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'''Strip photography''' (or '''slit photography''') is a [[photographic technique]] of capturing a 2-dimensional image as a sequence of 1-dimensional images over time, rather than a single 2-dimensional at one point in time (the full field). As one moves across (in the direction of scanning), one moves in ''time,'' rather than, or in addition to, moving in space. The image can be loosely interpreted as a collection of thin vertical or horizontal strips patched together, hence the name. This is correct if the strips are discrete, as in a digital sensor that captures one line at a time, but in film photography, the image is produced continuously, and thus the "strips" are [[infinitesimal]] – a smooth gradation.

== Implementation ==
Many photographic devices use a form of strip photography due to the use of a [[rolling shutter]] for engineering reasons, and exhibit similar effects. This is common both on cheaper cameras with an [[electronic shutter]] (more sophisticated electronic shutters are global, not rolling), as well as cameras with mechanical [[focal-plane shutter]]s.

This technique can be implemented in multiple ways. In film photography, a [[camera]] with a [[vertical slit aperture]] can either have fixed film and a moving slit, or a fixed slit and moving film. In digital photography, one can use a line sensor, generally one that is moving, as in a [[rotating line camera]], but also an [[image scanner]] (flatbed or hand).

This can also be done on some consumer digital cameras, such as via the [https://itunes.apple.com/il/app/scancamera/id495845771 ScanCamera] application on [[iOS]] ([[iPhone]], [[iPad]]).

== Aesthetics ==
The fundamental property of strip photography is that it is a 2-dimensional slice across [[space-time]]. In some cases this is a slice perpendicular to the frame, in 1 spacial dimension (the slit) and 1 temporal dimension (the exposure time), if the slit is stationary (as in a [[photo finish]]), showing one strip over time (e.g., the finish line), where the scanning direction (e.g., horizontal) represents time, not space. In other cases this is a slice diagonal (in space-time) to the frame, with 1 spacial dimension (the slit) and 1 spacial-temporal dimension (the exposure time and moving slit) if the slit moves, as in a panoramic camera, which shows a single frame, but different strips are at different times, in which case the scanning direction represents both space and time. Thus, even though the image is view as a 2-dimensional spacial image, it does not depict a single instant.

=== Characteristics ===
Strip photography has a number of distinctive characteristics, particularly fixed slit. These include:<ref name="dahlin" />
;Distortion
Moving objects are distorted based on the relative speed of their motion and the image capture. For objects moving in a fixed direction at a constant or almost constant rate, as is the case of racing photographs, notably photo finishes, this yields an approximately constant rate of distortion, so the image is stretched or compressed. If the speeds are in (approximate) sync, which can be done for racing, the image can look almost undistorted.

In strip photography, distance is interchanged (or mixed) with time, so width in the scanning direction (say, horizontal) is proportional to time, and thus [[inversely proportional]] to speed. Slower-moving objects occupy more time, and thus appear wider, while faster-moving objects are narrower, as they occupy the slit for a shorter period of time. In extreme cases a very rapidly moving object can be captured for only a single strip or even none at all (if discrete capture, as in a digital camera), while a stationary object (notably background) will appear as a horizontal line (a stripe). These differences are particularly notable in cases of movement at differing constant speeds, such as [[parallax]] from a train window or differing speeds of traffic (esp. if in differing directions diagonal to the camera) or people walking. Further, in the case of motion towards or away from the camera, size changes, creating additional distortion.

In the case of diagonal motion in the direction of capture and towards or away from the camera, object flare (expand vertically and compressing horizontally) as they approach and tapering (compress vertically and stretch out horizontally) as they recede; this is because (by perspective) objects appear larger the closer they are (approximately as the inverse of distance), with increase in horizontal size yielding faster movement (parallax) and thus ''decreased'' size in the strip photograph. These effects are inverse in magnitude (as horizontal shrinks vertical grows, so area does not change), so objects effectively undergo a [[squeeze mapping]], properly an inhomogeneous squeeze (magnitude of squeeze varies with distance to the camera), hence the flared shapes.

