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calibrating a lens/teleconverter combo using PTGui

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  • Yoram Bernet
    Greetings: I’m shooting close-ups of architectural models using a Canon 24mm TS lens combined with the Canon 1.4x teleconverter. Not surprisingly, the
    Message 1 of 9 , Dec 27, 2007
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      Greetings:



      I’m shooting close-ups of architectural models using a Canon 24mm TS lens
      combined with the Canon 1.4x teleconverter. Not surprisingly, the results
      show significant barrel distortion, especially near the edges of the image.
      I’ve tried correcting using PTLens but can only get so far as the particular
      lens/teleconverter/closeup combo is not specifically profiled in PTLens.



      I understand that it is possible to use PTGui to genberate a profile for my
      specific lens combo, then to use the profile to correct for the distortion.
      However – I’m unable to see how to do so. Can someone point me in the right
      direction? I expect that I’ll have to shoot a target in the form of a grid
      of known straight lines, using the lens combo at the distance of interest. I
      expect that I can then run the image through some kind of calibration
      software that will measure the distortion and provide the parameters needed
      to correct it. Am I being naïve? Do I need to calibrate for different
      apertures?



      Thanks for any assistance,

      Yoram



      Yoram Bernet

      Yoram Bernet Photography

      http://www.yorambernet.com





      [Non-text portions of this message have been removed]
    • Erik Krause
      ... To create a universal profile for a shift (and tilt) lens is virtually impossible. Let s cover the shift lens first: A shift lns covers a much larger image
      Message 2 of 9 , Dec 28, 2007
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        Yoram Bernet wrote:
        >
        > I’m shooting close-ups of architectural models using a Canon 24mm TS lens
        > combined with the Canon 1.4x teleconverter. Not surprisingly, the results
        > show significant barrel distortion, especially near the edges of the
        > image.
        > I’ve tried correcting using PTLens but can only get so far as the
        > particular
        > lens/teleconverter/closeup combo is not specifically profiled in PTLens.
        >
        > I understand that it is possible to use PTGui to genberate a profile for
        > my
        > specific lens combo, then to use the profile to correct for the
        > distortion.
        >

        To create a universal profile for a shift (and tilt) lens is virtually
        impossible. Let's cover the shift lens first: A shift lns covers a much
        larger image circle than the sensor/film sees. By shifting the lens you
        effectively choose a part of a much larger image. Lens distortion is
        symmetrical to the optical axis. Hence you see more or less distortion on
        one image side depending from the amount and direction you shift. In other
        words: The optical axis doesn't hit the image in it's center.

        Panotools lens correction model can take care of this fact by shifting the
        center of correction with the d and e parameters. However, to correct a
        single photo you would have to know where exactly that center is. It can not
        be optimized like in a panorama, where there is information from different
        images available.

        For details see http://wiki.panotools.org/Lens_correction_model

        There are two workarounds for that situation:
        1: Use a standard lens for shooting and correct perspective afterwards
        (simulate a shift lens):
        http://wiki.panotools.org/Perspective_correction

        2: Try to correct distortion in the image directly. This is only possible,
        if you have several straight lines in different distances to the image
        center. A short howto is found on
        http://erik-krause.de/verzeichnung/distort_en.htm
        Note, that you need to optimize for d and e shift parameters as well, since
        the optical axis is not in the image center. Your result image will be
        d-centerd in much the same as if you used perspective correction. Hence you
        should carefully rea the above articles.

        You could save the result of the above correction and reuse it for shots at
        exactly the same shift settings. If you use your TS-E tilted your only
        possibility is the second described above.

        Lens distortion is not aperture dependent, but it is focus distance
        dependent. So if you use your lens at very short distance, the necessary
        lens correction might be different.

        best regards
        Erik
        --
        View this message in context: http://www.nabble.com/calibrating-a-lens-teleconverter-combo-using-PTGui-tp14520822p14526295.html
        Sent from the PanoToolsNG mailing list archive at Nabble.com.
      • Yoram Bernet
        Erik: I m making slow progress. I m looking at http://erik-krause.de/index.htm?./verzeichnung/distort_en.htm, where it recommends downloading the patched
        Message 3 of 9 , Dec 28, 2007
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          Erik:



          I'm making slow progress. I'm looking at
          http://erik-krause.de/index.htm?./verzeichnung/distort_en.htm, where it
          recommends downloading the patched version of pano12.dll from
          http://www.ueckermann.de/pano12/:. I get a 404 when I try to download from
          this link. I'm pretty sure that I need the updated pano12 'cause I don't
          have the dialog boxes that you show in the tutorial (my version is from
          2001).



