Re: Epson coated paper negatives

Luis Nadeau (nadeaul@nbnet.nb.ca)
Sun, 26 Apr 1998 19:52:18 -0300

At 11:56 PM -0400 98/04/25, FotoDave wrote:
>In a message dated 98-04-25 23:05:51 EDT, lkv1@psu.edu writes:
>
><< Don't the "resolution" figures given for an ink-jet printer refer to how
> many positions on which it can place a dot in each inch, rather than the
> dot size?
>
>Yes, you are abosuletly correct, and thanks for pointing it out. I am sorry
>for being so inaccurate in what I said. What I normally do when using the ppi
>for calculation like this is to approximate and give someone just some crude
>idea of the magnitude of size we are talking about.
>
>>> That is, a printer with resolution rated at 600dpi can place a
> dot of its default size in any of 600 positions in each linear inch of
> image area. Those dots can and do overlap, and vary in size from one model
> to another. >>
---------------

Some more info on dpi, etc., from a review:

===============
Resolution results from a combination of dot size and dot spacing, so a
600-dpi-rated printer needn't have a 600-dpi printhead. Manufacturers
increase effective resolution through multiple passes of the printhead. For
example, a 600-dpi printhead can produce 1,200-dpi output through two
passes. The first pass lays down half the required dots, and the second
pass completes the image. To attain its 1,440-dpi resolution, the Epson
printers use eight passes of a 180-dpi printhead. A 300-dpi printhead like
that of the HP printers needs two passes to attain the maximum 600-dpi
output. Interestingly, we found no correlation between print speed and the
number of passes a printer needs to produce the complete image. Driver
efficiency and the printer's buffer have as much to do with the printer's
speed as the number of passes the printhead takes.
===============

It just goes to show that reading the specs of printers (and monitors) does
not tell the whole story. The final judge is the human eye.

Luis Nadeau
NADEAUL@NBNET.NB.CA
Fredericton, New Brunswick, Canada
http://www3.nbnet.nb.ca/nadeaul/