Optical feedback
Encyclopedia
Optics
Optics is the branch of physics which involves the behavior and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behavior of visible, ultraviolet, and infrared light...
equivalent of acoustic feedback. A simple example is the feedback
Feedback
Feedback describes the situation when output from an event or phenomenon in the past will influence an occurrence or occurrences of the same Feedback describes the situation when output from (or information about the result of) an event or phenomenon in the past will influence an occurrence or...
that occurs when a loop exists between an optical input, e.g., a video camera
Video camera
A video camera is a camera used for electronic motion picture acquisition, initially developed by the television industry but now common in other applications as well. The earliest video cameras were those of John Logie Baird, based on the electromechanical Nipkow disk and used by the BBC in...
, and an optical output, e.g., a television screen
Television
Television is a telecommunication medium for transmitting and receiving moving images that can be monochrome or colored, with accompanying sound...
or monitor
Video monitor
A video monitor also called a broadcast monitor, broadcast reference monitor or just reference monitor, is a display device similar to a television set, used to monitor the output of a video-generating device, such as playout from a video server, IRD, video camera, VCR, or DVD player. It may or...
. (A simple example of optical feedback is also an image cast between mirror
Mirror
A mirror is an object that reflects light or sound in a way that preserves much of its original quality prior to its contact with the mirror. Some mirrors also filter out some wavelengths, while preserving other wavelengths in the reflection...
s.)
In the GIF
GIF
The Graphics Interchange Format is a bitmap image format that was introduced by CompuServe in 1987 and has since come into widespread usage on the World Wide Web due to its wide support and portability....
movie, and the JPEG
JPEG
In computing, JPEG . The degree of compression can be adjusted, allowing a selectable tradeoff between storage size and image quality. JPEG typically achieves 10:1 compression with little perceptible loss in image quality....
still image examples (right), light from a candle is received by a video camera, amplified
Amplifier
Generally, an amplifier or simply amp, is a device for increasing the power of a signal.In popular use, the term usually describes an electronic amplifier, in which the input "signal" is usually a voltage or a current. In audio applications, amplifiers drive the loudspeakers used in PA systems to...
and then sent by cable to a monitor projecting electron
Electron
The electron is a subatomic particle with a negative elementary electric charge. It has no known components or substructure; in other words, it is generally thought to be an elementary particle. An electron has a mass that is approximately 1/1836 that of the proton...
beams to a monitor screen. The image on the monitor is then captured by the video camera again, and fed back to the monitor in a continuous loop.
The original light source, in this case from the candle, can then be extinguished, while the feedback loop continues. For each loop the image is doubled and the image interferes with itself. The electronic loop moves with near light speed
Speed of light
The speed of light in vacuum, usually denoted by c, is a physical constant important in many areas of physics. Its value is 299,792,458 metres per second, a figure that is exact since the length of the metre is defined from this constant and the international standard for time...
, but as the resulting image is projected onto the phosphor
Phosphor
A phosphor, most generally, is a substance that exhibits the phenomenon of luminescence. Somewhat confusingly, this includes both phosphorescent materials, which show a slow decay in brightness , and fluorescent materials, where the emission decay takes place over tens of nanoseconds...
dots on the inside of the screen by the electron beam, the phosphor points take time to begin and stop glowing, and this creates a persistence which prevents the patterns changing too fast, and thus they survive long enough to be perceived. (More recent types of screens, such as plasma display
Plasma display
A plasma display panel is a type of flat panel display common to large TV displays or larger. They are called "plasma" displays because the technology utilizes small cells containing electrically charged ionized gases, or what are in essence chambers more commonly known as fluorescent...
, LCD and LED
LEd
LEd is a TeX/LaTeX editing software working under Microsoft Windows. It is a freeware product....
, can also be used)).
The resulting images depend on different camera and monitor settings, such as light amplification, contrast, distance, angle and physical vibrations. Optical feedback can be combined with music, or other sound sources, to influence the image loop.
Video feedback
Video feedback or videofeedback is the process that starts and continues when a video cameraVideo camera
A video camera is a camera used for electronic motion picture acquisition, initially developed by the television industry but now common in other applications as well. The earliest video cameras were those of John Logie Baird, based on the electromechanical Nipkow disk and used by the BBC in...
is pointed at its playback video monitor
Video monitor
A video monitor also called a broadcast monitor, broadcast reference monitor or just reference monitor, is a display device similar to a television set, used to monitor the output of a video-generating device, such as playout from a video server, IRD, video camera, VCR, or DVD player. It may or...
. The image from the camera is delayed slightly in time as it travels through the extensive circuitry of the recording system and then is output to the video playback monitor.
