Do flatscreens have flicker problems at low refresh rates?


N

NoName

I recently purchased a Dell widescreen, flatscreen monitor, maximum
refresh rate of 60 Hz. I could swear I'm getting eyestrain. I
thought the flatscreens (unlike the old CRTs) were not supposed to
have flicker problems, because the pixels should stay illuminated
between screen updates. Is my understanding mistaken? I'm trying to
figure out if I'm just imaginging the problem or not.

This is also a concern because the company I work for is offering a
choice between two 17" monitors or one 24" monitor -- but the 17"
monitors have 75 MHz refresh rates, while the 24" (again, a Dell) has
a 60 Hz refresh rate. (I think the model on the 60 Hz is the E248WFP
24-inch Widescreen Black Flat Panel LCD Monitor.) So again, does the
60 Hz cause eyestrain?

Thanks in advance for all replies....
 
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B

Bob Myers

NoName said:
I recently purchased a Dell widescreen, flatscreen monitor, maximum
refresh rate of 60 Hz. I could swear I'm getting eyestrain. I
thought the flatscreens (unlike the old CRTs) were not supposed to
have flicker problems, because the pixels should stay illuminated
between screen updates. Is my understanding mistaken? I'm trying to
figure out if I'm just imaginging the problem or not.
Active-matrix LCD screens do not suffer from the same
sort of flicker problem as CRTs did. That doesn't mean
that there can't be other factors that may result in
eyestrain, however. And, of course, your eyes are going
to start to feel tired if you do any sort of close-up work
for too long without a break.

Bob M.
 
D

Darkknight

NoName said:
I recently purchased a Dell widescreen, flatscreen monitor, maximum
refresh rate of 60 Hz. I could swear I'm getting eyestrain. I
thought the flatscreens (unlike the old CRTs) were not supposed to
have flicker problems, because the pixels should stay illuminated
between screen updates. Is my understanding mistaken? I'm trying to
figure out if I'm just imaginging the problem or not.

This is also a concern because the company I work for is offering a
choice between two 17" monitors or one 24" monitor -- but the 17"
monitors have 75 MHz refresh rates, while the 24" (again, a Dell) has
a 60 Hz refresh rate. (I think the model on the 60 Hz is the E248WFP
24-inch Widescreen Black Flat Panel LCD Monitor.) So again, does the
60 Hz cause eyestrain?

Thanks in advance for all replies....
could possibly be because using the larger monitor your eyes are moving
more to cover the extra size of the screen,even though you don't realize
it. Try moving further away from the monitor
 
O

Ofnuts

NoName said:
I recently purchased a Dell widescreen, flatscreen monitor, maximum
refresh rate of 60 Hz. I could swear I'm getting eyestrain. I
thought the flatscreens (unlike the old CRTs) were not supposed to
have flicker problems, because the pixels should stay illuminated
between screen updates. Is my understanding mistaken? I'm trying to
figure out if I'm just imaginging the problem or not.

This is also a concern because the company I work for is offering a
choice between two 17" monitors or one 24" monitor -- but the 17"
monitors have 75 MHz refresh rates, while the 24" (again, a Dell) has
a 60 Hz refresh rate. (I think the model on the 60 Hz is the E248WFP
24-inch Widescreen Black Flat Panel LCD Monitor.) So again, does the
60 Hz cause eyestrain?
60Hz is normally OK. Check that you are using the native screen
resolution, appropriate contrast/gamma, and, if using windows, that you
have the font aliasing enabled (Display preoperties/Appearance/Effects:
smooth edge of screen fonts: cleartype
 
Y

Yousuf Khan

NoName said:
I recently purchased a Dell widescreen, flatscreen monitor, maximum
refresh rate of 60 Hz. I could swear I'm getting eyestrain. I
thought the flatscreens (unlike the old CRTs) were not supposed to
have flicker problems, because the pixels should stay illuminated
between screen updates. Is my understanding mistaken? I'm trying to
figure out if I'm just imaginging the problem or not.

This is also a concern because the company I work for is offering a
choice between two 17" monitors or one 24" monitor -- but the 17"
monitors have 75 MHz refresh rates, while the 24" (again, a Dell) has
a 60 Hz refresh rate. (I think the model on the 60 Hz is the E248WFP
24-inch Widescreen Black Flat Panel LCD Monitor.) So again, does the
60 Hz cause eyestrain?

Thanks in advance for all replies....
So I assume that you're talking about a flatscreen CRT monitor here,
rather than an LCD of some kind? I have noticed that 60Hz is often not
good enough for flicker-freedom, even though 60Hz is supposed to be
non-interleaved. It is the lowest of the non-interleaved refresh rates,
if you can get it upto 72Hz or higher it is better. I think the 60Hz
refresh makes it synchronous with the office lighting system, especially
the white fluorescent lamps. If the fluorescent lamps and the CRT are
just slightly out of sync with each other (e.g. one is at 59.9Hz, the
other at 60.1Hz, or something like that), then you'll see lines riding
up and down the screen. It's best to put the refresh rate up much higher
for the monitor to avoid this slightly-out-of-sync issue.

Yousuf Khan
 
B

Bob Myers

So I assume that you're talking about a flatscreen CRT monitor here,
rather than an LCD of some kind? I have noticed that 60Hz is often not
good enough for flicker-freedom, even though 60Hz is supposed to be
non-interleaved. It is the lowest of the non-interleaved refresh rates, if
you can get it upto 72Hz or higher it is better. I think the 60Hz refresh
makes it synchronous with the office lighting system, especially the white
fluorescent lamps. If the fluorescent lamps and the CRT are just slightly
out of sync with each other (e.g. one is at 59.9Hz, the other at 60.1Hz,
or something like that), then you'll see lines riding up and down the
screen.
If you see lines moving up or down the screen, etc., on a CRT,
it's a sign of magnetic interference from local power cords or
AC equipment such as motors, etc. - it has nothing to do with
the lighting per se, unless it's the power line to those lights that
is the source of the interfering field.

Bob M.
 
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R

rjn

I recently purchased a Dell widescreen, flatscreen monitor, ...

I think I found your problem :)
All seriousness aside, a co-worker's Dell monitor
has recently started jittering. We're pretty sure
it's a monitor malfunction (although a possible
issue with the graphics card needs to be ruled out).

See if you can borrow a monitor of the same geometry
(and a different brand or model) to confirm your problem.

Professor Myers wrote: >
Active-matrix LCD screens do not suffer from the same
sort of flicker problem as CRTs did.
Indeed. Bob won't mention it, but I just noticed that
the new hp LP2480zx (sku GV546A8) supports refresh
rates of 24, 48 and 60 Hz @ 1920x1200. I presume this
was done for SKG's benefit, to match film frame and
theatrical projection rates.

So when is hp going to do a DreamColor TV?
That might be a TV worthy of the hp badge.
 
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B

Bob Myers

Indeed. Bob won't mention it, but I just noticed that
the new hp LP2480zx (sku GV546A8) supports refresh
rates of 24, 48 and 60 Hz @ 1920x1200.
Well, Bob, since YOU'VE mentioned it...:)...I think
I should point out that the LP2480zx doesn't really support
a 24 Hz input rate; only 48 Hz (i.e., you would need to
double 24 FPS material), but at 48, 50, and 60 Hz inputs
the video is going straight through to the panel without
frame-rate conversion. And yes, this was done to allow
film-rate (and European-TV-rate) material to be shown
without the artifacts that can accompany a frame-rate
conversion step.

Bob M.
 

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