FLICKER FUSION RATE
Flicker Fusion Rate: The Flicker Fusion Rate is the repetition rate above which the eye can be counted on to perceive separate images as a continuous, non-flickering, image. The rate varies with the material being viewed, the environment, and the individual viewing it. There seems to be no real agreement on what the human FFR really is. A web search revealed that numbers from 12 Hz to 70 Hz are being used. Most sources say 50-60Hz. TVs and motion pictures display at rates in this range although there is some "magic" used to achieve these rates using materials that would appear superficially to be running at half the rate. Some people can detect flicker at 70Hz. Even an adequate image rate may still encounter problems if display frequencies coincide too closely with some natural frequency in the material or environment. For example, spoked wheels in motion pictures may appear stationary or even moving backwards if the frame frequency and the rotation speed coincide. Likewise, display frequencies near 60Hz may interact with fluorescent lighting to produce an aggravating low frequency "flicker".
Flicker sensitivity increases with brightness. Media that has a marginal repetition rate (e.g. motion pictures), may be deliberately shown with low brightness to minimize flicker.
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Copyright 1994-2002 by Donald Kenney.