Television
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Television (often abbreviated to TV, T.V., or more recently, tv) is a widely used telecommunication system for broadcasting and receiving moving pictures and sound over a distance from all around the world. The term may also be used to refer specifically to a television set, programming or television transmission. The word is derived from mixed Latin and Greek roots, meaning "far sight": Greek tele (τῆλε), far, and Latin vision, sight (from video, vis- to see, or to view in the first person).
Since it first became commercially available from the late 1930s, the television set has become a common household communications device in homes and institutions, particularly in the First World, as a source of entertainment and news. Since the 1970s, video recordings on VCR tapes and later, digital playback systems such as DVDs, have enabled the television to be used to view recorded movies and other programs.
A television system may be made up of multiple components, so a screen which lacks an internal tuner to receive the broadcast signals is called a monitor rather than a television. A television may be built to receive different broadcast or video formats, such as high-definition television, commonly referred to as HDTV. HDTV costs more than normal TV but is becoming more available.
Contents
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[edit] History
[edit] Technology
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It has been suggested that this section be split into a new article entitled Technology of Television. (Discuss) |
[edit] Elements of a television system
1. power switch / volume
2. brightness
3. pitch
4. vertical synchro
| 5. horizontal synchro 6. contrast 7. channel tuning 8. channel switch |
The elements of a simple broadcast television system are:
- An image source. This is the electrical signal representing the visual image, and may be from a camera in the case of live images, a video tape recorder for playback of recorded images, or a film chain-telecine-flying spot scanner for transmission of motion pictures (films).
- A sound source. This is an electrical signal from a microphone or from the audio output of a video tape recorder or motion picture film scanner.
- A transmitter, which generates radio signals (radio waves) and encodes them with picture and sound information.
- An antenna coupled to the output of the transmitter for broadcasting the encoded signals.
- An antenna to receive the broadcast signals.
- A receiver (also called a tuner), which decodes the picture and sound information from the broadcast signals, and whose input is coupled to the antenna.
- A display device, which turns the electrical signals into visual images.
- An audio amplifier and loudspeaker, which turns electrical signals into sound waves (speech, music, and other sounds) to accompany the images.
Practical television systems include equipment for selecting different image sources, mixing images from several sources at once, insertion of pre-recorded video signals, synchronizing signals from many sources, and direct image generation by computer for such purposes as station identification. The facility for housing such equipment, as well as providing space for stages, sets, offices, etc., is called a television studio, and may be located many miles from the transmitter. Communication from the studio to the transmitter is accomplished via a dedicated cable or radio system.
Television signals were originally transmitted exclusively via land-based transmitters. The quality of reception varied greatly, dependent in large part on the location and type of receiving antenna. This led to the proliferation of large rooftop antennas to improve reception in the 1960s, replacing set-top dipole or "rabbit ears" antennas, which however remained popular. Antenna rotors, set-top controlled servo motors to which the mast of the antenna is mounted, to enable rotating the antenna such that it points to the desired transmitter, would also become popular.
In most cities today, cable television providers deliver signals over coaxial or fiber-optic cables for a fee. Signals can also be delivered by radio from satellites in geosynchronous orbit and received by parabolic dish antennas, which are comparatively large for analog signals, but much smaller for digital. Like cable providers, satellite television providers also require a fee, often less than cable systems. The affordability and convenience of digital satellite reception has led to the proliferation of small dish antennas outside many houses and apartments.
Digital systems may be inserted anywhere in the chain to provide better image transmission quality, reduction in transmission bandwidth, special effects, or security of transmission from reception by non-subscribers. A home today might have the choice of receiving analog or HDTV over the air, analog or digital cable with HDTV from a cable television company over coaxial cable, or even from the phone company over fiber optic lines. On the road, television can be received by pocket sized televisions, recorded on tape or digital media players, or played back on wireless phones (mobile or "cell" phones) over a high-speed or "broadband" internet connection.
