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Television

Television

: Television is a telecommunication system for broadcasting and receiving moving pictures and sound over a distance. The term has come to refer to all the aspects of television programming and transmission as well. programming ]]

History

The development of television technology can be partitioned along two lines: those developments that depended upon both mechanical and electronic principles, and those which are purely electronic. From the latter descended all modern televisions, but these would not have been possible without discoveries and insights from the mechanical systems. The word television is a hybrid word, created from both Greek and Latin. Tele- is Greek for "far", while -vision is from the Latin visio, meaning "vision" or "sight". It is often abbreviated as TV or the telly.

Electromechanical television

The German student Paul Gottlieb Nipkow proposed and patented the first electromechanical television system in 1885. Nipkow's spinning disk design is credited with being the first television image rasterizer. However, it wasn't until 1907 that developments in amplification tube technology made the design practical. Meanwhile, Constantin Perskyi had coined the word television in a paper read to the International Electricity Congress at the International World Fair in Paris on August 25, 1900. Perskeyi's paper reviewed the existing electromechanical technologies, mentioning the work of Nipkow and others. 1900 In 1911, Boris Rosing and his student Vladimir Kosma Zworykin achieved a television system that used a mechanical mirror-drum scanner to transmit, in Zworykin's words, "very crude images" over wires to the electronic Braun tube (cathode ray tube) in the receiver. Moving images were not possible because, in the scanner, "the sensitivity was not enough and the selenium cell was very laggy." Zworykin later went to work for RCA to build a purely electronic television, the design of which was eventually found to violate patents by Philo Taylor Farnsworth. On March 25, 1925, Scottish inventor John Logie Baird gave a demonstration of televised silhouette images at Selfridge's Department Store in London. But if television is defined as the transmission of live, moving, half-tone (grayscale) images, and not silhouette or still images, Baird achieved this privately on October 2, 1925, and gave the world's first public demonstration of a working television system to members of the Royal Institution and a newspaper reporter on January 26, 1926 at his laboratory in London. Unlike later electronic systems with several hundred lines of resolution, Baird's vertically scanned image, using a scanning disc embedded with a double spiral of lenses, had only 30 lines, just enough to reproduce a recognizable human face. In 1928 Baird's company (Baird Television Development Company / Cinema Television) broadcast the first transatlantic television signal, between London and New York, and the first shore to ship transmission. He also demonstrated an electromechanical colour, infrared (dubbed "Noctovision"), and stereoscopic television, using additional lenses, disks and filters. In parallel he developed a video disk recording system dubbed "Phonovision"; a number of the Phonovision[http://www.tvdawn.com/tvimage.htm] recordings, dating back to 1927, still exist. In 1929 he became involved in the first experimental electromechanical television service in Germany. In 1931 he made the first live transmission, of the Epsom Derby. In 1932 he demonstrated ultra-short wave television. Baird's electromechanical system reached a peak of 240 lines of resolution on BBC television broadcasts in 1936, before being discontinued in favor of a 405 line all-electronic system. In the U.S., Charles Francis Jenkins was able to demonstrate on June 13, 1925, the transmission of the silhouette image of a toy windmill in motion from a naval radio station to his laboratory in Washington, using a lensed disc scanner with 48 lines per picture, 16 pictures per second. AT&T's Bell Telephone Laboratories transmitted half-tone images of transparencies in May 1925. But Bell Labs gave the most dramatic demonstration of television yet on April 7, 1927, when it field tested reflected-light television systems using small-scale (2 by 2.5 inches) and large-scale (24 by 30 inches) viewing screens over a wire link from Washington to New York City, and over-the-air broadcast from Whippany, New Jersey. The subjects, which included Secretary of Commerce Herbert Hoover, were illuminated by a flying spot beam and scanned by a 50-aperture disc at 16 pictures per second.

Electronic television

Herbert Hoover Although the discoveries of Nipkow, Rosing, Baird and others were extraordinary, little of their technology is used in modern television. By 1934, all electromechanical television systems were outmoded, although electromechanical broadcasts continued on some stations until 1939. A.A. Campbell-Swinton wrote a letter to Nature on the 18 June 1908 describing his concept of electronic television using the cathode ray tube, which had been invented in 1897 by the German physicist and Nobel prize winner Karl Ferdinand Braun. He proposed using an electron beam in both the camera and the receiver, which could be steered electronically to produce moving pictures. He lectured on the subject in 1911 and displayed circuit diagrams, but no one, including Swinton, knew how to realize the design. Although his system was never built, the cathode ray tube did come to be used to display images in almost all television sets and computer monitors until the invention of the LCD panel. A fully electronic system was first achieved by Philo Taylor Farnsworth on September 7, 1927, although the low-resolution, light-insensitive camera tube limited the image to a plate of glass painted black, with a straight line etched across it, rotated in front of a bright carbon arc lamp. Seven years later, on August 25, 1934, at the Franklin Institute in Philadelphia, Farnsworth gave the world's first public demonstration of a working, all-electronic television system, with 220 lines per picture, 30 pictures per second. Over a three week period, vaudeville acts, athletic and sports demonstrations, politicians, and hundreds of ordinary citizens were captured on Farnsworth's cameras in the open air and simultaneously shown on his receiving sets. Farnsworth, a Mormon farm boy from Rigby, Idaho, first envisioned his system at age 14. He discussed the idea with his high school chemistry teacher, who could think of no reason why it would not work (Farnsworth would later credit this teacher, Justin Tolman, as providing key insights into his invention). He continued to pursue the idea at Brigham Young Academy (now Brigham Young University). At age 21, he demonstrated a working system at his own laboratory in San Francisco. His breakthrough freed television from reliance on spinning discs and other mechanical parts. All modern picture tube televisions descend directly from his design. Vladimir Kosma Zworykin is also sometimes cited as the father of electronic television because of his invention of the iconoscope in 1923 and his invention of the kinescope in 1929. His design was one of the first to demonstrate a television system with all the features of modern picture tubes. His previous work with Rosing on electromechanical television gave him key insights into how to produce such a system, but his (and RCA's) claim to being its original inventor was largely invalidated by three facts: a) Zworykin's 1923 patent presented an incomplete design, incapable of working in its given form (it was not until 1933 that Zworykin achieved a working implementation), b) the 1923 patent application was not granted until 1938, and not until it had been seriously revised, and c) courts eventually found that RCA was in violation of the television design patented by Philo Taylor Farnsworth, whose lab Zworykin had visited while working on his designs for RCA. The controversy over whether it was first Farnsworth or Zworykin who invented modern television is still hotly debated today. Some of this debate stems from the fact that while Farnsworth appears to have gotten there first as an inventor, RCA brought television sets to market before Farnsworth, and it was RCA employees who first wrote the history of television. Even though Farnsworth eventually won the legal battle over this issue, he was never able to fully capitalize financially on his invention.