In other cases, however, particularly movement not in the direction of capture, very unusual distortions result, resembling smears. These may be compared with [[surrealism]], such as the work of [[Pablo Picasso]] or [[Salvador Dalí]]. In cases when the exposure time (for a given location on the sensor) is slow relative to movement, this distortion combines with motion blur, yielding soft blurs.

In the case of runners, the torso will be moving at an approximately constant rate, but the extremities will be moving rapidly in other directions, yielding distorted extremities. Particularly notable are relay runners, due to the combination of regular racing and the irregular transfer.

;Stripped background
For fixed slit photography, non-moving objects, particularly in the background, are rendered as a constant stripe, yielding a striped background. This is the extreme case of width being inversely proportional to speed.

;Perspective
More subtly, for fixed slit photography, as all capture is in a constant direction, there is no perspective in the image. This is conspicuous in long strips of races, where all the racers are viewed directly from the side, rather than from an angle depending on their position. This effect is the same as (rather, the extreme case of) the [[Perspective distortion (photography)|perspective distortion]] in a photo taken from very far away, in which case perspective flattens ("compression distortion").

;Changing scene
Because the photograph is not at a single instant, the scene can change during the exposure, including such features as duplication of a single object. Notably, extreme ends may be quite separated in time. For example: in a rollout photograph of a head that makes more than one revolution, the subject’s expression may change each time; in a race photo, a racer may go behind the camera (or around the track a second time) and pass the finish line repeatedly, or reverse direction and cross the finish line in the opposite direction; in a panoramic photo, a subject (e.g., a person) may be captured at one side, go behind the camera, and then re-enter the frame and be captured at the other side. This can also be used to tell a temporally authentic story, as in a comic strip – events at one end, and consequences or reactions at the other, later in time and space.

=== Layout ===
Vertical strips – so time is horizontal – is most common, and accords with horizontal scanning, as in reading, though horizontal strips – so time is vertical – are also found. In addition to horizontal and vertical strips, other forms are possible, such as radial strips.<ref>Radial strips are found in the work of [http://ansenseale.com/ Ansen Seale], starting from his ''[http://ansenseale.com/gallery.cfm?id=27 Vortex]'' series ([http://ansenseale.com/series_desc.cfm?id=27 description])</ref> [[Aspect ratio]] varies, with some photos being similar to ordinary photos ("tableau" format), emphasizing a single image, while others are long ("strip" format), emphasizing the passage of time, as in a (single panel) [[comic strip]] or traditional scroll paintings.

== Applications ==
This is most basically used in [[panoramic photography]], to capture a large, static scene that would be difficult to capture via other techniques; [[Panoramic photography#Full rotation|scanning cameras]] are designed for this.

Other applications include:
* [[Peripheral photography]], notably [[rollout photography]]
* [[Photo finish]] ([[Photo finish#Strip photography|photo finish: strip photography]])
* [[Scanography]]
* [[Slit-scan photography]]
* [[Strip aerial photography]]
* [[Synchroballistic photography]] (in [[ballistics]])

== Sports photography ==
{{external media
|image1="[http://cllctr.com/image/44588a04a82321766daa4a1103db94b4 Grand Prix de Circuit de la Seine]" (June 26th, 1912)<ref>"[http://cllctr.com/view/44588a04a82321766daa4a1103db94b4 Grand Prix de Circuit de la Seine]" (June 26th, 1912)</ref>
|image2="[http://www.sportsshooter.com/news_pix/2043_3.jpeg The Spirit and Frenzy of Olympic Efforts]"<ref name="life19600718" /><ref name="dahlin" /> 
}}
Sports are a common use of strip photography, both for photo finishes and artistic purposes. It is particularly common for racing, where movement is largely regular and predictable, but by no means limited to it. Due to the movement in sports, which is a combination of movement at a regular rate and at a changing rate, various forms of distortion are possible. An early accidental example of distortion is "[http://cllctr.com/view/44588a04a82321766daa4a1103db94b4 Grand Prix de Circuit de la Seine]" (June 26th, 1912) by [[Jacques Henri Lartigue]], where the skew caused by the vertically traveling slit makes the race car appear to lean forwards, creating a sense of speed.

