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RE: [PanoToolsNG] OT - Removing anti-alias filter

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  • Paul D. DeRocco
    ... I ve heard that too. I ve seen images from older Kodak digicams, as well as the Sigma/Foveon cameras, which appear to have little or no anti-aliasing, and
    Message 1 of 7 , Apr 10, 2009
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      > From: Fernando Chaves
      >
      > AFAIK the Canon AA filter makes stronger moire removal than Nikon's.

      I've heard that too. I've seen images from older Kodak digicams, as well as
      the Sigma/Foveon cameras, which appear to have little or no anti-aliasing,
      and you can see the aliasing quite clearly on edges.

      > Because of that Canon images looks softer than Nikon. Digital backs
      > have no AA filter at all. Phaseone software (capture one) does moire
      > removal.

      You can't do what an anti-alias filter does in software after the fact--it's
      mathematically impossible. Once high spatial frequencies are aliased down,
      they're indistinguishable from lower spatial frequencies. There's no
      automatic way to tell the difference between low spatial frequencies that
      are real and those that are aliases. If you, a human being, know the
      difference a priori, then you may be able to use Photoshop to clean things
      up in the places where it's a problem, but no software can know when to do
      that automatically.

      > Anyway, if I remove the AA filter, will I have no more sensor
      > cleaning? Does they replace the filter by a transparent glass?

      They almost certainly do. I know at least one IR conversion company that
      will also put in glass, if you prefer to use an IR filter in front of the
      lens. Trying to clean the sensor itself is probably impossible to do safely,
      since gawd only knows what solvents the Bayer filter can survive. They're
      some kind of plastic, and I don't believe they put glass passiviation over
      it.

      --

      Ciao, Paul D. DeRocco
      Paul mailto:pderocco@...
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