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From: jow@unccvax.UUCP (Jim Wiley)
Newsgroups: net.micro.amiga
Subject: Re: Interlaced monitor
Message-ID: <289@unccvax.UUCP>
Date: Wed, 11-Sep-85 16:04:40 EDT
Article-I.D.: unccvax.289
Posted: Wed Sep 11 16:04:40 1985
Date-Received: Fri, 13-Sep-85 03:38:54 EDT
Organization: UNC-Charlotte
Lines: 31

> A conventional TV, and almost all computer monitors, use an interlaced
> scan.  This means that 30 times a second the screen is drawn, first the odd-
> numbered lines and then the even ones. Thus each scan takes 1/60 second....

> Now, to the Amiga (and other displays with > 200 lines). 200 lines is 
> a common resolution because what can be done is repeat each pixel on 
> (say) line 69 in the same place on line 70. Then the pixel will be
> shown 60 times a second in one line or other,  and the objectionable
> flicker is not seen; the eye doesn't readily notice that the pixel is 
> actually jumping back and forth between lines. If you leave this 

actually, in noninterlaced video, the pixel is not jumping between
lines.  The SAME lines are updated each 1/60 sec.  No jumping.  If
there is jumping then the display is indeed interlaced with the even
and odd fields displaying the same data but interlacing.  To reiterate,
in non-interlaced video it is as if the odd lines are displayed every
1/60 of a second and no even lines are displayed so that the lines are
placed over one another and not between.

If characters are displayed on a non-interlaced monitor, there is no
flicker.  If the same characters are displayed interlaced with the
even and odd frames displaying the same data, there is noticable
flicker.  Here at DataSpan we have done such tests and the only way
to go for characters is non-interlaced.  A high persistance phosphor
helps reduce the flicker but does not remove it entirely.  Any flicker,
after looking at a display for more that 30 min. will drive you nuts.
Commodore did the right thing by going non-interlaced for the character
display!

James Wiley
DataSpan, Inc.