          Where do I get the current version of pano12.dll?



          Thanks,

          Y



          -----Original Message-----
          From: PanoToolsNG@yahoogroups.com [mailto:PanoToolsNG@yahoogroups.com] On
          Behalf Of Erik Krause
          Sent: Friday, December 28, 2007 6:21 AM
          To: PanoToolsNG@yahoogroups.com
          Subject: Re: [PanoToolsNG] calibrating a lens/teleconverter combo using
          PTGui





          Yoram Bernet wrote:
          >
          > I'm shooting close-ups of architectural models using a Canon 24mm TS lens
          > combined with the Canon 1.4x teleconverter. Not surprisingly, the results
          > show significant barrel distortion, especially near the edges of the
          > image.
          > I've tried correcting using PTLens but can only get so far as the
          > particular
          > lens/teleconverter/closeup combo is not specifically profiled in PTLens.
          >
          > I understand that it is possible to use PTGui to genberate a profile for
          > my
          > specific lens combo, then to use the profile to correct for the
          > distortion.
          >

          To create a universal profile for a shift (and tilt) lens is virtually
          impossible. Let's cover the shift lens first: A shift lns covers a much
          larger image circle than the sensor/film sees. By shifting the lens you
          effectively choose a part of a much larger image. Lens distortion is
          symmetrical to the optical axis. Hence you see more or less distortion on
          one image side depending from the amount and direction you shift. In other
          words: The optical axis doesn't hit the image in it's center.

          Panotools lens correction model can take care of this fact by shifting the
          center of correction with the d and e parameters. However, to correct a
          single photo you would have to know where exactly that center is. It can not
          be optimized like in a panorama, where there is information from different
          images available.

          For details see http://wiki.
          <http://wiki.panotools.org/Lens_correction_model>
          panotools.org/Lens_correction_model

          There are two workarounds for that situation:
          1: Use a standard lens for shooting and correct perspective afterwards
          (simulate a shift lens):
          http://wiki. <http://wiki.panotools.org/Perspective_correction>
          panotools.org/Perspective_correction

          2: Try to correct distortion in the image directly. This is only possible,
          if you have several straight lines in different distances to the image
          center. A short howto is found on
          http://erik- <http://erik-krause.de/verzeichnung/distort_en.htm>
          krause.de/verzeichnung/distort_en.htm
          Note, that you need to optimize for d and e shift parameters as well, since
          the optical axis is not in the image center. Your result image will be
          d-centerd in much the same as if you used perspective correction. Hence you
          should carefully rea the above articles.

          You could save the result of the above correction and reuse it for shots at
          exactly the same shift settings. If you use your TS-E tilted your only
          possibility is the second described above.

          Lens distortion is not aperture dependent, but it is focus distance
          dependent. So if you use your lens at very short distance, the necessary
          lens correction might be different.

          best regards
          Erik
          --
          View this message in context: http://www.nabble.
          <http://www.nabble.com/calibrating-a-lens-teleconverter-combo-using-PTGui-tp
          14520822p14526295.html>
          com/calibrating-a-lens-teleconverter-combo-using-PTGui-tp14520822p14526295.h
          tml
          Sent from the PanoToolsNG mailing list archive at Nabble.com.





          [Non-text portions of this message have been removed]
        • Jim Watters
          You can get it from here. http://photocreations.ca/panotools/index.html Jim ... -- Jim Watters Yahoo ID: j1vvy ymsgr:sendIM?j1vvy jwatters @ photocreations .
          Message 4 of 9 , Dec 28, 2007
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            You can get it from here.
            http://photocreations.ca/panotools/index.html
            Jim

            Yoram Bernet wrote:
            > I'm making slow progress. I'm looking at
            > http://erik-krause.de/index.htm?./verzeichnung/distort_en.htm, where it
            > recommends downloading the patched version of pano12.dll from
            > http://www.ueckermann.de/pano12/:. I get a 404 when I try to download from
            > this link.
            >
            > Where do I get the current version of pano12.dll?
            >
            >
            > Thanks,
            >
            > Y
            >
            --

            Jim Watters

            Yahoo ID: j1vvy ymsgr:sendIM?j1vvy
            jwatters @ photocreations . ca
            http://photocreations.ca
          • Yoram Bernet
            Erik and Jim Watters, thanks to you both. I m still stuck. I am following the tutorial that Erik pointed me towards. I ve downloaded the latest pano12.dll that
            Message 5 of 9 , Dec 28, 2007
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              Erik and Jim Watters, thanks to you both.



