Re: [Gimp-print-devel] TESTING needed for certain Epson printers

[Robert L K. <rl...@al...>]

   From: "Ian Young" <ia...@ia...>
   Cc: <gim...@so...>
   Date: Tue, 29 Aug 2000 21:11:19 +0100

   > OK.  The next question is whether it's possible to get useful
   > density out of the 360 dpi softweave modes on plain paper (which
   > needs a lot less ink).  If it's possible to use 360 softweave or
   > 360 high quality to proof on plain paper, I'll leave those modes
   > in.  If not, I'll rip them out.

   I did a few tests with the 1200 just cranking the global density
   value up with the slider.  My comparison point was a 75% gray patch
   printed in 720dpi Softweave on plain paper.  I'll give density
   values as the step number on a Kodak Q-13 gray scale I happen to
   have handy; it's roughly visually linear and the reference patch
   comes in around step 8 on it (0 being paper white).

That's not a bad way to do it.

   Plain 360dpi mode at density=1.0 is about step 3 (!); cranking the
   density up as far as it will go to 2.0 brings it up to around step
   5.  This is still significantly lighter than the reference patch.

I know that plain 360 DPI mode won't go high enough.  I don't know
why.  360 softweave doesn't put down bigger dots than plain 360 (to
the best of my knowledge), so it doesn't make much sense.

   360dpi softweave and high quality at density=1.0 both come in at
   step 4 or so; density=2.0 gives me step 6.  This is probably
   getting back into the realms of the usable.

   I'm guessing from this that making plain 360dpi mode match 720
   softweave would require a density setting of somewhere between 4.0
   and 5.0; 360dpi softweave and HQ probably need a density of 2.5 to
   3.0.

You won't be able to usefully go that high; once the density corrected
for the printer density factor and the paper type hits 1, that's the
limit.  If the software allowed you to push it higher, you could get
darker grays, but not darker blacks.

   If you think it's worth it, I can try and tweak the constants in
   the driver to figure out the real required values.  You might also
   want to comment on whether you thing the 1200 results can be
   extrapolated to the 740, or whether I should run some tests on it
   as well.

Sure.  I would think that the 1200 and the 740 are very similar, but
if you can test both, please do so.

   > That's fine.  The reason is that the special 0x11 mode on the 900 (and
   > the 0x12 mode on the 4 picolitre printers) has very different relative
   > ink dot sizes compared to the 0x10 mode.  That fix is quite easy.

   OK.  Comprehensible explanation.  Except that I had a quick peek at the
   documentation from the Epson site about dot sizes for these printers (just
   out of curiosity) and couldn't find any of these 0x1x values mentioned
   anywhere, even for the 900.  Where do they come from?

Ron van Ostayen was kind enough to send me actual samples of output
from the Windows driver for the 900, and that used the 0x11 mode in
addition to the 0x10 mode.  I took a guess that that mode also worked
on the 740, but I was wrong.  The documentation in 4color99a.pdf is
incomplete as far as the dot size setting goes.

The usual result when using an illegal dot size is something very much
like what you saw -- different planes print out in different widths,
things don't line up, and so forth.

-- 
Robert Krawitz <rl...@al...>      http://www.tiac.net/users/rlk/

Tall Clubs International  --  http://www.tall.org/ or 1-888-IM-TALL-2
Member of the League for Programming Freedom -- mail lp...@uu...
Project lead for The Gimp Print --  http://gimp-print.sourceforge.net

"Linux doesn't dictate how I work, I dictate how Linux works."
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