Slow motion

Source: Wikipedia, the free encyclopedia.
"SloMo" redirects here. For other uses, see SloMo (disambiguation) and Slow motion (disambiguation).
Slow motion video of a glass cup smashing on a concrete floor

Slow motion (commonly abbreviated as slo-mo or slow-mo) is an effect in film-making whereby

fps
, or in post production through the use of software.

Typically this style is achieved when each

rate much faster than it will be played back. When replayed at normal speed, time appears to be moving more slowly. A term for creating slow motion film is overcranking which refers to hand cranking an early camera at a faster rate than normal (i.e. faster than 24 frames per second). Slow motion can also be achieved by playing normally recorded footage at a slower speed. This technique is more often applied to video subjected to instant replay than to film. A third technique uses computer software post-processing to fabricate digitally interpolated frames between the frames that were shot. Motion can be slowed further by combining techniques, such as for example by interpolating between overcranked frames. The traditional method for achieving super-slow motion is through high-speed photography, a more sophisticated technique that uses specialized equipment to record fast phenomena, usually for scientific applications
.

Slow motion is ubiquitous in modern filmmaking. It is used by a diverse range of directors to achieve diverse effects. Some classic subjects of slow-motion include:

Slow motion can also be used for artistic effect, to create a romantic or suspenseful aura or to stress a moment in time.

director Sam Peckinpah was another classic lover of the use of slow motion. The technique is especially associated with explosion effect shots and underwater footage.[citation needed
]

The opposite of slow motion is

time lapse photography
; a frame of, say, a growing plant is taken every few hours; when the frames are played back at normal speed, the plant is seen to grow before the viewer's eyes.

The concept of slow motion may have existed before the invention of the motion picture: the Japanese theatrical form Noh employs very slow movements.

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.[1]

Overcranking

For purposes of making the above illustration readable, a projection speed of 10 frames per second (

fps film standard makes slow overcranking rare but nevertheless available on professional equipment).[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

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.

In action films

Speed ramping 120
fps

Slow motion is used widely in action films for dramatic effect, as well as the famous bullet-dodging effect, popularized by The Matrix. Formally, this effect is referred to as speed ramping and is a process whereby the capture frame rate of the camera changes over time. For example, if in the course of 10 seconds of capture, the capture frame rate is adjusted from 60 frames per second to 24 frames per second, when played back at the standard film rate of 24 frames per second, a unique time-manipulation effect is achieved. For example, someone pushing a door open and walking out into the street would appear to start off in slow motion, but in a few seconds later within the same shot the person would appear to walk in "realtime" (everyday speed). The opposite speed-ramping is done in The Matrix when Neo re-enters the Matrix for the first time to see the Oracle. As he comes out of the warehouse "load-point", the camera zooms into Neo at normal speed but as it gets closer to Neo's face, time seems to slow down, perhaps visually accentuating Neo pausing and reflecting a moment, and perhaps alluding to future manipulation of time itself within the Matrix later on in the movie.

In broadcasting

Slow-motion is widely used in sport broadcasting and its origins in this domain extend back to the earliest days of television, one example being the European Heavyweight Title in 1939 where Max Schmeling knocked out Adolf Heuser in 71 seconds.[3]

HS-100 at DC Video, [1]

In

fps
can be converted to both 50 and 60 fps transmission formats without major issues.

Scientific use

Main articles: High-speed photography § Video, and High-speed camera

In scientific and technical applications it is often necessary to slow motion by a very large factor, for example to examine the details of a nuclear explosion. Examples are sometimes published showing, for example, a bullet bursting a balloon.

Video file recording methods

Usually,

high framerate video
) into the video file: the real-time method and the menial method.

Real-time method

The real time method treats the video as a normal video while encoding it. The output video file contains the same framerate as the

framerate
. The duration of the video in the output file also matches the real-life recording duration. And the output video also contains an audio track, like usual videos.

This method is used by all

Galaxy S6
) for videos with 120 fps or higher.

Every

Galaxy Note 3 (late 2013) with 1080p at 60 fps,[5]
labelled "smooth motion"), recorded it using the real-time method.

Advantages

These advantages make the real-time method the more useful method for

power users
.

Menial method

The menial method saves recorded video files in a stretched way, and also without audio track. The framerate in the output file does not match the original sensor output framerate, but the former is lower. The real-life timespan of the recording (while holding the camera) does not match the length of the video in the output file, but the latter is longer. The opposite is the case for

time-lapse
videos, where the effectively saved framerate is lower than for normal videos

This means that the action visible inside the video runs at slower speeds than in real life, despite the indicated playback speed of ×1.

