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Thread: Dpi
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13th July 2007, 10:56 AM #1
Dpi
I am having trouble with the quality of the pictures I get when I scan photos from old newspaper articles. Can anyone tell me how DPI (dots per inch) a newspaper photograph usually is so I can set the scanner the same
Cheers,
Howdya
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13th July 2007, 12:31 PM #2
I'd suggest going to at least 600 dpi or higher. You want to scan at higher resolution (dpi) than the dots per inch in the newspaper picture, otherwise the dots in the picture interfere with the dots of the scan resulting in strange patterns (due to an effect called aliasing).
After you've scanned the picture, you may be able to use some software to smooth the image and subsequently reduce the resolution, if you need to.Those are my principles, and if you don't like them . . . well, I have others.
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13th July 2007, 12:39 PM #3
Yup, maximum DPI for scanning.
You'll never get great pictures from scanning newsprint. It's pretty poor quality to start with.Photo Gallery
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13th July 2007, 12:43 PM #4
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13th July 2007, 12:53 PM #5
Thanks Zen,
You were spot on the money. I was getting funny patterns but didn't know how to explain it.
Ruddy, I didn't know you were a journalist as wellCheers,
Howdya
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13th July 2007, 01:21 PM #6
They're called Moire patterns. There are lots of google hits on how to remove them, but it's easier to eliminate them from the start using high-res scanning.
Note: you may see moire patterns on your screen, without them being actually present in the scan. This will happen due to the interaction of the dots in the image with the pixels of your screen. Test for this by zooming in. If you see the individual dots when you zoom in, then your scanning resolution was high enough.
Here are some gory details:
http://www.wfu.edu/~matthews/misc/DigPhotog/alias/index.htmlThose are my principles, and if you don't like them . . . well, I have others.
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13th July 2007, 09:43 PM #7
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13th July 2007, 10:14 PM #8