History
First discovered shortly after Charlie Ginsburg invented the first video recorder for AmpexAmpex
Ampex is an American electronics company founded in 1944 by Alexander M. Poniatoff. The name AMPEX is an acronym, created by its founder, which stands for Alexander M. Poniatoff Excellence...
in 1956, video feedback was considered a nuisance and unwanted noise. Technicians and studio camera people were chastised for allowing a video camera to see its own monitor as the overload of self amplified video signal wreaked havoc with the 1950s video pickup, often ruining the pick up. It could also leave a video "burn" on a playback TV and/or monitors of the time as well.
In the 1960s early examples of videofeedback art become introduced into the psychedelic art
Psychedelic art
Psychedelic art is any kind of visual artwork inspired by psychedelic experiences induced by drugs such as LSD, mescaline, and psilocybin. The word "psychedelic" "mind manifesting". By that definition all artistic efforts to depict the inner world of the psyche may be considered "psychedelic"...
scene in New York City
New York City
New York is the most populous city in the United States and the center of the New York Metropolitan Area, one of the most populous metropolitan areas in the world. New York exerts a significant impact upon global commerce, finance, media, art, fashion, research, technology, education, and...
. Nam June Paik
Nam June Paik
Nam June Paik was a Korean American artist. He worked with a variety of media and is considered to be the first video artist....
is often cited as the first video art
Video art
Video art is a type of art which relies on moving pictures and comprises video and/or audio data. . Video art came into existence during the 1960s and 1970s, is still widely practiced and has given rise to the widespread use of video installations...
ist, although this is disputed, and had clips of videofeedback on display in New York City at the Greenwich Cafe in the mid 1960s.
Early videofeedback works were created by media artist/experimenters on the East and West Coasts in the late 1960s and early 70's. Videofeedback artists Woody and Steina Vasulkas, with Richard Lowenberg and others, formed the The Kitchen, which was located in the kitchen of a broken-down hotel in lower Manhattan; while Skip Sweeney and others founded Video Free America in San Francisco, to nurture their video art and feedback experiments.
David Sohn mentions videofeedback in his 1970 book Film, the Creative Eye. This book was part of the base curriculum for Richard Lederer
Richard Lederer
Richard Lederer is an American author, speaker, and teacher best known for his books on word play and the English language and his use of oxymorons...
of St. Paul's School
St. Paul's School (Concord, New Hampshire)
St. Paul's School is a highly selective college-preparatory, coeducational boarding school in Concord, New Hampshire affiliated with the Episcopal Church. The school is one of only six remaining 100% residential boarding schools in the U.S. The New Hampshire campus currently serves 533 students,...
in Concord, New Hampshire
Concord, New Hampshire
The city of Concord is the capital of the state of New Hampshire in the United States. It is also the county seat of Merrimack County. As of the 2010 census, its population was 42,695....
, when he introduced making videofeedback as 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 videofeedback. Sony
Sony
, commonly referred to as Sony, is a Japanese multinational conglomerate corporation headquartered in Minato, Tokyo, Japan and the world's fifth largest media conglomerate measured by revenues....
had released the VuMax series of recording video cameras and manually "hand-looped" video tape decks by this time which did 2 things; it increased the resolution of the video image, which made the picture prettier to behold, and it brought video tape recording technology within the general public's grasp for the first time and allowed for such video experimentation to take place by the general public.
During the 1980s and into the 1990s video technology became enhanced and evolved into high quality, high definition video recording. Michael C. Andersen generated the first known mathematical formula of the videofeedback process, and he has also generated a Mendeleev's square to show the gradual progressive formulaic change of the video image as certain parameters are adjusted.
In the 1990s the rave scene and a social return to art of a more psychedelic nature brought back displays of videofeedback on large disco dance floor video screens around the world. There are filters for Adobe Photoshop and non linear video editors that often have videofeedback as the filter description, or as a setting on a filter. These filter types either mimic or directly utilize videofeedback for its result effect and can be recognized by its vortex, phatasmagoric manipulation of the original recorded image.
In entertainment
Many artists have used optical feedback. An example is Queen'sQueen (band)
Queen are a British rock band formed in London in 1971, originally consisting of Freddie Mercury , Brian May , John Deacon , and Roger Taylor...
music video for "Bohemian Rhapsody
Bohemian Rhapsody
"Bohemian Rhapsody" is a song by the British rock band Queen. It was written by Freddie Mercury for the band's 1975 album A Night at the Opera...
