Removing scratches from video(not from lens)

Discussion in 'Amateur Video Production' started by scubayogi, Apr 16, 2013.

  1. scubayogi

    scubayogi Guest

    Hi everybody,

    I have an underwater movie to edit, problem is the dome of the housing
    has a big circular scratch right in the middle! how can I remove it
    effectively from the the video?
    I have this sw available:

    Adobe Premiere/Photoshop CS5
    Apple Final Cut Pro X 10.0.8

    Any suggestion?

    Thank you
     
    scubayogi, Apr 16, 2013
    #1
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  2. scubayogi

    Paul Guest

    This is not a systematic distortion. You can get editing software
    that can compensate for pincushion or the like. (PTlens uses
    EXIF data, which is cheating.) There is no EXIF data for your scratch.

    http://www.imagemagick.org/Usage/lens/correcting_lens_distortions.pdf

    http://docs.gimp.org/en/plug-in-lens-distortion.html

    If the scratch is in focus, it might be easier to correct. You might
    shoot reference images, of say, non-saturated background colors, and
    subtract the impact of the scratch, from all your frames. Since the
    scratch may move from frame to frame, you might need to autocorrelate
    the correction image, with the frame, so that it is aligned well. At
    this point, we don't know if the scratch moves, as you were using
    the camera.

    If it is out of focus, then the correction is more of a mathematical
    transform in the (X,Y) plane. Systematic lens distortions, tend
    to be correction in (R,THETA) - symmetric about the centerline
    of the lens. A transformation is a more general solution than
    subtraction would be. Subtraction is limited to the simplest of cases
    (it's a subset of a general transformation).

    In a few searches, all I seem to be able to find, is approaches
    for the pincushion effect. Nothing for truly arbitrary correction,
    like your scratch.

    The solution to any problem, is finding the right terminology
    to describe it. So your question is formed in the same terms,
    as the person providing the solution. And I don't seem to be
    using the right terms. It's pretty hard to coax useful results
    from a search engine.

    The last search I tried, was:

    "correcting image shot through old glass windows"

    and most of the returned articles discussed glare, rather than
    ripples in the image. You may need to think along parallel
    lines (correcting some other kind of distortion), to find
    a solution for yours.

    Paul
     
    Paul, Apr 16, 2013
    #2
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  3. scubayogi

    scubayogi Guest

    wow, thanks for the effort!
    ;-)
     
    scubayogi, Apr 16, 2013
    #3
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