jed@mb2c.UUCP (John Duncan) (06/07/85)
OK, I give up. In DRAFT mode, the Imagewriter prints bi-directionally. In High Quality mode the Imagewriter prints bi-directionally. But in STANDARD mode it only prints left-to-right. One would think that things could be sped up considerably in the intermediate quality mode by not wasting carriage motion and printing in both directions. Any gurus out there know the inside story? John Duncan mb2c!jed Michigan Bell (313) 968-9002
jer@peora.UUCP (J. Eric Roskos) (06/07/85)
Well, having written a program awhile back to make the IBM PC simulate the
Mac's font-printing (using TeX fonts), I can make a good guess.
The C. Itoh printers don't have perfect back-and-forth registration. I.e.,
when you print forward the dots come in a slightly different place from when
you print backwards. There's a potentiometer that is supposed to adjust
this, but it doesn't completely eliminate the problem in graphics mode.
For high-resolution mode, this slight offset would actually be a help. It
causes the overstruck dots to be shifted slightly, filling in the gaps that
would be otherwise left. But Standard mode doesn't overstrike like that; I
suspect if it printed forward-and-backward, the characters printed would
come out with noticeably shifted bands of dots (e.g., the top half of a
character might be offset to the right or left from the bottom half).
In draft mode, it doesn't matter, since you are just using the internal,
one-pass characters.
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