" (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:
- The Jacksons - Blame It On the BoogieBlame It on the Boogie"Blame It on the Boogie" is a disco song, originally released in 1978 both by English singer-songwriter Mick Jackson as well as by The Jacksons , and was later also covered by numerous other artists.-Background:...
(1978) - Kate BushKate BushKate Bush is an English singer-songwriter, musician and record producer. Her eclectic musical style and idiosyncratic vocal style have made her one of the United Kingdom's most successful solo female performers of the past 30 years.In 1978, at the age of 19, Bush topped the UK Singles Chart...
- Hammer HorrorHammer Horror (song)"Hammer Horror" was Kate Bush's third single release and first single from her second album Lionheart. It was released on 27 October 1978. Following the top ten success of her first two singles, this charted at a much lower #44 in the UK singles chart. The parent album released a few weeks later...
(1978) - Amii StewartAmii StewartAmy 'Amii' Paulette Stewart is an American contemporary R&B/disco/dance-pop singer, dancer and actress most famous for her hit disco record "Knock on Wood". Stewart is the stepsister of actress-singer Miquel Brown and aunt to Brown's actress-singer daughter Sinitta.-Career:Amy Stewart was the...
- Knock on WoodKnock on Wood (song)"Knock on Wood" is a hit 1966 song written by Eddie Floyd and Steve Cropper and originally performed by Eddie Floyd. The Eddie Floyd version peaked at number twenty-eight on the Hot 100, and spent one week at number one on the soul singles....
(1979) - Kool & the GangKool & the GangKool & the Gang are an American jazz, R&B, soul, and funk group, originally formed as the Jazziacs in Jersey City, New Jersey in 1964.They went through several musical phases during the course of their recording career, starting out with a purist jazz sound, then becoming practitioners of R&B and...
- Get Down On ItGet Down on It"Get Down on It" is a song originally recorded by the funk/R&B/pop band Kool & The Gang on their album Something Special in 1981. The song reached number 10 on the Billboard charts in early 1982, displaying some of the characteristics of a blend of pop and funk, with the title of the song repeating...
(1981) - Todd RundgrenTodd RundgrenTodd Harry Rundgren is an American multi-instrumentalist, songwriter and record producer. Hailed in the early stage of his career as a new pop-wunderkind, supported by the certified gold solo double LP Something/Anything? in 1972, Todd Rundgren's career has produced a diverse range of recordings...
- Something to Fall Back On (1985) - Smashing Pumpkins - Ava AdoreAva Adore"Ava Adore" is a song by American alternative rock band The Smashing Pumpkins. It was the first single from their fourth album, Adore, and exhibited a new sound from the band which integrated traditional instruments with loops and electronic music. "Ava Adore" and the B-sides were written by Billy...
(1998) - KlaxonsKlaxonsKlaxons are a British indie rock band, based in London. Following the release of numerous 7-inch singles on different independent record labels, as well as the success of previous singles "Magick" and "Golden Skans", the band released their debut album, Myths of the Near Future on 29 January 2007....
- Gravity's RainbowGravity's Rainbow (song)"Gravity's Rainbow" is a song by British act Klaxons which appears on their album Myths of the Near Future. It is named after Thomas Pynchon's novel of the same name. The song was first released on Angular Records as a Double A-side with "The Bouncer" in March 2006 and was limited to 500 copies on...
(2008) - BoxcutterBoxcutter (musician)Boxcutter is the pseudonym for Barry Lynn , an electronic musician from Northern Ireland whose work, due to its bass-led and rhythmically 2-step nature, is often categorised as dubstep, although in style and idiosyncrasies has more in common with IDM artists such as Squarepusher and µ-Ziq.-...
- TV Troubles (2011)
The opening titles sequence for the British sci-fi series Doctor Who
Doctor Who
Doctor Who is a British science fiction television programme produced by the BBC. The programme depicts the adventures of a time-travelling humanoid alien known as the Doctor who explores the universe in a sentient time machine called the TARDIS that flies through time and space, whose exterior...
employed this technique from 1963 to 1973 (black-and-white
Black-and-white
Black-and-white, often abbreviated B/W or B&W, is a term referring to a number of monochrome forms in visual arts.Black-and-white as a description is also something of a misnomer, for in addition to black and white, most of these media included varying shades of gray...
initially, redone from 1967, then redone again, in colour this time, from 1970).
In science
The optical feedback discussed so far—video feedback, created by a camera pointing at its own monitor—is actually just one particular example of optical feedback. Perhaps the most obvious example of optical feedback in science is the optical cavityOptical cavity
An optical cavity or optical resonator is an arrangement of mirrors that forms a standing wave cavity resonator for light waves. Optical cavities are a major component of lasers, surrounding the gain medium and providing feedback of the laser light. They are also used in optical parametric...
found in almost every laser
Laser
A laser is a device that emits light through a process of optical amplification based on the stimulated emission of photons. The term "laser" originated as an acronym for Light Amplification by Stimulated Emission of Radiation...
