[plug] [OT] Changing refresh rate to something higher than 85Hz??

[Arie Hol]

On 15 Nov 2004 at 8:15, James Devenish wrote:

> In message <200411142118.43198.sboak at westnet.com.au>
> on Sun, Nov 14, 2004 at 09:18:42PM +0800, Steve Boak wrote:
> > Probably just your phosphor is slower, i.e. it retains the picture
> > for longer between screen refreshes...
> 
> I thought of that, but why would other CRTs have less retentive
> phosphor? I.e. if you can get a steady image at 60Hz, why choose an
> alternative design that flickers below 100Hz, presumably wastes more
> energy in radiation, and presumably requires components with tighter
> tolerances? I assume 60Hz is necessary for fidelity of 30fps video, but
> I think it would be more uncomfortable for me to be scrolling text that
> fast than to be having the lower refresh rate ;-)
> 

Refresh rates on monitors that are consistently below 72 Hz can cause fatigue when the users spend 
an excessive amount of time staring at  the screen.

I read a white paper on this subject several years ago - because I was having problems with my 
vision after using older monitors for prolonged periods - I cannot find the white paper now but can 
recall some of its content.

When a user stares constantly at a screen refreshing at a rate below 72 Hz - the user can become 
subject to fatigue - this is especially obvious when the user is over tired or has had insufficient 
sleep. 

The obvious indicator is when the user may notice that the extreme corners of the screen appear to 
flicker slightly in the periphery of the field of vision, but appears almost normal when the user 
looks directly at a corner of the screen. 

It is often difficult to avoid when the user is concentrating intensely on the task at hand (games 
freaks and people learning new fields of skills) that require intense levels of mental focus.

It all happens because when you get tired your brain tries to slow down to match the "flicker" of 
the screen - similar to a strobe effect caused by aging fluorescent light fittings with inadequate 
reflectors and/or diffusers.

Constantly working under this combination of factors, can cause depression like symptoms to appear 
and the user is usually the last one to notice the true effects - they may notice that they are 
feeling really tired and sluggish all the time and their mental agility isn't quite what it used to 
be.

Their close friends usually notice the symptoms first but tend to think there are other causes.
(No allusions here please)

Many of our senior hacker friends may know what I am talking about, like long hours of extreme 
concentration in front of older monitors and little desire to take a break because "in five more 
minutes I will have this thing beaten" type attitudes (meanwhile two hours later).

Newer monitors are susceptible to similar problems because the development of modern video cards is 
way ahead of the development of suitably specified monitors and the finances of the average user.

I use one monitor on two machines( via a data switch) one machine has a low spec video card that 
cannot give better than 70Hz. I really notice the difference in a short space of time each time I 
switch over to the lower spec machine.

Users can obtain much relief from these negative effects by taking a break of at least 10-15 
minutes every hour and putting themselves in a situation where their eyes need to change the depth 
of field of their vision to focus correctly. 

Nothing kills eyes faster than constant staring with the eyes focused at the same focal length. 

Look away at objects that are at different distances from your position - ESPECIALLY IF YOU ALREADY 
WEAR SPECTACLES !!! 

Like me !!!!!

Regards Arie
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