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Thread: sharpening depends on size of image?

  1. #1

    Default sharpening depends on size of image?

    If my image is 1024 x 768 at 72ppi, I find using an agressive 400, 0.5, 0 in USM works well. But if I do a much larger image dimension at 240ppi say, then even 400, 0.5, 0 looks so mild. I need something much more!

    Does it mean the amount to sharpen an image depends on the resolution?

  2. #2


    Yes... it depends on the amount of details in the image...

    Ie.. for a 4MP image of a closeup potrait, my setting may be 120%, 2.0, 3
    But for a 4MP image of a group photo, the edge of each face is much smaller, thus less radius... and may turn out to be 90%, 1.0, 3

    When the images are reduced, each edge that defines a feature, ie, the line that defines the lips will be defined with less pixels as well, thus radius should also be reduced... for web images the radius is typically about 0.5-0.8.

  3. #3


    Thanks Willy... ic...

    I was shooting 8mp on the 20D and converted my images to jpg. Previously I had downsized to a small 1024 x 768 and had no problems with sharpening. At 8mp, the same sharpening wouldn't work at all, almost like no effect. I had to use a much drastic setting like 200, 1.4 (radius), 0.

  4. #4


    I suspect a larger radius would yield a more pleasing effect...
    Try 120, 2.0, 0 instead and compare the effects...

  5. #5


    I read in some magazines that it is most useful to do USM with the image in Lab colour mode, with the highlight in the lightness channel. I donno if it helps or not...


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