[edit] Display technology
- See also: Comparison of display technology, Liquid crystal display television, and Large-screen television technology
Thanks to the advances in display technology, there are now several kinds of video displays used in modern TV sets:
- CRT (cathode-ray tube): The most common screens were direct-view CRTs for up to roughly 100 cm (40 inch) (in 4:3 ratio) and 115 cm (45 inch) (in 16:9 ratio) diagonals. These are the least expensive, and are a refined technology that can still provide the best overall picture quality value. As they do not have a fixed native resolution, they are capable of displaying sources with different resolutions at the best possible image quality. The frame rate or refresh rate of a typical NTSC format CRT TV is 29.97 Hz, and for the PAL format, 25 Hz, both are scanned with two fields per frame in an interlaced fashion. A typical NTSC broadcast signal's visible portion has an equivalent resolution of about 640x480 pixels. It actually could be slightly higher than that, but the vertical blanking interval (VBI), allows other signals to be carried along with the broadcast.
- Rear projection (RPTV): Most very large screen TVs (to 254 cm (100 inches) or more) use projection technology. Three types of projection systems are used in projection TVs: CRT-based, LCD-based, and DLP (reflective micromirror chip) -based, D-ILA and LCOS-based. Projection television has been commercially available since the 1970s, but at that time could not match the image sharpness of the CRT; current models are vastly improved, and offer a cost-effective large-screen display.
- A variation is a video projector, using similar technology, which projects onto a screen. This is often referred to as "front projection".
- Flat panel (LCD or plasma): 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 25.4 mm (1 inch) thick and can be hung on a wall like a picture or put over a pedestal. Some models can also be used as computer monitors.
- LED technology has become one of the choices for outdoor video and stadium uses, since the advent of bright LEDs and driver circuits. LEDs enable scalable ultra-large flat panel video displays that other technologies may never be able to match in performance.
Each has its pros and cons. Flat panel LCD and plasma displays have a wide viewing angle (around 178 degrees) so they may best suited for a home theatre with a wide seating arrangement. Rear projection screens do not perform well in daylight or well-lit rooms and so are only suited to darker viewing areas.
[edit] Terminology for televisions
Pixel resolution is the amount of individual points known as pixels on a given screen. Use of the word pixel is fairly new, as it only dates to the introduction of the DVD digital display standard. Before the year 2000 horizontal lines of resolution was the standard method of measurement for analog video. For example, a VHS VCR might be described as having 250 lines of resolution as measured across a circle circumscribed in the center of the screen (approximately 440 pixels edge-to-edge).
A typical resolution of 720×480 means that the television display has 720 pixels across and 480 pixels on the vertical axis. The higher the resolution on a specified display the sharper the image. Contrast ratio is a measurement of the range between the brightest and darkest points on the screen.
The higher the contrast ratio, the better looking picture there is in terms of richness, deepness, and shadow detail. The brightness of a picture measures how vibrant and impacting the colors are. Measured in cd / m2 equivalent to the amount of candles required to power the image.
On the other hand, the so-called brightness and contrast adjustment controls on televisions and monitors are traditionally used to control different aspects of the picture display.
The brightness control shifts the black point, or shadow level, primarily affecting the contrast ratio or gamma of the image, while the contrast control primarily controls the image intensity or brightness.[1]
[edit] Transmission band
There are various bands on which televisions operate depending upon the country. The VHF and UHF signals in bands III to V are generally used. Lower frequencies do not have enough bandwidth available for television. Although the BBC initially used Band I VHF at 45 MHz, this frequency is (in the UK) no longer in use for this purpose. Band II is used for FM radio transmissions. Higher frequencies behave more like light and do not penetrate buildings or travel around obstructions well enough to be used in a conventional broadcast TV system, so they are generally only used for MMDS and satellite television, which uses frequencies from 2 to 12 GHz. TV systems in most countries relay the video as an AM (amplitude-modulation) signal and the sound as a FM (frequency-modulation) signal. An exception is France, where the sound is AM.
[edit] Aspect ratios
Aspect ratio refers to the ratio of the horizontal to vertical measurements of a television's picture. 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 technical aspect ratio limitations at all.) The BBC's television service used a more squarish 5:4 ratio from 1936 to 3 April 1950, when it too switched to a 4:3 ratio. This did not present significant problems, as most sets at the time used round tubes which were easily adjusted to the 4:3 ratio when the transmissions changed.
In the early 1950s, movie studios moved towards widescreen aspect ratios such as CinemaScope 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 4:3 aspect ratio movies are rare.
