Field-sequential color system

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A field-sequential color system (FSC) is a color television system in which the primary color information is transmitted in successive images and which relies on the human vision system to fuse the successive images into a color picture. One field-sequential system was developed by Dr. Peter Goldmark for CBS, which was its sole user in commercial broadcasting. It was first demonstrated to the press on September 4, 1940, [1] and first shown to the general public on January 12, 1950. [2] The Federal Communications Commission adopted it on October 11, 1950 as the standard for color television in the United States, but it was later withdrawn. [3]

Color television television transmission technology that includes information on the color of the picture, so the video image can be displayed in color on the television set

Color television is a television transmission technology that includes information on the color of the picture, so the video image can be displayed in color on the television set. It is an improvement on the earliest television technology, monochrome or black and white television, in which the image is displayed in shades of gray (grayscale). Television broadcasting stations and networks in most parts of the world upgraded from black and white to color transmission in the 1970s and 1980s. The invention of color television standards is an important part of the history of television, and it is described in the technology of television article.

Peter Carl Goldmark American inventor

Peter Carl Goldmark was a Hungarian-American engineer who, during his time with Columbia Records, was instrumental in developing the long-playing microgroove 33-1/3 rpm phonograph disc, the standard for incorporating multiple or lengthy recorded works on a single disc for two generations. The LP was introduced by Columbia's Goddard Lieberson in 1948. Lieberson was later president of Columbia Records from 1956–71 and 1973–75. According to György Marx he was one of The Martians.

CBS is an American English language commercial broadcast television and radio network that is a flagship property of CBS Corporation. The company is headquartered at the CBS Building in New York City with major production facilities and operations in New York City and Los Angeles.

Contents

The use of sequential color systems for moving images predates the invention of fully electronic television. Although usually known at the time simply as "additive" rather than sequential color systems, two-color Kinemacolor, in commercial use since 1906, and its predecessor three-color format, invented by Edward Raymond Turner and patented in 1899, were both sequential natural color systems for use with motion picture film. They utilized black-and-white film and rotating color filter wheels to record the amount of each color in the scene on alternating frames of the film, so that when the frames were projected by light of similar colors at a sufficiently rapid rate, those colors blended together in the viewer's eye and produced a wider range of hues. Due to litigation by William Friese-Greene, Kinemacolor ended up in the public domain in 1915, after which several derivative sequential color processes (such as Friese-Greene's Biocolour and the original Prisma Color) were developed. Some were brought to the point of being publicly shown, but during the 1920s they could not compete with rival bipack and other subtractive color processes, which were free of color flicker and did not require special projection equipment—the final multicolored images were right there on the film as transparent coloring matter.

Additive color the situation where color is created by mixing the visible light emitted from differently colored light sources

Additive color, or "additive mixing", is a property of a color model that predicts the appearance of colors made by coincident component lights with distinct colors, i.e. the perceived color can be predicted by summing the numeric representations of the component colors. Modern formulations of Grassmann's Laws describe the additivity in the color perception of light mixtures in terms of algebraic equations. It is important note that additive color predicts perception and not any sort of change in the photons of light themselves. These predictions are only applicable in the limited scope of color matching experiments where viewers match small patches of uniform color isolated against a grey or black background.

Kinemacolor color motion picture process

Kinemacolor was the first successful colour motion picture process, used commercially from 1908 to 1914. It was invented by George Albert Smith of Brighton, England in 1906. He was influenced by the work of William Norman Lascelles Davidson and, more directly, Edward Raymond Turner. It was launched by Charles Urban's Urban Trading Co. of London in 1908. From 1909 on, the process was known as Kinemacolor. It was a two-colour additive colour process, photographing and projecting a black-and-white film behind alternating red and green filters.

Edward Raymond Turner British inventor and cinematographer

Edward Raymond Turner was a pioneering British inventor and cinematographer. He produced the earliest known colour motion picture film footage

Operation

Patent diagrams of CBS field-sequential color system: Fig. 1 the transmission system, Fig. 2 the receiving system, Fig. 3 the color filter disk. Goldmark1940color.jpg
Patent diagrams of CBS field-sequential color system: Fig. 1 the transmission system, Fig. 2 the receiving system, Fig. 3 the color filter disk.