Color television

Most television researchers appreciated the value of color image transmission, with an early patent application in Russia in 1889 for a mechanically-scanned color system showing how early the importance of color was realized. John Logie Baird demonstrated the world's first color transmission on July 3, 1928, using scanning discs at the transmitting and receiving ends with three spirals of apertures, each spiral with filters of a different primary color; and three light sources at the receiving end, with a commutator to alternate their illumination. Color television in the United States had a protracted history due to conflicting technical systems vying for approval by the Federal Communications Commission for commercial use. Mechanically scanned color television was demonstrated by Bell Laboratories in June 1929 using three complete systems of photoelectric cells, amplifiers, glow-tubes, and color filters, with a series of mirrors to superimpose the red, green, and blue images into one full color image. In the electronically scanned era, the first color television demonstration was on February 5, 1940, when RCA privately showed to members of the FCC at the RCA plant in Camden, New Jersey, a television receiver producing images in color by a field sequential color system. CBS began non-broadcast color experiments using film as early as August 28, 1940, and live cameras by November 12. The CBS "field sequential" color system was partly mechanical, with a disc made of red, blue, and green filters spinning inside the television camera at 1,200 rpm, and a similar disc spinning in synchronization in front of the cathode ray tube inside the receiver set. RCA's later "dot sequential" color system had no moving parts, using a series of dichroic mirrors to separate and direct red, green, and blue light from the subject through three separate lenses into three scanning tubes, and electronic switching that allowed the tubes to send their signals in rotation, dot by dot. These signals were sorted by a second switching device in the receiver set and sent to red, green, and blue picture tubes, and combined by a second set of dichroic mirrors into a full color image. The first field test (i.e., broadcast) of color television was by NBC (owned by RCA) on February 20, 1941. CBS began daily color field tests on June 1, 1941. These color systems were not compatible with existing black and white television sets, and as no color television sets were available to the public at this time, viewership of the color field tests was limited to RCA and CBS engineers and the invited press. The War Production Board halted the manufacture of television and radio equipment for civilian use from April 1, 1942 to October 1, 1945, limiting any opportunity to introduce color television to the general public. The post-war development of color television was dominated by three systems competing for approval by the FCC as the U.S. color broadcasting standard: CBS's field sequential system, which was incompatible with existing black and white sets without an adaptor; RCA's dot sequential system, which in 1949 became compatible with existing black and white sets; and CTI's system (also incompatible with existing black and white sets), which used three camera lenses, behind which were color filters that produced red, green, and blue images side by side on a single scanning tube, and a receiver set that used lenses in front of the picture tube (which had sectors treated with different phosphorescent compounds to glow in red, green, or blue) to project these three side by side images into one combined picture on the viewing screen. After a series of hearings beginning in September 1949, the FCC found the RCA and CTI systems fraught with technical problems, inaccurate color reproduction, and expensive equipment, and so formally approved the CBS system as the U.S. color broadcasting standard on October 11 1950. An unsuccessful lawsuit by RCA delayed the world's first network color broadcast until June 25 1951, when a musical variety special titled simply Premiere was shown over a network of five east coast CBS affiliates. Viewership was again extremely limited: the program could not be seen on black and white sets, and Variety estimated that only thirty prototype color receivers were available in the New York area. Regular color broadcasts began that same week with the daytime series The World Is Yours and Modern Homemakers. While the CBS color broadcasting schedule gradually expanded to twelve hours per week (but never into prime time), and the color network expanded to eleven affiliates as far west as Chicago, its commercial success was doomed by the lack of color receivers necessary to watch the programs, the refusal of television manufacturers to create adaptor mechanisms for their existing black and white sets, and the unwillingness of advertisers to sponsor broadcasts seen by almost no one. In desperation, CBS bought a television manufacturer, and on September 20, 1951, production began on the first and only CBS color television model. But it was too little, too late. Only 200 sets had been shipped, and only 100 sold, when CBS pulled the plug on its color television system on October 20, 1951, and bought back all the CBS color sets it could to prevent law suits by disappointed customers. Starting before CBS color even got on the air, the U.S. television industry, represented by the National Television System Committee, worked in 1950-1953 to develop a color system that was compatible with existing black and white sets and would pass FCC quality standards, with RCA developing the hardware elements. When CBS testified before Congress in March 1953 that it had no further plans for its own color system, the path was open for the NTSC to submit its petition for FCC approval in July 1953, which was granted in December. The first publicly announced experimental TV broadcast of a program using the NTSC-RCA "compatible color" system was an episode of NBC's Kukla, Fran and Ollie on August 30, 1953. NBC made the first coast-to-coast color broadcast when it covered the Tournament of Roses Parade on January 1 1954, with public demonstrations given across the United States on prototype color receivers. A few days later Admiral brought out the first commercially made color television set using the RCA standards, followed in March by RCA's own model. Television's first prime time network color series was The Marriage, a situation comedy broadcast live by NBC in the summer of 1954. NBC's anthology series Ford Theatre became the first color filmed series that October. NBC was naturally at the forefront of color programming because its parent company RCA manufactured the most successful line of color sets in the 1950s. CBS and ABC, which were not affiliated with set manufacturers, and were not eager to promote their competitor's product, dragged their feet into color, with ABC delaying its first color series (The Flintstones and The Jetsons) until 1962. The Du Mont network, although it did have a television-manufacturing parent company, was in financial decline by 1954 and was dissolved two years later. Thus the relatively small amount of network color programming, combined with the high cost of color television sets, meant that as late as 1964 only 3.1 percent of television households in the U.S. had a color set. NBC provided the catalyst for rapid color expansion by announcing that its prime time schedule for fall 1965 would be almost entirely in color (the exception being I Dream of Jeannie). All three broadcast networks were airing full color prime time schedules by the 1966–67 broadcast season. But the number of color television sets sold in the U.S. did not exceed black and white sales until 1972, which was also the first year that more than fifty percent of television households in the U.S. had a color set. In Mexico, Guillermo González Camarena (1917–1965), invented the early color television transmission system. He received patents for color television systems in 1940 (U.S. Patent 1942 (2296019), 1960 and 1962. The 1942 patent was for a mechanically scanned color filter adapter for an existing monochrome electronic transmission system. In August 31, 1946 he sent his first color transmission from his lab in the offices of The Mexican League of Radio Experiments in Lucerna St. #1, in Mexico City. The video signal was transmitted at a frequency of 115 MHz. and the audio in the 40 metre band. European color television was developed somewhat later and was hindered by a continuing division on technical standards. Having decided to adopt a higher-definition 625-line system for monochrome transmissions, with a lower frame rate but with a higher overall bandwidth, Europeans could not directly adopt the U.S. color standard, which was widely perceived as wanting anyway, because of its tint control problems. There was also less urgency, since there were fewer commercial motivations, European television broadcasters being predominantly state-owned at the time. As a consequence, although work on various color encoding systems started already in the 1950s, with the first SECAM patent being registered in 1956, many years had passed till the first broadcasts actually started in 1967. Unsatisfied with the performance of NTSC and of initial SECAM implementations, the Germans unveiled PAL (phase alternating line) in 1963, staying closer to NTSC but borrowing some ideas from SECAM. The French continued with SECAM, notably involving Russians in the development. The first regular colour broadcasts in Europe were by BBC2 beginning on July 1, 1967, using PAL. Germans did their first broadcast in September (PAL), while the French in October (SECAM). PAL was eventually adopted by West Germany, the UK, Australia, New Zealand, much of Africa, Asia and South America, and most Western European countries except France. In addition to France and Luxembourg, SECAM was adopted by Soviet Union, much of Eastern Europe, much of Africa and of the Middle East. Both systems broadcast on UHF frequencies, the VHF being used for legacy black and white, 405 lines in UK or 819 lines in France, till the beginning of the eighties. It should be noted that some British television programmes, particularly those made by or for ITC Entertainment, were made in colour before the introduction of colour television to the UK, for the purpose of sales to US networks. The first British show to be made in colour was the drama series The Adventures of Sir Lancelot (1956-57), which was initially made in black and white but later shot in colour for sale to the NBC network in the United States. In Japan, NHK introduced color television in the year 1960.

