Frame rate
Encyclopedia
Frame rate is the frequency
(rate) at which an imaging device produces unique consecutive images called frame
s. The term applies equally well to computer graphics
, video camera
s, film
cameras, and motion capture
systems. Frame rate is most often expressed in frames per second (FPS), and is also expressed in progressive scan
monitors as hertz
(Hz).
, can process 10 to 12 separate images per second, perceiving them individually. The visual cortex
holds onto one image for about one-fifteenth of a second, so if another image is received during that period an illusion of continuity is created, allowing a sequence of still images to give the impression of smooth motion. Early silent film
s had a frame rate from 14 to 24 FPS but by using projectors with dual- and triple-blade shutters the rate was multiplied two or three times as seen by the audience. Studies by Thomas Edison
determined that any rate below 46 FPS "will strain the eye." In the mid- to late-1920s, the frame rate for silent films increased to about 20 to 26 FPS. When sound film
was first introduced in 1926, variations in film speed were no longer tolerated as the human ear was more sensitive to changes in audio frequency. From 1927 to 1930, the rate of 24 FPS became standardized for 35 mm sound film; a speed of 456 millimetres (18 in) per second. This allowed for simple two-blade shutters to give a projected series of images at 48 per second. Many modern 35 mm film projectors use three-blade shutters to give 72 images per second—each frame appearing three times.
and movie-making
business: 24p, 25p, and 30p. However, there are many variations on these as well as newer emerging standards.
Higher frame rates, including 300 FPS, have been tested by BBC Research over concerns with sports and other broadcasts where fast motion with large HD displays could have a disorientating effect on viewers. 300 FPS can be converted to both 50 and 60 FPS transmission formats without major issues.
Owing to their flexibility, software-based video formats can specify arbitrarily high frame rates, and many (cathode ray tube) consumer PC monitors operate at hundreds of frames per second, depending on the selected video mode. LCD screens are usually 24, 25, 50, 60, or 120 FPS.
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. Peter Jackson
is filming The Hobbit at 48 FPS.
. In a fashion somewhat comparable to the moving-picture definition presented above, a real-time frame is the time it takes to complete a full round of the system's processing tasks. If the frame rate of a real-time system is 60 hertz
, the system reevaluates all necessary inputs and updates the necessary outputs 60 times per second under all circumstances.
The designed frame rates of real-time systems vary depending on the equipment. For a real-time system that is steering an oil tanker
, a frame rate of 1 FPS may be sufficient, while a rate of even 100 FPS may not be adequate for steering a guided missile
. The designer must choose a frame rate appropriate to the application's requirements.
The first 3D first-person shooter game for a personal computer, 3D Monster Maze
, had a frame rate of approximately 6 FPS, and was still a success. In modern action-oriented games where players must visually track animated objects and react quickly, frame rates of between 30 to 60 FPS are considered acceptable by most, though this can vary significantly from game to game. Modern action games, including popular console shooters such as Halo 3
, are locked at 30 FPS maximum, while others, such as Unreal Tournament 3, can run well in excess of 100 FPS on sufficient hardware. The frame rate within games varies considerably depending upon what is currently happening at a given moment, or with the hardware configuration (especially in PC games.) When the computation of a frame consumes more time than is alloted between frames, the frame rate decreases.
A culture of competition has arisen among game enthusiasts with regard to frame rates, with players striving to obtain the highest FPS possible, due to their utility in demonstrating a system's power and efficiency. Indeed, many benchmarks (such as 3DMark
) released by the marketing departments of hardware manufacturers and published in hardware reviews focus on the FPS measurement. Even though the typical LCD monitors of today are locked at 60 FPS, making extremely high frame rates impossible to see in realtime, playthroughs of game “timedemos” at hundreds or thousands of FPS for benchmarking purposes are still common.
