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Thread: Visible contours after gaussian blur

  1. #1
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    Default Visible contours after gaussian blur

    hi anybody got this problem, when you apply gaussian blur to a gradient background, visible contours will appear? i am so frustrated, i tried different kinds of blur but still get this silly thing happening. anybody can help?

  2. #2

    Default Re: Visible contours after gaussian blur

    can post pic?

  3. #3
    Senior Member Sion's Avatar
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    Default Re: Visible contours after gaussian blur

    Contouring or banding is always a problem with digital photos especially if you stretch the curve severely.

    You may try:

    1. Work in 16 bits.

    2. Add a bit of noise.

    3. Replace the objectional banding part by creating a new gradient yourself if that is possible.

    Adding gaussian blur would aggravate contouring. Try a bit of motion blur if the photo allow you to do so.

    The lower the resolution the worse the contouring gets.

    Having changed from a 6mp camera to a 10mp one I notice I haven't encountered so much problem with contouring these days.

    Every photo would require a different treatment to reduce the contouring depending on the subject.
    Last edited by Sion; 21st November 2006 at 10:02 PM.

  4. #4
    Moderator Clown's Avatar
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    Default Re: Visible contours after gaussian blur

    most practical way to counter is to add noise..
    sigh.

  5. #5
    Senior Member jOhO's Avatar
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    Default Re: Visible contours after gaussian blur

    yeap.. i add noise.

    after upgrading to a better screen, i have been doing it more often...

  6. #6
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    Default Re: Visible contours after gaussian blur

    hello all, i see i am not the only one with this problem, when you get such a thing happening, does the contours appear when printed out?
    here is a sample of one picture with contours after gaussian blur on the top left area.


  7. #7

    Default Re: Visible contours after gaussian blur

    The methods mentioned by others are probably very useful in countering various severity of posterization (i.e. colour contouring) : such as using more bit depth etc.

    For those contourings which occur with very clean background such as in the picture shown, it can be solved by carefully selecting the area (either by magic wand tool and lasso tool or by a table PC pen etc.) and then apply adjustment levels to the selected area to narrow the output range so that the whole area is more uniform. There may be a slight loss of details at the edges, depending on how careful you're in selecting the area.

    Last edited by Clockunder; 22nd November 2006 at 03:55 PM.

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