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Old Aug 11, 2009, 10:25 PM   #1
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Default res of scanned photos

Scanned a photo as a jpg at 1200 DPIit came out at 9792 x 12256 which is 120mp, file size was 40mb. Print size 68.0 x 85.1 inches. Quiet excessive, but the quality was real good.At 300DPI, file size was 2.5mb, 2464 x 3072, 7.5mp.At 600DPI, file size was 8.3mb, 4912 x 6128, which comes out to 30mp, not 15mp?If doubling DPI, creates double res. why 3.3x files size, and 4x mp size? Interestingly, old b/w photos when reduced size by 50% look better and sharper. As scanned photos are much larger but not sharp and out of focus.
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Old Aug 11, 2009, 11:24 PM   #2
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When you double the resolution, you have to remember you are doubling it in two dimensions, so you get four times the number of pixels. Easy way to remember it is to think of a one inch square. If you have two inches square, that is four square inches, not two.
File size differences will not necessarily increase in a linear manner with pixel count, due to the way the compression algorithms work. (unless you are using a non-compressed file type)
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