Editing Slow motion (section)

== How slow motion works ==

There are two ways in which slow motion can be achieved in modern cinematography. Both involve a camera and a projector. A projector refers to a classical film projector in a movie theater, but the same basic rules apply to a television screen and any other device that displays consecutive images at a constant frame rate.<ref>{{cite book | doi=10.1007/978-90-481-2642-2_237 | chapter=Hindu Kush | title=Encyclopedia of Snow, Ice and Glaciers | series=Encyclopedia of Earth Sciences Series | date=2011 | last1=Shroder | first1=John F. | pages=523–525 | isbn=978-90-481-2641-5 }}</ref>
[[Image:OvercrankingTimeline.png|thumb|upright=2]]

=== Overcranking ===
For purposes of making the above illustration readable, a projection speed of 10 frames per second ([[frames per second|fps]]) has been selected (the 24{{nbsp}}[[frames per second|fps]] film standard makes slow overcranking rare but nevertheless available on professional equipment).<ref>{{cite web|url=https://www.sony.co.uk/pro/product/broadcast-products-camcorders-digital-motion-picture-camera/f23/overview/|title=Sony F23: Three 2/3-in CCD sensors with B4 lens mount CineAlta camera (discontinued)|website=Sony UK}} Offers frame rates of 1-60 [[frames per second|fps]]</ref>
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[[File:Time stretching.png|thumb|upright=2| Frames marked with an X must be fabricated.]]

=== Time stretching ===
The second type of slow motion is achieved during post production.  This is known as ''time-stretching'' or ''digital slow motion''. This type of slow motion is achieved by inserting new frames in between frames that have actually been photographed. The effect is similar to overcranking as the actual motion occurs over a longer time.
 
Since the necessary frames were never photographed, new frames must be fabricated. Sometimes the new frames are simply repeats of the preceding frames but more often they are created by interpolating between frames. (Often this [[motion interpolation]] is, effectively, a short [[Dissolve (film)|dissolve]] between still frames). Many complicated algorithms exist that can track motion between frames and generate intermediate frames within that scene. It is similar to half-speed, and is not true slow-motion but merely a longer display of each frame.