From: raymond@es.ele.tue.nl (Raymond Nijssen)
Newsgroups: comp.unix.sysv386,comp.os.linux
Subject: Re: What the 17" monitor reviews never tell you
Date: 22 Jul 92 12:00:17 GMT
Followup-To: comp.unix.sysv386
Organization: Eindhoven University of Technology, Eindhoven, The Netherlands
In-reply-to: shite@sinkhole.unf.edu's message of 22 Jul 92 04:17:43 GMT

In article <1992Jul22.041743.9806@sinkhole.unf.edu> shite@sinkhole.unf.edu (Stephen Hite) writes:

>      I just wanted to let anyone who is deciding to purchase a 17" monitor
>   for X386 work to be be cautious when making their decision.  I just
>   bought one of the highest rated monitors in the $1100 price range
>   (the Nanao 550i) and the one  I got has a tremendous problem with this
>   "rainbow effect" at 1024x768.  There's a term for it that starts with the
>   letter 'm' that I can't remember but the "look" is akin to a magnetic field

This effect is referred to as "Moire-patterns".
It shows up on VDUs under certain conditions, eg. if the video resolution 
has a specific value with respect to the dot pitch of the color raster 
of the tube, most notably if the dot-pitch is too small compared 
with the resolution. 

In other words: either your monitor is too good :-}, or increase or decrease
the resolution.

>   pattern.  I tried adjusting the horizontal and vertical stretching of the
>   image and it has absolutely no effect on the difference in display quality
>   (that is, the "rainbow patterns" stay just as obvious...

With X386, it's easy to almost eliminate it by tweaking some 
parameters (particularly the horizontal timing values) in Xconfig, which
is of course no problem is you have a [multi|flex]-[scan|sync] (tm) monitor
like the 550i.

>     I'm not putting down Nanoa.  I'm sure there are lots of F550i's that
>   are picture perfect at 1024x768 with no "rainbow effect" apparent to
>   the naked eye.  However, mine is not acceptable and NONE of the reviews
>   in magazines warn you that this can be a problem.  I don't know but maybe
>   some manufacturer's tubes have more of this kind of problem than others?

I have a 560i, which has a Trinitron tube, and I had exactly the same
problems at first. In my case, it was just a matter of playing a little
with those entries to make the effect go away.

>     Perhaps Thomas Roell can comment on this?  Is my case unusual or is it
>   all just a crap shoot?  I would strongly recommend that if you're in

On the contrary! The cheaper your monitor, the lesser the effect shows up:
with a dotpitch of >0.28 at <= 16" and resolution <500,000 pixels, like
99% of all monitors have, the effect won't be visible, but that doesn't
make your case unusual...

>   a big city to buy your 17" monitor locally even if it costs an extra
>   $100 because at least you can try before you buy.  

With the resolution and dot-pitch you're using, the effect would probably
be even worse on a larger monitor.
The effect is certainly not typical for or limited to 17" monitors.

Look at it this way: experts can tell that you have a good monitor if they
see the effect  :-}, only non-experts would think the opposite.

-Raymond
--
| Raymond Nijssen         | Eindhoven University of Techology                 |
|                         | Department of Electrical Engineering              |
| phone: +31-40-473373    | Design Automation Section (ES),  Room EH 7.16     |
| raymond@es.ele.tue.nl   | P.O. Box 513, 5600 MB Eindhoven, The Netherlands  |
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