Yet the various television systems were not originally designed to be compatible with film at all. Traditional, narrow-screen movies are projected onto a television camera either so that the top of the screens line up to show facial features, or, for films with subtitles, the bottoms. What this means is that filmed newspapers or long captions filling the screen for explanation are cut off at each end. Similarly, while the frame rate of sound films is 24 per second, the screen scanning rate of the NTSC is 29.97 Hz (per second), which requires a complex scanning schedule. That of PAL and SECAM are 50 Hz, which means that films are shortened (and the sound is offkey) by scanning each frame twice for 25 per second.
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 (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 1.66:1 through 1.85:1 to 2.35:1. There are two methods for transporting widescreen content, the most common 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 35 mm film frame. The image is compressed horizontally when recorded, then expanded again when played back. The anamorphic widescreen 16:9 format was first introduced via European PALPlus television broadcasts and then later on "widescreen" DVDs; the ATSC HDTV system uses straight widescreen format, no horizontal compression or expansion is used.
Recently "widescreen" has spread from television to computing where both desktop and laptop computers are commonly equipped with widescreen displays. There are some complaints about distortions of movie picture ratio due to some DVD playback software not taking account of aspect ratios; but this may 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' assumption that people viewing 16:9 content on their computer would prefer that an area of the screen be reserved for playback controls, subtitles or their Taskbar, as opposed to viewing content full-screen.
[edit] Aspect ratio incompatibility
The television industry's changing of aspect ratios is not without difficulties, and can present a considerable problem.
Displaying a widescreen aspect (rectangular) image on a conventional aspect (square or 4:3) 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 or a viewer)
- with the image horizontally compressed
A conventional aspect (square or 4:3) image on a widescreen aspect (rectangular with longer horizon) display can be shown:
- in "pillar box" format, with black vertical bars to the left and right
- with upper and lower portions of the image cut off (or in "tilt and scan", parts selected by an operator)
- with the image vertically compressed
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. In recent years, the cinematographic process known as Super 35 (championed by James Cameron) has been used to film a number of major movies such as Titanic, Legally Blonde, Austin Powers, and Crouching Tiger, Hidden Dragon (see also: Films shot in Super 35). This process results in a camera-negative which can then be used to create both wide-screen theatrical prints, and standard "full screen" releases for television/VHS/DVD which avoid the need for either "letterboxing" or the severe loss of information caused by conventional "pan-and-scan" cropping.
[edit] Sound
- Further information: NICAM, MTS, and Zweikanalton
[edit] Data
- Further information: Teletext
[edit] The end of analog television broadcasting
[edit] NTSC
In North America, the basic signal standards since 1941 have been compatible enough that even the oldest monochrome televisions can still receive color broadcasts in 2007. However, the United States Congress has passed a law which requires the cessation of all conventional television broadcast signals by February 2009. If the law is not changed again, then after that date all NTSC standard televisions, with analog-only tuners, will go dark unless fitted with digital ATSC tuners, and the spectrum previously occupied by those analog channels will be auctioned off by the United States' Federal Communications Commission for other uses. The analog cut-off date has been changed by Congress in the past.
[edit] PAL and SECAM
PAL and SECAM are expected not to be broadcast in Europe and Eurasia by the mid-2020s. PAL-M may have a similar decommissioning timeline.
The European Union has recommended its members to have closed down analogue terrestrial television by 2012. Luxembourg and the Netherlands had already completed their closedowns in 2006, and Finland and Sweden will have closed down their analogue broadcasts in 2007. Meanwhile, some countries may have difficulties making the 2012 deadline.
Britain started its programme of switching off analogue transmitters in October 2007. At 2am on Wednesday 17 October 2007 the BBC2 transmitter covering the Whitehaven and Copeland areas (NW England) was turned off. The remaining four analogue channels cease broadcasting in the region on Wednesday 14 November. The original five channels will then only be available in digital form, alongside some 15 additional free to air channels.
[edit] Television add-ons
The television was the first consumer mass market for video displays. Today there are many television add-ons including video game consoles, VCRs, Set-top boxes for Cable, Satellite and DVB-T compliant Digital Television reception, DVD players, or Digital Video Recorders (including personal video recorders, PVRs). The add-on market continues to grow as new technologies are developed. Computers, the internet, and even pocket devices such as the iPod provide other ways to consume video content.
