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Chromatic Aberration on fisheye lenses images (comparative test)

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  • michel thoby
    Hi all, Six different fisheye lenses have been subjected to a comparative test in order to assess their respective propensity to TCA. The influence of light
    Message 1 of 6 , Jul 1, 2007
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      Hi all,

      Six different fisheye lenses have been subjected to a comparative
      test in order to assess their respective propensity to TCA.
      The influence of light illumination spectrum on TCA has also been
      studied.

      You may read the report here:
      http://tinyurl.com/32jjdz

      Regards,

      Michel
    • William Donelson
      Michel Very interesting, but hard to understand. How about sample images? Thanks William
      Message 2 of 6 , Jul 1, 2007
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        Michel

        Very interesting, but hard to understand. How about sample images?

        Thanks
        William


        --- In PanoToolsNG@yahoogroups.com, michel thoby <thobymichel@...> wrote:
        >
        > Hi all,
        >
        > Six different fisheye lenses have been subjected to a comparative
        > test in order to assess their respective propensity to TCA.
        > The influence of light illumination spectrum on TCA has also been
        > studied.
        >
        > You may read the report here:
        > http://tinyurl.com/32jjdz
        >
        > Regards,
        >
        > Michel
        >
      • Serge Maandag (yahoo)
        ... That s a weird result... You would expect the blue abberation to be more pronounced under light that simply contains a bigger part of the blue spectrum.
        Message 3 of 6 , Jul 1, 2007
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          > Six different fisheye lenses have been subjected to a comparative
          > test in order to assess their respective propensity to TCA.
          > The influence of light illumination spectrum on TCA has also been
          > studied.
          >
          > You may read the report here:
          > http://tinyurl.com/32jjdz

          That's a weird result...

          You would expect the blue abberation to be more pronounced under light that simply
          contains a bigger part of the blue spectrum. But not that the light source would
          change the scaling of the abberation.

          Do you think this would happen in a single element lens too? Or is it a side product
          of the compounding of elements?

          Serge.
        • Rik Littlefield
          ... Serge, The thing to remember is that the aberration depends on wavelength, not just on red versus green versus blue . Two different wavelengths may
          Message 4 of 6 , Jul 1, 2007
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            --- In PanoToolsNG@yahoogroups.com, "Serge Maandag (yahoo)"
            <yahoo@...> wrote:
            >
            > > Six different fisheye lenses have been subjected
            > > to a comparative test in order to assess
            > > their respective propensity to TCA.
            > > The influence of light illumination spectrum
            > > on TCA has also been studied.
            > >
            > > You may read the report here:
            > > http://tinyurl.com/32jjdz
            >
            > That's a weird result...
            >
            > You would expect the blue abberation to be more pronounced
            > under light that simply contains a bigger part of the
            > blue spectrum. But not that the light source would
            > change the scaling of the abberation.

            Serge,

            The thing to remember is that the aberration depends on wavelength,
            not just on "red" versus "green" versus "blue".

            Two different wavelengths may both record only in the "blue" channel,
            but nonetheless be shifted by different amounts.

            What gets recorded in the "blue" channel is a kind of weighted
            average of the shifts over all of the different "blue" wavelengths
            that were present in the illumination.

            If the different light sources have different proportions of various
            wavelengths in the "blue" band, then those sources will show
            different TCA.

            In summary, it is the detailed shape of the spectrum -- where are the
            peaks and valleys? -- that cause TCA to be different for different
            light sources.

            The phenomenon called "metamerism" is due to a similar cause. Much
            info about that can be found by googling. A good place to start is
            to Google "define: metamerism" and to read
            http://en.wikipedia.org/wiki/Metamerism_(color) .

            --Rik
          • michel thoby
            http://tinyurl.com/2zzjsl Based on other experiment that you may replicate, I have proposed some additional conjectures on the same subject. Regards, Michel
            Message 5 of 6 , Jul 2, 2007
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              http://tinyurl.com/2zzjsl

              Based on other experiment that you may replicate, I have proposed
              some additional conjectures on the same subject.

              Regards,

              Michel


              Le 1 juil. 07 à 20:03, Rik Littlefield a écrit :

              > --- In PanoToolsNG@yahoogroups.com, "Serge Maandag (yahoo)"
              > <yahoo@...> wrote:
              > >
              > > > Six different fisheye lenses have been subjected
              > > > to a comparative test in order to assess
              > > > their respective propensity to TCA.
              > > > The influence of light illumination spectrum
              > > > on TCA has also been studied.
              > > >
              > > > You may read the report here:
              > > > http://tinyurl.com/32jjdz
              > >
              > > That's a weird result...
              > >
              > > You would expect the blue abberation to be more pronounced
              > > under light that simply contains a bigger part of the
              > > blue spectrum. But not that the light source would
              > > change the scaling of the abberation.
              >
              > Serge,
              >
              > The thing to remember is that the aberration depends on wavelength,
              > not just on "red" versus "green" versus "blue".
              >
              > Two different wavelengths may both record only in the "blue" channel,
              > but nonetheless be shifted by different amounts.
              >
              > What gets recorded in the "blue" channel is a kind of weighted
              > average of the shifts over all of the different "blue" wavelengths
              > that were present in the illumination.
              >
              > If the different light sources have different proportions of various
              > wavelengths in the "blue" band, then those sources will show
              > different TCA.
              >
              > In summary, it is the detailed shape of the spectrum -- where are the
              > peaks and valleys? -- that cause TCA to be different for different
              > light sources.
              >
              > The phenomenon called "metamerism" is due to a similar cause. Much
              > info about that can be found by googling. A good place to start is
              > to Google "define: metamerism" and to read
              > http://en.wikipedia.org/wiki/Metamerism_(color) .
              >
              > --Rik

              >
              >



              [Non-text portions of this message have been removed]
            • Serge Maandag (yahoo)
              ... Ah, it is sort of like a quantification error. Then I just got Michel wrong. This does sound logical to me. I can imagine colours leaning towards infrared
              Message 6 of 6 , Jul 2, 2007
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                > What gets recorded in the "blue" channel is a kind of weighted
                > average of the shifts over all of the different "blue" wavelengths
                > that were present in the illumination.

                Ah, it is sort of like a quantification error. Then I just got Michel wrong.
                This does sound logical to me. I can imagine colours leaning towards infrared or
                ultraviolet could have a substantial influence.

                > In summary, it is the detailed shape of the spectrum -- where are the
                > peaks and valleys? -- that cause TCA to be different for different
                > light sources.

                I believe ignited-gas lamps usually have weird peaked spectrums, so I can imagine
                them causing these weird aliasing type of effects.

                > The phenomenon called "metamerism" is due to a similar cause. Much
                > info about that can be found by googling.

                Ah, I knew the effect, but not the name.

                Thanks for the great explanation (as usual)!
                Serge.
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