Beyond measurement and bragging rights, such exercises do have practical bearing in some cases. A certain amount of discarded “headroom” frames are beneficial for the elimination of uneven (“choppy” or “jumpy”) output, and to prevent FPS from plummeting during the intense sequences when players need smooth feedback most.
Aside from frame rate, a separate but related factor unique to interactive applications such as gaming is latency
. Excessive preprocessing can result in a noticeable delay between player commands and computer feedback, even when a full frame rate is maintained, often referred to as input lag.
Without realistic motion blur
ring, video games and computer animations do not look as fluid as film, even with a higher frame rate. When a fast moving object is present on two consecutive frames, a gap between the images on the two frames contributes to a noticeable separation of the object and its afterimage
in the eye. Motion blurring mitigates this effect, since it tends to reduce the image gap when the two frames are strung together The effect of motion blurring is essentially superimposing multiple images of the fast-moving object on a single frame. Motion blurring makes the motion more fluid to the human eye, even as the image of the object becomes blurry on each individual frame.
A high frame rate still does not guarantee fluid movements, especially on hardware with more than one GPU
. This effect is known as micro stuttering
.
at frame rates slower than 30 FPS (interlaced). In other words, the flicker fusion
point, where the eyes see gray instead of flickering tends to be around 60 FPS (inconsistent). However, fast moving objects may require higher frame rates to avoid judder (non-smooth, linear motion) artifacts — and the retinal fusion point can vary in different people, as in different lighting conditions. The flicker-fusion point can only be applied to digital image
s of absolute value
s, such as black and white. Where as a more analogous representation can run at lower frame rates, and still be perceived by a viewer. For example, motion blurring in digital games allows the frame rate to be lowered, while the human perception of motion remains unaffected. This would be the equivalent of introducing shades of gray into the black–white flicker.
Although human vision has no “frame rate”, it may be possible to investigate the consequences of changes in frame rate for human observers. The most famous example may be the wagon-wheel effect
, a form of aliasing
in the time domain
; in which a spinning wheel suddenly appears to change direction when its speed approaches the frame rate of the image capture/reproduction system.
Different capture/playback systems may operate at the same frame rate, and still give a different level of "realism" or artifacts attributed to frame rate. One reason for this may be the temporal characteristics of the camera and display device.
Judder is a real problem in this day where 46 and 52 inches (1,320.8 mm) television sets have become the norm. The amount an object moves between frames physically on screen is now of such a magnitude that objects and backgrounds can no longer be classed as "clear". Letters cannot be read and looking at vertical objects like trees and lamp posts while the camera is panning sideways have even been known to cause headaches. The actual amount of motion blur needed to make 24 frames per second smooth eliminates every remnant of detail from the frames. Where adding the right amount of motion blur eliminates the uncomfortable side effects, it is more than often simply not done. It requires extra processing to turn the extra frames of a 120 FPS source (which is the current recording "standard") into adequate motion blur for a 24 FPS target. It would also potentially remove the detail and clarity of background advertising. Today, devices are up to the task of displaying 60 frames per second, using them all on the source media is very much possible. For example, the amount of data that can be stored on Blu-ray and the processing power to decode it is more than adequate. Though the extra frames when not filtered correctly, can produce a somewhat video-esque quality to the whole, the improvement to motion heavy sequences is undeniable. Many televisions now have an option to do some kind of frame interpolation (what would be a frame between 2 real frames gets calculated to some degree) using technologies like Trimension DNM. Sophisticated algorithms can utilize motion compensation information to achieve a very high degree of accuracy with few artifacts.
A JavaScript
, web-browser based application is available for users to be able to observe the visual differences between frame rates as a form of reference.
Frequency
Frequency is the number of occurrences of a repeating event per unit time. It is also referred to as temporal frequency.The period is the duration of one cycle in a repeating event, so the period is the reciprocal of the frequency...