Strip photography was notably used by [[George Silk]] at the US tryouts for the [[1960 Summer Olympics]],<ref name="life19600718">''[[Life (magazine)|Life]],'' July 18, 1960</ref><ref name="dahlin">"[http://www.sportsshooter.com/news/2043 Strip Tease: An introduction to the strip camera, how Tom Dahlin made his, and how you can too.]", Tom Dahlin, ''[http://www.sportsshooter.com/ SportsShooter],'' 2008-08-18</ref> Further photography at ''Life'' and ''[[Sports Illustrated]]'' that used strip photography included [[John G. Zimmerman]], who borrowed Silk's camera to photography [[Pete Rose]] and later photographed basketball players [[Nate Archibald]] and [[Dr. J]] using a slit-scan camera for ''Sports Illustrated,'' and [[Neil Leifer]], who used it frequently in the 1970s for athletes including [[Gaylord Perry]] and [[Billy Kidd]], and for sports such as [[IndyCar]] racing.<ref name="dahlin" /><ref>[[Neil Leifer]], ''Sports!'' features several such images</ref> More recently, [[Bill Frakes]] (assisted by David Callow) captured [[Marion Jones]] winning the 100m event at the [[2000 Summer Olympics]] using a strip camera.<ref name="dahlin" />

== Artistic uses ==
Strip photography can be used for artistic effect, which has been done on a regular basis since the 1960s.<ref name="vanvolsemjena">"[http://www2.uni-jena.de/philosophie/medien/MovingStills/eng_personen_vanvolsem.html How strip-photography complicated the interpretation of the still photographic image]", Maarten Vanvolsem</ref> In addition to sports, early examples include work by Silk and other ''[[Life (magazine)|Life]]'' (later ''[[Time–Life]]'') photographers for various subjects,<ref>Davidhazy</ref> such as the cover of the [[Halloween]] issue of ''Life'' 1960.<ref name="dahlin" /> [[William Larson]] pioneered modern artistic uses of strip photography from the late 1960s. [http://golembewski.awardspace.com/ Michael Golembewski] has been a noted practitioner of [[scanography]].

More recently, [http://ansenseale.com/ Ansen Seale]<ref>"[http://ansenseale.com/series_desc.cfm?id=10 X and Time: a dimensional exchange]", [http://ansenseale.com/series.cfm Series], [http://ansenseale.com/series.cfm Ansen Seale Photography]</ref> and [http://www.jaymarkjohnson.com/ Jay Mark Johnson] have used slit cameras for artistic effect,<ref name="slate">{{Cite web
| title = A Very Unusual Camera That Emphasizes Time Over Space
| work = [http://www.slate.com/blogs/behold.html Behold], ''Slate''
| accessdate = 2012-10-16
| first = Judith B.
| last = Herman
| date = Oct. 15, 2012
| url = http://www.slate.com/blogs/behold/2012/10/15/jay_mark_johnson_s_very_unusual_camera_emphasizes_time_over_space.html
}}</ref> while [http://www.sintlukas.be/cms/index.php?option=com_content&view=article&id=248:maarten-vanvolsem-&catid=60:onderzoekers-en-kunstenaars&Itemid=188 Maarten Vanvolsem]<ref>Also: [http://www.intellectbooks.co.uk/journals/view-Contributor,a=V/view-Contact-Page,id=14564/ Maarten Vanvolsem] at [http://www.intellectbooks.co.uk/ Intellect]</ref> has produced art and written academic articles and a book on strip photography. A common subject is dance, which Vanvolsem argues is well-suited to strip photography, as it captures the motion over time.<ref>{{Cite journal
| first = Maarten
| last = Vanvolsem
| url = http://www.imageandnarrative.be/inarchive/Timeandphotography/vanvolsem.html
| title = Motion! On how to deal with the paradox in dance photography.
| journal = Image <nowiki>[&]</nowiki> Narrative
| volume = 23
|date=November 2008
}}</ref>

== Video ==
{{also|Slit-scan photography}}

In [[cinematography]], strip photography can be used manually as a [[special effect]], assembling a video sequence strip-by-strip, particularly in science-fiction movies of the 1960s through 1980s – see [[slit-scan photography]].

