RE: Lexmark Z65 4800 DPI printer

"Laurie Solomon" <laurie@advancenet.net> · Tue, 4 Jun 2002 22:42:06 -0500

Bob,

First, I want to thank you for both saving Robert Krawitz's post and for
pointing it out to me.

Second, it does seem to refute what I said with some good arguments; I guess
part of the reason why I was not aware of the post or its points would have
been that it tends to be a little too technical for me to easily comprehend
in detail (not being an engineer)which may have resulted in my either
glossing over it or not reading it in a way that the information stuck in my
mind.  This is not meant as an excuse merely a statement of my limitations
and proclivities. :-(

The one point he makes sort of confuses me: "Download one of the manuals for
a newer printer (the older manuals aren't very good, since they were playing
things closer to the chest)...."   I tried to check the link but the web
site is one for developers which caused me to think that I would not
understand anything on it - being a non-engineer and non-computer scientist.
What confuses me is that I would have thought that "manuals that played
things closer to the chest" would be more conservative and accurrate in
their statements and specifications and, hence, better than those which
"played things farther from the cheast and a little looser."  If this is the
case, than I would think the manuals for the older printers would be more
accurrate and informative and therefore better.  Other than that, I am
willing to accept what he has said that I understand. :-)

-----Original Message-----
From: owner-epson-inkjet@leben.com
[mailto:owner-epson-inkjet@leben.com]On Behalf Of Bob Frost
Sent: Tuesday, June 04, 2002 3:18 PM
To: epson-inkjet@leben.com
Subject: Re: Lexmark Z65 4800 DPI printer

Laurie,

It seems you do have it wrong for Epsons; Robert Krawitz answered this point
a while ago. I have copied his answer below:-

I don't care what the Epson product manager said, the Stylus Photo 1280 can
print with a resolution of 2880 dots horizontally and 720 vertically.
It's a lot easier to position the head precisely than it is to
position the paper precisely.  Download one of the manuals for a newer
printer (the older manuals aren't very good, since they were playing
things closer to the chest) from
http://www.epsondevelopers.com/isv/downloadList.jsp.

The 1280 (which I use as an example because everyone here knows what it is)
can be looked at as having a printing resolution of 360, 720, or 2880 DPI
horizontally:

1/360" is the minimum spacing between dots if the printer is set to
use variable-size dots (dot size setting of 0x10, 0x11, or 0x12)

1/720" DPI is the minimum spacing between dots if the printer is set
to use single-size dots (dot size setting of 0, 1, 2, 3, or 4)

1/2880" is the smallest addressable positioning of the print head.  So
you need 8 passes of the print head to print every addressable dot on
a line.

This isn't purely a semantic issue; it is important to know what
you're referring to.

"Droplet offset" is probably the best way to describe this.  You can
set the line to start at horizontal positions of 0, 1/2880, 2/2880,
etc. and then lay dots down at 0, 8/2880, 16/2880 or 1/2880, 9/2880,
17/2880, etc.  You wouldn't actually do it in that sequence (the
banding would be disastrous), but that is about what it amounts to.
So OK, "droplet offset" and "motor stepping" are reasonable, if vague,
ways of describing what's going on.

However, variable drop sizes don't actually change the grid (2880x720)
of printable dots.  If you're printing line art or text, having the
ability to print dots of 3 different sizes on the same page doesn't
actually get you anywhere; you'll either be printing nothing or the
largest dot used at that resolution.  What it does enable you to do is
print more, smaller dots at intermediate resolutions (particularly
720x360, 720 and 1440x720; 360 DPI is intended for fast output and
2880x720 can fill the page with the smallest dots), which produces a
smoother texture.

How do you use variable dots?  Say you're printing at 720 DPI, and you
choose the medium range of dot sizes, which are something like 6, 12,
and 24 pl (I'm not certain exactly what they are, but that roughly
matches what we've determined for at least some printers).  By
experimentation, it typically takes about 11 pl dots to completely
fill the page with glossy paper.  We could simply use 12 or 24 (to be
safe) pl dots (which is what we do on the Stylus Photo EX, which only
offers single dot sizes, albeit in about 4 different sizes).  However,
the results will be less smooth than if we use 6 pl dots in pale
areas.

If we're printing at 2880x720, we'll use the smallest set of variable
dots, which is something like 4, 6, and 12 pl.  However, we don't
actually need larger dots at this resolution; there are so many dot
positions that even 3 pl drops will solidly fill the page.  However,
the 1280 doesn't offer a single drop size that small; we have to use
the variable dot size (which means that the output is twice as large,
and it takes twice as many passes to print), but in practice we only
use the smallest drop size.

So maybe it's semantics (remember that I'm a driver developer, so
perhaps I look at things a bit differently), but I don't think of
variable drop size as actually changing the resolution available from
the printer.  High resolutions enable you to use very small dots, for
improved quality, and the way Epson printers are set up you have to
use variable drop sizes to get the small dots (the smallest *single*
dot size I'm aware of is about 10 pl, on the Stylus Photo 700, EX, and
the Stylus Color 800 and 850).  Admittedly there would be little point
in using 10 pl dots to print at 2880x720.

--
Robert Krawitz <rlk@alum.mit.edu>      http://www.tiac.net/users/rlk/

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