Broadcast television

NHK The first regularly scheduled television service in the United States began on July 2, 1928. The Federal Radio Commission authorized C.F. Jenkins to broadcast from experimental station W3XK in a suburb of Washington, D.C. But for at least the first eighteen months, only silhouette images from motion picture film were broadcast due to the narrow 10kHz bandwidth allotted by the FRC. General Electric's experimental station in Schenectady, New York, on the air sporadically since January 13, 1928, was able to broadcast reflected-light, 48-line images via shortwave as far as Los Angeles, and by September was making four television broadcasts weekly. CBS's New York City station W2XAB began broadcasting the first regular seven days a week television schedule in the United States on July 21, 1931, with a 60-line electromechanical system. The first broadcast included Mayor Jimmy Walker, the Boswell Sisters, Kate Smith, and George Gershwin. The service ended in February 1933. By 1935, electromechanical television broadcasting had ceased in the United States except for a handful of stations run by public universities that continued to 1939. The Federal Communications Commission saw television in the continual flux of development with no consistent technical standards, hence all such stations in the U.S. were granted only experimental and not commercial licenses, hampering television's economic development. Just as importantly, Philo Farnsworth's 1934 demonstration of an all-electronic system pointed the direction of television's future. On June 15, 1936, Don Lee Broadcasting began a month-long demonstration of all-electronic television in Los Angeles on W6XAO (later KTSL) with a 300-line image from motion picture film. RCA demonstrated in New York City a 343-line electronic television broadcast, with live and film segments, to its licensees on July 7, 1936, and made its first public demonstration to the press on November 6. By April 1939, regularly scheduled 441-line electronic television broadcasts were available in New York City and Los Angeles, and by November on General Electric's station in Schenectady. With the adoption of NTSC television engineering standards in 1941, the FCC saw television ready for commercial licensing, with the first such licenses issued to NBC and CBS owned stations in New York on July 1, 1941, followed by Philco's station in Philadelphia. Electromechanical broadcasts began in Germany in 1929, but were without sound until 1934. Network electronic service started on March 22, 1935, on 180 lines using only telecine transmission of film or an intermediate film system. Live transmissions began on January 15, 1936. The Berlin Summer Olympic Games were televised, using both direct television and intermediate film cameras, to 28 public television rooms in Berlin and Hamburg in August 1936. The Germans had a 441-line system on the air in February 1937, and during World War II brought it to France, where they broadcast off the Eiffel Tower. The first British television broadcast was made by Baird Television's electromechanical system over the BBC radio transmitter in September 1929. Baird provided a limited amount of programming five days a week by 1930. On August 22, 1932, BBC launched its own regular service using Baird's 30-line electromechanical system, continuing until September 11, 1935. On November 2, 1936 the BBC began broadcasting a dual-system service, alternating on a weekly basis between Marconi-EMI's 405-line standard and Baird's improved 240-line standard, from Alexandra Palace in London, making the BBC the world's first regular high-definition television service. The corporation decided that Marconi-EMI's electronic picture gave the superior picture, and the Baird system was dropped in February 1937. The outbreak of the Second World War caused the BBC service to be suspended on September 1, 1939, resuming from Alexandra Palace on June 7, 1946. The Soviet Union began offering 30-line electromechanical test broadcasts in Moscow on October 31, 1931, and a commercially manufactured television set in 1932. The first experimental transmissions of electronic television took place in Moscow on March 9, 1937, using equipment manufactured and installed by RCA. Regular broadcasting began on December 31, 1938. The first regular television transmissions in Canada began in 1952 when the CBC put two stations on the air, one in Montreal, Quebec on September 6, and another in Toronto, Ontario two days later. two days later The first live transcontinental television broadcast took place in San Francisco, California from the Japanese Peace Treaty Conference on September 4, 1951. In 1958, the CBC completed the longest television network in the world, from Sydney, Nova Scotia to Victoria, British Columbia. Reportedly, the first continuous live broadcast of a breaking news story in the world was conducted by the CBC during the Springhill Mining Disaster which began on October 23 of that year. Programming is broadcast on television stations (sometimes called channels). At first, terrestrial broadcasting was the only way television could be distributed. Because bandwidth was limited, government regulation was normal. In the U.S., the Federal Communications Commission allowed stations to broadcast advertisements, but insisted on public service programming commitments as a requirement for a license. By contrast, the United Kingdom chose a different route, imposing a television licence fee on owners of television reception equipment, to fund the BBC, which had public service as part of its Royal Charter. Development of cable and satellite means of distribution in the 1970s pushed businessmen to target channels towards a certain audience, and enabled the rise of subscription-based television channels, such as HBO and Sky. Practically every country in the world now has developed at least one television channel. Television has grown up all over the world, enabling every country to share aspects of their culture and society with others. By the late 1980s, 98% of all homes in the U.S. had at least one TV set. On average, Americans watch four hours of television per day. An estimated two-thirds of Americans got most of their news about the world from TV, and nearly half got all of their news from TV. These figures are now estimated to be significantly higher.

Technology

Broadcasting

There are many means of distributing television broadcasts, including both analogue and digital versions of:
- Terrestrial television
- Stratovision (From aircraft flying in a loop)
- Satellite television
- Cable television
- MMDS (Wireless cable)

Receiving

Television sets

In television's electromechanical era, commercially made television sets were sold from 1928 to 1934 in the United Kingdom, United States, and Russia. The earliest commercially made sets sold by Baird in the U.K. and the U.S. in 1928 were radios with the addition of a television device consisting of a neon tube behind a mechanically spinning disk (the Nipkow disk) with a spiral of apertures that produced a red postage-stamp size image, enlarged to twice that size by a magnifying glass. The "televisor" was also available without the radio. The Baird televisor sold in 1930-1933 is considered the first mass-produced set, selling about a thousand units. The first commercially made electronic television sets with cathode ray tubes were manufactured by Telefunken in Germany in 1934, followed by other makers in Britain (1936) and America (1938). The cheapest of the pre-War World II factory-made American sets, a 1938 image-only model with a 3-inch (8 cm) screen, cost US$125, the equivalent of US$1,732 in 2005. The cheapest model with a 12-inch (30 cm) screen was $445 ($6,256). An estimated 19,000 electronic television sets were manufactured in Britain, and about 1,600 in Germany, before World War II. About 7,000-8,000 electronic sets were made in the U.S. before the War Production Board halted manufacture in April 1942, which resumed in October 1945. Television usage in the United States skyrocketed after World War II with the lifting of the manufacturing freeze, war-related technological advances, the gradual expansion of the television networks westward, the drop in set prices caused by mass production, increased leisure time, and additional disposable income. While only 0.5% of U.S. households had a television set in 1946, 55.7% had one in 1954, and 90% by 1962. In Britain, there were 15,000 television households in 1947, 1.4 million in 1952, and 15.1 million by 1968. For many years different countries used different technical standards. France initially adopted the German 441-line standard but later upgraded to 819 lines, which gave the highest picture definition of any analogue TV system, approximately four times the resolution of the British 405-line system. Eventually the whole of Europe switched to the 625-line PAL standard, once more following Germany's example. Meanwhile in North America the original NTSC 525-line standard from 1941 was retained. NTSC Television in its original form involves sending images and sound over radio waves in the VHF and UHF bands, which are received by a television set. Over-the-air broadcast television requires an antenna (aerial). This can be an outdoor Yagi antenna. In strong signal areas the antenna can be indoors, attached to or near the receiver, such as an adjustable dipole antenna called "rabbit ears" for the VHF band and a small loop antenna for the UHF band.

