lord loh. said:
audioguru is right... Human eye persistence is just about 1/24 of a second. any changes faster would be unresolvable...
Common mistake! PWM is visually noticible at freq FAR higher than eye response when motion is involved.
For example, I have an LED flashlight that uses PWM for its power-saving "dimming" mode. If I swing the thing around, it appears as a string of pulses. LED taillights using PWM annoy the hell out of me at night, when I move my eyes back and forth to look at other things they appear as jittering strings of pulses. I wonder if I am the only one annoyed by this or what?
Whenever there is relative motion so that the light falls on a different part of the retina, the PWM nature becomes apparent. How high a freq this effect is still perceivable depends entirely on how much motion- if an LED were fired out of a gun, even 100KHz would probably be perceived as a string of pulses.