Editing Color television (section)

===Hybrid systems===
{{more citations needed section|date=September 2012}}
As was the case with black-and-white television, an electronic means of scanning would be superior to the mechanical systems like Baird's. The obvious solution on the broadcast end would be to use three conventional Iconoscopes with colored filters in front of them to produce an RGB signal. Using three separate tubes each looking at the same scene would produce slight differences in parallax between the frames, so in practice a single lens was used with a mirror or prism system to separate the colors for the separate tubes. Each tube captured a complete frame and the signal was converted into radio in a fashion essentially identical to the existing black-and-white systems.

The problem with this approach was there was no simple way to recombine them on the receiver end. If each image was sent at the same time on different frequencies, the images would have to be "stacked" somehow on the display, in real time. 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]]. [[RCA]] built just such a system in order to present the first electronically scanned color television demonstration on 5 February 1940, privately shown to members of the US Federal Communications Commission at the RCA plant in [[Camden, New Jersey]].<ref>Kenyon Kilbon, ''Pioneering in Electronics: A Short History of the Origins and Growth of RCA Laboratories, Radio Corporation of America, 1919 to 1964'', [http://www.davidsarnoff.org/kil-chapter09.html Chapter Nine – Television: Monochrome to Color] {{webarchive|url=https://web.archive.org/web/20080430082903/http://www.davidsarnoff.org/kil-chapter09.html |date=30 April 2008 }}, 1964. V.K. Zworykin with Frederick Olessi, ''Iconoscope: An Autobiography of Vladimir Zworykin'', [http://www.davidsarnoff.org/vkz-chapter10.html Chapter 10 – Television Becomes a Reality, 1945–1954] {{webarchive|url=https://web.archive.org/web/20080419083408/http://www.davidsarnoff.org/vkz-chapter10.html |date=19 April 2008 }}, 1971. "The system used two color filters in combination with photocells and a flying spot scanner for pickup." Alfred V. Roman, ''The Historical Development of Color Television Systems'', doctoral dissertation, New York University, 1967, p. 49.</ref> 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. Projection systems of this sort would become common decades later, however, with improvements in technology.

Another solution would be to use a single screen, but break it up into a pattern of closely spaced colored phosphors instead of an even coating of white. Three receivers would be used, each sending its output to a separate electron gun, aimed at its colored phosphor. However, this solution was not practical. The [[electron gun]]s used in monochrome televisions had limited resolution, and if one wanted to retain the resolution of existing monochrome displays, the guns would have to focus on individual dots three times smaller. This was beyond the [[state of the art]] of the technology at the time.

Instead, a number of hybrid solutions were developed that combined a conventional monochrome display with a colored disk or mirror. In these systems the three colored images were sent one after each other, in either complete frames in the "[[field-sequential color system]]", or for each line in the "line-sequential" system. In both cases a colored filter was rotated in front of the display in sync with the broadcast. 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.

The first practical example of this sort of system was again pioneered by John Logie Baird. In 1940 he publicly demonstrated a color television combining a traditional black-and-white display with a rotating colored disk. This device was very "deep", but was later improved with a mirror folding the light path into an entirely practical device resembling a large conventional console.<ref>{{cite web|url=http://www.bairdtelevision.com/colour.html|title=The World's First High Definition Colour Television System|website=www.bairdtelevision.com|url-status=live|archive-url=https://web.archive.org/web/20150403170543/http://www.bairdtelevision.com/colour.html|archive-date=3 April 2015}}</ref> However, Baird was not happy with the design, and as early as 1944 had commented to a British government committee that a fully electronic device would be better.

In 1939, Hungarian engineer [[Peter Carl Goldmark]] introduced an electro-mechanical system while at [[CBS]], which contained an [[Iconoscope]] sensor. 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&nbsp;rpm, and a similar disc spinning in synchronization in front of the cathode ray tube inside the receiver set.<ref name="Goldmark1">Peter C. Goldmark, assignor to Columbia Broadcasting System, "Color Television", [https://patents.google.com/patent/US2480571 U.S. Patent 2,480,571], filed 7 September 1940.</ref> The system was first demonstrated to the [[Federal Communications Commission]] (FCC) on 29 August 1940, and shown to the press on 4 September.<ref>Current Broadcasting 1940</ref><ref>"Color Television Success in Test", ''[[The New York Times]]'', 30 August 1940, p. 21.</ref><ref>"Color Television Achieves Realism", ''The New York Times'', 5 September 1940, p. 18.</ref><ref>"[https://books.google.com/books?id=JScDAAAAMBAJ&pg=PA120 New Television System Transmits Images in Full Color]", ''Popular Science'', December 1940, p. 120.</ref>

CBS began experimental color field tests using film as early as 28 August 1940, and live cameras by 12 November.<ref>"Color Television Success in Test", ''The New York Times'', 30 August 1940, p. 21. "CBS Demonstrates Full Color Television", ''[[The Wall Street Journal]]'', 5 September 1940, p. 1. "Television Hearing Set", ''The New York Times'', 13 November 1940, p. 26.</ref> [[NBC]] (owned by RCA) made its first field test of color television on 20 February 1941. CBS began daily color field tests on 1 June 1941.<ref>Ed Reitan, [http://colortelevision.info/rca-nbc_firsts.html RCA-NBC Color Firsts in Television (commented)] {{webarchive |url=http://archive.wikiwix.com/cache/20141225155750/http://colortelevision.info/rca-nbc_firsts.html |date=25 December 2014}}</ref> 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, viewing of the color field tests was restricted 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 22 April 1942, to 20 August 1945, limiting any opportunity to introduce color television to the general public.<ref>"Making of Radios and Phonographs to End April 22", ''The New York Times'', 8 March 1942, p. 1. "Radio Production Curbs Cover All Combinations", ''The Wall Street Journal'', 3 June 1942, p. 4. "WPB Cancels 210 Controls; Radios, Trucks in Full Output", ''The New York Times'', 21 August 1945, p. 1.</ref><ref>Bob Cooper, "[http://www.earlytelevision.org/color_tv_cooper.html Television: The Technology That Changed Our Lives] {{webarchive |url=https://web.archive.org/web/20141223155937/http://www.earlytelevision.org/color_tv_cooper.html |date=December 23, 2014}}", Early Television Foundation.</ref>