This encoding method is used by the camera software of the following devices (incomplete list):

Advantages
  • The output video file is directly playable as slow motion in video players that do not support adjusting the playback speed (e.g. on a
    Galaxy S3 Mini
    ).
  • The output video file is directly playable in video players and/or on devices that can only handle limited framerates (e.g. on a
    Galaxy S3 Mini
    ).

Comparison

Example

A 120

Note 4
(example devices that use the menial method for 120fps video recording).

In this example, the real-time-method recording device can be an

Xperia Z5
.

This table also includes references from other video recording types (normal, low-framerate,

time-lapse
) to facilitate understanding for novice people.

🎬
Encoding
mode		 Complies with real-time? 📹 Exemplary
framerate
 Effectively saved framerate
Relative to real-life time		 🎞️📝 Output video file framerate 🕒🎥 Exemplary real-life recording duration 🕒📽️ Output video duration Total number of recorded frames 🎤 Audio recorded?
🎞️ Slow-motion ½ (menial ×1/2) ✗ 120fps   60fps (because half truncated)   30fps (60fps if no frames truncated) 00:00:10 00:00:20 600 (1200 if no frames truncated) No 🔇
🎞️ Slow-motion ¼ (menial ×1/4) ✗ 120fps 120fps   30fps 00:00:10 00:00:40 1200 No 🔇
🎞️ Slow-motion ⅛ (menial ×1/8) ✗ 120fps 120fps   15fps 00:00:10 00:01:20 (80 seconds) 1200 No 🔇
🎞️ Real-time slow-motion[a] (HFR) ✓ 120fps 120fps 120fps 00:00:10 00:00:10 1200 Yes 🔊
🎞️
Normal video
(as reference)		 ✓ 30fps[b] 30fps 30fps 00:00:10 00:00:10 300 Yes 🔊
🎞️ Low-framerate (as reference)[c][d][e] ✓ 10fps 10fps 10fps 00:00:10 00:00:10 100 Yes 🔊 [f]
🎞️
Time-Lapse
(×4) (opposite example reference)		 ✗ (menial)[g] 30fps (for digital viewfinder preview) 7.5 fps 30fps 00:00:10 00:00:02.500ms 75 No 🔇
🎞️ Time-Lapse (×8) (opposite example reference) ✗ (menial) 30fps (for digital viewfinder preview) 3.75 fps 30fps 00:00:10 00:00:01.250ms 37.5 No 🔇

Notes

  1. computer monitors
    that support displaying higher framerates (i.e. gaming monitors).
  2. ^ Some cameras might use/offer variable frame rates, although it is less common than constant framerates.
  3. surveillance cameras
    . It might also be 5 fps, but 10 fps is most suitable for this example.
  4. time-lapse
    .
  5. ^ Some cameras might record at lower framerates due to technical limitations, e.g. the Panasonic Lumix DMC-CM1 records 2160p@15fps instead of the usual 30fps, likely due to insufficient processing performance. On the Lumix CM1, 30fps can only be achieved at lower video resolutions such as 1080p.
  6. CCTV
    's record audio, but they do usually.
  7. ^ In this example, the time lapse video gets saved in a sped-up (condensed) way, in the same way it is elongated in the menial slow motion method. One second of playback at an indicated playback speed of ×1 shows 4 seconds of real-life action.

See also

References

  1. ISBN 978-90-481-2641-5
    .
  2. fps
  3. ^ Kloft, Michael (Director) (1999). Das Fernsehen unter dem Hakenkreuz (Documentary). Germany: Spiegel TV.
  4. ^ Asus PadFone 2 on GSMarena
  5. ^ Specifications of the Samsung Galaxy Note 3 at GSMArena.
  6. ^ Samsung GT-i8000 Omnia II review: "A surprising experience" – Page 1: Introduction.
  7. ^ PhoneArena review: Samsung Omnia 2 GT-i8000 – Page 3: "Camera, multimedia and software".
  8. ^ Sony FDR-AX100 user manual (help guide) page 93: "This product records approximately 3-second-long fast actions or motions as an approximately 12-second-long slow-motion movie."
  9. ^ GSMArena: "OnePlus One review: When opportunity strikes" – Page 8: "Camera and video": "And finally here's a 720p video at 120 fps – slow motion. The phone captures the footage at 120 fps but then renders it in-house to 30 fps […]."

External links

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