Unsharp mask

Discussion in 'Digital Photography' started by Daniel Dravot, Apr 4, 2004.

  1. So what exactly is this unsharp mask my photo editing software has? What
    does it do, when would I want to use it and why?

    Dan'l.
     
    Daniel Dravot, Apr 4, 2004
    #1
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  2. Daniel Dravot

    Lucas Tam Guest

    Lucas Tam, Apr 4, 2004
    #2
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  3. Daniel Dravot

    JJD Guest

    On Sun, 04 Apr 2004 20:44:12 GMT, "Daniel Dravot"
    <> wrote:

    >So what exactly is this unsharp mask my photo editing software has? What
    >does it do, when would I want to use it and why?
    >

    It takes lines of differing contrast - say, a person's head against a
    sky background - and amplifies the intensity of the sky's lightness
    and the darkness of the person's head for a few (selected number of)
    pixels on either side. This separates the two from each other more
    distinctly and gives the impression of a sharper picture.

    If you use just "Sharpen", then everything is "sharpened" and you end
    up with a grainier, or noisier picture. Unsharp mask only deals with
    lines of contrast difference and leaves the rest of the picture
    largely unaffected. Use it judiciously, however, or you'll end up
    with an unpleasant halo effect.

    JJD
     
    JJD, Apr 4, 2004
    #3
  4. Daniel Dravot

    misifus Guest

    Daniel Dravot wrote:

    > So what exactly is this unsharp mask my photo editing software has? What
    > does it do, when would I want to use it and why?
    >
    > Dan'l.
    >
    >



    It's the most sophisticated image sharpening tool in most image
    software. It does, however, take some practice and knowledge to
    use effectively.

    -Raf

    --
    Misifus-
    Rafael Seibert
    mailto:
    http://www.ralphandsue.com
     
    misifus, Apr 5, 2004
    #4
  5. Daniel Dravot

    Mark Johnson Guest

    "Daniel Dravot" <> wrote:

    >So what exactly is this unsharp mask my photo editing software has? What
    >does it do, when would I want to use it and why?


    Here's a brief article:

    http://scenic-route.com/tutorial/psp/tutor/unsharp/Unsharp.htm


    There's more to sharpening, however, than just this. Generally, the
    method is to use a 'find lines' or 'find contours' filter, and then
    apply similar blur subtraction as described in the article. Try a
    google search for 'deadman' PS actions. These will cleanly sharpen any
    image.
     
    Mark Johnson, Apr 5, 2004
    #5
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