Why 'leds' may give a pulsing 'light' effect, is due to how LEDs are handled electronically. Usually a short high voltage pulse is applied, since that yields a higher lumen value, than a 'steady state' voltage. Provided the duty cycle is such that the LED does not burnout.
However, this can produce problems in cameras that are scanning out regions of the sensor, depending.
I've never tested this out, relative to effect on Digital film... but I have noticed that if I see brake lights that when I avert my eyes, I see a sort of 'pulse stutter', rather than a smooth blur (what else are you going to do at a traffic light...), that the brake light is most likely pulsed LED.
Edited by John E Clark, 21 September 2014 - 11:43 AM.