Frame rate

"Update rate" redirects here. It is not to be confused with RAM update rate.
"Burst rate" redirects here. It is not to be confused with Burstable rate.

Frame rate, also known as frame frequency, is the frequency (rate) at which an imaging device displays consecutive images called frames. The term applies equally to film and video cameras, computer graphics, and motion capture systems. Frame rate is expressed in frames per second (FPS).

Background

The human eye and its brain interface, the human visual system, can process 10 to 12 separate images per second, perceiving them individually.[1] The threshold of human visual perception varies depending on what is being measured. When looking at a lighted display, people begin to notice a brief interruption of darkness if it is about 16 milliseconds or longer.[2] Observers can recall one specific image in an unbroken series of different images, each of which lasts as little as 13 milliseconds.[3] When given very short single-millisecond visual stimulus people report a duration of between 100 ms and 400 ms due to persistence of vision in the visual cortex. This may cause images perceived in this duration to appear as one stimulus, such as a 10 ms green flash of light immediately followed by a 10 ms red flash of light perceived as a single yellow flash of light.[4] Persistence of vision may also create an illusion of continuity, allowing a sequence of still images to give the impression of motion.

Early silent films had stated frame rates anywhere from 16 to 24 FPS,[5] but since the cameras were hand-cranked, the rate often changed during the scene to fit the mood. Projectionists could also change the frame rate in the theater by adjusting a rheostat controlling the voltage powering the film-carrying mechanism in the projector.[6] Silent films were often intended to be shown at higher frame rates than those used during filming.[7] These frame rates were enough for the sense of motion, but it was perceived as jerky motion. By using projectors with dual- and triple-blade shutters, the rate was multiplied two or three times as seen by the audience. Thomas Edison said that 46 frames per second was the minimum needed by the visual cortex: "Anything less will strain the eye."[8][9] In the mid to late 1920s, the frame rate for silent films increased to between 20 and 26 FPS.[8]

When sound film was introduced in 1926, variations in film speed were no longer tolerated as the human ear is more sensitive to changes in audio frequency. Many theaters had shown silent films at 22 to 26 FPS which is why 24 FPS was chosen for sound. From 1927 to 1930, as various studios updated equipment, the rate of 24 FPS became standard for 35 mm sound film.[1] At 24 FPS the film travels through the projector at a rate of 456 millimetres (18.0 in) per second. This allowed for simple two-blade shutters to give a projected series of images at 48 per second, satisfying Edison's recommendation. Many modern 35 mm film projectors use three-blade shutters to give 72 images per second—each frame is flashed on screen three times.[8]

However recent studies have shown that the Retina actually juggles when processing information. In 2014, it was shown during research that the human eye could see at various frame rates varying from person to person.[10] It is still unsettled on what the average "frame rate" of the human eye is, but so far based on recent studies within the last decade, show the human eye seeing anywhere between 75 to 150 fps with an average of about 140 fps.

Motion picture film

In the motion picture industry, where traditional film stock is used, the industry standard filming and projection formats are 24 frames per second (FPS). Shooting at a slower frame rate would create fast motion when projected, while shooting at a frame rate higher than 24 FPS would create slow motion when projected. Other examples of historical experiments in frame rates that were not widely accepted were Maxivision 48 and Showscan, developed by 2001: A Space Odyssey special effects creator Douglas Trumbull.

The silent home movie film frame rate was 16 FPS or 18 FPS for 16 mm and standard 8 mm, 18 FPS for Super 8. Sound speed was normally 24 FPS for all formats. Yet it was possible to record sound at 18 FPS on super 8, but with bad results.

Digital video and television

There are three main frame rate standards in the TV and digital cinema business: 24p, 25p, and 30p. However, there are many variations on these as well as newer emerging standards.

See also

References

  1. 1 2 Read, Paul; Meyer, Mark-Paul; Gamma Group (2000). Restoration of motion picture film. Conservation and Museology. Butterworth-Heinemann. pp. 24–26. ISBN 0-7506-2793-X.
  2. ↑ Andrew B. Watson (1986), "Temporal sensitivity" (PDF), Handbook of Perception and Human Performance (Wiley)
  3. ↑ "Detecting meaning in RSVP at 13 ms per picture". SpringerLink. December 28, 2013.
  4. ↑ Robert Efron. "Conservation of temporal information by perceptual systems". Perception & Psychophysics 14 (3): 518–530. doi:10.3758/bf03211193.
  5. ↑ Brown, Julie (2014). "Audio-visual Palimpsests: Resynchronizing Silent Films with 'Special' Music". In David Neumeyer. The Oxford Handbook of Film Music Studies. Oxford University Press. p. 588. ISBN 0195328493.
  6. ↑ Kerr, Walter (1975). Silent Clowns. Knopf. p. 36. ISBN 0394469070.
  7. ↑ Card, James (1994). Seductive cinema: the art of silent film. Knopf. p. 53. ISBN 0394572181.
  8. 1 2 3 4 Brownlow, Kevin (Summer 1980). "Silent Films: What Was the Right Speed?". Sight & Sound 49 (3): 164–167. Archived from the original on 8 July 2011. Retrieved 2 May 2012.
  9. ↑ Thomas Elsaesser, Thomas Elsaesser; Barker, Adam (1990). Early cinema: space, frame, narrative. BFI Publishing. p. 284. ISBN 0-85170-244-9.
  10. ↑ http://www.extremetech.com/extreme/196406-retinal-jiggles-why-your-eyes-and-brain-strongly-prefer-games-at-60-fps
  11. ↑ "How many cels does a typical cartoon yield?"
  12. ↑ Todd-AO Specifications at a Glance, Widescreen Museum.
  13. ↑ Giardina, Carolyn (March 30, 2011). "James Cameron 'Fully Intends' to Make 'Avatar 2 and 3' at Higher Frame Rates". The Hollywood Reporter. Retrieved April 4, 2010.
  14. ↑ Jackson, Peter (12 April 2011). "48 Frames Per Second". Peter Jackson's Facebook page. Facebook. Retrieved 12 April 2011.
  15. ↑ Walters, Florence (25 April 2012). "The Hobbit previews to mixed reactions". The Daily Telegraph (London). Retrieved 30 April 2012.
  16. ↑ Gary Edgerton, The Columbia History of American Television, Columbia University Press, 2009, p. 51–52. ISBN 978-0-231-12165-1.
  17. ↑ Hoffmann, Hans; Takebumi Itagaki; David Wood; Alois Bock (December 2006). "Studies on the Bit Rate Requirements for a HDTV Format With 1920 × 1080 pixel Resolution, Progressive Scanning at 50 Hz Frame Rate Targeting Large Flat Panel Displays" (PDF). IEEE Transactions on Broadcasting 52 (4): 420–434. doi:10.1109/tbc.2006.884735.
  18. ↑ "10 Things You Need to Know about 1080p50" (PDF). EBU Technical.
  19. ↑ Snell & Willcox
  20. 1 2 List of 120Hz Monitors – Includes 144Hz, 240Hz
  21. ↑ High Frame-Rate Television, BBC White Paper WHP 169, September 2008, M Armstrong, D Flynn, M Hammond, S Jolly, R Salmon

External links

This article is issued from Wikipedia - version of the Wednesday, February 10, 2016. The text is available under the Creative Commons Attribution/Share Alike but additional terms may apply for the media files.