On 2014-09-12 08:58, Ian Webb wrote:
> There is no flicker or refresh rate for flat screens.
> Ian Webb Centre Manager ATOP Ltd
> I am wondering if there is any empirical/medical evidence
> that the refresh/flicker rate from a PC screen can detrimentally
> affect someone with epilepsy; i.e. induce [...] a seizure?
> John Hodgson Study Needs Assessor
Well, Actually, I would like to dis-agree!
"refresh rate" is the rate the display content is updated.
The "flicker rate" on an LCD screen basically comes from the
backlight driving circuitry, I have seen a lot of backlights
which (depending on your definition) you might consider to have
flicker.
On CRT screens both Refresh and Flicker rate were the same
thing, but that is no longer the case with LCD screens.
This backlight flicker is often in the ~200hz range and
typically depends upon brightness setting (full brightness
sometimes eliminates the modulation of PWM dimming).
I suspect this is too fast to affect epileptics but
especially at lower frequencies it can definitely cause
headaches in some people.
We were actually lent a BenQ "eye-care" monitor which
explicitly gets rid of the flickering backlight, see
my report/notes:-
http://www.iremonger.me.uk/noidx/BenQ-BL2710.pdf
Although, as I say, its' perfectly possible to find
'other' flicker-free monitors, but the trouble is
knowing what-is-what... Is good to see at least one
manufacturer making the issue explicit and selling
a range that definitely don't have that problem.
Hope thats' helpful,
--Simon
p.s. Is possible to make a very lo-tech simple gadget
with headphones, battery, switch, resistor, and a LDR
(Light dependent resistor) so as to allow you to 'hear'
the flicker from various sources...
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