Field-sequential color system
Encyclopedia
A field-sequential color system 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, and first shown to the general public on January 12, 1950. 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, but it was later withdrawn.
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.
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).
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
. Only 200 color sets had been manufactured for commercial sale, and only 100 of those had shipped, when CBS suspended its color broadcasts. CBS announced in March 1953 that it had abandoned any further plans for its color system. 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.
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 tube
s, and producing a vertical color image about 4 inches (10 cm) high. It was described in the journal Nature
:
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.
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.
The field sequential system was used in specialized applications long after it had been replaced for broadcast television. A notable example was the Apollo lunar landing cameras
which transmitted color television images from the Moon during missions
from 1969 to 1972. Another system was used in NASA's Voyager program
in 1979, to take pictures and video of Jupiter.
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.
Television
Television is a telecommunication medium for transmitting and receiving moving images that can be monochrome or colored, with accompanying sound...
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
Peter Carl Goldmark
Peter Carl Goldmark was a German-Hungarian engineer who, during his time with Columbia Records, was instrumental in developing the long-playing microgroove 33-1/3 rpm vinyl phonograph disc, the standard for incorporating multiple or lengthy recorded works on a single disc for two generations...
for CBS
CBS
CBS Broadcasting Inc. is a major US commercial broadcasting television network, which started as a radio network. The name is derived from the initials of the network's former name, Columbia Broadcasting System. The network is sometimes referred to as the "Eye Network" in reference to the shape of...
, which was its sole user in commercial broadcasting. It was first demonstrated to the press on September 4, 1940, and first shown to the general public on January 12, 1950. The Federal Communications Commission
Federal Communications Commission
The Federal Communications Commission is an independent agency of the United States government, created, Congressional statute , and with the majority of its commissioners appointed by the current President. The FCC works towards six goals in the areas of broadband, competition, the spectrum, the...
adopted it on October 11, 1950 as the standard for color television
Color television
Color television is part of the history of television, the technology of television and practices associated with television's transmission of moving images in color video....
in the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
, but it was later withdrawn.
Operation
Mechanical television
Mechanical television was a broadcast television system that used mechanical or electromechanical devices to capture and display video images. However, the images themselves were usually transmitted electronically and via radio waves...
system because it relied in part on a disc of color filters rotating at 1440 rpm
Revolutions per minute
Revolutions per minute is a measure of the frequency of a rotation. It annotates the number of full rotations completed in one minute around a fixed axis...
inside the camera and the receiver, capturing and displaying red, green, and blue television images in sequence. The field
Field (video)
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...
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
Image resolution
Image resolution is an umbrella term that describes the detail an image holds. The term applies to raster digital images, film images, and other types of images. Higher resolution means more image detail....
was reduced from 525 lines to 405. The vertical resolution was 77% of monochrome, and the horizontal resolution was 54% of monochrome.
Because of these variances in resolution and frame rate from the NTSC
NTSC
NTSC, named for the National Television System Committee, is the analog television system that is used in most of North America, most of South America , Burma, South Korea, Taiwan, Japan, the Philippines, and some Pacific island nations and territories .Most countries using the NTSC standard, as...
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).
Commercial failure
CBS purchased its own television manufacturer in April 1951 when no other company would produce color sets using the system. Production of CBS-Columbia color receivers began in September, and 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
National Production Authority
The National Production Authority was an agency of the United States government which developed and promoted the production and supply of materials and facilities necessary for defense mobilization...
, which in November 1951 prohibited the manufacture of color sets for the general public during the Korean War
Korean War
The Korean War was a conventional war between South Korea, supported by the United Nations, and North Korea, supported by the People's Republic of China , with military material aid from the Soviet Union...
. Only 200 color sets had been manufactured for commercial sale, and only 100 of those had shipped, when CBS suspended its color broadcasts. CBS announced in March 1953 that it had abandoned any further plans for its color system. 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
Color television
Color television is part of the history of television, the technology of television and practices associated with television's transmission of moving images in color video....
system. RCA developed the hardware for NTSC which superseded the field-sequential system as the U.S. standard in December 1953.
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. 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. This patent probably inspired John Logie Baird to use a similar color wheel in his system.John Logie Baird
John Logie Baird
John Logie Baird FRSE was a Scottish engineer and inventor of the world's first practical, publicly demonstrated television system, and also the world's first fully electronic colour television tube...
demonstrated a version of field-sequential color television on July 3, 1928, using a mechanical television system before his use of cathode ray tube
Cathode ray tube
The cathode ray tube is a vacuum tube containing an electron gun and a fluorescent screen used to view images. It has a means to accelerate and deflect the electron beam onto the fluorescent screen to create the images. The image may represent electrical waveforms , pictures , radar targets and...
s, and producing a vertical color image about 4 inches (10 cm) high. It was described in the journal Nature
Nature (journal)
Nature, first published on 4 November 1869, is ranked the world's most cited interdisciplinary scientific journal by the Science Edition of the 2010 Journal Citation Reports...
:
- 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 commutatorCommutator (electric)A commutator is a rotary electrical switch in certain types of electric motors or electrical generators that periodically reverses the current direction between the rotor and the external circuit. In a motor, it applies power to the best location on the rotor, and in a generator, picks off power...
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.
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.
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
Soviet Union
The Soviet Union , officially the Union of Soviet Socialist Republics , was a constitutionally socialist state that existed in Eurasia between 1922 and 1991....
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.
The field sequential system was used in specialized applications long after it had been replaced for broadcast television. A notable example was the Apollo lunar landing cameras
Apollo TV camera
Television cameras used on the Apollo Project's missions varied in design, with image quality improving significantly with each design. A camera was carried in the Apollo Command Module...
which transmitted color television images from the Moon during missions
Human spaceflight
Human spaceflight is spaceflight with humans on the spacecraft. When a spacecraft is manned, it can be piloted directly, as opposed to machine or robotic space probes and remotely-controlled satellites....
from 1969 to 1972. Another system was used in NASA's Voyager program
Voyager program
The Voyager program is a U.S program that launched two unmanned space missions, scientific probes Voyager 1 and Voyager 2. They were launched in 1977 to take advantage of a favorable planetary alignment of the late 1970s...
in 1979, to take pictures and video of Jupiter.
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.
See also
- NTSCNTSCNTSC, named for the National Television System Committee, is the analog television system that is used in most of North America, most of South America , Burma, South Korea, Taiwan, Japan, the Philippines, and some Pacific island nations and territories .Most countries using the NTSC standard, as...
Broadcast system that encodes color information into a compatible signal - SECAMSECAMSECAM, also written SÉCAM , is an analog color television system first used in France....
Broadcast system that sends color information sequentially by scan line - Mechanical televisionMechanical televisionMechanical television was a broadcast television system that used mechanical or electromechanical devices to capture and display video images. However, the images themselves were usually transmitted electronically and via radio waves...
- Guillermo González CamarenaGuillermo González CamarenaGuillermo González Camarena , was a Mexican engineer who was the inventor of a color-wheel type of color television, and who also introduced color television to Mexico....
Chromoscopic adapter for television - History of televisionHistory of televisionThe history of television records the work of numerous engineers and inventors in several countries over many decades. The fundamental principles of television were initially explored using electromechanical methods to scan, transmit and reproduce an image...
External links
- Ed Reitan's Color Television History.
- Early Television Foundation: Early Color TV.
- Comparison of CBS, Col-R-Tel and Apollo moon TV technology.
- How experimenters converted NTSC sets to receive CBS System color.
- About.com: Color Television History.
- John Logie Baird, U.S. patent for color television, filed 1929.