Alternatively, a digital video can be sourced to produce either a single strip photograph or an entire video; with the advent of consumer video editing, some amateurs have created such videos, from circa 2008.<ref name="tve">"[http://vimeo.com/26076063 Temporal Video Experiment]", Peter Marquardt ([http://vimeo.com/user362478 lastfuture]), July 6th, 2011</ref><ref name="tvemo">"[http://vimeo.com/26082284 Temporal Video Experiment - Making Of]" Peter Marquardt ([http://vimeo.com/user362478 lastfuture]), July 6th, 2011</ref><ref name="c52">{{cite web
|author=Alex Hunsley
|title=8/52: Video space-time transposition
|archiveurl=http://web.archive.org/web/20081121152954/http://create52.com/blog/2008/08/09/852-video-space-time-transposition/
|archivedate=21 Nov 2008
|url=http://create52.com/blog/2008/08/09/852-video-space-time-transposition/
}}</ref><ref "hunsleyflkr">"[http://www.flickr.com/photos/redlex/sets/72157606249489942/ Video space/time rotation]", Alex Hunsley ([http://www.flickr.com/photos/redlex/ lardus])</ref> For clarity assume that the strips are vertical, so they are lined up horizontally; this is commonly done in actual strip photography, due to the frequency of left-right motion in the real world.<ref name="cbc52">{{cite web
|title=Video space/time transposition
|author=Alex Hunsley
|archiveurl=http://archive.org/details/wiki-cookbookcreate52com
|archivedate=2012-04-08
|url=http://cookbook.create52.com/index.php?title=Video_space/time_transposition
}}</ref> In the latter case, this corresponds to considering the video as a three-dimensional array and [[Transposition (mathematics)|transposing]] one spacial variable with the temporal variable,<ref name="cbc52" /> transforming <math>(x,y,t)</math> to <math>(t,y,x).</math> Assuming ''x'' starts at 0 on the left, as usual, this corresponds to time increasing from left to right; using the opposite convention of time increasing right to left corresponds to adding a reflection, so <math>(x,y,t)</math> to <math>(t_\text{max}-t,y,x),</math> which can also be interpreted as [[rotation]] in the <math>(x,t)</math> plane (followed by a translation).

The output video switches width and number of frames from the input – number of frames in the output is the width of the input, while width of the output is number of frames in the input.<ref name="cbc52" /> For a given resolution, the resulting output video has a fixed height and number of frames, and variable width (depending on the duration of the input video). The duration of the output video is determined by the width (''x''-resolution) of the input frame, which form the frames of the output video, and the frame rate (fps) of the output video, which need not be related to the frame rate of the input video. For example, 1920 × 1080 input images (as in [[1080p]]) output at 24 fps yield 1920/24 = 80 seconds, while at 60 fps yields 1920/60 = 32 seconds. The width of the output video is exactly the number of frames in the input video, hence the frame rate times the duration. A single frame input video (a photo) thus yields a single line of output video, while a very long input video yields a very wide output video, though in both cases they last the same time (assuming the same output frame rate).

As with static strip photography, videos can be produced both in "tableau" format (conventional almost square aspect ratio), or in "strip" format (very wide), and in fact can have exactly the same dimensions as the input video if input frames = input ''x''-resolution (so the <math>(x,y,t)</math> array is square in the <math>(x,t)</math> dimensions); in this case if input and output frame rate are the same, then the input and output videos will have the same duration as well.