Specifications

Modern displays
Starting in the 1990s, modern television sets diverged into three different trends:
- standalone TV sets;
- integrated systems with DVD players and/or VHS VCR capabilities built into the TV set itself (mostly for small size TVs with up to 21" screen, the main idea is to have a complete portable system);
- component systems with separate big-screen video monitor, tuner, audio system which the owner connects the pieces together as a high-end home theater system. This approach appeals to videophiles who prefer components that can be upgraded separately. There are many kinds of video monitors used in modern TV sets. The most common are direct view CRTs for up to 40in (100cm) (in 4:3) and 46in (115cm) (in 16:9) diagonally; most big screen TVs (up to over 100 inch (254 cm)) use projection technology. Three types of projection systems are used in projection TVs: CRT-based, LCD-based, and DLP(reflective micromirror chip)-based. Modern advances have brought flat panels to TV that use active matrix LCD or plasma display technology. Flat panel LCDs and plasma displays are as little as 4in (10cm) thick and can be hung on a wall like a picture or put over a pedestal. They are multifunctional, because they are used like computer monitors too (VGA and DVI or HDMI connections). Some TVs integrate a pair of ports to connect computer cases and peripherals to it or to connect the set to an A/V home network (HAVI) (USB port for cord connection and BlueTooth/WiFi for wireless). Today, some LCD and Plasma sets have SD Card slots, so users can view pictures from a digital camera. On the new Panasonic LCDs and Plasmas (Viera), users have the capability to record onto SD card and then play it back on a hand-held PC or digital camera (anything that allows MPEG4). With SD cards now available with 1G of memory (soon 2GB, and Panasonic is also working on one that contains over 30GB of memory), a user can record over 1,000 minutes at low quality, and around 80 minutes on the highest quality. The playback of the recording is not brilliant, but these are the first generation. They will get better with time.
Signal connections
The number of ways to connect a video device to a television has increased over the years: WiFi
- HDMI - a compact 19 to 29 pin connector that carries digital video and digital audio signals. Essentially an enhanced version of DVI that includes digital audio. This is the most advanced form of connection currently available. DVI
- DVI - a 17 to 29 pin connector that carries digital video signals, designed to carry HDTV but also used in current DVD players and latest digital displays. Copy protection is available using HDCP. HDCP
- Component video - three separate RCA jacks (colored red, green and blue) carry three video signals, one brightness (luminance) and two colors (chromas), and is usually referred to as "Y, B-Y, R-Y", "Y Cr Cb" (interlaced) or "Y Pr Pb" (progressive), or YUV. Audio is not carried on this cable. This connection provides for picture quality superior to S-Video and is typically used in home theater for DVDs, satellite and analogue HDTV; less common in Europe but is starting to become more widely available. Europe
- SCART - a large 21 pin connector that may carry: one video signal composite video; or two video signals S-Video; or for picture quality similar to component video, three signals of separate red, green and blue or RGB; or for best picture quality, four video signals of separate red, green, blue and sync or RGBS; plus right and left line-level audio channels; along with a number of control signals including an aspect-ratio flag (e.g. widescreen). This system has been standard in Europe since mid-1980s for all consumer electronics, which meant that RGBS was available on even the earliest PAL DVD players and satellite receivers. Japan uses a 21 pin RGB connector which is visually similar to SCART but with different pin configurations. Japan
- S-Video - small round connector with two separate video signals, one carrying brightness (luminance), the other carrying color (chroma). Also referred to as Y/C video. Provides most of the benefit of component video, with slightly less color fidelity. Use started in the 1980s for S-VHS, Hi-8, and early NTSC DVD players to relay high quality video before component was available. Audio is not carried on this cable. Hi-8
- Composite video - The most common form of connecting external devices, putting all the video information into one signal. Most televisions provide this option with a yellow RCA jack. Audio is not carried on this cable, though two separate cables with similar red and white RCA jacks for right and left line-level audio are commonly bonded to composite video cables.
- Coaxial RF - All audio channels and picture components are transmitted through one coaxial cable and modulated on a radio frequency. Most TVs manufactured during the past 15–20 years accept coaxial connection, and the video is typically "tuned" on channel 3 or 4. This is the type of cable usually used for cable television. Most modern DVD players and other video devices no longer modulate RF output, so very old TV sets made before composite video jacks became commonplace will need a modulator.
Aspect ratios
Mechanically scanned television as first demonstrated by John Logie Baird in 1926 used a 7:3 vertical aspect ratio, oriented for the head and shoulders of a single person in close-up. Most of the early electronic TV systems from the mid-1930s onward shared the same aspect ratio of 4:3 which was chosen to match the Academy Ratio used in cinema films at the time. This ratio was also square enough to be conveniently viewed on round cathode-ray tubes (CRTs), which were all that could be produced given the manufacturing technology of the time. (Today's CRT technology allows the manufacture of much wider tubes, and the flat screen technologies which are becoming steadily more popular have no aspect ratio limitations at all.) The BBC's television service used a more squarish [http://tcc.members.beeb.net/tchistory.html 5:4] ratio from 1936 to circa 1949, when it too switched to a 4:3 ratio. In the 1950s, movie studios moved towards widescreen aspect ratios such as Cinerama in an effort to distance their product from television. Although this was initially just a gimmick widescreen is still the format of choice today and square aspect ratio movies are rare. Some people argued that widescreen is actually a disadvantage when showing objects that are tall instead of panoramic, others would say that natural vision is more panoramic than tall, and therefore widescreen is easier on the eye. The switch to digital television systems has been used as an opportunity to change the standard television picture format from the old ratio of 4:3 (approximately 1.33:1) to an aspect ratio of 16:9 (approximately 1.78:1). This enables TV to get closer to the aspect ratio of modern widescreen movies, which range from 1.78:1 through 1.85:1 to 2.35:1. There are two methods for transporting widescreen content, the better of which uses what is called anamorphic widescreen format. This format is very similar to the technique used to fit a widescreen movie frame inside a 1.33:1 35mm film frame. The image is squashed horizontally when recorded, then expanded again when played back. The anamorphic widescreen 16:9 format was first introduced via European PAL-Plus television broadcasts and then later on "widescreen" DVDs; the ATSC HDTV system uses straight widescreen format, no image squashing or expanding is used. Recently "widescreen" has spread from television to computing where both desktop and laptop computers are commonly equipped with widescreen displays, and it remains to be seen whether Work or movie enjoyment will take over. There are some complaints about distortions of movie picture ratio due to some DVD playback software not taking account of aspect ratios; but this will subside as the DVD playback software matures. Furthermore, computer and laptop widescreen displays are in the 16:10 aspect ratio both physically in size and in pixel counts, and not in 16:9 of consumer televisions, leading to further complexity. This was a result of widescreen computer display engineers' uninformed assumption that people viewing 16:9 content on their computer would prefer that an area of the screen be reserved for playback controls or subtitles, as opposed to viewing content full-screen.
Aspect ratio incompatibility
The television industry changing aspect ratios is not without teething difficulties, and can present a considerable problem. Displaying a widescreen aspect (rectangular) image on a conventional aspect (square) display can be shown:
- in "letterbox" format, with black horizontal bars at the top and bottom
- with part of the image being cropped, usually the extreme left and right of the image being cut off (or in "pan and scan", parts selected by an operator)
- with the image horizontally compressed A conventional aspect (square) image on a widescreen aspect (rectangular) display can be shown:
- in "pillarbox" format, with black vertical bars to the left and right
- with upper and lower portions of the image cut off
- with the image horizontally distorted A common compromise is to shoot or create material at an aspect ratio of 14:9, and to lose some image at each side for 4:3 presentation, and some image at top and bottom for 16:9 presentation. Horizontal expansion has advantages in situations in which several people are watching the same set, as it compensates for watching at an oblique angle.
Sound
Television add-ons
Today there are many add-ons for the television set. A few add-ons include Video Game Consoles, VCRs, Cable Boxes, Satellite Boxes, DVD players, or Digital Video Recorders, the television add-on market is ever growing.

