Word: coloring
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Dates: during 1940-1949
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...last step, adding color, is easy in theory but exceedingly difficult in practice. The systems proposed by CBS and RCA approach the problem in fundamentally different ways...
...Color with Fields, In the CBS color system (called "field sequential"), the transmitting camera, like the ordinary black & white camera, has a single Image Orthicon "seeing" tube. In front of it is a spinning disc with segments of blue, green and red transparent plastic. When a blue segment is in front of the tube, the camera sees only the blue light coming from the scene being televised. When the disc has turned a little, putting a red segment in front of the tube, the camera sees only the scene's red light. Next, it sees green through a green...
...disc is properly synchronized with the scanning speed of the tube, one-color "fields" go out over the airwaves and appear one after the other on the face of the receiving "picture" tube. All of them are white, since the "phosphor" (the luminescent substance) on the tube's face glows only in white light. But in front of the receiving set's picture tube is a second spinning "color disc" (see diagram). This disc is synchronized so that a blue segment is between the tube and the eye of the viewer whenever a "blue" field is flashing...
...Color with Dots. RCA's system, called "dot interlacing," is entirely electronic, needs no spinning disc. In the transmitting camera are three tubes. In front of them is a system of "dichroic mirrors" (see below) which allow each tube to "see" in one color only. All three tubes scan the scene continuously, but an electronic switching device, turning their signals on & off 11.4 million times a second, allows each tube to transmit over the telecasting station only one-third of the time. In this way the "video signals" from all three tubes are strung together like trains made...
...receiving set at the other end has three picture tubes. They are like black & white tubes except that each has on its face a phosphor that glows in a different basic color. Each little impulse (the colored freight cars) arriving over the beam is electronically switched to the properly colored tube. They arrive so fast that each tube-face is covered 15 times a second with a pattern of tiny dots corresponding to the blues, reds and greens in the scene being televised. The more red there is in a part of the scene (e.g., a red dress), the brighter...