🚀 go-pugleaf

maupb@csv.warwick.ac.uk (Mr J L Saunders) wrote:

(In reply to my stuff about not doing interlaced colour dot matrix
printing.)

>Why not just print the yellow first? This seems obvious to me.

Indeed for horizontal interlacing this is actually what happens. I realised
this while writing the technical documentation for the PRM. So 360 by 180
would be safe, but it'll probably still look bad because 8 head passes is
over the top. Anyway 180 by 180 on a 24 pin printer is fine, what isn't is
120 by 72 on an 8 pin printer, which is the maximum resolution without
interlacing. 240 by 72 would also be feasible, but what you really want is
120 by 144 which is vertically interlaced and so the yellow would overprint
on dark colours. To print the yellow first, you'd need to reverse feed the
paper by 1/216". A lot of printers don't support reverse paper feed at all,
and those that do tend to do it inacurrately. The sequence would be:

Yellow pass, forward paper feed 1/216 inch
Yellow pass, reverse paper feed 1/216 inch
Cyan pass, forward paper feed 1/216 inch
Cyan pass, reverse paper feed 1/216 inch
Magenta pass, forward paper feed 1/216 inch
Magenta pass, reverse paper feed 1/216 inch
Black pass, forward paper feed 1/216 inch
Black pass, forward paper feed 23/216 inch

Any bets on whether the paper will still be remotely close to where it ought
to be after this sequence? Whiplash and mechanical tolerances may well mean
that the reverse feeds do nothing at all and just take up the slack in the
gearing instead. Many of the newest dot matrix printer models have removed
support for the reverse paper feed command completely or have written DO NOT
USE in big letters in the manual. So using it does not seem like a good
idea.

Owen.