> So, what's going on? When I select lineart or whatever, I assume that
> this is setting the scanner to scan in a particular mode...so shouldn't
> it be able to resolve b/w text better in lineart mode?
The scanner hardware actually resolves greyscale, and lineart mode sets
a threshold, just like the filter of the same name in e.g. GIMP. So
the results of the threshold would pick up black-on-white art work while
ignoring the noise from the grain of the paper, smudges etc. For text
this is probably not what you want, unless you have an algorithm which
works only on BW data, perhaps some OCR does this?
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.
NB. You should be able to get *acceptable* results if you can tune the
brightness or threshold parameters for the scanner hardware. I can get
readable text from 400dpi lineart with the ScanJet IIc here.
Nick.
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