Motion blur
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Motion blur is the apparent streaking of moving objects in a
photograph A photograph (also known as a photo, or more generically referred to as an ''image'' or ''picture'') is an image created by light falling on a photosensitivity, photosensitive surface, usually photographic film or an electronic image sensor. Th ...
or a sequence of frames, such as a
film A film, also known as a movie or motion picture, is a work of visual art that simulates experiences and otherwise communicates ideas, stories, perceptions, emotions, or atmosphere through the use of moving images that are generally, sinc ...
or
animation Animation is a filmmaking technique whereby still images are manipulated to create moving images. In traditional animation, images are drawn or painted by hand on transparent celluloid sheets to be photographed and exhibited on film. Animati ...
. It results when the image being recorded changes during the recording of a single exposure, due to rapid movement or long exposure.


Usages / Effects of motion blur


Photography

When a
camera A camera is an instrument used to capture and store images and videos, either digitally via an electronic image sensor, or chemically via a light-sensitive material such as photographic film. As a pivotal technology in the fields of photograp ...
creates an image, that image does not represent a single instant of time. Because of technological constraints or artistic requirements, the image may represent the scene over a period of time. Most often this exposure time is brief enough that the image captured by the camera appears to capture an instantaneous moment, but this is not always so, and a fast moving object or a longer exposure time may result in blurring artifacts which make this apparent. As objects in a scene move, an image of that scene must represent an integration of all positions of those objects, as well as the camera's viewpoint, over the period of exposure determined by the
shutter speed In photography, shutter speed or exposure time is the length of time that the film or digital sensor inside the camera is exposed to light (that is, when the camera's shutter (photography), shutter is open) when taking a photograph. The am ...
. In such an image, any object moving with respect to the camera will look blurred or smeared along the direction of relative motion. This smearing may occur on an object that is moving or on a static background if the camera is moving. In a
film A film, also known as a movie or motion picture, is a work of visual art that simulates experiences and otherwise communicates ideas, stories, perceptions, emotions, or atmosphere through the use of moving images that are generally, sinc ...
or
television Television (TV) is a telecommunication medium for transmitting moving images and sound. Additionally, the term can refer to a physical television set rather than the medium of transmission. Television is a mass medium for advertising, ...
image, this looks natural because the human eye behaves in much the same way. Because the effect is caused by the relative motion between the camera, and the objects and scene, motion blur may be manipulated by
panning Pan or PAN may refer to: Food * Pan (cooking), a piece of cooking equipment * Harina P.A.N., a pre-cooked corn meal * Pan or Paan, a North Indian term for betel Prefix * ''Pan-'', a prefix meaning "all", "of everything", or "involving all ...
the camera to track those moving objects. In this case, even with long exposure times, the moving objects will appear sharper while the background will become more blurred, with the resulting image conveying a sense of movement and speed.


