How Do High Definition Televisions Differ From Traditional Ones ~UPD~
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High-definition, or digital lenses, have been described as the most important improvement in prescription eyewear in the last 100 years. The improvement wearers see in moving from traditional lenses to digital lenses has been compared to the difference between a tube television and a new high-definition television, or an off the rack suit compared to a custom suit. If you are dissatisfied with the clarity of your eyesight with your current traditional glasses, fully custom digital free-form eyeglass lenses can provide you with clearer vision in every gaze direction and in all lighting conditions.
The result is that high-definition lenses provide the widest fields of view, sharper image quality, better peripheral vision, and improve your ability to distinguish subtle differences in light versus dark.
High-definition televisions were once the best way to watch your favorite shows or movies to enjoy viewing them at their very best resolution. Now, even regular HDTVs are becoming obsolete with the rise of ultra-high-definition sets that offer four times the resolution.
All televisions make their pictures the same way, building up onelarge image from many small dots, squares, or rectangles calledpixels. The biggest single difference between HDTV and whatcame before it (which is known as standard definition TV or SDTV) isthe sheer number of these pixels.
Another way in which HDTV differs from SDTV lies in the way thepixels are painted on the screen. In SDTV and in earlier versions ofHDTV, odd-numbered rows were "painted" first and theneven-numbered rows were painted in between them, before theodd-numbered rows were painted with the next frame (the next movingpicture in the sequence). This is called interlacing, and itmeans you can fill the screen more quickly with an image than if youpainted every single row in turn (which is called progressivescanning). It worked very well on old-style cathode-raytelevisions, and cruder LCD televisions that built picturesmore slowly than they do today, but it's not really necessary anymorenow there are better LCD technologies. For this reason, the bestHDTVs use progressive scanning instead, which means they drawfast-action pictures (for example baseball games) both in more detailand more smoothly. So when you see an HDTV described as 1080p, itmeans it has 1080 rows of pixels and the picture is made byprogressive scanning; an HDTV labeled 720i has only 720 rows and usesinterlacing; a 720p has 720 rows and uses progressive scanning. (SDTVwould be technically described as 480i using the same jargon.)
Artwork: How many more pixels do you get for your money? This artwork compares the pixel dimensions of common SDTV and HDTV formats: SDTV (yellow, 640 × 480), Full HD/HDTV 1080p (orange, 1920 × 1080), 4K UHD (blue, 3840 × 2160), and 8K UHD (red, 7680 × 4320). If all were the same size, you can imagine how much more detail would be packed into the higher-resolution screens.You can see that there's a big difference between Full HD and 4K.Lesser versions of HD, such as 720p, come in between the orange and yellow rectangles.Decent smartphones typically now have Quad HD (2560 × 1440) or Quad HD+ (~3000 × 1440)screens.
Herbert E. Ives and Frank Gray of Bell Telephone Laboratories gave a dramatic demonstration of mechanical television on 7 April 1927. Their reflected-light television system included both small and large viewing screens. The small receiver had a 2-inch-wide by 2.5-inch-high screen (5 by 6 cm). The large receiver had a screen 24 inches wide by 30 inches high (60 by 75 cm). Both sets could reproduce reasonably accurate, monochromatic, moving images. Along with the pictures, the sets received synchronized sound. The system transmitted images over two paths: first, a copper wire link from Washington to New York City, then a radio link from Whippany, New Jersey. Comparing the two transmission methods, viewers noted no difference in quality. Subjects of the telecast included Secretary of Commerce Herbert Hoover. A flying-spot scanner beam illuminated these subjects. The scanner that produced the beam had a 50-aperture disk. The disc revolved at a rate of 18 frames per second, capturing one frame about every 56 milliseconds. (Today's systems typically transmit 30 or 60 frames per second, or one frame every 33.3 or 16.7 milliseconds respectively.) Television historian Albert Abramson underscored the significance of the Bell Labs demonstration: "It was in fact the best demonstration of a mechanical television system ever made to this time. It would be several years before any other system could even begin to compare with it in picture quality."
