
Contents:
=========

    * General purpose printer definitions.
    * Using "Top_Left" to calibrate your printer
      paper offsets.
    * Print density variation from RISC OS 2.


General purpose printer definitions
---------------------------------------------------------
The "Text" printer definition file is a very basic
raw text printer definition file. It assumes
virtually nothing - it uses form-feed (12)
carriage-return (13) and line-feed (10) and the
normal ASCII printable characters from 32 to 127.
There are text highlights. ISO Latin 1
international character mappings are supplied, but
every character is simply mapped to the closest
available normal ASCII character.

You would only use this file when attaching an
unusual printer for the purposes of doing text
printing only eg. daisy wheel printers, golf ball
printers, line printers etc.

The graphics resolution in this file is a dummy as
all DP printers must have at least one graphics
resolution. (It is in fact an MX-80 Type II
resolution).

The "PostScript" printer definition file should be
used if you cannot find a definition file for your
PostScript printer.

It defines a colour PostScript printer with a
resolution of 300 by 300 dpi, with the standard 35
fonts that Adobe provides.

The "PstScrptFP" printer definition file should be
used if you have a PostScript printer with a fast
parallel interface and your computer has suitable
hardware. In all other respects, it is identical
to the "PostScript" printer defintion file.


Using "Top_Left" to calibrate your printer paper
offsets.
---------------------------------------------------------
The "Printers.Top_Left" printout file can be used
to calibrate the position of output on Epson and
IBM compatible dot matrix printers. To do this,
you should first ensure your printer is in its
default state eg. switch it off and switch it back
on again, and feed paper into it if necessary.
Then send the Top_Left file directly to the
printer. The easiest way to do this is to set
!Printers up for printing to your printer, and
then drag the "Top_Left" file icon onto the icon
for your printer on the icon bar. Alternatively,
you can use the command line; the command "*Copy
Top_Left Printer:" will send the file to the
printer, assuming you are in the Printers
directory and the print destination has already
been set up correctly (eg. by !Printers).

On the paper there should be a small vertical and
horizontal line (like an inverted "L") close to
the top left corner of the paper. Start !PrintEdit
(in App1) and drag the printer definition file you
wish to use into the !PrintEdit window. Measure
the distance from the left hand edge of the paper
to the left hand edge of the inverted "L" mark (do
not measure to the middle of the mark). The
distance you have just measured is the "Paper X
offset" for your printer, so you should enter it
into the "Paper X offset:" field in the !PrintEdit
window. Now measure the distance from the top of
the paper to the top edge of the inverted "L" mark
(again do not measure to the middle of the mark).
This distance is the "Paper Y offset" for your
printer, and should also be entered in the
!PrintEdit window. Now click the MENU button in
the !PrintEdit window (avoiding the "Graphics
modes:" icons or you will get the wrong menu), and
use the "Save" option to save your customised
printer definition file. It is recommended that
you do not overwrite your master printer
definition file. Either make sure you have
backups, or save your new file somewhere else.

Now quit !Printers, restart it, and load in your
new printer definition file using the "Printer
control" window. Printed output on your printer
should now appear in the correct position.


Print density variation from RISC OS 2.
---------------------------------------

You may find that printouts are lighter or darker
under RISC OS 3 than they were in RISC OS 2. This
is usually due to a change in the amount of
interlacing being performed ie. the number of
passes the print head makes over the same section
of the paper.

For example a Canon BJ-300 printer under RISC OS 2
with !PrinterDM set to "EPSON LQ-850 compatible
(360 by 360 dpi)" and the printer set to Epson LQ
emulation mode will make two passes over the paper
due to using vertical interlacing. The same
printer under RISC OS 3 with !Printers using the
Canon.BubbleJet file set to 360 by 360 DPI and the
printer set to IBM emulation mode will only make
one pass over the paper. So the printout will be
lighter, but on the other hand it will take less
time to print and the quality will be higher since
no interlacing is being used. Also the ink
cartridge will last longer. In this example
running the printer in Epson LQ emulation mode
with the Epson.LQ-860 file set to 180 by 360 DPI
will give results which are almost identical to
the RISC OS 2 configuration.

In the general case, if you use 360 by 360 DPI in
any printer definition file which gives true 360
DPI vertical resolution (non-interlaced), then
this will give lighter print than any of the 360
by 360 DPI standard Acorn !PrinterDM settings,
which are all interlaced. The files which use true
360 DPI vertical resolution are Canon.BJ-130e,
Canon.BJC-800 (usable with Star SJ-48) and
Canon.BJ-130e. Switch to a 180 by 360 DPI
resolution in a more standard file (eg.
Epson.LQ-860) if you need the interlacing to get
darker print.

Conversely take an Epson LQ-850 printer under RISC
OS 2 with !PrinterDM set to "EPSON LQ-850
compatible (360 by 360 dpi)". This again will make
two passes over the paper. The same printer under
RISC OS 3 with !Printers using the Epson.LQ-860
file set to 360 by 360 DPI will make four passes
over the paper since it is now horizontally
interlaced as well as vertically interlaced. (In
fact RISC OS 2 never really achieved 360 DPI
horizontal resolution since it didn't interlace it
and the printer will not print adjacent dots. The
only benefit this gave was 360 DPI positional
accuracy of left hand edges.) So the printout will
be darker and the resolution will be better, but
on the other hand it will take longer to print and
will wear the ribbon out faster. In this
particular example using 180 by 360 DPI in
!Printers will give results which are almost
identical to the RISC OS 2 configuration.

In the general case, if you use any resolution in
any printer definition file which is horizontally
interlaced, this will give darker print than the
same resolution under !PrinterDM. In practice this
is 240 DPI horizontal for 9 pin printers (240 by
72, 240 by 144 and 240 by 216) and 360 DPI
horizontal for 24 pin printers (360 by 180 and 360
by 360) although not all of these resolutions are
available as standard in !PrinterDM. If you need
to get the same print density as you did on RISC
OS 2, halve the horizontal resolution you are
using to 120 DPI or 180 DPI. If the extra
positional accuracy of left hand edges that RISC
OS 2 gave you turns out to be important, then edit
the horizontally interlaced graphics resolution
you are using (eg. 240 by 216) with !PrintEdit and
change the "X interlace:" field from 1 to 0 which
will disable the horizontal interlacing. (Note
that you cannot simply disable vertical
interlacing in a similar manner. Other changes
would be required.)