Animation

In computer animation this effect must be simulated as a virtual camera actually does capture a discrete moment in time. This simulated motion blur is typically applied when either the camera or objects in the scene move rapidly. Without this simulated effect each frame shows a perfect instant in time (analogous to a camera with an infinitely fast shutter), with zero motion blur. This is why a video game with a frame rate of 25-30
frames per second A frame is often a structural system that supports other components of a physical construction and/or steel frame that limits the construction's extent. Frame and FRAME may also refer to: Physical objects In building construction *Framing (co ...
will seem staggered, while natural motion filmed at the same frame rate appears rather more continuous. Many modern video games feature motion blur, especially
vehicle simulation game Vehicle simulation games are a video game genre, genre of video games which attempt to provide the player with a realistic interpretation of operating various kinds of vehicles. This includes automobiles, aircraft, watercraft, spacecraft, milita ...
s. Some of the better-known games that utilise this are the recent Need for Speed titles, Unreal Tournament III, The Legend of Zelda: Majora's Mask, among many others. There are two main methods used in video games to achieve motion blur: cheaper full-screen effects, which typically only take camera movement (and sometimes how fast the camera is moving in 3-D Space to create a radial blur) into mind, and more "selective" or "per-object" motion blur, which typically uses a
shader In computer graphics, a shader is a computer program that calculates the appropriate levels of light, darkness, and color during the rendering of a 3D scene—a process known as '' shading''. Shaders have evolved to perform a variety of s ...
to create a velocity buffer to mark motion intensity for a motion blurring effect to be applied to or uses a shader to perform geometry extrusion. Classic "motion blur" effects prior to modern per-pixel shading pipelines often simply drew successive frames on top of each other with slight transparency, which is strictly speaking a form of
video feedback Video feedback is the process that starts and continues when a video camera is pointed at its own playback video monitor. The loop delay from camera to display back to camera is at least one video frame time, due to the input and output scannin ...
. In pre-rendered computer animation, such as CGI movies, realistic motion blur can be drawn because the renderer has more time to draw each frame.
Temporal anti-aliasing Temporal anti-aliasing (TAA), also known as TXAA (a proprietary technology) or TMAA/TSSAA (''Temporal Super-Sampling Anti-Aliasing''), is a spatial anti-aliasing technique for computer-generated video that combines information from past frames and ...
produces frames as a composite of many instants. Frames are not points in time, they are periods of time. If an object makes a trip at a linear speed along a path from 0% to 100% in four time periods, and if those time periods are considered frames, then the object would exhibit motion blur streaks in each frame that are 25% of the path length. If the shutter speed is shortened to less than the duration of a frame, and it may be so shortened as to approach zero time in duration, then the computer animator must choose which portion of the quarter paths (in our 4 frame example) they wish to feature as "open shutter" times. They may choose to render the beginnings of each frame, in which case they will never see the arrival of the object at the end of the path, or they may choose to render the ends of each frame, in which case they will miss the starting point of the trip. Most computer animations systems make the classic "fence-post error" in the way they handle time, confusing the periods of time of an animation with the instantaneous moments that delimit them. Thus most computer animation systems will incorrectly place an object on a four frame trip along a path at 0%, 0.33%, 0.66%, and 1.0% and when called upon to render motion blur will have to cut one or more frames short, or look beyond the boundaries of the animation, compromises that real cameras don't do and synthetic cameras needn't do.
Motion lines In comics and art more broadly, motion lines (also known as movement lines, action lines, speed lines, or zip ribbons) are the abstract lines that appear behind a moving object or person, parallel to its direction of movement, to make it appea ...
in
cel animation Traditional animation (or classical animation, cel animation, or hand-drawn animation) is an animation technique in which each frame is drawn by hand. The technique was the dominant form of animation of the 20th century, until there was a shif ...
are drawn in the same direction as motion blur and perform much the same duty.
Go motion Go motion is a variation of stop motion animation which incorporates motion blur into each frame involving motion. It was co-developed by Industrial Light & Magic and Phil Tippett. Stop motion animation can create a distinctive and disorienting sta ...
is a variant of
stop motion Stop-motion (also known as stop frame animation) is an animated filmmaking and special effects technique in which objects are physically manipulated in small increments between individually photographed frames so that they will appear to exh ...
animation that moves the models during the exposure to create a less staggered effect.


Computer graphics

In
2D computer graphics 2D computer graphics is the computer-based generation of digital images—mostly from two-dimensional models (such as 2D geometric models, text, and digital images) and by techniques specific to them. It may refer to the branch of computer s ...
, motion blur is an artistic filter that converts the
digital image A digital image is an image composed of picture elements, also known as pixels, each with '' finite'', '' discrete quantities'' of numeric representation for its intensity or gray level that is an output from its two-dimensional functions f ...
/
bitmap In computing, a bitmap (also called raster) graphic is an image formed from rows of different colored pixels. A GIF is an example of a graphics image file that uses a bitmap. As a noun, the term "bitmap" is very often used to refer to a partic ...
/
raster image upright=1, The Smiley, smiley face in the top left corner is a raster image. When enlarged, individual pixels appear as squares. Enlarging further, each pixel can be analyzed, with their colors constructed through combination of the values for ...
in order to simulate the effect. Many graphical software products (e.g.
Adobe Photoshop Adobe Photoshop is a raster graphics editor developed and published by Adobe Inc., Adobe for Microsoft Windows, Windows and macOS. It was created in 1987 by Thomas Knoll, Thomas and John Knoll. It is the most used tool for professional digital ...
or
GIMP Gimp or GIMP may refer to: Clothing * Bondage suit, also called a gimp suit, a type of suit used in BDSM * Bondage mask, also called a gimp mask, often worn in conjunction with a gimp suit Embroidery and crafts * Gimp (thread), an ornamental tr ...
) offer simple motion blur filters. However, for advanced motion blur filtering including curves or non-uniform speed adjustment, specialized software products (e.g. VirtualRig Studio) are necessary.


