I have 'normal' persistence so low refresh rates don't bother me.
But I can also spot LED lights or other strobed lighting (LED sign
boards) because they make distinct spots of light as I pan my
viewpoint across them.

Some people do appear to have much shorter persistence than normal.
One friend of mine, who was a military pilot, can't stand to look
at my CRTs because they flicker too much for him. Having shorter
persistence, and so lower blur when flying near ground,
is probably an advantage to a pilot. I wonder what the chemistry
difference is.

E... has no problem looking at laptops since their LCDs are very
slow to respond (80msec IMS), so I rather doubt that laptops can be
causing headaches from the REFRESH. They may be causing headaches
because of seating posture or other mechanical issues (close focus etc.).

I think the important issue about reading LEDs is to have a clear
contrast between light and dark states, and broader spectrum
(yellow green rather than pure green) to address color blindness
issues. Ideally, you have indicators that are UNIcolor and only
light for ONE state, rather that trying to multiplex the function.
e.g. Power led on monitors, green=on, yellow=powersave, red=standby/off
A R-G color blind person would have a difficult time distinguishing red and
green states.

Robert

Jose Da Silva wrote:
> On April 22, 2005 09:33 am, Robert Rolf wrote:
> 
>>Simple way to get LED Xmas lights to double flicker rate is to put a
>>bridge rectifier in front of them. Also makes them brighter. I am
>>surprised that the manufacturers don't already to this. I rather
>>doubt that a normal viewer could perceive flicker above 70Hz since
>>persistence of vision is typically 40 msec.
>>http://www.pisavisionlab.org/downloads/motion_blur_97.pdf
> 
> 
> Yes, 40mSec is typical (25Hz), but since a friend of mine notices the 
> street XMAS lights, I can say that there are still cases where some 
> people are still sensitive to 60Hz.
> 
> You can either design scissors or cameras to be used by right-handed 
> people (9 out of 10 people), or you can put a little more thought into 
> the process to include that 1-out-of-10 as well.
> Since the question seemed to apply, I thought it was worth suggesting 
> this as well.
> Hopefully, my suggesting pushing above 60Hz helps influence your 
> thoughts to include people in a minority, or in other words, include 
> the left-handed scissor or camera users too  ;-)
> 
> cheers!
> 
> 
> 
>>Jose Da Silva wrote:
>>
>>>On April 21, 2005 08:05 pm, PicDude wrote:
>>>
>>>>Anyone have a link or doc that indicates which colors of (LED)
>>>>light are generally better for displays -- easier on the eyes,
>>>>quicker to read, etc? I'm trying to find some facts on this,
>>>>rather than just "generally known" info.
>>>
>>>Nothing to do with colour, but I had to repair the fluorescent in a
>>>laptop, and while digging for information, I recall reading that
>>>the frequency can cause headaches.  I lost the article, but
>>>hopefully one of these helps.
>>>http://www.google.ca/search?hl=en&ie=ISO-8859-1&q=laptop+fluorescen
>>>t+headache&btnG=Google+Search&meta=
>>>
>>>Some people are sensitive to the 60Hz Xmas lights that seem to be
>>>common this last Xmas, so you may want to increase the refresh rate
>>>somewhere above 60Hz.  you may notice some computer monitors are 75
>>>or 80Hz, so perhaps those are good numbers to work with to avoid
>>>headaches or sensitivities, yet low enough to allow you to use more
>>>generic driver circuitry.
>>>You will also want to avoid multiples of 60Hz, like 120Hz, 180Hz in
>>>countries with 60Hz power, or multiples of 50Hz in countries with
>>>50Hz power.
>>>
>>>Otherwise, traffic safety seems to know about this type of stuff,
>>>which also brings up the subject of colour blindness too.
>>>Here's something:
>>>http://www.tc.gc.ca/tdc/summary/14000/14030.htm
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