New developments


- Broadcast flag
- CableCARD™
- Digital Light Processing (DLP)
- Digital Rights Management (DRM)
- Digital television (DTV)
- Digital Video Recorders
- Direct Broadcast Satellite TV (DBS)
- DVD
- Flicker-free (100Hz)
- High Definition TV (HDTV)
- High-Definition Multimedia Interface (HDMI)
- IPTV
- Internet television
- LCD and Plasma display Flat Screen TV
- Pay Per View
- Picture-in-picture (PiP)
- Video on-demand (VOD)
- Ultra High Definition Video (UHDV)
- Web TV

Geographical usage

Content

Advertising

Since their inception in the USA in 1941, TV commercials have become one of the most effective, most pervasive, and most popular methods of selling products of many sorts, especially consumer goods. U.S. advertising rates are determined primarily by Nielsen ratings. The exception to this is the publicly-funded British Broadcasting Corporation.

Programming

Getting TV programming shown to the public can happen in many different ways. After production the next step is to market and deliver the product to whatever markets are open to using it. This typically happens on two levels: #Original Run or First Run - a producer creates a program of one or multiple episodes and shows it on a station or network which has either paid for the production itself or to which a license has been granted by the producers to do the same. #Syndication - this is the terminology rather broadly used to describe secondary programming usages (beyond original run). It includes secondary runs in the country of first issue, but also international usage which may or may not be managed by the originating producer. In many cases other companies, TV stations or individuals are engaged to do the syndication work, in other words to sell the product into the markets they are allowed to sell into by contract from the copyright holders, in most cases the producers. In most countries, the first wave occurs primarily on FTA television, while the second wave happens on subscription TV and in other countries. In the U.S. however, the first wave occurs on the FTA networks and subscription services, and the second wave travels via all means of distribution. First run programming is increasing on subscription services outside the U.S., but few domestically produced programs are syndicated on domestic FTA elsewhere. This practice is increasing however, generally on digital only FTA channels, or with subscriber-only first run material appearing on FTA. Unlike the U.S., repeat FTA screenings of a FTA network program almost only occur only on that network. Also, affiliates rarely buy or produce non-network programming that isn't intensely local.

Social aspects

Alleged dangers

Paralleling television's growing primacy in family life and society, an increasingly vocal chorus of legislators, scientists and parents are raising objections to the uncritical acceptance of the medium. For example, the Swedish government imposed a total ban on advertising to children under twelve in 1991 (see advertising). In the U.S., the [http://www.mediafamily.org/facts/facts_tveffect.shtml National Institute on Media and the Family] (not a government agency) points out that U.S. children watch an average of 25 hours of television per week and features studies showing it interferes with the educational and maturational process. A February 23 2002 article in [http://www.sciam.com/print_version.cfm?articleID=0005339B-A694-1CC5-B4A8809EC588EEDF Scientific American] suggested that compulsive television watching was no different from any other addiction, a finding backed up by reports of withdrawal symptoms among families forced by

Telecommunication

Telecommunication refers to communication over long distances. In practice, something of the message may be lost in the process. Telecommunication covers all forms of distance and/or conversion of the original communications, including radio, telegraphy, television, telephony, data communication and computer networking. The elements of a telecommunication system are a transmitter, a medium (line) and possibly a channel imposed upon the medium (see baseband and broadband as well as multiplexing), and a receiver. The transmitter is a device that transforms or encodes the message into a physical phenomenon; the signal. The transmission medium, by its physical nature, is likely to modify or degrade the signal on its path from the transmitter to the receiver. The receiver has a decoding mechanism capable of recovering the message within certain limits of signal degradation. Sometimes, the final "receiver" is the human eye and/or ear (or in some extreme cases other sensory organs) and the recovery of the message is done by the brain (see psychoacoustics.) Telecommunication can be point-to-point, point-to-multipoint or broadcasting, which is a particular form of point-to-multipoint that goes only from the transmitter to the receivers. One of the roles of the telecommunications engineer is to analyse the physical properties of the line or transmission medium, and the statistical properties of the message in order to design the most effective encoding and decoding mechanisms. When systems are designed to communicate through human sensory organs (mainly those for vision and hearing), physiological and psychological characteristics of human perception must be taken into account. This has important economic implications and engineers must research what defects can be tolerated in the signal and not significantly degrade the viewing or hearing experience.

Examples of human (tele)communications

In a simplistic example, consider a normal conversation between two people. The message is the sentence that the speaker decides to communicate to the listener. The transmitter is the language areas in the brain, the motor cortex, the vocal cords, the larynx, and the mouth that produce those sounds called speech. The signal is the sound waves (pressure fluctuations in air particles) that can be identified as speech. The channel is the air carrying those sound waves, and all the acoustic properties of the surrounding space: echoes, ambient noise, reverberation. Between the speaker and the listener, there might be other devices that do or do not introduce their own distortions of the original vocal signal (for example a telephone, a HAM radio, an IP phone, etc.) The receiver is the listener's ear and auditory system, the auditory nerve, and the language areas in the listener's brain that will "decode" the signal into meaningful information and filter out background noise. All channels have noise. Another important aspect of the channel is called the bandwidth. A low bandwidth channel, such as a telephone, cannot carry all of the audio information that is transmitted in normal conversation, causing distortion and irregularities in the speaker's voice, as compared to normal, in-person speech.

See also


- History of telecommunication
- ITU
- Federal Standard 1037C for a glossary of telecommunications terms.
- Public utility
- Lists of public utilities
- Internet traffic engineering

External links


- [http://web.archive.org/web/20040413074912/www.ericsson.com/support/telecom/index.shtml Ericsson's Understanding Telecommunications] at archive.org (Ericsson removed the book from their site in Sep 2005)
- [http://www.carrieraccessbilling.com/telecommunications-glossary-a.asp Intec Telecom Systems' Telecom Dictionary]
- [http://www.mobile-phone-directory.org/Glossary/ Mobile Phone Directory Telecommunications Glossary]
- [http://www.tiaonline.org Telecommunications Industry Association (TIA)]
- [http://www.aronsson.se/hist.html Aronsson's Telecom History Timeline]
- [http://www.alcatel.com/atr Alcatel Telecommunications Review] Telecom magazine published since 1922
- [http://www.teleclick.ca Telecommunications Industry News]
- [http://www.bt.com BT] British Telecommunications company
- Category:Digital Revolution ms:Telekomunikasi ja:電気通信 th:โทรคมนาคม

Television program

A television program is the content of television broadcasting. The content of an individual broadcast may be referred to as a television program (U.S., Canada, and Australia), television programme (UK, NZ, Ireland and South Africa) or television show. A program may be a one-off broadcast or, more usually, part of a periodically returning television series. A television series that is intended to air a finite number of episodes is usually called a miniseries. Americans call a short run lasting less than a year a season; Europeans call this a series. This season or series usually consists of 10–24 installments of the series. A single instance of a program is called an episode, although this is sometimes also called a "show" or "program." A one-off broadcast may be called a "special." A television movie is a movie that is initially aired on television rather than being released in cinemas or direct-to-video, although many successful television movies are later released on video.