Biology

When an animal's eye is in motion, the image will suffer from motion blur, resulting in an inability to resolve details. To cope with this, humans generally alternate between
saccade In vision science, a saccade ( ; ; ) is a quick, simultaneous movement of both Eye movement (sensory), eyes between two or more phases of focal points in the same direction. In contrast, in Smooth pursuit, smooth-pursuit movements, the eyes mov ...
s (quick eye movements) and fixation (focusing on a single point).
Saccadic masking Saccadic masking, also known as (visual) saccadic suppression, is the phenomenon in visual perception where the brain selectively blocks visual processing during Eye movement (sensory), eye movements in such a way that neither the motion of the eye ...
makes motion blur during a saccade invisible. Similarly,
smooth pursuit In the scientific study of vision, smooth pursuit describes a type of eye movement in which the eyes remain fixated on a moving object. It is one of two ways that visual animals can voluntarily shift gaze, the other being saccadic eye movement ...
allows the eye to track a target in rapid motion, eliminating motion blur of that target instead of the scene.


Negative effects of motion blur


Television

In televised
sport Sport is a physical activity or game, often Competition, competitive and organization, organized, that maintains or improves physical ability and skills. Sport may provide enjoyment to participants and entertainment to spectators. The numbe ...
s, where conventional cameras expose pictures 25 or 30 times per second, motion blur can be inconvenient because it obscures the exact position of a projectile or athlete in
slow motion Slow motion (commonly abbreviated as slow-mo or slo-mo) is an effect in film-making whereby time appears to be slowed down. It was invented by the Austrian priest August Musger in the early 20th century. This can be accomplished through the use ...
. For this reason special cameras are often used which eliminate motion blurring by taking rapid exposures on the order of 1 millisecond, and then transmitting them over the course of the next 30 to 40 milliseconds. Although this gives sharper slow motion replays, it can look strange at normal speeds because the eye expects to see motion blurring and is not provided with blurred images. Conversely, extra motion blur can unavoidably occur on displays when it is not desired. This occurs with some video displays (especially
LCD A liquid-crystal display (LCD) is a flat-panel display or other electronically modulated optical device that uses the light-modulating properties of liquid crystals combined with polarizers to display information. Liquid crystals do not em ...
) that exhibits motion blur during fast motion. This can lead to more perceived motion blurring above and beyond the preexisting motion blur in the video material. See
display motion blur In modern displays, motion blur is an unwanted artifact caused primarily by: # Retinal blur resulting from your eyes ''continuously'' tracking ''discrete'' movement. While your eyes move, the object you're tracking remains stationary throu ...
. Sometimes, motion blur can be removed from images with the help of
deconvolution In mathematics, deconvolution is the inverse of convolution. Both operations are used in signal processing and image processing. For example, it may be possible to recover the original signal after a filter (convolution) by using a deconvolution ...
.


Video games

In video games the use or not of motion blur is somewhat controversial. Some players claim that the blur actually makes the game worse, as it does blur images, making it more difficult to recognize objects (especially so in fast-paced moments). This does become more noticeable (and more problematic) with a reduction in framerate. Improvements in the visual quality of modern post-process motion blur shaders as well as a tendency towards higher framerates have lessened the visual detriment of undersampled motion blur effects.


