TPUG - Toronto PET Users Group/TPUG Users Group CD/TPUG Users Group CD.iso/AMIGA/AMICUS/AMICUS14.ADF/Text/LongPersist.DOC

Text File | 1989-01-28 | 8KB | 137 lines

TITLE: Long Persistence Color Monitors

I strongly suggest you look into the possibility of using a "long-persistence"
analog RGB color monitor with your Amiga computer.

Use of such a monitor allows you to use your Amiga at 640x400 resolution
without regard to choice of colors or contrast and the effect they may
have on flicker.  In a simple static image, this means that you can have
true 16-color displays where each color is choosen out of the Amiga
palette of 4096.  NOT JUST MONOCHROME!

Given the screen and COPPER software already in your Amiga, you can, of
course, have many more than just 16 colors simultaneously displayed
on your hi-res display -- mixed with even more colors from your low-res
screens simultaneously displayed!

Need I point out the advantage of having to use only one monitor for both
low-res and glorious, multi-color hi-res?

There are already Amiga application programs available which take advantage
of the Amiga's full-color hi-res displays.  For instance Deluxe Paint from
Electronic Arts.  At a recent IEEE conference, all of the technical slides
we presented about the Amiga were constructed ON an Amiga, in hi-res, using
Deluxe Paint.  Needless to say, the (er...) competition couldn't make such
a claim due to an unfortunate lack of sufficient color in THEIR hi-res.

In addition, the V1.2 system software will support standardized Workbench
display at 640x400 resolution as a Preferences selectable option.

The limiting factor, up to now, in getting people to use hi-res on the Amiga
has been annoying display flicker.

The physiology of flicker perception is pretty well understood.  The eye's
ability to perceive flicker goes up as the contrast between adjacent
horizontal lines goes up and, also, as the overall illumination (screen plus
room lighting) goes up.  Back when the current TV standards were designed,
the engineers realized that the physics of TV cameras would keep the
contrast down -- so they took the cheap way out and choose a 30Hz interlaced
frame rate.  It turns out the eye can perceive flicker at anything under
about a 50Hz rate if the contrast is high enough.  That's why you don't
see flicker on your TV screen until someone puts up a good contrasty image
such as the computer generated graphics they put on during football games.

The Amiga computer is designed to be compatible with the NTSC standard (which
defines broadcast quality TV).  That means we update our 320x200 and 640x200
displays at a 60Hz rate and we update our 320x400 and 640x400 displays at
a 30Hz rate (actually, every other line is displayed in one pass and then
the skipped lines are displayed in a second pass -- each pass takes a 60th
of a second, so the whole picture takes a 30th of a second to redisplay --
this is, in essence, what "interlace" is all about).

Because of that, if you have a sufficiently contrasty image (such as
alternating black and white horizontal lines (cringe!)) you will see flicker
on a regular persistence monitor -- such as the Amiga 1080.

Many people already use the x400 displays on the Amiga by dint of adjusting
the display colors, the room lighting, and the brightness of their monitor
display to the point where they, personally, do not see an objectionable
amount of flicker.

The other way to do it is to use a different style of monitor.

The competition does it by using a monitor (and the corresponding display
hardware inside the computer) that receives all 400 lines in one pass and,
thus, updates at a rate faster than the eye can follow.  That works fine,
but requires so much data to come out of the computer each 60th of a second
that they don't have sufficient memory bandwidth to put out lots of colors.

We suggest you use a long persistence monitor.  This is a monitor that uses
color phosphers on the display tube that retain the image of one display frame
just long enough for the computer to come around and put up another display
frame.  Effectively this eliminates flicker.

There are two commonly heard objections to long persistence monitors.  First
is the objection that they "smear" a moving image.  This is certainly true
to an annoying degree on MONOCHROME long persistence monitors where the
"real" image is the same color (usually green) as the "smeared" image left
behind when it is moved.

On a COLOR long persistence monitor there are 3 color phosphers in use.  The
green phospher retains the image longer than the other two so that whatever
smear is produced is, basically, green.  But in a color image, most if not
all of the "real" image is NOT green.  Thus the brain readily rejects the
smear and perceives only the moving real image.  My personal experience
with these monitors is that you don't "see" the smear unless you are "looking"
for it -- something which I didn't believe until I tried it myself.  We've
now got enough people using these beasties on Amigas that I'm happy to
report that everybody agrees.  You only see smearing on really active
animations such as the "Fields" graphics demo.  In practical applications
it is no problem.

The other common objection is that long persistence color monitors are too
expensive.  This is true now, but not likely to be true for long.  Basically
the pricing on these monitors is about where the pricing on regular
persistence analog RGB monitors was early last year -- AND FOR THE SAME
REASON -- namely that volume sales are just starting.  There is NOTHING
inherent in the long persistence monitor which should increase the price
over a comparably featured regular persistence monitor -- it's the same
electronics, just a different phospher painted on the tube.  I predict
that by the end of this year there will be no significant difference in
price between the two types of monitors.

Of course you have the PRICE ADVANTAGE of being able to use JUST ONE monitor
for both hi-res and low-res images.  With both resolutions in beautiful full
color.

-----------------

For those of you who'd like to try out a long persistence monitor, here
is info on two such monitors you can buy right now and use with your
Amiga computer.  Note that both of them are a little spendy, but that's
because both of them (particularly the Electrohome) are lab-grade high end
monitors.

Electrohome model #ECM1301, High Resolution Color Monitor.  Be sure to
order the RS170 RGB Module as well.  We recently purchased such a combination
for $1360 (plus tax) from Videomedia, 211 Weddell Drive, Sunnyvale,
Ca.  94089,  phone [phone].  If you're out of the area, you might
try getting in touch with Electrohome directly in Kitchener, Ontario,
Canada.  This monitor is truly a high end monitor with all the goodies
built-in, and thus the price.

Mitsubishi model #c-3479LPAG-WC, High Resolution Color Display Monitor.  The
WC in that model number means "with cabinet" -- otherwise you get something
that looks like the inside of your TV set.  We recently purchased one of
these for $1000 (plus tax) from Computer Modules, Inc., 1190 Miraloma Way
Suite Y, Sunnyvale Ca.  94086,  phone [phone].  If that doesn't do
it for you, I'm not sure how you can find your local Mitsubishi rep.

There are undoubtedly other such monitors around -- if you lobby with your
friends in the biz there will be even more (and cheaper ones) soon!  If
you find another one you like, let me know and I'll spread the word.

Enjoy!    Robert S. Pariseau