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Thread: Need help on Gaussian blur

  1. #1

    Default Need help on Gaussian blur

    Due to the small CCD of digicam, the photos taken usually have a tremendous DOF. Therefore, if taking portrait, i have to blur the background with Gaussian blur. I usually select the subject with magnetic lasso, then invert the selection and blur the background. However, i find it very hard to select the strands of hairs that stray away from the rest, or hairs with irregular edges. This makes the gaussian blur looks unnatural (well, perhaps it is not natural in the first place ). I tried using history tool but i found trying to trace out the blurred hair strands after applying Gaussian blur is painstaking. Can any kind soul enlighten me on how to do this better?

    Thanks in advance!

  2. #2
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    how about using the extraction tools?
    Create a duplicate layer, then filter --> extract. Extract the subject, blur the background layer, then flatten all layers.

  3. #3
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    erm... try to take pics with clean background in the first place?

  4. #4
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    Quote Originally Posted by cheersjy
    Due to the small CCD of digicam, the photos taken usually have a tremendous DOF. Therefore, if taking portrait, i have to blur the background with Gaussian blur. I usually select the subject with magnetic lasso, then invert the selection and blur the background. However, i find it very hard to select the strands of hairs that stray away from the rest, or hairs with irregular edges. This makes the gaussian blur looks unnatural (well, perhaps it is not natural in the first place ). I tried using history tool but i found trying to trace out the blurred hair strands after applying Gaussian blur is painstaking. Can any kind soul enlighten me on how to do this better?

    Thanks in advance!
    Have you tried varying the opacity of the history brush as you reach the edges of where you want to blur? Reduce to 50% or less. It might help to make it look less obvious.

  5. #5

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    Thanks pal, i have never tried the extraction tools or history tool opacity before, will play around with them.Thanks for the great advice!!

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    Quote Originally Posted by tsdh
    how about using the extraction tools?
    Create a duplicate layer, then filter --> extract. Extract the subject, blur the background layer, then flatten all layers.

    This method is quite a good one to blur the background but maintain the focus on the subject...
    but have to be careful when selecting the subject to extract...

    One question...like what cheersjy posted... how do we sekect the strands of hair which is so thin and tiny??

    cheers

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    Quote Originally Posted by SuRfTeC
    One question...like what cheersjy posted... how do we sekect the strands of hair which is so thin and tiny??
    cheers
    The extraction tools in PS works by detecting the edge's contrast/color difference, as long as the hair-strands have adequate contrast/color difference with the background, then the extraction tools will select it nicely. No need to strain your eyes trying to select individual hair-strands.

  8. #8

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    what i'd normally do is duplicate a layer of the image, apply gaussian blur, then add a layer mask, then slowly paint away the regions i don't want...this way i can control how much blurness to apply by varying the amount of mask I keep.

    also help to do all these b4 u reduce the size..allows you to magnify and choose a smaller brush to edit the mask.

  9. #9

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    ya, it is easy to select the background if you take a clean and plain background ...

    Click here to see how to blur the background
    See my Photo Gallery at the Clubsnap

  10. #10
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    Quote Originally Posted by tsdh
    The extraction tools in PS works by detecting the edge's contrast/color difference, as long as the hair-strands have adequate contrast/color difference with the background, then the extraction tools will select it nicely. No need to strain your eyes trying to select individual hair-strands.

    erm... how to let the extract tool select for you automatically?
    been trying but still dunno how... now only suing highlight tool to select the area to extract then use the fill tool...
    this way is very tedious right??

    can share on the procedures of using extraction tool...??

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