(rate) at which an imaging device produces unique consecutive images called frame
Film frame
In filmmaking, video production, animation, and related fields, a film frame or video frame is one of the many still images which compose the complete moving picture...
s. The term applies equally well to computer graphics
Computer graphics
Computer graphics are graphics created using computers and, more generally, the representation and manipulation of image data by a computer with help from specialized software and hardware....
, video camera
Video camera
A video camera is a camera used for electronic motion picture acquisition, initially developed by the television industry but now common in other applications as well. The earliest video cameras were those of John Logie Baird, based on the electromechanical Nipkow disk and used by the BBC in...
s, film
Film
A film, also called a movie or motion picture, is a series of still or moving images. It is produced by recording photographic images with cameras, or by creating images using animation techniques or visual effects...
cameras, and motion capture
Motion capture
Motion capture, motion tracking, or mocap are terms used to describe the process of recording movement and translating that movement on to a digital model. It is used in military, entertainment, sports, and medical applications, and for validation of computer vision and robotics...
systems. Frame rate is most often expressed in frames per second (FPS), and is also expressed in progressive scan
Progressive scan
Progressive scanning is a way of displaying, storing, or transmitting moving images in which all the lines of each frame are drawn in sequence...
monitors as hertz
Hertz
The hertz is the SI unit of frequency defined as the number of cycles per second of a periodic phenomenon. One of its most common uses is the description of the sine wave, particularly those used in radio and audio applications....
(Hz).
Background
The human eye and its brain interface, the human visual systemVisual system
The visual system is the part of the central nervous system which enables organisms to process visual detail, as well as enabling several non-image forming photoresponse functions. It interprets information from visible light to build a representation of the surrounding world...
, can process 10 to 12 separate images per second, perceiving them individually. The visual cortex
Visual cortex
The visual cortex of the brain is the part of the cerebral cortex responsible for processing visual information. It is located in the occipital lobe, in the back of the brain....
holds onto one image for about one-fifteenth of a second, so if another image is received during that period an illusion of continuity is created, allowing a sequence of still images to give the impression of smooth motion. Early silent film
Silent film
A silent film is a film with no synchronized recorded sound, especially with no spoken dialogue. In silent films for entertainment the dialogue is transmitted through muted gestures, pantomime and title cards...
s had a frame rate from 14 to 24 FPS but by using projectors with dual- and triple-blade shutters the rate was multiplied two or three times as seen by the audience. Studies by Thomas Edison
Thomas Edison
Thomas Alva Edison was an American inventor and businessman. He developed many devices that greatly influenced life around the world, including the phonograph, the motion picture camera, and a long-lasting, practical electric light bulb. In addition, he created the world’s first industrial...
determined that any rate below 46 FPS "will strain the eye." In the mid- to late-1920s, the frame rate for silent films increased to about 20 to 26 FPS. When sound film
Sound film
A sound film is a motion picture with synchronized sound, or sound technologically coupled to image, as opposed to a silent film. The first known public exhibition of projected sound films took place in Paris in 1900, but decades would pass before sound motion pictures were made commercially...
was first introduced in 1926, variations in film speed were no longer tolerated as the human ear was more sensitive to changes in audio frequency. From 1927 to 1930, the rate of 24 FPS became standardized for 35 mm sound film; a speed of 456 millimetres (18 in) per second. This allowed for simple two-blade shutters to give a projected series of images at 48 per second. Many modern 35 mm film projectors use three-blade shutters to give 72 images per second—each frame appearing three times.
Frame rates in film and television
As of 2011, there are currently three main frame rate standards in the TVTelevision
Television is a telecommunication medium for transmitting and receiving moving images that can be monochrome or colored, with accompanying sound...
and movie-making
Film
A film, also called a movie or motion picture, is a series of still or moving images. It is produced by recording photographic images with cameras, or by creating images using animation techniques or visual effects...
business: 24p, 25p, and 30p. However, there are many variations on these as well as newer emerging standards.