[edit] New developments
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[edit] Exterior designs
In the early days of television, cabinets were made of wood grain, however, they were phased out in the 1980s. There has been a modern comeback of woodgrain.[2][3]
[edit] Geographical usage
[edit] Content
[edit] Programming
- See also: Category:Television genres
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 free-to-air (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 on that network. Also, Affiliates rarely buy or produce non-network programming that is not centred around local events.
[edit] Advertising
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The examples and perspective in this section may not represent a worldwide view of the subject. Please improve this article or discuss the issue on the talk page. |
Since inception in the U.S. in 1940, TV commercials have become one of the most effective, most persuasive, and most popular methods of selling products of many sorts, especially consumer goods. U.S. advertising rates are determined primarily by Nielsen Ratings. The time of the day and popularity of the channel determine how much a television commercial can cost. For example, the highly popular American Idol can cost approximately $750,000 for a thirty second block of commercial time; while the same amount of time for the World Cup and the Super Bowl can cost several million dollars.
In recent years, the paid program or infomercial has become common, usually in lengths of 30 minutes or one hour. Some drug companies have even created "news" items for broadcast, paying program directors to use them.[4]
Some TV programs also weave advertisements into their shows, a practice begun in film and known as product placement. For example, a character could be drinking a certain kind of soda, going to a particular chain restaurant, or driving a certain make of car. (This is sometimes very subtle, where shows have vehicles provided by manufacturers for low cost, rather than wrangling them.) Sometimes a specific brand or trade mark, or music from a certain artist or group, is used. (This excludes guest appearances by artists, who perform on the show.)
[edit] Television genres
Television genres include a broad range of programming types that entertain, inform, and educate viewers. The most expensive entertainment genres to produce are usually drama and dramatic miniseries. However, other genres such as historical Western genres may also have high production costs.
Popular entertainment genres include action-oriented shows such as police, crime, detective dramas, horror or thriller shows. As well, there are also other variants of the drama genre, such as medical dramas and daytime Soap Operas. Sci-fi (Science fiction) shows can fall into either the drama category or the action category, depending on whether they emphasize philosophical questions or explosive space battles. Comedy is a popular genre which includes sitcoms (Situation Comedy) and animated shows for the adult demographic such as South Park.
The least expensive forms of entertainment programming are game shows, talk shows, variety shows, and reality TV. Game shows show contestants answering questions and solving puzzles to win prizes. Talk shows feature interviews with film, television and music celebrities and public figures. Variety shows feature a range of musical performers and other entertainers such as comedians and magicians introduced by a host or Master of Ceremonies. There is some crossover between some talk shows and variety shows, because leading talk shows often feature performances by bands, singers, comedians, and other performers in between the interview segments.
Reality TV shows show "regular" people (i.e., not actors) who are facing unusual challenges or experiences, ranging from arrest by police officers (COPS) to weight loss (The Biggest Loser). A variant version of reality shows depicts celebrities doing mundane activities such as going about their everyday life (The Osbournes) or doing manual labour jobs (Simple Life).
One of the television genres, the children's and youth genre is defined by the audience, rather than by the content of the programming. Children's programming includes animated programs aimed at the child demographic, documentaries for children, and music/variety shows targeted at kids. There is overlap between the children's/youth genre and other genres, such as the educational genre.
Television genres that aim to educate and inform viewers include educational shows, DIY programs on cooking, gardening, or home renovation, history shows, performing arts programs, and documentaries. Other genres which inform viewers include news, sports, and public affairs programming.
[edit] Social aspects
Television has played a pivotal role in the socialisation of the 20th and 21st centuries. There are many social aspects of television that can be addressed, including:
- Positive effects
- Negative effects
- Gender and television
- Politics and television
- Socialising children
- Technology trends
- Suitability for audience
- Alleged dangers
- Propaganda delivery
- Educational advantages
[edit] Environmental aspects
With high lead content in CRTs, and the rapid diffusion of new, flat-panel display technologies, some of which (LCDs) use lamps containing mercury, there is growing concern about electronic waste from discarded televisions. Related occupational health concerns exist, as well, for disassemblers removing copper wiring and other materials from CRTs. Further environmental concerns related to television design and use relate to the devices' increasing electrical energy requirements.[5]
[edit] References
- ^ John Watkinson, Convergence in Broadcast and Communications Media: The Fundamentals of Audio, Video, Data, Focal Press, 2001, ISBN 0240515099
- ^ HANNSwood 10 inch LCD Television, HANNspree
- ^ Retro Thing: Video + TV.
