PICTURE FREQUENCY

Film or video pictures are "flashed" on the screen. Film is a parallel format, where the entire film frame is flashed at once. Video is a serial format, where the picture is usually drawn on the screen, one pixel at a time. Newer fixed array types of displays, such as the DLP or D-ILA technology, are parallel imagers. Flashing information on a screen creates flicker. In basic terms, if the flicker rate is fast enough light from the picture is perceive as steady. Depending on duty cycle and brightness of light, something in the order of 50 flashes per second is the threshold of what many human beings consider steady. Something faster than that will improve perception of a steady state, up to a point. In most light output conditions the upper limit is somewhere between 72 and 75 Herz.