Video feedback
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Video feedbackis the process that starts and continues when avideo camerais pointed at its own playbackvideo monitor.The loop delay from camera to display back to camera is at least onevideoframe time, due to the input and output scanning processes; it can be more if there is more processing in the loop.
History[edit]
First discovered shortly afterCharlie Ginsburginvented the first video recorder forAmpexin 1956, video feedback was considered a nuisance and unwanted noise.[citation needed]Technicians and studio camera operators were chastised for allowing a video camera to see its own monitor as the overload of self-amplified video signal caused significant problems with the 1950s video pickup, often ruining the pickup.[citation needed]It could also causescreen burn-inon television screens and monitors of the time as well, by generating static brightly illuminated display patterns.
In the 1960s early examples of video feedback art became introduced into thepsychedelic artscene inNew York City.Nam June Paikis often cited as the firstvideo artist;he had clips of video feedback on display in New York City at theGreenwich Cafein the mid 1960s.
Early video feedback works were produced by media artist experimenters on the East and West Coasts of North America in the late 1960s and early 1970s. Video feedback artistsSteina and Woody Vasulka,withRichard Lowenbergand others, formed The Kitchen, which was located in the kitchen of a broken-down hotel in lower Manhattan; whileSkip Sweeneyand others founded Video Free America inSan Francisco,to nurture their video art and feedback experiments.
David Sohnmentions video feedback in his 1970 bookFilm, the Creative Eye.This book was part of the base curriculum forRichard LedererofSt. Paul's SchoolinConcord, New Hampshire,when he made video feedback part of an English curriculum in his 1970s course Creative Eye in Film. Several students in this class participated regularly in the making and recording of video feedback.Sonyhad released the VuMax series of recording video cameras and manually "hand-looped" video tape decks by this time which did two things: it increased the resolution of the video image, which improved picture quality, and it made video tape recording technology available to the general public for the first time and allowed for such video experimentation by anyone.
During the 1980s and into the 1990s video technology became enhanced and evolved into high quality, high definition video recording.Michael C. Andersengenerated the first known mathematical formula of the video feedback process,[1]and he has also generated aMendeleev's square to show the gradual progressive formulaic change of the video image as certain parameters are adjusted.[2]
In the 1990s the rave scene and a social return to art of a more psychedelic nature brought back displays of video feedback on large disco dance floor video screens around the world. There are filters for Adobe Photoshop and non-linear video editors that often have video feedback as the filter description, or as a setting on a filter. These filter types either mimic or directly utilize video feedback for its result effect and can be recognized by its vortex, phantasmagoric manipulation of the original recorded image.
In entertainment[edit]
Many artists have used optical feedback. A famous example isQueen'smusic video for "Bohemian Rhapsody"(1975). The effect (in this simple case) can be compared to looking at oneself between two mirrors.
Other videos that use variations of video feedback include:
- Doctor Who–An Unearthly Child(series, 1963–1973, opening title sequence.)
- Earth, Wind & Fire— "September"(1978)
- The Jacksons– "Blame It On the Boogie"(1978)
- Kate Bush– "Hammer Horror"(1978)
- Amii Stewart– "Knock on Wood"(1979)
- Kool & the Gang– "Get Down On It"(1981)
- Todd Rundgren– "Something to Fall Back On" (1985)
- Smashing Pumpkins– "Ava Adore"(1998)
- Klaxons– "Gravity's Rainbow"(2008)
- Boxcutter– "TV Troubles" (2011)
- Django Django– "Life's A Beach" (2012)
"Howl-around" and Doctor Who title sequence[edit]
This technique—under the name "howl-around" —was employed for the opening titles sequence for the Britishscience fictionseriesDoctor Who,[3]which employed this technique from 1963 to 1973.
Initially this was in black and white, and redone in 1967 to showcase the show's new625-linebroadcast resolution and feature theDoctor's face (Patrick Troughtonat that time). It was redone again, in colour this time, in 1970. The next title sequence for the show, which debuted in 1973, abandoned this technique in favour ofslit-scan photography.
In science[edit]
An example of optical feedback in science is theoptical cavityfound in almost everylaser,which typically consists of two mirrors between which light is amplified. In the late 1990s it was found that so-called unstable-cavity lasers produce light beams whose cross-section present a fractal pattern.[4]
Optical feedback in science is often closely related to video feedback, so an understanding of video feedback can be useful for other applications of optical feedback. Video feedback has been used to explain the essence of fractal structure of unstable-cavity laser beams.[5]
Video feedback is also useful as an experimental-mathematics tool. Examples of its use include the making ofFractalpatterns using multiple monitors, and multiple images produced using mirrors.
Optical feedback is also found in theimage intensifiertube and its variants. Here the feedback is usually an undesirable phenomenon, where the light generated by the phosphor screen "feeds back" to the photocathode, causing the tube to oscillate, and ruining the image. This is typically suppressed by an aluminum reflective screen deposited on the back of the phosphor screen, or by incorporating amicrochannel plate detector.
Optical feedback has been used experimentally in these tubes to amplify an image, in the manner of the cavity laser, but this technique has had limited use.
Optical feedback has also been experimented with as an electron source, since a photocathode-phosphor cell will 'latch' when triggered, providing a steady stream of electrons. See US Patent 4,531,122 for a typical application.
In philosophy[edit]
Douglas Hofstadterdiscusses video feedback in his bookI Am a Strange Loopabout the human mind and consciousness. He devotes a chapter to describing his experiments with video feedback.
At some point during the session, I accidentally stuck my hand momentarily in front of the camera's lens. Of course the screen went all dark, but when I removed my hand, the previous pattern did not just pop right back onto the screen, as expected. Instead I saw a different pattern on the screen, but this pattern, unlike anything I'd seen before, was not stationary.[6]
See also[edit]
- Audio/Acoustic feedback
- Computer graphics
- Cymatics
- Droste effect
- Feedback
- Real-time computer graphics
- Recursion
- Self-reference
- Strange loop
- Video art
References[edit]
- ^"Formula for Videofeedback"ArchivedJuly 19, 2011, at theWayback Machine.videofeedback.dk. Retrieved 2010-12-28.
- ^"Simulation of video feedback"ArchivedOctober 7, 2009, at theWayback Machine.videofeedback.dk. Retrieved 2010-12-28.
- ^"Obituaries: Norman Taylor: Creator of the 'howl-around' visual in the original 'Dr Who' title sequence".independent.co.uk.2011-03-10. Archived fromthe originalon 2011-05-31.Retrieved2022-01-21.
Long before the days of hi-tech special effects, Norman Taylor accidentally created the swirling "howl-around" visual seen in the original, 1963 title sequence of Doctor Who – by pointing a camera at a monitor showing its own picture.
- ^Karman, G. P.; McDonald, G. S.; New, G. H. C.;Woerdman, J. P.(1999)."Fractal modes in unstable resonators".Nature.402(6758): 138.doi:10.1038/45960.S2CID205046813.
- ^"Fractal video feedback"ArchivedMay 20, 2011, at theWayback Machine.Optics Group (University of Glasgow). Retrieved 2010-12-28.
- ^Hofstadter, Douglas (2007).I Am a Strange loop.New York: Basic Books. p.67.ISBN978-0-465-03079-8.