- 24p24pIn video technology, 24p refers to a video format that operates at 24 frames per second frame rate with progressive scanning . Originally, 24p was used in the non-linear editing of film-originated material...
is a progressiveProgressive scanProgressive scanning is a way of displaying, storing, or transmitting moving images in which all the lines of each frame are drawn in sequence...
format and is now widely adopted by those planning on transferring a videoVideoVideo is the technology of electronically capturing, recording, processing, storing, transmitting, and reconstructing a sequence of still images representing scenes in motion.- History :...
signal to filmFilmA film, also called a movie or motion picture, is a series of still or moving images. It is produced by recording photographic images with cameras, or by creating images using animation techniques or visual effects...
. 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 factoDe factoDe facto is a Latin expression that means "concerning fact." In law, it often means "in practice but not necessarily ordained by law" or "in practice or actuality, but not officially established." It is commonly used in contrast to de jure when referring to matters of law, governance, or...
standard for sound motion pictures in the mid-1920s. Practically all hand-drawn animationTraditional animationTraditional animation, is an animation technique where each frame is drawn by hand...
is designed to be played at 24 FPS. Actually hand-drawing 24 unique frames per second ("1's") is costly. Even big budget films usually hand-draw animation shooting on "2's" (one hand-drawn frame is shown 2 times, so only 12 unique frames per second) and a lot of animation is drawn on "4's" (one hand-drawn frame is shown 4 times, so only 6 unique frames per second).
- 25p is a progressiveProgressive scanProgressive scanning is a way of displaying, storing, or transmitting moving images in which all the lines of each frame are drawn in sequence...
format and runs 25 progressive frames per second. This frame rate derives from the PALPALPAL, short for Phase Alternating Line, is an analogue television colour encoding system used in broadcast television systems in many countries. Other common analogue television systems are NTSC and SECAM. This page primarily discusses the PAL colour encoding system...
televisionTelevisionTelevision is a telecommunication medium for transmitting and receiving moving images that can be monochrome or colored, with accompanying sound...
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 pulldown. While 25p captures half the temporal resolution or motion that normal 50i PAL registers, it yields a higher vertical spacial resolution per frame. Like 24p, 25p is often used to achieve "cine"-look, albeit with virtually the same motion artifacts. 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 progressiveProgressive scanProgressive scanning is a way of displaying, storing, or transmitting moving images in which all the lines of each frame are drawn in sequence...
format and produces video at 30 frames per second. Progressive (noninterlaced) 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 artifacts but can introduce judder on image movement and on some camera pans. The widescreen film process Todd-AOTodd-AOTodd-AO is a post-production company founded in 1953, providing sound-related services to the motion picture and television industries. The company operates three facilities in the Los Angeles area.-History:...
used this frame rate in 1954–1956.
- 50i (50 interlaced fields = 25 frames) is an interlaced format and is the standard video field rate per second for PALPALPAL, short for Phase Alternating Line, is an analogue television colour encoding system used in broadcast television systems in many countries. Other common analogue television systems are NTSC and SECAM. This page primarily discusses the PAL colour encoding system...
and SECAMSECAMSECAM, also written SÉCAM , is an analog color television system first used in France....
television.
- 60i (actually 59.94, or 60 x 1000/1001 to be more precise; 60 interlaced fields = 30 frames) is an interlaced format and is the standard video fieldField (video)In video, a field is one of the many still images which are displayed sequentially to create the impression of motion on the screen. Two fields comprise one video frame...
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 FarnsworthPhilo FarnsworthPhilo Taylor Farnsworth was an American inventor and television pioneer. Although he made many contributions that were crucial to the early development of all-electronic television, he is perhaps best known for inventing the first fully functional all-electronic image pickup device , the "image...
and Zworykin in 1934, and was part of the NTSCNTSCNTSC, named for the National Television System Committee, is the analog television system that is used in most of North America, most of South America , Burma, South Korea, Taiwan, Japan, the Philippines, and some Pacific island nations and territories .Most countries using the NTSC standard, as...
