Cels Forum

If the colors on your scan are texturized (you get
pattern inside what should be a uniform color area),
there is a few things to check :

1) Scan in 16, 24, or 32 bit colors mode. (true colors).
   If you scan with a 256 color palette or less, not
   all colors can be displayed so some are composed by
   puting several pixel of other colors near each others.

2) Save the scan in "jpg" and not "gif" : "gif" can only
   handle 256 colors so it will dither the picture to
   generate a 256 palette colors. (see above).

3) Don't use a high "jpg" compression factor : "jpg"
   compression works by removing similar hues and
   replace them by a single color (it assumes that
   human eye can only make the differance between two
   hues if they are not too similars).
   A side effect of the algorithm used is that it
   give very poor result on uniform colors : pattern
   of differant shades will appears where it was uniform
   before compressing. (the bigger the compression
   factor, the most patterns you get).
   "jpg" works very well on photography. Much less on
   cel-like picture.

4) If after checking all this, you still have patterns
   where you shouldn't, that probably mean that they
   realy exist on the original document. (even if you
   can see it, the scanner may be able to see them
   and amplify them).

   So how to get ride of them ? Most editing software
   have filters to "remove spot", "remove pattern" or
   "smooth". You can use them. Down side is that the
   whole picture will look less sharp.

   Another way is to scan the picture so that it's bigger
   than the final result you want. Then, resize it :
   when calculating the new size, the software will
   have to discard details and so remove the small patterns.
   It has the same effect as a "smooth" filter.

   After doing that, you can try to "sharpen" back the
   picture a little (so it will look less out-of-focus).
   Don't forget that such filters are losing information :
   smoothing a picture than sharpening it again won't
   give you the same picture : the sharpening won't
   sharpen back details that were lost during the
   smoothing... :)

Cheers,
Yann Stettler