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From: neal@weitek.UUCP (Neal Bedard)
Newsgroups: net.micro.amiga
Subject: Re: on interlace
Message-ID: <270@weitek.UUCP>
Date: Tue, 17-Sep-85 00:01:38 EDT
Article-I.D.: weitek.270
Posted: Tue Sep 17 00:01:38 1985
Date-Received: Sat, 21-Sep-85 03:47:26 EDT
References: <3629@topaz.RUTGERS.EDU>
Organization: Weitek Corporation, Sunnyvale
Lines: 42

In article <3629@topaz.RUTGERS.EDU>, keithe%tekgvs%tektronix.csnet@csnet-relay.arpa writes:
> From: keithe%tekgvs%tektronix.csnet@csnet-relay.arpa
> >> I can't figure out what an interlaced monitor is.
> >> What will look better in the Amiga: 640x400, or
> >> 640x200? Does it matter?
> 
> >The price one pays is flicker, since screen sweeps are only done 30
> >times a second, as opposed to 60 times a second during non-interlace.
> >Thus a higher persistance monitor is needed to eliminate flicker.
> 
> Well, not really... One of the *advantages* of interlace is that
> flicker is reduced. A "half" frame is generated every 1/60 of a second,
> but that half-frame is distributed over the entire face of the crt.
> Then, 1/60th of a second later, the intervening lines are drawn for the
> other half of the frame. (P.S., each half-frame is referred to as a
> "field.")

Er, not exactly. The rationale for using interlace is to increase the
spatial resolution of the screen *without* increasing video bandwith.
Interlace would be fine, except that long-persistence monitors tend to be
not as bright, and the `flicker' is *still* noticeable on long, bright
horizontal lines - headache fodder for the operator. Also, lp monitors
tend to leave afterimages, annoying if stuff is happening in realtime on
the screen.

Most medium-to-high end 1280 x 1024 terminals nowadays use 60hz
non-interlaced scanning with high-bandwidth (120+ MHz) monitors - including
the Tek 4115/4129 series (don't forget to ask about the F59 solids modelling
option ... :-))

Some manufacturers opt for a slightly higher scan rate - 33hz int/66hz non -
(33hz field-rate) to eliminate all vestiges of flicker noticeable on even the
best 30/60hz terminals. You have to be really picky to tell the difference,
and the difference is dependent on the viewing brightness and ambient light
level.

Just wanted to set the record straight, Time to go back to net.graphics :-)

-Neal
-- 
"whaddya mean there were bullet-holes in his mirror..."
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