The CBS field-sequential system was an example of a mechanical television system because it relied in part on a disc of color filters rotating at 1440 rpm inside the camera and the receiver, capturing and displaying red, green, and blue television images in sequence. The field rate was increased from 60 to 144 fields per second to overcome the flicker from the separate color images, resulting in 24 complete color frames per second (each of the three colors was scanned twice, double interlacing being standard for all electronic television: 2 scans × 3 colors × 24 frames per second = 144 fields per second), instead of the standard 30 frames/60 fields per second of monochrome. If the 144-field color signal were transmitted with the same detail as a 60-field monochrome signal, 2.4 times the bandwidth would be required. Therefore, to keep the signal within the standard 6-MHz bandwidth of a channel, the image's vertical resolution was reduced from 525 lines to 405. The vertical resolution was 77% of monochrome, and the horizontal resolution was 54% of monochrome. [4]

Mechanical television television system that relies on a mechanical scanning device, such as a rotating disk with holes in it or a rotating mirror, to scan the scene and generate the video signal, and a similar mechanical device at the receiver to display the picture

Mechanical television or mechanical scan television is a television system that relies on a mechanical scanning device, such as a rotating disk with holes in it or a rotating mirror, to scan the scene and generate the video signal, and a similar mechanical device at the receiver to display the picture. This contrasts with modern television technology, which uses electronic scanning methods, for example electron beams in cathode ray tube (CRT) televisions, and liquid-crystal displays (LCD), to create and display the picture.

Revolutions per minute is the number of turns in one minute. It is a unit of rotational speed or the frequency of rotation around a fixed axis.

In video, a field is one of the many still images which are displayed sequentially to create the impression of motion on the screen. Two fields comprise one video frame. When the fields are displayed on a video monitor they are "interlaced" so that the content of one field will be used on all of the odd-numbered lines on the screen and the other field will be displayed on the even lines. Converting fields to a still frame image requires a process called deinterlacing, in which the missing lines are duplicated or interpolated to recreate the information that would have been contained in the discarded field. Since each field contains only half of the information of a full frame, however, deinterlaced images do not have the resolution of a full frame.

Because of these variances in resolution and frame rate from the NTSC standards for television broadcasting, field-sequential color broadcasts could not be seen on existing black and white receivers without an adapter (to see them in monochrome), or adapter-converter (to see them in color). [5]

NTSC analog television system

NTSC, named after the National Television System Committee, is the analog television color system that was used in North America from 1954 and until digital conversion, was used in most of the Americas ; Myanmar; South Korea; Taiwan; Philippines; Japan; and some Pacific island nations and territories.

Commercial failure

CBS purchased its own television manufacturer in April 1951 when no other company would produce color sets using the system. [6] Production of CBS-Columbia color receivers began in September; [7] they were first offered for retail sale in October.

Field-sequential color broadcasts were suspended by CBS on October 21, 1951, ostensibly by request of the National Production Authority, which in November 1951 prohibited the manufacture of color sets for the general public during the Korean War. [8] Only 200 color sets had been manufactured for commercial sale, and only 100 of those had shipped, when CBS suspended its color broadcasts. [9] CBS announced in March 1953 that it had abandoned any further plans for its color system. [10] RCA was the leading company in the television field, with a larger technical staff, more development funds, and more political success in getting the NTSC compatible color television system. RCA developed the hardware for NTSC which superseded the field-sequential system as the U.S. standard in December 1953.

The National Production Authority (NPA) was an agency of the United States government which developed and promoted the production and supply of materials and facilities necessary for defense mobilization. It was part of the Department of Commerce.

Korean War 1950–1953 war between North Korea and South Korea

The Korean War was a war between North Korea and South Korea. The war began on 25 June 1950 when North Korea invaded South Korea following a series of clashes along the border.

Predecessor inventions

According to television historian Albert Abramson, A. A. Polumordvinov invented the first field-sequential color system. Polumordvinov applied for his Russian patent 10738 in 1899. This system scanned images with two rotating cylinders. [11] A later German patent by A. Frankenstein and Werner von Jaworski described another field-sequential system. Like the CBS System, this patent included a color wheel. Frankenstein and Jaworski applied for their patent 172376 in 1904. [12] This patent probably inspired John Logie Baird to use a similar color wheel in his system.

John Logie Baird demonstrated a version of field-sequential color television on July 3, 1928, using a mechanical television system before his use of cathode ray tubes, and producing a vertical color image about 4 inches (10 cm) high. It was described in the journal Nature :

The process consisted of first exploring the object, the image of which is to be transmitted, with a spot of red light, next with a spot of green light, and finally with a spot of blue light. At the receiving station a similar process is employed, red, blue and green images being presented in rapid success to the eye. The apparatus used at the transmitter consists of a disc perforated with three successive spiral curves of holes. The holes in the first spiral are covered with red filters, in the second with green filters and in the third with blue. Light is projected through these holes and an image of the moving holes is projected onto the object. The disc revolves at 10 revolutions per second and so thirty complete images are transmitted every second — ten blue, ten red, and ten green.
At the receiving station a similar disc revolves synchronously with the transmitting disc, and behind this disc, in line with the eye of the observer, are two glow discharge lamps. One of these lamps is a neon tube and the other a tube containing mercury vapour and helium. By means of a commutator the mercury vapour and helium tube is placed in circuit for two-thirds of a revolution and the neon tube for the remaining third. The red light from the neon is accentuated by placing red filters over the view holes for the red image. Similarly, the view holes corresponding to the green and blue images are covered by suitable filters. The blue and green lights both come from the mercury helium tube, which emits rays rich in both colours. [13]