What television programming is

The content of television programs may be factual, as in documentaries, news, and reality television, or fictional as in comedy and drama. It may be topical as in the case of news and some made-for-television movies or historical as in the case of such documentaries or fictional series. It may be primarily instructional as in the case of educational programming, or entertaining as is the case in situation comedy, reality TV, and variety shows. A drama program usually features a set of actors in a somewhat familiar setting. The program follows their lives and their adventures. Many shows, especially before the 1980s, maintained a status quo where the main characters and the premise changed little. If some change happened to the characters lives during the episode, it was usually undone by the end. (Because of this, the episodes could usually be watched in any order.) Since the 1980s, there are many series that feature progressive change to the plot, the characters, or both. Common TV program periods include regular broadcasts (like TV news), TV series (usually seasonal and ongoing with a duration of only a few episodes to many seasons), or TV miniseries which is an extended film, usually with a small pre-determined number of episodes and a set plot and timeline. Miniseries usually range from about 3 to 10 hours in length, though critics often complain when programs hit the short end of that range and are still marketed as "minis." In the UK, the term "miniseries" is only usually used in references to imported programmes, and such short-run series are usually called "serials" there. In the United States, most regular television series have 22 episodes per year. In general, dramas usually last 44 minutes (an hour with commercials), while comedies last 22 (30 with commercials). However, with the rise of cable networks, especially pay ones, series and episode lengths have been changing. Cable networks usually feature series lasting thirteen episodes. Many British series have significantly shorter yearly runs. Old television shows begin with a title sequence, show opening credits at the bottom of the screen over the beginning of the show, and include closing credits at the end of the show. However, in the 1990s shows began cold opening with a "teaser" (a short beginning to the episode, designed to catch the viewer's attention), followed by a title sequence, and a commercial break. More plot-driven shows begin with a "previously" (a short introduction to past major plot events through excerpts), even before the teaser. And, to save time, some shows omit the title sequence altogether, folding the names normally featured there into the opening credits. While television series appearing in TV networks are usually commissioned by the networks themselves, the real revenue for the producers is typically when the product is sold into syndication. However, with the rise of the DVD home video format, box sets containing entire seasons or the complete run have become a significant revenue source as well.

How programs are made

:What follows is the standard procedure for shows on network television in the United States. Someone (called the show "creator") comes up with the idea for a new television series. This consists of the concept, the characters, usually some crew, and sometimes some big-name actors. They "pitch" it to the various television networks, hoping to find one that's interested. If a network is interested, they will "order" a pilot (a prototype first episode of the series). To create the pilot, the structure and team of the whole series needs to be put together. If the network likes the pilot, they will "pick up" the show for their next season (UK: series). Sometimes they'll save it for "midseason" or request re-writes and further review (know in the industry as "Development hell"). And other times they'll pass entirely, leaving the show's creator forced to "shop it around"' to other networks. Many shows never make it past the pilot stage. If the show is picked up, a "run" of episodes is ordered. Usually only 13 episodes are ordered at first, although a series will typically last for at least 22 episodes (the last nine episodes sometimes being known as the "back nine", borrowing a term from golf). The show hires a "stable" of writers, who usually work in parallel: the first writer works on the first episode, the second on the second episode, and so forth. When all of the writers have been used, the assignment of episodes continues starting with the first writer again. On other shows, however, the writers work as a team. Sometimes they will develop story ideas individually, and pitch them to the show's creator, who then folds them together into a script and rewrites them. The executive producer, often the show's creator, is in charge of running the show. They pick crew and cast (subject to approval by the network), approve and often write series plots, and sometimes write and direct major episodes. A whole host of other producers of various names work under him or her, to make sure the show is always running smoothly. Once the script for a show is written, a director is found for the episodes. The director's job is to turn the words of the script into film. They decide how scenes should be "staged" and where the cameras should be placed; they also often coach the actors, including any guest stars who may be in the particular episode. On television shows, directors are often interchangeable, mainly serving the dictates of the writer. A director of photography takes care of making the show look good, doing things with lighting and so on. Finally, an editor cuts the various pieces of film together, adds the musical score, and assembles the completed show. The show is then turned over to the network, which sends it out to its affiliates, which air it in the specified timeslot. If the Nielsen Ratings are good, the show is kept alive as long as possible. If not, the show is usually cancelled. The show's creators are then left to shop around remaining episodes, and the possibility of future episodes, to other networks. On especially successful series, the producers sometimes call a halt to a series on their own like M
- A
- S
- H and end it with a concluding episode which sometimes is a big production called a series finale. If the show is popular or lucrative, and a number of episodes (usually 100 episodes or more) are made, it goes into syndication where broadcast rights are then resold.

Common genres


- TV comedy (typically situation comedy or sketch comedy)
- TV documentary
- TV drama (including dramedy)
- TV talk shows
- TV news
- TV current affairs shows
- TV cartoons
- TV infomercials
- TV miniseries
- Game shows
- Soap operas
- Reality TV

See also


- Alphabetical list of television programs
- Continuity
- Dead air
- List of television program categories
- TV series (China) ja:テレビ番組

Hybrid word

A word that has one part derived from one language and another part derived from a different language is etymologically a hybrid word. The most common form of hybrid word in English is one which etymologically has both Latin and Greek parts. Since many prefixes and suffixes in English have Latin or Greek etymology, it is straightforward to tack a prefix or a suffix from one language onto an English word that comes from a different language, thus creating a hybrid word. This mixing of etymology is considered by some to be bad form, but others consider that, since both (or all) parts have entered the English lexicon, it is a simple conflation of two (or more) English words to make a new English word that connotes some thing that these parts clearly indicate, regardless of the history of its parts, and so is well constituted. Although the prevailing thought is that such word construction is ill-formed, there are hybrid words in common English usage. Some examples of hybrid words are listed below:
- Homosexual - from the Greek prefix homo meaning "same" and the Latin root sex meaning "gender"
- Hyperactive - from the Greek huper meaning "over" and the Latin activus
- Mega-annum - from the Greek mega, "million", and the Latin annum, "year"
- Monolingual - from the Greek mono meaning "one" and the Latin lingua meaning "tongue"
- Mormon - It was alleged by Joseph Smith that Mormon comes from the English "more" and the Reformed Egyptian mon meaning "good".
- Neonate - from the Greek neo, "new", and the Latin natus, "birth"
- Polyamory - from the Greek poly meaning "many" and the Latin amory meaning "love"
- Sociology - from the Latin socius, "comrade", and the Greek logos meaning "word", "reason", "discourse"
- Television - from the Greek tele meaning "far" and the Latin video meaning "to see" Category:Types of words

Greek language

Greek (Greek Ελληνικά, IPA – "Hellenic") is an Indo-European language with a documented history of 3,500 years. Today, it is spoken by 15 million people in Greece, Cyprus, the former Yugoslavia, particularly The Former Yugoslav Republic of Macedonia, Bulgaria, Albania and Turkey. There are also many Greek emigrant communities around the world, such as those in Melbourne, Australia which is the third-largest Greek-populated city in the world, after Athens and Thessaloniki. Greek has been written in the Greek alphabet, the first true alphabet, since the 9th century B.C. and before that, in Linear B and the Cypriot syllabaries. Greek literature has a long and rich tradition.

