http://en.wikipedia.org/wiki/Frame_rate
Once in a while I like to read up on a topic that I know only superficially. Today’s topic was “frame rate” or “frame frequency”. Here are a couple of more interesting snippets of the Wikipedia page:
Frame rate, or frame frequency, is the measurement of how quickly an imaging device produces unique consecutive images called frames. The term applies equally well to computer graphics, video cameras, film cameras, and motion capture systems. Frame rate is most often expressed in frames per second (fps) or simply, hertz (Hz).
The frame rate is related to but not identical to a physiological concept called the flicker fusion threshold or flicker fusion rate. Light that is pulsating below this rate is perceived by humans as flickering; light that is pulsating above this rate is perceived by humans as being continuous. The exact rate varies depending upon the person, their level of fatigue, the brightness of the light source, and the area of the retina that is being used to observe the light source. Few people perceive flicker above 75 hertz or so.
There are three main frame rate standards in the TV and movie making business.
- 60i (interlaced; 50i in Europe and Australia), is the standard video frame rate that has been in use for decades; it’s what you see on your home TV, whether from a broadcast signal, rented DVD, or home camcorder.
- 30p, or 30-frame progressive, is a non-interlaced format and produces video at 30 frames per second. Progressive (non-interlaced) scanning mimics a film camera’s frame-by-frame image capture and gives clarity for high speed subjects and a cinematic-like appearance. Shooting in 30p mode offers video with no interlace artifacts.
- The 24p frame rate is also a non-interlaced format, and is now widely adopted by those planning on transferring the video signal to film. But film- and video-makers turn to 24p for the “cine”-look even if their productions are not going to be transferred to film, simply because of the “look” of the frame rate.
A culture of competition has arisen among game enthusiasts with regards to frame rates, with players striving to obtain the highest fps count possible. Indeed, many benchmarks released by the marketing departments of hardware manufacturers and published in hardware reviews focus on the fps measurement. Modern video cards, often featuring nVidia or ATI chipsets, can perform at over 160 FPS on intensive games such as F.E.A.R. This does not apply to all games - some games apply a limit on the frame rate. For example, in the Grand Theft Auto series, Grand Theft Auto III and Grand Theft Auto: Vice City have a standard 30 fps (Grand Theft Auto: San Andreas runs at 25 FPS) and this limit can only be removed at the cost of graphical and gameplay stability. It is also doubtful whether striving for such high frame rates is worthwhile. An average 17″ monitor can reach 85 Hz, meaning that any performance reached by the game over 85 fps is discarded. For that reason it is not uncommon to limit the frame rate to the refresh rate of the monitor in a process called vertical synchronization. However, many players feel that NOT synchronizing every frame produces better in-game performance, at the cost of some “tearing” of the images