Wind turbines

Birds cannot properly see the swirling blades of wind turbines and can get struck by them fatally. A newly published report from Norway suggests that painting one of the three blades with a black tip makes the blades more visible and hence more avoidable. This reduces the motion blur of the unpainted blades, and cuts bird deaths by up to 70 percent.


Aerial mapping/surveying

During aerial mapping an aircraft or drone is used to take pictures of the ground during flight. If the flight speed is too high or if shutter speeds are too long, this can lead to motion blur. Motion blur reduces the quality of the images and has a negative effect on the mapping products. Motion blur can be avoided by adjusting the flight altitude, flight velocity, or shutter speed.


Restoration

An example of blurred image restoration with
Wiener deconvolution In mathematics, Wiener deconvolution is an application of the Wiener filter to the noise problems inherent in deconvolution. It works in the frequency domain, attempting to minimize the impact of deconvolved noise at frequencies which have a poor ...
:


Gallery

File:Motorbike rider mono.jpg, Motion blur is frequently employed in
sports photography Sports photography refers to the genre of photography that covers all types of sports. In the majority of cases, professional sports photography is a branch of ''photojournalism,'' while amateur sports photography, such as photos of childre ...
(particularly motorsports) to convey a sense of speed. To achieve this effect it is necessary to use a slow shutter speed and pan the lens of the camera in time with the motion of the object. File:A Teito Group Taxi in Tokyo.jpg, Another example of a photo where the camera is panned at the same speed as the object being photographed File:Nightly Rotation above San Jose International Airport.jpg, Taken aboard an airplane turning above San Jose at night. The city lights form concentric strips. File:Tj pullingout.jpg, The traffic on this street leaves brilliant streaks due to the low shutter speed of the camera and the cars' relatively fast speed. File:Strickland Falls Shadows Lifted.jpg, Strickland Falls in Tasmania, Australia, taken using a
neutral density filter In photography and optics, a neutral-density filter, or ND filter, is a photographic filter, filter that reduces or modifies the intensity of all wavelengths, or colors, of light equally, giving no changes in hue of color rendition. It can be a ...
. ND filters reduce light from the entire visible spectrum equally, allowing an increase in aperture and decrease in shutter speed without overexposing the image. To create the motion blur seen here, the shutter must be kept open for a relatively long time, making it necessary to reduce the amount of light coming through the lens. File:Moths attracted by floodlight.jpg, Long exposure photograph of moths showing exaggerated rod effect File:Weims20060325.jpg,
Mammals A mammal () is a vertebrate animal of the class Mammalia (). Mammals are characterised by the presence of milk-producing mammary glands for feeding their young, a broad neocortex region of the brain, fur or hair, and three middle e ...
are especially prone to motion blur as some can reach high speeds of movement. File:Worker on bicycle at Tsukiji Fish Market.jpg, Motion blur is evident in this photo of a worker at the former
Tsukiji fish market is a major tourist attraction for both domestic and overseas visitors in Tokyo. Located in Tsukiji in central Tokyo between the Sumida River and the upmarket Ginza shopping district, the area contains retail markets, restaurants, and associ ...
in Tokyo.


See also

*
Motion lines In comics and art more broadly, motion lines (also known as movement lines, action lines, speed lines, or zip ribbons) are the abstract lines that appear behind a moving object or person, parallel to its direction of movement, to make it appea ...
, a technique found in comics which conveys a sense of motion *
Rolling shutter effect Rolling shutter describes the process of image capture in which a still picture (in a still camera) or each frame of a video (in a video camera) is captured not by taking a snapshot of the entire scene at a single instant in time but rather b ...
*
Smear frame In animation, a smear frame is a Film frame, frame used to simulate motion blur. Smear frames are used in between key frames. This animation technique has been used since the 1940s. Smear frames are used to stylistically visualize fast movement a ...


References

Science of photography Photographic techniques Animation techniques


External links

{{Commons category
Mosso creativo
Creative motion blur