History

This article does not cover the reconstructed history of Greek prior to the use of writing. For more information, see main article on Proto-Greek language. Greek has been spoken in the Balkan Peninsula since the 2nd millennium BC. The earliest evidence of this is found in the Linear B tablets dating from 1500 BC. The later Greek alphabet (q.v.) is unrelated to Linear B, and was derived from the Phoenician alphabet (abjad); with minor modifications, it is still used today. Greek is conventionally divided into the following periods:
- Mycenean Greek: the language of the Mycenean civilisation. It is recorded in the Linear B script on tablets dating from the 16th century BC onwards.
- Classical Greek (also known as Ancient Greek): In its various dialects was the language of the Archaic and Classical periods of Greek civilisation. It was widely known throughout the Roman empire. Classical Greek fell into disuse in western Europe in the Middle Ages, but remained known in the Byzantine world, and was reintroduced to the rest of Europe with the Fall of Constantinople and Greek migration to Italy.
- Hellenistic Greek (also known as Koine Greek): The fusion of various ancient Greek dialects with Attic (the dialect of Athens) resulted in the creation of the first common Greek dialect, which gradually turned into one of the world's first international languages. Koine Greek can be initially traced within the armies and conquered territories of Alexander the Great, but after the Hellenistic colonisation of the known world, it was spoken from Egypt to the fringes of India. After the Roman conquest of Greece, an unofficial diglossy of Greek and Latin was established in the city of Rome and Koine Greek became a first or second language in the Roman Empire. Through Koine Greek it is also traced the origin of Christianity, as the Apostles used it to preach in Greece and the Greek-speaking world. It is also known as the Alexandrian dialect, Post-Classical Greek or even New Testament Greek (after its most famous work of literature).
- Medieval Greek: The continuation of Hellenistic Greek during medieval Greek history as the official and vernacular (if not the literary nor the ecclesiastic) language of the Byzantine Empire, and continued to be used until, and after the fall of that Empire in the 15th century. Also known as Byzantine Greek.
- Modern Greek: Stemming independently from Koine Greek, Modern Greek usages can be traced in the late Byzantine period (as early as 11th century). Two main forms of the language have been in use since the end of the medieval Greek period: Dhimotikí (Δημοτική), the Demotic (vernacular) language, and Katharévousa (Καθαρεύουσα), an imitation of classical Greek, which was used for literary, juridic, and scientific purposes during the 19th and early 20th centuries. Demotic Greek is now the official language of the modern Greek state, and the most widely spoken by Greeks today. It has been claimed that an "educated" speaker of the modern language can understand an ancient text, but this is surely as much a function of education as of the similarity of the languages. Still, Koinē , the version of Greek used to write the New Testament and the Septuagint, is relatively easy to understand for modern speakers. Greek words have been widely borrowed into the European languages: astronomy, democracy, philosophy, thespian, etc. Moreover, Greek words and word elements continue to be productive as a basis for coinages: anthropology, photography, isomer, biomechanics etc. and form, with Latin words, the foundation of international scientific and technical vocabulary. See English words of Greek origin, and List of Greek words with English derivatives.

Classification

Greek is an independent branch of the Indo-European language family. The ancient languages which were probably most closely related to it, Ancient Macedonian language (which may be regarded as a dialect of Greek) and Phrygian, are not well enough documented to permit detailed comparison. Among living languages, Armenian seems to be the most closely related to it.

Geographic distribution

Modern Greek is spoken by about 15 million people mainly in Greece and Cyprus. There are also Greek-speaking populations in Georgia, Ukraine, Egypt, Turkey, Albania, Former Yugoslav Republic of Macedonia and Southern Italy. The language is spoken also in many other countries where Greeks have settled, including Armenia, Australia, Austria, Belgium, Bulgaria, Canada, Denmark, France, Germany, Netherlands, Sweden, United Kingdom, and the United States.

Official status

Greek is the official language of Greece where it is spoken by about 99.5% of the population. It is also, alongside Turkish, the official language of Cyprus. Due to the membership of Greece and Cyprus, Greek is one of the 20 official languages of the European Union.

Phonology

This section generally describes the post-Classic phonology of the Greek language. :All phonetic transcriptions in this section use the International Phonetic Alphabet

Vowel sounds

Greek has 5 vowel sounds, all phonemic:

Visual perception

Visual perception is one of the senses, consisting of the ability to detect light and interpret (see) it as the perception known as sight or naked eye vision. Vision has a specific sensory system, the visual system. There is disagreement as to whether or not this constitutes one, two or even three distinct senses. Some people make a distinction between "black and white" vision and the perception of colour, and others point out that vision using rod cells uses different physical detectors on the retina from cone cells. Some argue that the perception of depth also constitutes a sense, but others argue that this is really cognition (that is, post-sensory) function derived from having stereoscopic vision (two eyes) and is not a sensory perception as such. Many people are also able to perceive the polarization of light.

The visual system

thumbnailThe eye is the light-sensitive organ that is the first component of the visual system. The eye's retina performs the first stages of visual perception processing, with the remaining stages of visual perception occurring in the optic nerve, the lateral geniculate nucleus, and the visual cortex of the brain.

Sources of information

To perform its task, visual perception takes into account not only patterns of illumination on the retina, but also our other senses and our past experiences. Consider the task of bird sighting (an instance of object recognition): to be able to identify a bird against a background of tree and brushes, one needs prior exposure to general properties of the bird category. From past experiences, we expect birds to have a certain shape, color, etc. Hearing a sound that is characteristic of birds, a song for example, will help us locate one: information from the other senses is used in visual perception. In this case, locational information from the auditory domain is used.

Individual and group differences in visual perception

Most of the general processes of visual perception have been shown to be universal, as opposed to being dependant on culture, although there are specific instances where cultural variability appears to come into play. It has also been shown that certain individual differences such as impairment of sight and spatial skills can also affect our visual perception. There are also other factors that influence how we perceive things such as personality, cognitive styles, gender, occupation, age, values, attitudes, motivation, religious beliefs, economic status, education and habits.

Theoretical perspectives in the study of visual perception

Unconscious inference

Hermann von Helmholtz is often credited with the founding of the scientific study of visual perception. Helmholtz held vision to be a form of unconscious inference: vision is a matter of deriving a probable interpretation for incomplete data. The general goal of vision is to identify, as accurately as possible, the features of our environment: roughly, what objects are present where. Other features are irrelevant to this task : illumination patterns, viewing position, etc. Those are confounding variables. Call S = (F,C) the scene, with F the features we’re interested in and C the confounding variables. S determines I, the pattern of illumination on the retina, which is all the information our visual system has on the current scene. The task is to find S given I. This problem is under-constrained: many different S correspond to the same I, and many I could correspond to the same S. One of the reasons is that much information is lost when a 3-dimensional world is collapsed into a 2-dimensional array. To see why, consider the figure of a circle such as this one: O. It could correspond to an infinity of ellipses viewed at a certain slant. But we always interpret it as a circle viewed on the frontal plane – the explanation we infer from the data for this particular stimulus. Inference requires prior assumptions about the world: two well-known assumptions that we make in processing visual information are that light comes from above and that objects are viewed from above not below. The study of visual illusions (cases when the inference process goes wrong) has yielded a lot of insight into what sort of assumptions the visual system makes.

Gestalt

Psychologists of the Gestalt school have raised a large part of the research questions that still preoccupy vision scientists today. The so-called Gestalt Laws of Organisation have broadened the study of how people perceive objects to be organized patterns or wholes, instead of collections of many separate parts. Gestalt is a German word that translates to "configuration or pattern". According to this theory, there are four main factors that determine how we group things according to visual perception.
- Proximity – Depending on how close object are to one other, we tend to group the ones closest to each other as a group.
- Similarity – If objects are similar in shape or size to one another we tend to group them together.
- Closure – How we complete a pattern because of how the items are grouped together even though the pattern is not complete.
- Simplicity – How we group items according to symmetry, regularity, and smoothness.

Ecological psychology

Psychologist James J. Gibson developed a theoretical perspective on vision that is radically different from that of Helmholtz. Gibson considers that enough visual perception is available in normal environments to allow for veridical perception (accurate perception of the world). Gibson replaces inference with information pickup. Although most researchers today feel closer to Helmholtz's unconscious inference theory, Gibson has done much in identifying what sort of information is available to the visual system.