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.
- 50p/60p is a progressiveProgressive scanProgressive scanning is a way of displaying, storing, or transmitting moving images in which all the lines of each frame are drawn in sequence...
format and is used in high-end HDTV systems. While it is not technically part of the ATSCATSCATSC standards are a set of standards developed by the Advanced Television Systems Committee for digital television transmission over terrestrial, cable, and satellite networks....
or DVB broadcast standards, it is rapidly gaining ground in the areas of set-top boxes and video recordings.
- 72p is a progressiveProgressive scanProgressive scanning is a way of displaying, storing, or transmitting moving images in which all the lines of each frame are drawn in sequence...
format and is currently in experimental stages. Major institutions such as Snell have demonstrated 720p72 pictures as a result of earlier analogueAnalog televisionAnalog television is the analog transmission that involves the broadcasting of encoded analog audio and analog video signal: one in which the message conveyed by the broadcast signal is a function of deliberate variations in the amplitude and/or frequency of the signal...
experiments, where 768 line television at 75 FPS looked subjectively better than 1150 line 50 FPS progressive pictures with higher shutterShutterShutter may refer to:Windows:*Window shutter, a solid window covering used to block light and winds*Plantation Shutters/Jigsaw Shutters, interior wooden louvred shutters to control heat, light and privacy...
speeds available (and a corresponding lower data rateBit rateIn telecommunications and computing, bit rate is the number of bits that are conveyed or processed per unit of time....
). Modern cameras such as the Red One can use this frame rate to produce slow motionSlow motionSlow motion is an effect in film-making whereby time appears to be slowed down. It was invented by the Austrian priest August Musger....
replays at 24 FPS. Douglas TrumbullDouglas TrumbullDouglas Huntley Trumbull is an American film director, special effects supervisor, and inventor. He contributed to, or was responsible for, the special photographic effects of 2001: A Space Odyssey, Close Encounters of the Third Kind, Star Trek: The Motion Picture, Blade Runner and The Tree of...
, who undertook experiments with different frame rates that led to the ShowscanShowscanShowscan is a cinematic process developed by Douglas Trumbull. Similar to 70 mm wide-screen processes, it uses 65 mm film, but photographs and projects it at 60 frames per second – 2.5 times faster than standard movie film...
film format, found that emotional impact peaked at 72 FPS for viewers. 72 FPS is the maximum rate available in the WMVWindows Media Video'Windows Media Video is a video compression format for several proprietary codecs developed by Microsoft. The original video format, known as WMV, was originally designed for Internet streaming applications, as a competitor to RealVideo. The other formats, such as WMV Screen and WMV Image, cater...
video file format.
Higher frame rates, including 300 FPS, have been tested by BBC Research over concerns with sports and other broadcasts where fast motion with large HD displays could have a disorientating effect on viewers. 300 FPS can be converted to both 50 and 60 FPS transmission formats without major issues.
Owing to their flexibility, software-based video formats can specify arbitrarily high frame rates, and many (cathode ray tube) consumer PC monitors operate at hundreds of frames per second, depending on the selected video mode. LCD screens are usually 24, 25, 50, 60, or 120 FPS.
Director James Cameron
James Cameron
James Francis Cameron is a Canadian-American film director, film producer, screenwriter, editor, environmentalist and inventor...
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. Peter Jackson
Peter Jackson
Sir Peter Robert Jackson, KNZM is a New Zealand film director, producer, actor, and screenwriter, known for his The Lord of the Rings film trilogy , adapted from the novel by J. R. R...
is filming The Hobbit at 48 FPS.
Computing
Frame rate is also a term used in real-time computingReal-time computing
In computer science, real-time computing , or reactive computing, is the study of hardware and software systems that are subject to a "real-time constraint"— e.g. operational deadlines from event to system response. Real-time programs must guarantee response within strict time constraints...
