26 Jun
2004
26 Jun
'04
10:05 a.m.
Tom Owad wrote:
I was doing 150dpi greyscale jpegs. I've changed to 400dpi 1bpp tiffs,
and now I'm ending up with each page about 700K... (scan as greyscale
tiff (unknown compression), convert to 1-bit with lzw compression, save
as pdf in Photoshop).
You need to scan at 1bpp, not grayscale. When you are converting from
grayscale to 1bpp, you are probably getting dithering (a pseudo-random
scattering of black and white pixels) in order to approximate the
original grays at the edges of characters. This dithering will ruin the
achievable compression in G4, which is a fax algorithm optimised for
runs of white and black pixels.