3054) How do I maximize the quality of a picture from a scanner?
Description
This article is from the Hong Kong FAQ, by John Ho john@jho.com with numerous contributions by others.
3054) How do I maximize the quality of a picture from a scanner?
This is not an easy question. It depends on what scanner software
you have. If you have a color scanner which offers 256 (8-bit) colors
or less, don't expect too much from it.
If your color scanner offers more than 8-bit colors, but the picture
doesn't look "smooth" or looks grainy, the problem may be in one/more
of the following:
i) The scanner software. How it records the information from the
scanner. If the software can save in 16 million color (24-bit)
picture format such as TIFF, TGA, BMP, the problem may be in
the next items. If the software can only save in 8-bit color
format, don't worry. Read the next items first!!
ii) The paper quality. You won't get good quality scan from pictures
on un-smooth glossy paper. Also, it is no good too when you scan
small pictures on thin magazine paper (such as the paper used
in the large "nosey megazines"). Matte paper is the best.
iii) The quality of publishings. All pictures you see in every kinds
of publishings are dithered (i.e.: consists of tiny dots/pixels.
Look at a picture closely and you'll see). Depends on the dot
pattern and size, you may see the "wrinkles" on the scanned
picture. The quality can be improved by turning the source by a
small angle and rescan it. Also, use lower resolution (200 DPI
or less) with large picture source may help. Photographs don't
have such problem anyway.
If the scanned image is a bit out of focus, you can apply sharpness or
edge enhancement filter in your image processor to improve the focus.
However, it also emphasizes the "wrinkles" if scanned from publishings.
Moreover, excessive application of filtering will degrade image quality.
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