#Flicker Flustered
10 messages in this thread
I have yet to install "MagicWB", even though I have been ready to do so
for sometime. It is the Interlace flicker that bothers me. I have the same
problem with "Autopilot." Is there any way at all to fix this problem
without going out and buying a High Res monitor? I am using a TV/RGB
monitor combination and I find the flicker very aggravating.
Nancy
NO.
The flicker is a result of the frequency that the monitor & computer run
at. The only way is to buy a MultiScan or VGA monitor AND a scan doubling
device (FlickerFixer). The Commodore display enhancer is on sale through
mail order for $130 which is the losest I have ever seen it. You could
probably get a second hand VGA for about the same or less.
The only other solution is to reduce the contrast and choose "flicker
friendly" colours.
Andrew Porter
Nancy,
If you've got an AGA Amiga, the EURO 36 interlace modes have much more
bearable flicker. Personally, I found that if you just force yourself to
look at an interlace screen for several weeks, you get used to it. I use
interlace exclusively. It took two or three weeks to get used to it, and
now I don't notice it anymore. It also helps if you avoid using a lot of
one-pixel horizontal lines, and don't use highly saturated (bright) and
contrasting colors.
Stay cool B-)
-Larry
Thanks Larry, however, your reply was much too technical for me. What is
the EURO 36 interlace mode and what do you mean by avoiding a lot of one-
pixel horizontal lines? Sorry I'm such a thicky! Oh yes, I do have an AGA
machine.
A 'trying to be laid-back' Nancy
Nancy,
Ronald gave a fabulous explanation of Interlace, so I'll spare you a
re-hash, except to say that one-pixel lines, when there are a lot of them,
make interlace flicker more noticeable.
If you look in your Sys:Storage/Monitors drawer, you'll see a bunch of
icons that look like TV sets. Each one represents a different screen mode
you can add to your system. The name under each is the mode name. you
drag these icons over to your Devs:Monitors drawer, reboot, then open the
ScreenMode Prefs Editor. You'll see the names of the modes added to the
list in the window, and can select whatever screen mode you want to use.
EURO 36 is one of the modes available. Its "scan rate" (i.e. how fast the
monitor draws the screen) is faster than the default modes, so there's
less noticeable flicker.
Stay cool B-)
-Larry
Larry… I inadvertently deleted Ronald's very detailed message on
flicker, so if you're still out there Ron, thanks for going to all that
trouble, I appreciate it. And Larry, I shall certainly give your
suggestion a try…thanks!
(Later that evening) Well I tried the Euro 36 in all the modes and they
all produced a triple image effect. I don't quite know what to do next.
Nancy (who's not feeling too cool at the moment! :-))
Nancy >> Well I tried the Euro 36 in all the modes and they all produced a
triple image effect. I don't quite know what to do next. <<
When using the Euro36 mode, some monitors need you to adjust the Vertical
Hold knob. The knob controls what vertical speed the monitor should be
set to display at. This speed is normally 60-Hz, but can be turned down
to 50-Hz and upto 73-Hz.
The Euro36 uses a 72-Hz speed. Some monitor allow you to turn the knob
"midway" and will display at both 60Hz & 72Hz (or 50Hz & 60Hz). The
screen may "hop" each time it jumps between two speeds, but this is
normal.
Your monitor might only handle 50Hz & 60Hz vertical speeds. If so, you
will not be able to use the Euro36 mode.
Ron.
– ap'ing with AP. (Eagles may fly, but weasels aren't sucked
into jet engines.)
Larry,
Why don't you use the DBLPAL or DBLNTSC high res no flicker mode. You get
similar resolution and….no flicker.
Pete Jones, flying on AutoPilot from Brussels, Belgium
Pete:
But DBLPAL and DBLNTSC don't have Super-HiRes Interlace. I like LOTS and
LOTS of room for windows. B-) My current EURO 36 WB is 1340×400. And as
I said, the flicker doesn't bother me.
For any other lurkers out there, I also remembered that flourescent
lighting makes flicker more noticeable because those types of lights
flicker very rapidly as well, and you get a "strobe" effect.
Stay cool B-)
-Larry
Interlace flicker is normal for a TV/RGB monitor. It part of the NTSC and
PAL video standard. These standards are the "formats" used for drawing
and re-drawing the TV's picture.
—
The screen is actually a large tube (or bulb), with a set of rayguns
inside the "backend" — this tube is called a CRT. The inside of the
"front" of the CRT (or screen) is coated with a phosphoresent (a chemical
that glows when struck by light).
Three rayguns (one red, one green, & one blue) start in the top left
corner, and fire at the screen moving the raybeams from left to right.
This draws a single straight line called a "scanline". After the scanline
is drawn, the rayguns reset to the left and drop down to draw the next
scan line under the previous, repeating until the bottom of the screen is
reached. The rayguns then reset to the top of the tube and repeat.
The phosphoresent "spots" the raybeams hit, are called phosphors. The
phosphor will glow the color the of light beam that hits it, then slowly
fade to black. The three rayguns are aligned to hit the same phosphor, at
the same time. By mixing the raybeams' R,B,G beams, you create new
colors.
Since the phosphor's glow fades, it has to be "re-freshed", either to the
same old color, or switched to a new color. If you wait too long before
re-freshs, the human eye will see the fade.
Under the NTSC standard, uses 525 scanlines drawn from left-to-right at a
speed of ~15-kHz (15,000-Hz). The top-to-bottom speed is 60-Hz. This was
still a little slow to hide the fade/re-fresh with TVs. The answer was to
interlace the screen. This resulted in 262.5 scanlines being draw first
then a reset to the top of the screen and the other 262.5 scanlines being
drawn inbetween the first set.
One "field" was the all the even numbered scanlines, and the other field
was the odd numdered. Scanlines 1,3,5,etc. were drawn first, then 2,4,6,
etc were drawn after the first set was. This interlacing worked for TV.
NTSC-interlacing, fails with computers. The computer generates colors
that are unused under the NTSC standard, being too bright. These bright
phosphors fade faster than the duller ones, faster than the raygun can
re-fresh them. Second, the computers draws the screen in finer detail,
with the picture being "frozen" instead of moving to different scenes.
The human eye sees the two fields, the differences between their
brightness levels, and the detect refresh. By using dull & mid-bright
colors, the color fade is less detectable. And "glare screens" can help
hide much of the flixer.
To fix this limit (flickering) some have switched to "VGA" monitors. These
monitors refresh at ~31-kHz (31,000-Hz) and normally use one field of 480
scanlines. The VGA monitor can be interlaced to 960 scanlines, but the
flicker then becomes as ugly as NTSC interlace.
However, most VGA monitors can run only at ~31-kHz — not the ~15-kHz NTSC
standard. This is like having a modem that runs at 9600bps, but not lower
at 2400bps. Both the computer and the monitor must be "VGA" compatible to
use "VGA."
Some monitors can run at both NTSC and VGA speeds, and a few higher
speeds, but they will cost more.
Ron.
– ap'ing with AP. (Eagles may fly, but weasels aren't sucked
into jet engines.)