f.lux based on PWM?
I'm new to the topic and I read that one method of "dimming" is pulse width modulation (PWM), which is not good for the eyes. Does f.lux use this technique in order to dim displays?
@Ike3000 NO. f.lux changes the gamma ramps on the video card's "color lookup table" to change the screen colors.
If you're referring to the "ALT + Page Down" to "dim the screen" this is just a black transparent overlay darkening the screen but without at all changing the amount of power the backlight is using.
This decreases contrast in a way that is not as good as just reducing your screen brightness (unless your screen DOES use pwm, then please do use the software dimming function instead).
How can I check whether my screen uses PWM?
@Ike3000 turn down your screen brightness to either 50 or lower (preferably very low, near minimum) and wave your hand in front of the screen. It will look very choppy and strange in front of a flickering back light. If it looks like a smooth blur, (like it should in natural light) then you've either got a flicker free LED back light, or a CCFL (cold cathode fluorescent lamp) monitor.
F.lux doesn't adjust the brightness of the monitor's backlight. The Alt+Page Up and Down brightness control is simply an adjustment to the black level.
The same is true when you're changing the color temperature: there's no dimming involved; it's just a color adjustment.
Also, PWM is purely a hardware thing. So, whether your dimming is done with PWM or not is entirely up to the physical and electrical design of your monitor. Software cannot force PWM.