Editing Trinitron (section)

===Color television===

[[File:Namibia - Windhoek train station 23.jpg|thumb|A 1970s tabletop size Trinitron]]

{{See also|Color television}}

Color television had been demonstrable since the 1920s starting with [[John Logie Baird]]'s system. However, it was only in the late 1940s that it was perfected by both CBS and RCA. At the time, a number of systems were being proposed that used separate red, green and blue signals (RGB), broadcast in succession. Most systems broadcast entire frames in sequence, with a colored filter (or "[[Color gel|gel]]") that rotated in front of an otherwise conventional black and white television tube.{{citation needed|date=December 2017}} Because they broadcast separate signals for the different colors, all of these systems were incompatible with existing black and white sets. Another problem was that the mechanical filter made them flicker unless very high refresh rates were used. In spite of these problems, the United States Federal Communications Commission selected a sequential-frame 144 frame/s standard from [[CBS]] as their color broadcast in 1950.<ref>Ed Reitan, [http://novia.net/~ereitan/Color_Sys_CBS.html "CBS Field Sequential Color System"] {{Webarchive|url=https://web.archive.org/web/20100105183213/http://novia.net/~ereitan/Color_Sys_CBS.html |date=2010-01-05 }}, 24 August 1997</ref>

[[RCA]] worked along different lines entirely, using the luminance-chrominance system. This system did not directly encode or transmit the RGB signals; instead it combined these colors into one overall brightness figure, the "[[luminance]]". Luminance closely matched the black and white signal of existing broadcasts, allowing it to be displayed on existing televisions. This was a major advantage over the mechanical systems being proposed by other groups. Color information was then separately encoded and folded into the signal as a high-frequency modification to produce a [[composite video]] signal – on a black and white television this extra information would be seen as a slight randomization of the image intensity, but the limited resolution of existing sets made this invisible in practice. On color sets the signal would be extracted, decoded back into RGB, and displayed.
Although RCA's system had enormous benefits, it had not been successfully developed because it was difficult to produce the display tubes. Black and white TVs used a continuous signal and the tube could be coated with an even deposit of phosphor. With the [[Color television#Compatible color|compatible color]] encoding scheme originally developed by [[Georges Valensi]] in 1938, the color was changing continually along the line, which was far too fast for any sort of mechanical filter to follow. Instead, the phosphor had to be broken down into a discrete pattern of colored spots. Focusing the proper signal on each of these tiny spots was beyond the capability of [[electron gun]]s of the era, and RCA's early experiments used three-tube projectors, or mirror-based systems known as "[[Triniscope]]".<ref name=rca>Ed Reitan, [http://novia.net/~ereitan/Color_Sys_RCA.html "RCA Dot Sequential Color System"] {{Webarchive|url=https://web.archive.org/web/20100107142004/http://novia.net/~ereitan/Color_Sys_RCA.html |date=2010-01-07 }}, 28 August 1997</ref>