              I'm still stuck. I am following the tutorial that Erik pointed me towards.
              I've downloaded the latest pano12.dll that Jim pointed me towards and yet I
              seem to have a substantially different version of the Gui than the one in
              the tutorial. In particular, it does not allow me to designate control
              points of type 'Line' (just vertical or horizontal line) and miscellaneous
              other differences. Here's the gui that the tutorial shows:







              and here's the gui that I have:







              Obviously, I have a different version of (probably) PTGui. I'm running
              version 7.5 (according to the 'Help/About'.



              ANy suggestions on how I can get the straight line control points out of
              this version of PTGui? Or alternatively - how do I get the version of PTGui
              that supports the slcps?



              Many thanks and my apologies for the noise on the list. Hopefully - this is
              useful to others as well.



              Yoram



              -----Original Message-----
              From: PanoToolsNG@yahoogroups.com [mailto:PanoToolsNG@yahoogroups.com] On
              Behalf Of Erik Krause
              Sent: Friday, December 28, 2007 6:21 AM
              To: PanoToolsNG@yahoogroups.com
              Subject: Re: [PanoToolsNG] calibrating a lens/teleconverter combo using
              PTGui





              Yoram Bernet wrote:
              >
              > I'm shooting close-ups of architectural models using a Canon 24mm TS lens
              > combined with the Canon 1.4x teleconverter. Not surprisingly, the results
              > show significant barrel distortion, especially near the edges of the
              > image.
              > I've tried correcting using PTLens but can only get so far as the
              > particular
              > lens/teleconverter/closeup combo is not specifically profiled in PTLens.
              >
              > I understand that it is possible to use PTGui to genberate a profile for
              > my
              > specific lens combo, then to use the profile to correct for the
              > distortion.
              >

              To create a universal profile for a shift (and tilt) lens is virtually
              impossible. Let's cover the shift lens first: A shift lns covers a much
              larger image circle than the sensor/film sees. By shifting the lens you
              effectively choose a part of a much larger image. Lens distortion is
              symmetrical to the optical axis. Hence you see more or less distortion on
              one image side depending from the amount and direction you shift. In other
              words: The optical axis doesn't hit the image in it's center.

              Panotools lens correction model can take care of this fact by shifting the
              center of correction with the d and e parameters. However, to correct a
              single photo you would have to know where exactly that center is. It can not
              be optimized like in a panorama, where there is information from different
              images available.

              For details see http://wiki.
              <http://wiki.panotools.org/Lens_correction_model>
              panotools.org/Lens_correction_model

              There are two workarounds for that situation:
              1: Use a standard lens for shooting and correct perspective afterwards
              (simulate a shift lens):
              http://wiki. <http://wiki.panotools.org/Perspective_correction>
              panotools.org/Perspective_correction

              2: Try to correct distortion in the image directly. This is only possible,
              if you have several straight lines in different distances to the image
              center. A short howto is found on
              http://erik- <http://erik-krause.de/verzeichnung/distort_en.htm>
              krause.de/verzeichnung/distort_en.htm
              Note, that you need to optimize for d and e shift parameters as well, since
              the optical axis is not in the image center. Your result image will be
              d-centerd in much the same as if you used perspective correction. Hence you
              should carefully rea the above articles.

              You could save the result of the above correction and reuse it for shots at
              exactly the same shift settings. If you use your TS-E tilted your only
              possibility is the second described above.

              Lens distortion is not aperture dependent, but it is focus distance
              dependent. So if you use your lens at very short distance, the necessary
              lens correction might be different.

              best regards
              Erik
              --
              View this message in context: http://www.nabble.
              <http://www.nabble.com/calibrating-a-lens-teleconverter-combo-using-PTGui-tp
              14520822p14526295.html>
              com/calibrating-a-lens-teleconverter-combo-using-PTGui-tp14520822p14526295.h
              tml
              Sent from the PanoToolsNG mailing list archive at Nabble.com.





