Color television
However, post-processing of the optic nerve and other portions of the human visual system combine the information from the rods and cones to re-create what appears to be a high-resolution color image.
Modern TV sets can display multiple field rates (50, 59.94, or 60, in either interlaced or progressive scan) while accepting power at various frequencies (often the operating range is specified as 48–62 Hz).
Being mechanically driven, perfect synchronization of the sending and receiving discs was not easy to ensure, and irregularities could result in major image distortion.
With these systems, the BBC began regularly scheduled black-and-white television broadcasts in 1936, but these were shut down again with the start of World War II in 1939.
[6] Polish inventor Jan Szczepanik patented a color television system in 1897, using a selenium photoelectric cell at the transmitter and an electromagnet controlling an oscillating mirror and a moving prism at the receiver.
The simplest way to do this would be to reverse the system used in the camera: arrange three separate black-and-white displays behind colored filters and then optically combine their images using mirrors or prisms onto a suitable screen, like frosted glass.
[15] This system, however, suffered from the twin problems of costing at least three times as much as a conventional black-and-white set, as well as having very dim pictures, the result of the fairly low illumination given off by tubes of the era.
Since three separate images were being sent in sequence, if they used existing monochrome radio signaling standards they would have an effective refresh rate of only 20 fields, or 10 frames, a second, well into the region where flicker would become visible.
In order to avoid this, these systems increased the frame rate considerably, making the signal incompatible with existing monochrome standards.
Since no existing television would be able to tune in these stations, they were free to pick an incompatible system and allow the older VHF channels to die off over time.
CBS displayed improved versions of its original design, now using a single 6 MHz channel (like the existing black-and-white signals) at 144 fields per second and 405 lines of resolution.
[37] Viewing was again restricted: 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.
[45][46] RCA chairman David Sarnoff later charged that the NPA's order had come "out of a situation artificially created by one company to solve its own perplexing problems" because CBS had been unsuccessful in its color venture.
Unlike the hybrid systems, dot-sequential televisions used a signal very similar to existing black-and-white broadcasts, with the intensity of every dot on the screen being sent in succession.
In his system the output of the three camera tubes were re-combined to produce a single "luminance" value that was very similar to a monochrome signal and could be broadcast on the existing VHF frequencies.
But solutions to these problems were in the pipeline, and RCA in particular was investing massive sums (later estimated at $100 million) to develop a usable dot-sequential tube.
In July 1938 the shadow mask color television was patented by Werner Flechsig (1900–1981) in Germany, and was demonstrated at the International radio exhibition Berlin in 1939.
The possibility of a compatible color broadcast system was so compelling that the NTSC decided to re-form, and held a second series of meetings starting in January 1950.
Unlike the FCC approach where a standard was simply selected from the existing candidates, the NTSC would produce a board that was considerably more pro-active in development.
RCA first made publicly announced field tests of the dot sequential color system over its New York station WNBT in July 1951.
[57][58] Goldmark had actually applied for a patent for the same field-sequential tricolor system in the US on 7 September 1940,[17] while González Camarena had made his Mexican filing 19 days before, on 19 August.
[citation needed] In 1956, NBC's The Perry Como Show became the first live network television series to present a majority of episodes in color.
[63] CBS's The Big Record, starring pop vocalist Patti Page, in 1957–1958 became the first television show broadcast in color for an entire season.
[101] Early color sets were either floor-standing console models or tabletop versions nearly as bulky and heavy, so in practice, they remained firmly anchored in one place.
The introduction of GE's relatively compact and lightweight Porta-Color set in the spring of 1966 made watching color television a more flexible and convenient proposition.
[citation needed] The first two color television broadcasts in Europe were made by early tests in France (SECAM) between 1963 and 1966, then officially launched in October 1967 and by the UK's BBC2 beginning on 1 July 1967 and West Germany's Das Erste and ZDF in August, both using the PAL system.
As a result, and after a test during the 1972 Summer Olympics, Italy was one of the last European countries to officially adopt the PAL system in the 1976–1977 season.
Saudi Arabia, the United Arab Emirates, Kuwait, Bahrain, and Qatar followed in the mid-1970s, but Israel and Cyprus continued to broadcast in black and white until the early 1980s.
[117] Some other countries in South America, including Bolivia, Paraguay, Peru, and Uruguay [1981], did not broadcast full-time color television until the early 1980s.
Most of Asia, Western Europe, Australia, Africa, and Eastern South America use PAL (though Brazil and Cambodia uses a hybrid PAL-M system).