At the Berlin Radio Show in August 1931, Manfred von Ardenne gave a public demonstration of a television system using a CRT for both transmission and reception. However, Ardenne had not developed a camera tube, using the CRT instead as a flying-spot scanner to scan slides and film. Philo Farnsworth gave the world's first public demonstration of an all-electronic television system, using a live camera, at the Franklin Institute of Philadelphia on 25 August 1934, and for ten days afterwards. Mexican inventor Guillermo González Camarena also played an important role in early television. His experiments with television (known as telectroescopía at first) began in 1931 and led to a patent for the "trichromatic field sequential system" color television in 1940. In Britain, the EMI engineering team led by Isaac Shoenberg applied in 1932 for a patent for a new device they called "the Emitron", which formed the heart of the cameras they designed for the BBC. On 2 November 1936, a 405-line broadcasting service employing the Emitron began at studios in Alexandra Palace, and transmitted from a specially built mast atop one of the Victorian building's towers. It alternated for a short time with Baird's mechanical system in adjoining studios, but was more reliable and visibly superior. This was the world's first regular "high-definition" television service.
The original U.S. iconoscope was noisy, had a high ratio of interference to signal, and ultimately gave disappointing results, especially when compared to the high definition mechanical scanning systems then becoming available. The EMI team, under the supervision of Isaac Shoenberg, analyzed how the iconoscope (or Emitron) produces an electronic signal and concluded that its real efficiency was only about 5% of the theoretical maximum. They solved this problem by developing, and patenting in 1934, two new camera tubes dubbed super-Emitron and CPS Emitron. The super-Emitron was between ten and fifteen times more sensitive than the original Emitron and iconoscope tubes and, in some cases, this ratio was considerably greater. It was used for outside broadcasting by the BBC, for the first time, on Armistice Day 1937, when the general public could watch on a television set as the King laid a wreath at the Cenotaph. This was the first time that anyone had broadcast a live street scene from cameras installed on the roof of neighboring buildings, because neither Farnsworth nor RCA would do the same until the 1939 New York World's Fair.
One of the great technical challenges of introducing color broadcast television was the desire to conserve bandwidth, potentially three times that of the existing black-and-white standards, and not use an excessive amount of radio spectrum. In the United States, after considerable research, the National Television Systems Committee approved an all-electronic system developed by RCA, which encoded the color information separately from the brightness information and greatly reduced the resolution of the color information to conserve bandwidth. As black-and-white televisions could receive the same transmission and display it in black-and-white, the color system adopted is [backwards] "compatible". ("Compatible Color", featured in RCA advertisements of the period, is mentioned in the song "America", of West Side Story, 1957.) The brightness image remained compatible with existing black-and-white television sets at slightly reduced resolution, while color televisions could decode the extra information in the signal and produce a limited-resolution color display. The higher resolution black-and-white and lower resolution color images combine in the brain to produce a seemingly high-resolution color image. The NTSC standard represented a major technical achievement.
WRGB claims to be the world's oldest television station, tracing its roots to an experimental station founded on 13 January 1928, broadcasting from the General Electric factory in Schenectady, NY, under the call letters W2XB. It was popularly known as "WGY Television" after its sister radio station. Later in 1928, General Electric started a second facility, this one in New York City, which had the call letters W2XBS and which today is known as WNBC. The two stations were experimental in nature and had no regular programming, as receivers were operated by engineers within the company. The image of a Felix the Cat doll rotating on a turntable was broadcast for 2 hours every day for several years as new technology was being tested by the engineers. On 2 November 1936, the BBC began transmitting the world's first public regular high-definition service from the Victorian Alexandra Palace in north London. It therefore claims to be the birthplace of television broadcasting as we know it from now on.
Cable television is a system of broadcasting television programming to paying subscribers via radio frequency (RF) signals transmitted through coaxial cables or light pulses through fiber-optic cables. This contrasts with traditional terrestrial television, in which the television signal is transmitted over the air by radio waves and received by a television antenna attached to the television. In the 2000s, FM radio programming, high-speed Internet, telephone service, and similar non-television services may also be provided through these cables. The abbreviation CATV is sometimes used for cable television in the United States. It originally stood for Community Access Television or Community Antenna Television, from cable television's origins in 1948: in areas where over-the-air reception was limited by distance from transmitters or mountainous terrain, large "community antennas" were constructed, and cable was run from them to individual homes. 2b1af7f3a8