              [Non-text portions of this message have been removed]
            • Jim Watters
              The images are missing because the group does not allow them. I have an idea of what is going wrong. The images used in the tutorial on Erik s site are fairly
              Message 6 of 9 , Dec 28, 2007
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                The images are missing because the group does not allow them.
                I have an idea of what is going wrong.
                The images used in the tutorial on Erik's site are fairly old.

                In PTGui, menu - Tools | Options | Panotools
                Ensure PTStitcher / Nora / PTMender application is correct.
                In PTGui on Optimizer tab, Optimize using : "Panorama Tools Optimizer"

                If this does not work send me the images directly so I can see.

                Jim

                Yoram Bernet wrote:
                > Erik and Jim Watters, thanks to you both.
                >
                >
                >
                > I'm still stuck. I am following the tutorial that Erik pointed me towards.
                > I've downloaded the latest pano12.dll that Jim pointed me towards and yet I
                > seem to have a substantially different version of the Gui than the one in
                > the tutorial. In particular, it does not allow me to designate control
                > points of type 'Line' (just vertical or horizontal line) and miscellaneous
                > other differences. Here's the gui that the tutorial shows:
                >
                >
                > and here's the gui that I have:
                >
                >
                > Obviously, I have a different version of (probably) PTGui. I'm running
                > version 7.5 (according to the 'Help/About'.
                >
                >
                > ANy suggestions on how I can get the straight line control points out of
                > this version of PTGui? Or alternatively - how do I get the version of PTGui
                > that supports the slcps?
                >
                >
                > Many thanks and my apologies for the noise on the list. Hopefully - this is
                > useful to others as well.
                >
                >
                >
                > Yoram
                >
                >
                >

                --
                Jim Watters

                Yahoo ID: j1vvy ymsgr:sendIM?j1vvy
                jwatters @ photocreations . ca
                http://photocreations.ca
              • John Houghton
                ... Indeed - the version of PTGui used there is very old (V1.05 b3!). In PTGui V7 you will need to click the Advanced button and then select the Control
                Message 7 of 9 , Dec 29, 2007
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                  --- In PanoToolsNG@yahoogroups.com, "Yoram Bernet" <yoram@...> wrote:
                  >
                  > I seem to have a substantially different version of the Gui than
                  > the one in the tutorial.

                  Indeed - the version of PTGui used there is very old (V1.05 b3!). In
                  PTGui V7 you will need to click the Advanced button and then select the
                  Control Points tab. You select the control point type on the pull down
                  menu beneath the two image windows. You might notice a change in the
                  labelling. t1 points used to be described as "horizontal" since the
                  optimizer optimizes only the x coordinates of the points. As t1 points
                  are generally assigned on vertical lines to get them vertical (by
                  equalizing the x coodinates), t1 points are now called vertical line
                  control points, which felt to be less confusing.

                  John
                • Erik Krause
                  ... I have to apologize! I will have to update the tutorial if it should be of any use. I simply forgot, that it is so old. Just give me some time.... best
                  Message 8 of 9 , Dec 29, 2007
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                    Yoram Bernet wrote:
                    >
                    > I'm making slow progress. I'm looking at
                    > http://erik-krause.de/index.htm?./verzeichnung/distort_en.htm, where it
                    > recommends downloading the patched version of pano12.dll from
                    > http://www.ueckermann.de/pano12/:. I get a 404 when I try to download from
                    > this link.
                    >

                    I have to apologize! I will have to update the tutorial if it should be of
                    any use. I simply forgot, that it is so old. Just give me some time....

                    best regards
                    Erik
                    --
                    View this message in context: http://www.nabble.com/calibrating-a-lens-teleconverter-combo-using-PTGui-tp14520822p14538646.html
                    Sent from the PanoToolsNG mailing list archive at Nabble.com.
                  • Erik Krause
                    ... I ve updated the above tutorial now. Hopefully it s less confusing now... best regards Erik Krause http://www.erik-krause.de
                    Message 9 of 9 , Jan 5, 2008
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                      On Saturday, December 29, 2007 at 7:47, Erik Krause wrote:

                      > > I'm making slow progress. I'm looking at
                      > > http://erik-krause.de/index.htm?./verzeichnung/distort_en.htm

                      > I have to apologize! I will have to update the tutorial if it should be of any
                      > use. I simply forgot, that it is so old. Just give me some time....

                      I've updated the above tutorial now. Hopefully it's less confusing
                      now...

                      best regards


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