[net.graphics] Print resolution

cdr (02/01/83)

     The following is a quote from a wonderful book called
TEX and METAFONT, New Directions in Typesetting by Donald E.
(Art of Computer Programming) Knuth.  He is talking about why
the output from a digital typography system was indistinguishable
from metal type.

	The reason for this is not that our eyes can't distinguish
	more than 1000 points per inch; in appropriate circumstances
	they can.  The reason is that particles of ink can't
	distinguish such fine details - you can't print the edge
	of an ink line that zigzags 1000 times on the diagonal of
	a square inch, the ink will round off the edges.  In fact the
	critical number seems to be more like 500 than 1000.

(The ink physically performs the anti-aliasing.)

I have not had the chance to experiment but I think this indicates
that you need about 500 lines per inch to produce camera ready copy
for a standard printing process. (Several laser printers come
close to this by having >400 lines per inch.)
In many cases the printing company will accept oversize copy, so you
can increase the resolution by using larger size fonts and requesting
a reduction. (Another reason to buy a printer that can
handle more than 8 1/2 by 11 paper.)
This doesn't mean that your output will look great; Knuth is talking
about a liquid ink process.  Laser or dry ink processes might well
zigzag 500 or 1000 times on the diagonal of a square inch; however,
if the output will later go through a standard printing process,
this does not matter.

Perhaps those that have such printers can report their
experience to the net.  A short report on the make and resolution
of the device and the appearance of the output after it was
xeroxed and/or printed.

Note: Knuth's book is published by Digital Press, Educational
Services, Digital Equipment Corporation, Beford, Mass. 01730
The quote is from page 16.  I can highly recommend it to
anyone who is at all interested in typesetting, especially if you
have ever used nroff or troff.

Note also that Xerox is a trademark but nobody cares anymore.

			Durward Rogers
			decvax!mcnc!cdr