From: Denton Taylor <denton@xxxxxxxx>
"I am new to this scanner thing and I thought that you should scan
at 600dpi and print at 600 or better."
Don't open THAT can of worms! :-) I'm in the field, so I'm biased, but I
think ANYONE who is contemplating doing ANYTHING with images and computers
could study Shannon and Nyquist.
Basically, dot matrix printers use creative marketing. The 1440 you see
advertised is a white lie. True, it can pack 1440 dots into an inch, but
each one cannot be any one of the colors in the printer's gamut. Typically,
such printers fill a 4x4 matrix with CYMK dots to achieve about 200 lines
per inch for arbitrary colors.
Also, when scanning, you need to scan at a minimum of twice the desired
output line grid to preserve its detail. This is the so-called "Nyquist
number," and is why audio CDs are sampled at 44 kHz when no human can hear
anything above 22 kHz.
What does this mean? For "same size" work, scanning at above 400 samples
per inch is a waste, and scanning above 200 samples per inch doesn't buy
you much. The value of such high scan densities is if you intend to blow it
up. You can blow up a 600 spi scan by a factor of three with little impact
on the output.
Personally, I sample at 300 spi for same-size printing, then run the Epson
at 720, which is REALLY only 360, at best, on perfect paper.
: Jan Steinman <mailto:jans@xxxxxxxxxxx>
: 19280 Rydman Court, West Linn, OR 97068-1331 USA
: +1.503.635.3229
< This message was delivered via the Olympus Mailing List >
< For questions, mailto:owner-olympus@xxxxxxxxxxxxxxx >
< Web Page: http://Zuiko.sls.bc.ca/swright/olympuslist.html >
|