. In a fashion somewhat comparable to the moving-picture definition presented above, a real-time frame is the time it takes to complete a full round of the system's processing tasks. If the frame rate of a real-time system is 60 hertz
Hertz
The hertz is the SI unit of frequency defined as the number of cycles per second of a periodic phenomenon. One of its most common uses is the description of the sine wave, particularly those used in radio and audio applications....
, the system reevaluates all necessary inputs and updates the necessary outputs 60 times per second under all circumstances.
The designed frame rates of real-time systems vary depending on the equipment. For a real-time system that is steering an oil tanker
Oil tanker
An oil tanker, also known as a petroleum tanker, is a merchant ship designed for the bulk transport of oil. There are two basic types of oil tankers: the crude tanker and the product tanker. Crude tankers move large quantities of unrefined crude oil from its point of extraction to refineries...
, a frame rate of 1 FPS may be sufficient, while a rate of even 100 FPS may not be adequate for steering a guided missile
Guided Missile
Guided Missile is a London based independent record label set up by Paul Kearney in 1994.Guided Missile has always focused on 'the underground', preferring to put out a steady flow of releases and developing the numerous GM events around London and beyond....
. The designer must choose a frame rate appropriate to the application's requirements.
Frame rates in video games
Frame rates in video games refer to the speed at which the image is refreshed (typically in frames per second, or FPS). Many underlying processes, such as collision detection and network processing, run at different or inconsistent frequencies or in different physical components of a computer. FPS affect the experience in two ways: low FPS does not give the illusion of motion effectively and affects the user's capacity to interact with the game, while FPS that vary substantially from one second to the next depending on computational load produce uneven, “choppy” animation. Many games lock their frame rate at lower but more sustainable levels to give consistently smooth motion.The first 3D first-person shooter game for a personal computer, 3D Monster Maze
3D Monster Maze
3D Monster Maze is a computer game developed from an idea by J.K.Greye and programmed by Malcolm Evans in 1981 for the Sinclair ZX81 platform with the 16 KB memory expansion. The game was initially released by J. K. Greye Software in early 1982 and re-released later the same year by...
, had a frame rate of approximately 6 FPS, and was still a success. In modern action-oriented games where players must visually track animated objects and react quickly, frame rates of between 30 to 60 FPS are considered acceptable by most, though this can vary significantly from game to game. Modern action games, including popular console shooters such as Halo 3
Halo 3
Halo 3 is a first-person shooter video game developed by Bungie for the Xbox 360 console. The third installment in the Halo franchise, the game concludes the story arc begun in Halo: Combat Evolved and continued in Halo 2...
, are locked at 30 FPS maximum, while others, such as Unreal Tournament 3, can run well in excess of 100 FPS on sufficient hardware. The frame rate within games varies considerably depending upon what is currently happening at a given moment, or with the hardware configuration (especially in PC games.) When the computation of a frame consumes more time than is alloted between frames, the frame rate decreases.
A culture of competition has arisen among game enthusiasts with regard to frame rates, with players striving to obtain the highest FPS possible, due to their utility in demonstrating a system's power and efficiency. Indeed, many benchmarks (such as 3DMark
3DMark
3DMark is a computer benchmarking tool created and developed by Futuremark Corporation to determine the performance of a computer's 3D graphic rendering and CPU workload processing capabilities. Running 3DMark produces a 3DMark score with higher numbers indicating better performance...
) released by the marketing departments of hardware manufacturers and published in hardware reviews focus on the FPS measurement. Even though the typical LCD monitors of today are locked at 60 FPS, making extremely high frame rates impossible to see in realtime, playthroughs of game “timedemos” at hundreds or thousands of FPS for benchmarking purposes are still common.
Beyond measurement and bragging rights, such exercises do have practical bearing in some cases. A certain amount of discarded “headroom” frames are beneficial for the elimination of uneven (“choppy” or “jumpy”) output, and to prevent FPS from plummeting during the intense sequences when players need smooth feedback most.