Videos in the wide "strip" format can be arbitrarily wide, possibly too wide to fit on a given display. One way to view them is by [[Panning (camera)|panning]] the image horizontally (display only part of the image, panning the frame sideways) while looping through the video.<ref name="tvemo" /> Geometrically this corresponds to replicating the output <math>(t,y,x)</math> array in the third variable, then cutting diagonally. If the frame advances 1 pixel at a time and the output resolution and frame rate are the same as the input, then the entire strip video will be seen and (with technical assumptions on start and end) the output video will be the same resolution and duration as the input. Rather than looping, which introduces a jump, the video can bounce back and forth between endpoints.<ref name="tvemo" />

Many distortion effects can be more clearly understood in video, such as effects of speed and distance, notably parallax. Further, in addition to lengths in the output being inverse to speed in the input, speed in the output is inverse to speed in the input.<ref name="cbc52" /> In the extreme, a stationary point in one strip in the input becomes a stripe across a single frame in the output, approximating crossing the frame at infinite speed. Further, mirrors in the input function as mirrors in the output, and due to parallax (reflections are further away), reflections move faster than the images they are reflecting.<ref name="c52" />

== History ==
Strip photography dates to early panoramic cameras in the 19th century, from 1843.<ref name="vanvolsemjena" /> It was initially used for technical and scientific purposes, with Italian scientist [[Ignazio Porro]] developing a strip-based camera for mapping in 1853; a similar device was developed by the French inventor [[Charles Chevallier]] in the same year.<ref name="vanvolsemjena" /> [[Peripheral photography]] was pioneered by the [[British Museum]] for photographs of [[Greek vase]]s in the late 19th century. The development of aviation allowed [[strip aerial photography]] to replace previous land-based, which was notably used during the [[Palestine campaign]] (1915–18).<ref name="vanvolsemjena" /> Photo finish cameras were used from 1937 onward,<ref name="vanvolsemjena" /> and strip photography was used in [[synchroballistic photography]] for [[ballistics]] research. Artistic uses have occurred since the 1960s, with the pioneering work of George Silk, and markedly increased since the 1980s, though irregularly, with practitioners often rediscovering the technique independently and being unaware of the history.<ref name="vanvolsemjena" /> The articles of Andrew Davidhazy from the 1970s have provided both a scientific background and technical guide for constructing strip cameras and engaging in strip photography.<ref name="vanvolsemjena" />

== Gallery ==
<gallery>
File:Stevemann selfportrait home-made slit-shutter camera1992.png|[[Peripheral photography]] of a head, with changing expression
File:Triple dead-heat.jpg|[[Photo finish]]
File:Waving goodbye.jpg|[[Scanography]]
</gallery>

== References ==
{{reflist}}
{{refbegin}}
* {{cite doi|10.1386/jvap.4.1.49/1}}
* {{Cite book
| publisher = Leuven University Press
| isbn = 978-90-5867-840-9
| last = Vanvolsem
| first = Maarten
| title = The Art of Strip Photography: Making Still Images with a Moving Camera
| location = Leuven
| series = Lieven Gevaert Series
| date = 2011-07
| url = http://upers.kuleuven.be/en/titel/9789058678409
}}
* "[http://people.rit.edu/andpph/text-strip-basics.html Basics of Strip Photography]", [http://www.davidhazy.org/andpph Andrew Davidhazy] ([http://people.rit.edu/andpph/articles.html Articles])
{{refend}}

== External links ==
* "[http://lemagazine.jeudepaume.org/blogs/hildevangelder/2011/05/27/the-art-of-strip-photography-making-still-images-with-a-moving-camera/ The Art of Strip Photography]", [http://lemagazine.jeudepaume.org/blogs/hildevangelder/ Hilde Van Gelde], 2011 May 27

[[Category:Photographic techniques]]

Touschek effect - Revision history

en>CmdrObot: sp: et. al.→et al.