Types of visual perception


- Black and white vision
- Color vision
- Gestalt perception
- Motion perception

Disorders/Dysfuntions


- Achromatopsia
- Color blindness
- Scotopic Sensitivity Syndrome

See also


- Color, Color circle, and Color vision
- Flicker fusion and the Persistence of vision
- Binocular vision and Depth perception
- Binocular rivalry and Multistable perception
- Blindsight
- Brightness and Contrast
- Consciousness and visual qualia
- Entoptic phenomenon
- Optometry
- Ophthalmology
- Optic flow
- Optical illusion
- Peripheral vision
- Phi phenomenon
- Philosophy of perception
- Phosphenes
- Photoreceptor
- Pattern recognition and Computer vision
- Primary sensory cortex
- Neuroscience and Cognitive science
- Saccade
- Visual perception in Dreams
- Vestibulo-ocular reflex
- Visual acuity
- Visual aid
- Visual cortex
- Visual deprivation
- Visual feedback
- Visual field
- Visual fixation
- Visual pathway
- Visual photosensitivity
- Visual phototransduction
- Visual pigment
- Visual stimulus
- Visual tectum
- Visual threshold
- Eye tracking

References


- Rudolph Arnheim (1954). Art and Visual Perception: A Psychology of the Creative Eye. Berkeley: University of California Press.
- Lothar Kleine-Horst (2001). Empiristic Theory of Visual Gestalt Perception. Hierarchy and Interactions of Visual Functions. Koeln: Enane. ISBN 3-928955-42X

External links


- [http://enane.de/cont.htm Empiristic theory of visual gestalt perception]
- [http://www.aber.ac.uk/media/Modules/MC10220/visper03.html Visual Perception 3 - Cultural and Environmental Factors]
- [http://www.sapdesignguild.org/resources/optical_illusions/gestalt_laws.html Gestalt Laws]
- [http://www.aber.ac.uk/media/Modules/MC10220/visper04.html Visual Perception 4 - Individual Differences, Purposes and Needs] Category:Computer visionCategory:Vision ja:視覚

Sight

Sight may refer to one of the following:
- Visual perception
- Sight, a device used to assist aim by guiding the eye.



Paul Gottlieb Nipkow

Paul Julius Gottlieb Nipkow, born 22nd August 1860 in Lauenburg in Pomerania, died 24th August 1940 in Berlin), was a German technician and inventor.

Beginnings

While at school in Neustadt, West Prussia, Nipkow experimented in telephony and the transmission of moving pictures. After graduation, he went to Berlin in order to study science. He studied physiological optics with Hermann von Helmholtz, and physiological optics and electro-physics with Adolf Slaby.

Nipkow Disk

While still a student, he invented the Nipkow disk. Accounts of its invention state that on Christmas Eve, 1883 when he sat alone at home with an oil lamp and conceived the idea to use a spiral-perforated disk to divide a picture into a mosaic of points and lines. It should be noted here that Alexander Bain had transmitted images telegraphically in the 1840s but the Nipkow disk improved on the encoding process. He applied for a patent in the imperial patent office in Berlin for an electric telescope for the electric reproduction of illuminating objects, in the category "electric apparatuses". This was granted on 15th January 1885, retroactive to 6th January 1884. It is not known whether Nipkow ever attempted a practical realization of this disk but one may assume that he himself never constructed one. Due to lack of interest the patent lapsed after 15 years. Nipkow took a position as a designer in a Berlin-Buchloh institute and did not continue work on picture broadcasting.

First TV systems

The first telecasts used an optical-mechanical picture scanning method, the method that Nipkow had helped create with his disk; he could claim some credit for the invention. Nipkow recounted his first sight of television at a Berlin radio show in 1928: "the televisions stood in dark cells. Hundreds stood and waited patiently for the moment at which they would see television for the first time. I waited among them, growing ever more nervous. Now for the first time I would see what I had devised 45 years ago. Finally I reached the front row; a dark cloth was pushed to the side, and I saw before me a flickering image, not easy to discern." By the beginning of the 1930's electronic picture scanning, based on the iconoscope invented by Vladimir Zworykin was prevalent and Nipkow's invention ceased to have direct relevance.

Transmitter Paul Nipkow

The leadership of the Third Reich saw the propaganda value in claiming television as a German invention, and in 1935 named the first public television station after Nipkow. He became honorary president of the "television council" of the "Reich Broadcasting Chamber" -- a "German television-pioneer" who long before had dreamed up an method of broadcasting he did not implement.

Death

Nipkow died alone in 1940 in Berlin.

External links


- [http://inventors.about.com/library/inventors/blnipkov.htm The Television System of Paul Nipkow] Nipkow, Paul Gottlieb Nipkow, Paul Gottlieb Nipkow, Paul Gottlieb

Electromechanical

In engineering, electromechanics combines the sciences of electromagnetism of electrical engineering and mechanics. Mechatronics is the discipline of engineering that combines mechanics, electronics and information technology. Electromechanical devices are those that combine electrical and mechanical parts. These include electric motors and mechanical devices powered by them, such as calculators and adding machines; switches, solenoids, relays, crossbar switches and stepping switches. Early on, "repeaters" originated with telegraphy and were electromechanical devices used to regenerate telegraph signals. The telephony crossbar switch is an electromechanical device for switching telephone calls. They were first widely installed in the 1950s in both the United States and England, and from there quickly spread to the rest of the world. They replaced most earlier designs like the Strowger switch in larger installations. Nikola Tesla, one of the great engineers, pioneered the field of electromechanics. Paul Nipkow proposed and patented the first electromechanical television system in 1885. Electrical typewriters developed, up to the 1980s, as "power-assisted typewriters." They contained a single electrical component in them, the motor. Where the keystroke had previously moved a typebar directly, now it engaged mechanical linkages that directed mechanical power from the motor into the typebar. This was also true of the forthcoming IBM Selectric. At Bell Labs, in the 1940s, the Bell Model V computer was developed. It was an electromechanical relay-based monster with cycle times in seconds. In 1968 Garrett Systems were invited to produce a digital computer to compete with electromechanical systems then under development for the main flight control computer in the US Navy's new F-14 Tomcat fighter. Today, though, common items which would have used electromechanical devices for control, today use, less expensive and more effectively, a standard integrated circuit (containing a few million transistors) and write a computer program to carry out the same task through logic. Transistors have replaced almost all electromechanical devices, are used in most simple feedback control systems, and appear in huge numbers in everything from traffic lights to washing machines.

See also


- Linear feedback shift register
- Adding machine
- Kerrison Predictor
- Thermostat
- Automatic transmission system
- Power engineering
- Power conversion
- Torpedo Data Computer
- Power rating
- Stepping switch
- Robotic telescope
- Electricity meter
- Solenoid valve
- Relay ---- Category:Electrical engineering

1907

1907 (MCMVII) was a common year starting on Tuesday (see link for calendar).

Events

January


- January 6 - Maria Montessori opens her first school and daycare center for working class children in Rome (Casa dei Bambini in San Lorenzo).
- January 14 - An earthquake in Kingston, Jamaica kills more than 1,000.
- January 23 - Charles Curtis from Kansas, becomes the first Native American US Senator.

February


- February 22 - Scouting is founded by Robert Baden-Powell in the United Kingdom.

March


- March 5 - The new Duma is opened in St. Petersburg, Russia and 40,000 demonstrators had to be dispersed by Russian troops.
- March 18 - Train robbery in Sweden (first and only as of 2004)
- March 22 - The first cabs with taxi meters began operating in London.

May


- May 8 - Mount Peleé erupts
- May 27 - A Bubonic plague outbreak begins in San Francisco, California.

June


- June 1 - Colin Blythe takes 17 wickets for 48 runs against Northamptonshire at Northampton in one day. It is the best analysis ever recorded for a county cricket match (or for a single day's bowling), and not bettered in first-class cricket until 1956.
- June 5 - BAPS Swaminarayan religion established.
- June 11 - George Dennett, aided by Gilbert Jessop, dismisses Northamptonshire for 12 runs, the lowest total in first-class cricket.

July


- July 6 - Guardians of Irish Crown Jewels notice that they have been stolen
- July 25 - Korea becomes a protectorate of Japan.

August


- August 1-9 - Baden-Powell leads the first Scout camp on Brownsea Island, England.
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