Does Arc Light Flickering Interfere With Video?
Arc discharge sources, such as the High Pressure Mercury Vapor lamp, the High/Low Pressure Sodium lamp, the Fluorescent lamp and the Metal Halide lamp flicker twice at the mains frequency, that is 100 times/sec at 50 Hz and 120 times/sec at 60 Hz. As the current has usually a sinusoidal shape, the produced arc extinguishes twice in each cycle, giving 50 maxima/sec where the light intensity is maximum and 50 minima/sec where light intensity is off. Video cameras capture the scenery at a fixed rate per second (fps: frames/sec). Here we show that for certain values of fps, the light flickering for such light sources interferes with the captured scene. Assume then that the scene is illuminated by high intensity discharge lamps and that the mains frequency is 50 Hz. Assume that the video captures the scenery with a rate of 40 fps. Assume that we start at t=0, with both lamps ON and video ON. Therefore the light intensity becomes maximum at t=k/100 sec, k EVEN and off at k ODD. The video tri
