Jose Da Silva wrote:
> On April 22, 2005 09:30 pm, Robert Rolf wrote:

>>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.
> 
> They also lack persistence, which you may note if you were to compare, 
> let us say, taillights and turn signals on cars, tucks, buses, etc.

I was referring specifically to AC powered or strobed LEDs.
DC powered LEDs leave a streak trail, and yes, they certainly
turn on/off instantly.

>>causing headaches from the REFRESH. They may be causing headaches
>>because of seating posture or other mechanical issues (close focus
>>etc.).

> The article (which I couldn't find) was referring to the refresh rate of 
> the fluorescent tube.  Some laptops use PWM to brighten/dim the screen.

Hadn't thought of that since every laptop whose upconverter I can hear
has been in the khz range. They'd need a much larger transformer to run
at rates low enough to get flicker (10's of Hz).

> The refresh rate of the LCD itself is rather slow because you are 
> working on a liquid. Liquid has mass, therefore rather slow. I would 
> not expect an LCD screen to refresh any higher than, let us say, 15Hz, 
> and even that may be an optimistic figure.

The response time is very much depends on the type of LCD chemistry.
TN (twisted nematic) STN (super..) etc.
http://www.perfectlcd.com/productlcd_type.htm

Newer LCD monitors are now specifying response time in addition to
contrast ratio and pixel count/pitch. I see adverts for 'super fast 8 ms'
displays since gamers want a fast responding display, so 125Hz refresh
seems possible now.

Robert

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