at infinity. Since lens distortion might change
      with focus distance this gives potentially bad results for infinity.
      Hence I think it's not worth the effort: Shoot a panorama from the exact
      no-parallax-point (or with only distant subjects) with good overlap and
      get your true correction parameters from panotools (PTGui, hugin...)

      --
      Erik Krause
      http://www.erik-krause.de
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