Sunday, June 23, 2013

Is doing genealogy on your computer making you go blind?

Editor's note: Today's post was written by Richard Hanson.

If you purchased a new smart phone, smart tablet, laptop or desktop computer within the the last few years, chances are that it comes with an LED-backlit screen. Various technical support forums contain complaints about LED-backlit displays causing eye strain in susceptible people. Unlike the older liquid crystal display (LCD) technology, screen brightness cannot be controlled by varying the voltage. LEDs are basically on or off. Changing voltage to an LED changes its color. So dimming an LED-backlit screen is accomplished by rapidly turning the LED pixels on and off in a snow-like pattern faster than the human eye can detect. This is known as PWM (Pulse Width Modulation).

Apparently, some people can detect a flicker in such screens. Prolonged exposure for such people reportedly causes many of the symptoms of eye strain. Complaints seem to be more about the newer energy-efficient screens that have appeared during and since 2011. A number of solutions were suggested and each had its advocates.

  • Set screen resolution to maximum. Smaller pixels mean the flicker is less apparent.
  • Turn screen brightness up to maximum. That reportedly eliminates the flicker but creates a second problem – glare. Increased lighting behind the screen can help with glare.
  • Attach an external monitor which has an LCD display.
  • Some people also say that given time, their eyes adjust.

An interesting and a very very long thread on this subject:
https://discussions.apple.com/thread/1677617?threadID=1677617&start=75&tstart=0

A description of the PWM versus analog dimming technologies:
http://www.em.avnet.com/en-us/design/designzones/leds/Documents/Aimtec-PWM-vs-Analog-Dimming-of-LEDs.pdf


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