- ^ Jon Stewart of "The Daily Show" was mock-outraged at this, saying, "That's what we do!", and calling it a new form of television, "infoganda".
- ^ The Rise of the Machines: A Review of Energy Using Products in the Home from the 1970s to Today (PDF). Energy Saving Trust (July 3, 2006). Retrieved on 2007-08-31.
[edit] Further reading
| Find more information on Television by searching Wikipedia's sister projects | |
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- Albert Abramson, The History of Television, 1942 to 2000, Jefferson, NC, and London, McFarland, 2003, ISBN 0786412208.
- Pierre Bourdieu, On Television, The New Press, 2001.
- Tim Brooks and Earle March, The Complete Guide to Prime Time Network and Cable TV Shows, 8th ed., Ballantine, 2002.
- Jacques Derrida and Bernard Stiegler, Echographies of Television, Polity Press, 2002.
- David E. Fisher and Marshall J. Fisher, Tube: the Invention of Television, Counterpoint, Washington, DC, 1996, ISBN 1887178171.
- Steven Johnson, Everything Bad is Good for You: How Today's Popular Culture Is Actually Making Us Smarter, New York, Riverhead (Penguin), 2005, 2006, ISBN 1594481946.
- Jerry Mander, Four Arguments for the Elimination of Television, Perennial, 1978.
- Jerry Mander, In the Absence of the Sacred, Sierra Club Books, 1992, ISBN 0871565099.
- Neil Postman, Amusing Ourselves to Death: Public Discourse in the Age of Show Business, New York, Penguin US, 1985, ISBN 0670804541.
- Evan I. Schwartz, The Last Lone Inventor: A Tale of Genius, Deceit, and the Birth of Television, New York, Harper Paperbacks, 2003, ISBN 0060935596.
- Beretta E. Smith-Shomade, Shaded Lives: African-American Women and Television, Rutgers University Press, 2002.
- Alan Taylor, We, the Media: Pedagogic Intrusions into US Mainstream Film and Television News Broadcasting Rhetoric, Peter Lang, 2005, ISBN 3631518528.
[edit] External links
- The Farnsworth Invention: Fact -v- Fiction
- Farnovision
- The Canadian Museum of Civilization - History of Television
- Early Television Foundation and Museum
- Television's History — The First 75 Years
- The Encyclopedia of Television at the Museum of Broadcast Communications
- MZTV Museum of Television Some of the rarest sets in America
- A History of Television at the Canada Science and Technology Museum
- TV Fool - Coverage maps and info for US broadcast television stations
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| Analog broadcast | 525 lines: NTSC • NTSC-J • PAL-M
625 lines: PAL • PAL-N • PALplus • SECAM Defunct systems: Pre-1940 • 405 lines • 819 lines • Baird-Nipkow • MAC • MUSE Multichannel audio: BTSC (MTS) • NICAM-728 • Zweiton (A2, IGR) • EIAJ Hidden signals: Captioning • Teletext • CGMS-A • GCR • PDC • VBI • VEIL • VITC • WSS • XDS |
| Digital broadcast | Interlaced: SDTV (480i, 576i) • HDTV (1080i)
Progressive: LDTV (240p, 288p, 1seg) • EDTV (480p, 576p) • HDTV (720p, 1080p) Digital TV standards (MPEG-2):ATSC, DVB, ISDB, DMB-T/H Digital TV standards (MPEG-4 AVC):DMB-T/H,DVB,SBTVD,ISDB (1seg) Multichannel audio: AAC (5.1) • Musicam • PCM • LPCM Hidden signals: Captioning • Teletext • (CPCM/Broadcast flag) • AFD • EPG Digital cinema: UHDV (2540p, 4320p) • DCI |
| Technical issues | 14:9 • MPEG transport • Standards conversion • Video processing • VOD • HDTV blur |
