Chromatic aberration removal in software, camera, etc

Discussion in 'Digital Cameras' started by RichA, Mar 10, 2014.

  1. RichA

    RichA Guest

    I'm wondering how it works, exactly. Does it just remove chromatic fringesfrom light-dark edges, or does it really remove it completely? Reason is,we don't see chromatic aberration with our eyes except on light-dark edges, but CA is actually suffused across the entire image, resulting in loweredcontrast. So, I was wondering if the software actually removed the defocused blue and red across the image, or just on the edges?
     
    RichA, Mar 10, 2014
    #1
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  2. RichA

    Savageduck Guest

    Both LR5 and ACR do a pretty good job of correcting CA.

    Here is an example, before and after showing some purple fringing,
    corrected in LR5.
    < https://dl.dropbox.com/u/1295663/FileChute/screenshot_612.jpg >

    Do not mistake chroma noise for CA, that is also correctable provided
    you correct luminance noise first.

    Then color casts are something else altogether, and are also fixable.
     
    Savageduck, Mar 10, 2014
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  3. RichA

    RichA Guest

    No, chroma noise isn't CA. But having used achromatic telescopes, I've seen the effect on images of unfocussed light at either end of the visible spectrum. It's generally more pronounced than in modern camera lenses.
     
    RichA, Mar 10, 2014
    #3
  4. RichA

    Martin Brown Guest

    It is doing neither.

    The chromatic aberration compensation is to separate the image into red,
    green and blue and then correct the slightly different effective
    magnifications of the red and blue images using the green as a
    reference. It is a correction of lateral chromatic aberration which gets
    worse the closer to the edge of field that you go.

    This is different from the hardline diffraction limited optics case in
    astronomical telescopes where the red and blue images are noticeably out
    of focus relative to the green image. Residual transverse chromatic
    aberration being the hardest thing to remove. See:

    http://en.wikipedia.org/wiki/Chromatic_aberration
     
    Martin Brown, Mar 10, 2014
    #4
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