, 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.
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. The page discovery of fractal lasers gives an account of laser fractals, the developments of this work, links to further reading, and relates the laser context with video feedback systems.
Video feedback is also useful as an experimental-mathematics tool. Examples of its use include the creation of Fractal
Fractal
A fractal has been defined as "a rough or fragmented geometric shape that can be split into parts, each of which is a reduced-size copy of the whole," a property called self-similarity...
patterns using multiple monitors or multiple images created using mirrors.
The page video feedback in science provides an overview.
Softology's Video Feedback page provides links and information about real and simulated video feedback.
Optical feedback is also found in the image intensifier
Image intensifier
An image intensifier tube is a vacuum tube device for increasing the intensity of available light in an optical system to allow use under low light conditions such as at night, to facilitate visual imaging of low-light processes such as fluorescence of materials to X-rays or gamma rays, or for...
tube 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 a microchannel plate detector
Microchannel plate detector
A micro-channel plate is a planar component used for detection of particles and impinging radiation . It is closely related to an electron multiplier, as both intensify single particles or photons by the multiplication of electrons via secondary emission...
.
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
Douglas HofstadterDouglas Hofstadter
Douglas Richard Hofstadter is an American academic whose research focuses on consciousness, analogy-making, artistic creation, literary translation, and discovery in mathematics and physics...
uses a direct analogy to Optical feedback (Video feedback) in his book I Am a Strange Loop
I Am a Strange Loop
I Am a Strange Loop is a 2007 book by Douglas Hofstadter, examining in depth the concept of a strange loop originally developed in his 1979 book Gödel, Escher, Bach....
about the human mind and consciousness.
See also
- CymaticsCymaticsCymatics is the study of visible sound and vibration, a subset of modal phenomena. Typically the surface of a plate, diaphragm, or membrane is vibrated, and regions of maximum and minimum displacement are made visible in a thin coating of particles, paste, or liquid...
- Audio/Acoustic feedbackAudio feedbackAudio feedback is a special kind of positive feedback which occurs when a sound loop exists between an audio input and an audio output...
- Computer graphicsComputer graphicsComputer graphics are graphics created using computers and, more generally, the representation and manipulation of image data by a computer with help from specialized software and hardware....
- Droste effectDroste effectThe Droste effect is a specific kind of recursive picture, one that in heraldry is termed mise en abyme. An image exhibiting the Droste effect depicts a smaller version of itself in a place where a similar picture would realistically be expected to appear. This smaller version then depicts an even...
- FeedbackFeedbackFeedback describes the situation when output from an event or phenomenon in the past will influence an occurrence or occurrences of the same Feedback describes the situation when output from (or information about the result of) an event or phenomenon in the past will influence an occurrence or...
- Interference
- Real-time computer graphicsReal-time computer graphicsReal-time computer graphics is the subfield of computer graphics focused on producing and analyzing images in real time. The term is most often used in reference to interactive 3D computer graphics, typically using a GPU, with video games the most noticeable users...
- RecursionRecursionRecursion is the process of repeating items in a self-similar way. For instance, when the surfaces of two mirrors are exactly parallel with each other the nested images that occur are a form of infinite recursion. The term has a variety of meanings specific to a variety of disciplines ranging from...
- Self-referenceSelf-referenceSelf-reference occurs in natural or formal languages when a sentence or formula refers to itself. The reference may be expressed either directly—through some intermediate sentence or formula—or by means of some encoding...
- Strange loopStrange loopA strange loop arises when, by moving up or down through a hierarchical system, one finds oneself back where one started.Strange loops may involve self-reference and paradox...
- Video artVideo artVideo art is a type of art which relies on moving pictures and comprises video and/or audio data. . Video art came into existence during the 1960s and 1970s, is still widely practiced and has given rise to the widespread use of video installations...
- VideoVideoVideo is the technology of electronically capturing, recording, processing, storing, transmitting, and reconstructing a sequence of still images representing scenes in motion.- History :...
External links
- Videofeedback
- The San Francisco Exploratorium
- http://babuliababa.free.fr/ (Ultimaya the doors of feedback phenomena. Ultimaya impulsion is a virtual area that promotes the investigation into consciousness through feedback process and its modulation. It supports multidisciplinary research into video, sound, art, science, advaita vedanta ... )