Editing Motion blur (media)

{{About|motion blur in recorded media||display motion blur}}
{{Short description|Photography artifact from moving objects}}
{{Refimprove|date=December 2009}}
[[File:Star Rain in the Desert.jpg|thumb|300px|[[Earth's rotation]] causes motion blur in [[long-exposure photography|long-exposure photos]] of the [[night sky]]. This [[diurnal motion]] leaves [[star trail]]s in exposures like this one taken at [[La Silla Observatory]].<ref>{{cite web |title=Star Rain in the Desert |url=http://www.eso.org/public/images/potw1434a/ |website=eso.org
|publisher=[[European Southern Observatory]] |access-date=26 August 2014}}</ref>]]

'''Motion blur''' is the apparent streaking of moving objects in a [[photograph]] or a sequence of frames, such as a [[film]] or [[animation]]. It results when the image being recorded changes during the recording of a single exposure, due to rapid movement or [[long-exposure photography|long exposure]].

==Usages / Effects of motion blur==
=== Photography ===
[[Image:London bus and telephone box on Haymarket.jpg|thumb|An example of motion blur showing a [[Buses in London|London bus]] passing a telephone box in [[London]]]]
[[File:Dog Leaping.jpg|thumb|1920s example of motion blur]]
When a [[camera]] 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 [[Integral|integration]] of all positions of those objects, as well as the camera's viewpoint, over the period of [[exposure (photography)|exposure]] determined by the [[shutter speed]]. 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]] or [[television]] 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 (camera)|panning]] 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.<ref>[https://www.clickandlearnphotography.com/latest/how-to-use-motion-blur-in-your-photography/ Motion blur in photography], Click and Learn Photography</ref>

===Animation{{anchor|Computer animation}}===
[[File:Figure-Animation2.gif|400px|thumb|Two animations rotating around a figure, with motion blur (left) and without]]
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]] 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]]s. 

Some of the better-known games that utilise this are the recent [[Need for Speed]] titles, [[Unreal Tournament 3|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]] 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]].

In pre-rendered computer animation, such as [[Computer Generated Imagery|CGI]] movies, realistic motion blur can be drawn because the renderer has more time to draw each frame. [[Temporal anti-aliasing]] 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 [[cel animation]] are drawn in the same direction as motion blur and perform much the same duty.
[[Go motion]] is a variant of [[stop motion]] animation that moves the models during the exposure to create a less staggered effect.

===Computer graphics===
In [[2D computer graphics]], motion blur is an artistic filter that converts the [[digital image]]<ref>[http://www.tutorialsroom.com/tutorials/graphics/motion_blur.html Motion Blur Effect], TutorialsRoom</ref>/[[bitmap]]<ref>[http://artist.tizag.com/photoshopTutorial/motionblur.php Photoshop - Motion Blur], tizag.com</ref>/[[raster image]] in order to [[computer simulation|simulate]] the effect.
Many graphical software products (e.g. [[Adobe Photoshop]] or [[GIMP]]) 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.<ref>[http://www.virtualrig-studio.com/traditional-motion-blur Traditional motion blur methods], virtualrig-studio.com</ref>

=== 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]]s (quick eye movements) and [[fixation (visual)|fixation]] (focusing on a single point). [[Saccadic masking]] makes motion blur during a saccade invisible. Similarly, [[smooth pursuit]] 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==
[[File:Three women in a taxi in Manhattan who said hello.jpg|thumb|A taxicab starting to drive off blurred the girls' faces in the image.]]
===Television===
In televised [[sport]]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]]. 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 [[Liquid-crystal display|LCD]]) 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]].

Sometimes, motion blur can be removed from images with the help of [[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.<ref name="PC Gamer 2023-05-10">{{cite web|url=https://www.pcgamer.com/why-people-hate-motion-blur-in-videogames/|title=Why you're right to hate motion blur in games (but devs aren't wrong to include it)|last=Wilde|first=Tyler|date=10 May 2023|website=[[PC Gamer]]|access-date=21 October 2023}}</ref> Improvements in the visual quality of modern post-process motion blur shaders as well as a tendency towards higher [[frame rate|framerate]]s have lessened the visual detriment of undersampled motion blur effects.<ref name="PC Gamer 2023-05-10" />

===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.<ref>{{Cite news|date=2020-08-26|title=Black turbine blade 'can cut bird deaths'|language=en-GB|work=BBC News|url=https://www.bbc.com/news/science-environment-53909825|access-date=2020-12-20}}</ref>

===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. <ref>{{Cite web|last=richard-hann|title=Preventing motion blur in drone mapping – Richard Hann|date=7 October 2021 |url=https://www.ntnu.no/blogger/richard-hann/2021/10/07/preventing-motion-blur-in-drone-mapping/|access-date=2021-10-11|language=en-GB}}</ref>

==Restoration==
An example of blurred [[Digital photograph restoration|image restoration]] with [[Wiener deconvolution]]:
{{Wide image|Image restoration (motion blur, Wiener filtering).png|732px|From left: original image, blurred image and de-blurred image. Notice some artifacts in the de-blurred image.}}

==Gallery==
<gallery perrow="6">
File:Motorbike rider mono.jpg|Motion blur is frequently employed in [[sports photography]] (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]]. 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 (optical phenomenon)|rod effect]]
File:Weims20060325.jpg|[[Mammals]] 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]] in Tokyo.
</gallery>

==See also==
*[[Motion lines]], a technique found in comics which conveys a sense of motion
*[[Rolling shutter|Rolling shutter effect]]
*[[Smear frame]]

==References==
{{reflist}}

{{DEFAULTSORT:Motion Blur}}
[[Category:Science of photography]]
[[Category:Photographic techniques]]
[[Category:Animation techniques]]

==External links==
{{Commons category}}[https://www.giacomobucci.it/mosso-creativo/ Mosso creativo], Creative motion blur