Baird demonstrated a modified two-color version in February 1938, using a red and blue-green filter arrangement in the transmitter; on July 27, 1939 he further demonstrated that color scanning system in combination with a cathode ray tube with filter wheel as the receiver. [14]

Later use

For the first nine months of NTSC color in 1953–1954, CBS continued to use its field-sequential color television cameras, with the field rate and signal adapted for NTSC standards, until RCA delivered its first production model of an NTSC color camera in time for the 1954–55 season.

The Soviet Union was the only other country to experiment with a field-sequential color system. It manufactured a small number of color receivers in 1954 that used a mechanical color disc. [15]

The field-sequential system was used in specialized applications long after it had been replaced for broadcast television. A notable user of the technology was NASA. Field-sequential color cameras were used on the Apollo lunar landing cameras which transmitted color television images from the Moon during missions from 1969 to 1972. Another system was used for the Voyager program in 1979, to take pictures and video of Jupiter. Early Space Shuttle flights (from 1981 to 1995) used cameras with interchangeable lenses. For color transmissions, a field-sequential color system was built into the lens assembly. For the NASA transmissions, the video from space was field sequential, converted by a duty cycle extension technique to component RGB color video on the ground, and thereafter converted to NTSC and other world standards like PAL and SECAM. [16] [17]

Modern day Digital Light Processing (DLP) projectors commonly use color wheels to generate color images, typically running at a multiple of the video frame rate.

Modern day LCD displays implement FSC by using several colors of LED backlight, by cycling the backlights, and gain several advantages such as brighter colors, darker blacks, and lower cost. [18] These displays are used in LCD Camera viewfinders and other industrial applications.

See also

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References

  1. "Color Television Achieves Realism", New York Times, September 5, 1940, p. 18. A color 16mm film was shown; live pick-ups were first demonstrated to the press in 1941. "Columbia Broadcasting Exhibits Color Television", Wall Street Journal, January 10, 1941, p. 4. "CBS Makes Live Pick-up in Color Television Archived October 14, 2007, at the Wayback Machine .", Radio & Television, April 1941.
  2. "Washington Chosen for First Color Showing; From Ages 4 to 90, Audience Amazed", The Washington Post, January 13, 1950, p. B2.
  3. "C.B.S. Color Video Starts Nov. 20; Adapters Needed by Present Sets", New York Times, October 12, 1950, p. 1. Hugh Richard Slotten (2000). Radio and Television Regulation: Broadcast Technology in the United States 1920–1960. JHU Press. ISBN   0-8018-6450-X.
  4. William F. Schreiber, "Introduction to 'Color Television—Part I'", Proceedings of the IEEE, vol. 87, no. 1, January 1999, p. 175.
  5. CBS Field Sequential System: Advertisements, Early Television Foundation.
  6. "Hytron's Deal With CBS Seen TV Color Aid", The Washington Post, April 12, 1951, p. 15. In June 1951, Philco offered 11 television models that could show CBS color broadcasts in black and white. "Philco Offers 11 TV Sets To Receive CBS Color TV in Black and White", Wall Street Journal, June 4, 1951, p. 9.
  7. "CBS Subsidiary Starts Mass Production of Color Television Sets", Wall Street Journal, September 13, 1951, p. 18.
  8. "Color TV Shelved As a Defense Step," New York Times, October 20, 1951, p. 1. "Action of Defense Mobilizer in Postponing Color TV Poses Many Question for the Industry," New York Times, October 22, 1951, p. 23. Ed Reitan, CBS Field Sequential Color System, 1997.
  9. Ed Reitan, CBS Field Sequential Color System, 1997.
  10. "CBS Says Confusion Now Bars Color TV," Washington Post, March 26, 1953, p. 39.
  11. Albert Abramson, The History of Television, 1880 to 1941 (Jefferson, North Carolina: 1987), pp. 22, 277.
  12. Albert Abramson, The History of Television, 1880 to 1941 (Jefferson, North Carolina: 1987), pp. 24, 277.
  13. Dr. Alexander Russell, Nature, August 18, 1928.
  14. "Colour Television: Baird Experimental System Described", Wireless World, August 17, 1939.
  15. 1954 Russian Raduga (Rainbow) Field Sequential Color Set, Early Television Foundation.
  16. "Charles Poynton – Biography" . Retrieved March 24, 2013.
  17. "NSTS 1988 News Reference Manual" . Retrieved March 14, 2013.
  18. "The Advantages to Field Sequential Color Technology" . Retrieved May 2, 2016.