Aside from frame rate, a separate but related factor unique to interactive applications such as gaming is latency
Latency (engineering)
Latency is a measure of time delay experienced in a system, the precise definition of which depends on the system and the time being measured. Latencies may have different meaning in different contexts.-Packet-switched networks:...
. Excessive preprocessing can result in a noticeable delay between player commands and computer feedback, even when a full frame rate is maintained, often referred to as input lag.
Without realistic motion blur
Motion blur
Motion blur is the apparent streaking of rapidly moving objects in a still image or a sequence of images such as a movie or animation. It results when the image being recorded changes during the recording of a single frame, either due to rapid movement or long exposure.- Photography :When a camera...
ring, video games and computer animations do not look as fluid as film, even with a higher frame rate. When a fast moving object is present on two consecutive frames, a gap between the images on the two frames contributes to a noticeable separation of the object and its afterimage
Afterimage
An afterimage or ghost image or image burn-in is an optical illusion that refers to an image continuing to appear in one's vision after the exposure to the original image has ceased...
in the eye. Motion blurring mitigates this effect, since it tends to reduce the image gap when the two frames are strung together The effect of motion blurring is essentially superimposing multiple images of the fast-moving object on a single frame. Motion blurring makes the motion more fluid to the human eye, even as the image of the object becomes blurry on each individual frame.
A high frame rate still does not guarantee fluid movements, especially on hardware with more than one GPU
Graphics processing unit
A graphics processing unit or GPU is a specialized circuit designed to rapidly manipulate and alter memory in such a way so as to accelerate the building of images in a frame buffer intended for output to a display...
. This effect is known as micro stuttering
Micro stuttering
Micro stuttering is a term used in computing to describe a quality defect inherent to multi-GPU configurations, such as nVidia SLi and AMD CrossFireX, using AFR...
.
Visible frame rate
The human visual system does not see in terms of frames; it works with a continuous flow of light information. A related question is, “how many frames per second are needed for an observer to not see artifacts?” However, this question also does not have a single straight-forward answer. If the image switches between black and white each frame, the image appears to flickerFlicker
Flicker may refer to any of the following:* Flickers, woodpeckers of the subgenus Colaptes* Flicker , a fading between frames that occurs on a cathode-ray screen at low refresh rates...
at frame rates slower than 30 FPS (interlaced). In other words, the flicker fusion
Flicker fusion threshold
The flicker fusion threshold is a concept in the psychophysics of vision. It is defined as the frequency at which an intermittent light stimulus appears to be completely steady to the observer...
point, where the eyes see gray instead of flickering tends to be around 60 FPS (inconsistent). However, fast moving objects may require higher frame rates to avoid judder (non-smooth, linear motion) artifacts — and the retinal fusion point can vary in different people, as in different lighting conditions. The flicker-fusion point can only be applied to digital image
Digital image
A digital image is a numeric representation of a two-dimensional image. Depending on whether or not the image resolution is fixed, it may be of vector or raster type...
s of absolute value
Absolute value
In mathematics, the absolute value |a| of a real number a is the numerical value of a without regard to its sign. So, for example, the absolute value of 3 is 3, and the absolute value of -3 is also 3...
s, such as black and white. Where as a more analogous representation can run at lower frame rates, and still be perceived by a viewer. For example, motion blurring in digital games allows the frame rate to be lowered, while the human perception of motion remains unaffected. This would be the equivalent of introducing shades of gray into the black–white flicker.
Although human vision has no “frame rate”, it may be possible to investigate the consequences of changes in frame rate for human observers. The most famous example may be the wagon-wheel effect
Wagon-wheel effect
The wagon-wheel effect is an optical illusion in which a spoked wheel appears to rotate differently from its true rotation. The wheel can appear to rotate more slowly than the true rotation, it can appear stationary, or it can appear to rotate in the opposite direction from the true rotation...
