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From: oeschi@netmbx.UUCP (Johann Deutinger)
Newsgroups: comp.dcom.fax
Subject: Re: Fine mode in Group III faxes
Keywords: fax, resolutions
Message-ID: <2266@netmbx.UUCP>
Date: 14 Apr 91 22:46:26 GMT
References: <10335@pitt.UUCP> <1281@gammafax.gammalink.com> <1991Apr10.144829.4271@cbnewsi.att.com>
Organization: netmbx, Berlin, Germany
Lines: 34

In article <1991Apr10.144829.4271@cbnewsi.att.com> hrs1@cbnewsi.att.com (herman.r.silbiger) writes:
>In article <1281@gammafax.gammalink.com>, mikes@gammafax.gammalink.com (mike spann) writes:
>> In article <10335@pitt.UUCP> jonathan@cs.pitt.edu (Jonathan Eunice) writes:
>> >I read in the May, 1991 MacUser that Group 3 faxes have a Standard
>> >resolution of 203x98 dpi, and a Fine resolution of 203x196 dpi.  The
[stuff deleted]
>
>Since the T.30 protocol allows for renegotiation after evry page, you can go
>from normal mode to fine mode between pages.  This is useful if you have only 
>one or two pages in  a document that really need the higher resolution, since
>invoking high resolution increases transmission time.
>
If the pages don't contain much information, the additional time required
for renegotiating the resolution (maybe even twice if you send pages
standard-fine-standard) may be as evil as sending the whole thing in
fine resolution.

If you send a short memo, the transmission time of the document is by far
not twice the time in fine resolution, compared to standard resolution
because the initial handshake (T30 phase B) takes several seconds by itself.

Of course, if you use a faxcard which uses the same character generator
for standard and fine resolution (in that case doubling every scanline)
there is no reason not to use standard resolution all the time. If your
faxcard has a separate (better looking) character generator for fine
resolution or if you create faxes using an MS-Windows driver you might
want to use fine resolution for important business documents where the
appearance of the fax could have some influence on the receiver.


-- 
oeschi@netmbx.UUCP     | Johann Deutinger
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