Video Frame Rates
There are three main frame rate standards in the TV and digital cinema business: 24p, 25p, and 30p. However, there are many variations on these as well as newer emerging standards.
24p is a progressive format and is now widely adopted by those planning on transferring a video signal to film. Film and video makers use 24p even if their productions are not going to be transferred to film, simply because of the on-screen “look” of the (low) frame rate which matches native film. When transferred to NTSC television, the rate is effectively slowed to 23.976 FPS (24×1000÷1001 to be exact), and when transferred to PAL or SECAM it is sped up to 25 FPS. 35 mm movie cameras use a standard exposure rate of 24 FPS, though many cameras offer rates of 23.976 FPS for NTSC television and 25 FPS for PAL/SECAM. The 24 FPS rate became the de facto standard for sound motion pictures in the mid-1920s. Practically all hand drawn animation is designed to be played at 24 FPS. Actually hand-drawing 24 unique frames per second (“1’s”) are costly. Even in big budget films usually hand-draw animation shooting on “2’s” (one hand-drawn frame is shown twice, so only 12 unique frames per second) and some animation is even drawn on “4’s” (one hand-drawn frame is shown four times, so only six unique frames per second).
25p is a progressive format and runs 25 progressive frames per second. This frame rate derives from the PAL television standard of 50i (or 50 interlaced fields per second). Film and Television companies use this rate in 50 Hz regions for direct compatibility with television field and frame rates. Conversion for 60 Hz countries is enabled by slowing down the media to 24p then converted to 60 Hz systems using pull down. While 25p captures half the temporal resolution or motion that normal 50i PAL registers, it yields a higher vertical spatial resolution per frame. Like 24p, 25p is often used to achieve “cine”-look, albeit with virtually the same motion artefacts. It is also better suited to progressive-scan output (e.g., on LCD displays, computer monitors and projectors) because the interlacing is absent.
30p is a progressive format and produces video at 30 frames per second. Progressive (non interlaced) scanning mimics a film camera’s frame-by-frame image capture. The effects of inter-frame judder are less noticeable than 24p yet retains a cinematic-like appearance. Shooting video in 30p mode gives no interlace artefacts but can introduce judder on image movement and on some camera pans. The widescreen film process Tood-AO used this frame rate in 1954–1956.
48p is a progressive format and is currently being trailed in the film industry. At twice the traditional rate of 24p, this frame rate attempts to reduce motion blur and flicker found in films. Director James Cameron stated his intention to film the two sequels to his film Avatar at a higher frame rate than 24 frames per second, in order to add a heightened sense of reality. The first film to be filmed at 48 FPS was The Hobbit, a decision made by its director Peter Jackson. At a preview screening at CinemaCon, the audience’s reaction was mixed after being shown some of the film’s footage at 48p; with some arguing that the feel of the footage was too lifelike (thus breaking the suspension of disbelief).
50i is an interlaced format and is the standard video field rate per second for PAL and SECAM television.
60i is an interlaced format and is the standard video field rate per second for NTSC television (e.g., in the US), whether from a broadcast signal, DVD, or home camcorder. This interlaced field rate was developed separately by Farnsworth and Zworykin in 1934, and was part of the NTSC television standards mandated by the FCC in 1941. When NTSC color was introduced in 1953, the older rate of 60 fields per second was reduced by a factor of 1000/1001 to avoid interference between the chroma subcarrier and the broadcast sound carrier. (Hence the usual designation “29.97 fps” = 30 frames(60 fields)/1.001)
50p/60p is a progressive format and is used in high-end HDTV systems. While it is not technically part of the ATSC or DVB broadcast standards yet, reports suggest that higher progressive frame rates will be a feature of the next-generation high-definition television broadcast standards. In Europe, the EBU considers 1080p50 the next step future proof system for TV broadcasts and is encouraging broadcasters to upgrade their equipment for the future.
72p is a progressive format and is currently in experimental stages. Major institutions such as Snell have demonstrated 720p72 pictures as a result of earlier analogue experiments, where 768 line television at 75 FPS looked subjectively better than 1150 line 50 FPS progressive pictures with higher shutter speeds available (and a corresponding lower data rate). Modern cameras such as the Red one can use this frame rate to produce slow motion replays at 24 FPS.Douglas Trumbull, who undertook experiments with different frame rates that led to the Show scan film format, found that emotional impact peaked at 72 FPS for viewers. 72 FPS is the maximum rate available in the WMV video file format.
120p (120.00 Hz exactly) is a progressive format and is standardized for UHDTV by the ITU-RBT.2020 recommendation. It will be the single global “double-precision” frame rate for UHDTV (instead of using 100 Hz for PAL-based countries and 119.88 Hz for NTSC-based countries).
300 FPS, interpolated 300 FPS along with other high frame rates, have been tested by BBC Research for use in sports broadcasts. 300 FPS can be converted to both 50 and 60 FPS transmission formats without major issues.