, a form of aliasing
Aliasing
In signal processing and related disciplines, aliasing refers to an effect that causes different signals to become indistinguishable when sampled...
in the time domain
Time domain
Time domain is a term used to describe the analysis of mathematical functions, physical signals or time series of economic or environmental data, with respect to time. In the time domain, the signal or function's value is known for all real numbers, for the case of continuous time, or at various...
; in which a spinning wheel suddenly appears to change direction when its speed approaches the frame rate of the image capture/reproduction system.
Different capture/playback systems may operate at the same frame rate, and still give a different level of "realism" or artifacts attributed to frame rate. One reason for this may be the temporal characteristics of the camera and display device.
Judder is a real problem in this day where 46 and 52 inches (1,320.8 mm) television sets have become the norm. The amount an object moves between frames physically on screen is now of such a magnitude that objects and backgrounds can no longer be classed as "clear". Letters cannot be read and looking at vertical objects like trees and lamp posts while the camera is panning sideways have even been known to cause headaches. The actual amount of motion blur needed to make 24 frames per second smooth eliminates every remnant of detail from the frames. Where adding the right amount of motion blur eliminates the uncomfortable side effects, it is more than often simply not done. It requires extra processing to turn the extra frames of a 120 FPS source (which is the current recording "standard") into adequate motion blur for a 24 FPS target. It would also potentially remove the detail and clarity of background advertising. Today, devices are up to the task of displaying 60 frames per second, using them all on the source media is very much possible. For example, the amount of data that can be stored on Blu-ray and the processing power to decode it is more than adequate. Though the extra frames when not filtered correctly, can produce a somewhat video-esque quality to the whole, the improvement to motion heavy sequences is undeniable. Many televisions now have an option to do some kind of frame interpolation (what would be a frame between 2 real frames gets calculated to some degree) using technologies like Trimension DNM. Sophisticated algorithms can utilize motion compensation information to achieve a very high degree of accuracy with few artifacts.
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, web-browser based application is available for users to be able to observe the visual differences between frame rates as a form of reference.
See also
- Federal Standard 1037CFederal Standard 1037CFederal Standard 1037C, titled Telecommunications: Glossary of Telecommunication Terms is a United States Federal Standard, issued by the General Services Administration pursuant to the Federal Property and Administrative Services Act of 1949, as amended....
- MIL-STD-188MIL-STD-188MIL-STD-188 is a series of U.S. military standards relating to telecommunications.-Purpose:Faced with “past technical deficiencies in telecommunications systems and equipment and software…that were traced to basic inadequacies in the application of telecommunication standards and to the lack of a...
- Movie projectorMovie projectorA movie projector is an opto-mechanical device for displaying moving pictures by projecting them on a projection screen. Most of the optical and mechanical elements, except for the illumination and sound devices, are present in movie cameras.-Physiology:...
- Moving image formatsMoving image formatsThis article discusses moving image capture, transmission and presentation from today's technical and creative points of view; concentrating on aspects of frame rates.- Essential parameters :...
- Persistence of visionPersistence of visionPersistence of vision is the phenomenon of the eye by which an afterimage is thought to persist for approximately one twenty-fifth of a second on the retina....
- List of film formats
- TelecineTelecineTelecine is transferring motion picture film into video and is performed in a color suite. The term is also used to refer to the equipment used in the post-production process....
- Film-outFilm-outFilm-out is the process in the computer graphics, video production and filmmaking disciplines of transferring images or animation from videotape or digital files to a traditional film print...
- Video compression
- 24p24pIn video technology, 24p refers to a video format that operates at 24 frames per second frame rate with progressive scanning . Originally, 24p was used in the non-linear editing of film-originated material...
- Refresh rateRefresh rateThe refresh rate is the number of times in a second that a display hardware draws the data...
- Delta timingDelta timingDelta Time or Delta Timing is a concept used amongst game programmers. A user with a slow internet connection or computer is often prone to experience lag or slowness...