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From: naegle@icon.asd.sgi.com (David Naegle)
Newsgroups: comp.sys.next,comp.graphics,comp.misc
Subject: Re: RFI: monitor's resolution < video signal
Message-ID: <1991Apr10.022848.14504@odin.corp.sgi.com>
Date: 10 Apr 91 02:28:48 GMT
References: <1991Mar28.072150.5375@cunixf.cc.columbia.edu>
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In article <1991Mar28.072150.5375@cunixf.cc.columbia.edu>,
toshi@cunixf.cc.columbia.edu (Toshi Kawanishi) writes:

>Does anyone know what happens to the image on the screen when
>the resolution of the monitor is smaller than the resolution
>required by the video signal?

>I found out from Next that the slab requires a monitor with:
>	- 68Hz refresh
>	- 1120 x 832 resolution
>	- 3 BNC inputs (I guess Sync is on the Green)

>My multisync has enough bandwidth to handle the timing, but falls
>short on the resolution.  My sparse understanding of this subject
>leads me to believe that I will just lose some pixels.  However, my
>worry is that the beam will stay at the right most pixels and the last
>line waiting for the sync signals during those missing pixels.

>If this is true, can it damage my monitor?  Or do I worry too much?

It won't damage your monitor and you won't 'lose' any pixels.  The
worst that will happen is that the color shadow mask will not 'sample'
the pixels well enough for you to distinguish fine features in the
image.  Text may not look as good as you'd expect.  The problem is
*not* that you won't have *some* of the pixels; *all* of the pixels
will either have problems, or appear to be fine.

Ideally, the color shadow mask should be small enough to sample a
pixel raster such that the Nyquist criterion is satisfied, i.e., at
twice the pixel resolution or greater.  In practice, this is almost
never the case.  Effects like moire patterns commonly result from
the shadow mask under-sampling the raster.

The actual results depend on a number of other factors as well, such
as the beam size and shape, the color shadow mask pitch, hole size and
hole pattern, beam focus, etc.  The only way to know for sure is to
try it, preferably before you buy.

>/toshi (toshi@cunixf.cc.columbia.edu)

--
naegle@sgi.com (David Naegle)
{sun|decwrl|pyramid|ucbvax}!sgi!naegle 
The difference between theory and practice 
is always greater in practice than in theory.
disclaimer: The opinions above are strictly my own.