Re: [Gimp-print-devel] First experiences with an 870

[Jean-Marc V. <ver...@if...>]

         1) The standard Epson density (.6`ish) is all wrong for this printer.
         I had to scale it to 1.3 (which really means 1.3 * .6, or about .8)
         to get anything that looked even remotely reasonable.  Even that`s
              a bit too low (I`m using photo glossy paper).  I also had to
knock
         down both gamma and brightness a bit (.9 gamma and 80 brightness;
         that gamma might be just a bit too low).  Ron van Ostayen suggested
         a value of 1.6 for his ESC 900; that creates solid blacks, but it
         definitely drops too much ink (see below).

         This might explain why people with 900`s are complaining that
         output is too light.  Maybe all the variable dot size printers need
         adjustment.

I had mentionned that in my first mail to you (not to this list).

        2) The ink dries very slowly.

True on most papers. I have found that ink dried very quickly on TDK pro
quality paper. I find it's a very good paper too. Unfortunately a bit
expensive.

        3) Pale tones are very good indeed.  Gray is very neutral.  However,
        under a loupe there`s some weirdness going on.  I think that the
        error spread setting (controlling how widely the error is diffused)
        is too high.  That`s not surprising; the spread settings are set up
        for single dot size.

Could that have something to do with my magenta problem ?

	4) Mid and dark tones are grainy.  It`s less obvious when I push the
        density up.  It might be a sign that the dither algorithm has
        problems here; it might also simply be a sign that the density is
        too low.  The grain looks a little bit like "shadowing" from large
        dots, but not entirely.

I would agree, wouldn't I ?

        5) Using the smallest dot size from the dark inks makes the grain
        worse.  That doesn`t particularly surprise me; it`s not laying down
        a lot of ink, but it`s printing quite dark.  We may be better off
        not using this.  Or maybe we need to find a way to use it only in
        heavy gray situations.

That was my point a few days ago. I would not recommend not using small dots at
all. The problem really occurs with dark cyan, dark magenta and black only
(dark inks). Even with these inks not using small dots will sometimes result in
using too much of the light inks and laying down too much ink.

       6) The printer is nearly silent -- a nice change after the noisy EX.

That is a pleasure, isn't it ? I'm no longer afraid of wakening my son at 3 am.

       7) I think the high density results in too much ink being dropped
       (which is bad because of the slow drying ink and its expense).
       Jean-Marc Verbavatz had an idea about an ink budget.  I think
       that`s a great idea and needs some more study.  We also need to
       look at other ink reduction techniques.

Yes, increasing density until you get solid colors is not the answer. I'll
try to implement that again with the current version of gimp-print.

For a full description of this printer's features one should add that the
bottom margin is quite small ~6-7 mm as far as I can tell and it does not keep
printing on the next page if you go over the margin.


-- 
--
Jean-Marc Verbavatz		<ver...@if...>
5, rue La Fontaine		"http://perso.cybercable.fr/verbavat"
F-75016 Paris