> To the human eye greyscale will always look better because it reduces
> aliasing. So if you're just going to look at the results (or use an
> algorithm which permits greyscale) you should use greyscale.
>
> The other advantage of line art is that it returns much less data (of
> course 8 times less normally, or better with RLE) and so can be saved
> to a smaller file and transmitted more quickly over SCSI. This might be
> important for scanning A4 documents at high resolution quickly.
Though greyscale is certainly better for legibility, if you're planning on
archiving the documents, you'll want to futz around with the
brightness/contrast settings as mentioned, and stick with lineart. The
reason, in a nutshell, is that Group 4 Compression (FAX, TIFF, etc.) is
the "best compromise" compression for archival storage, and it only does
BW (ie: lineart).
I say it's the "best compromise" because it's not /exactly/ a "general
purpose" compression algorithm. It was designed for FAX transmission, and
the designers chose certain constant parameters of the algorithm based on
statistical analysis of lots of images of text documents in European
languages. So it doesn't do quite as well on a BW scan of a full page
magazine ad as it would on a full page of magazine text.
In any case, TIFF or CALS with G4 compression is by far the most pervasive
encoding in archival document management systems.
-- Tripp Lilley + Innovative Workflow Engineering, Inc. + (tripp@iweinc.com) ------------------------------------------------------------------------------ "It all comes from health and good nutrition, and not just from giving them a nice bath before the show."- Mary Papadopoulos, on horses showing well
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