NTSC (an acronym of National Television System Committee) was the first American standard for analog television, published and adopted in 1941. It was one of three major color formats for analog television; the others were PAL and SECAM. NTSC color was usually associated with System M, and this combination was sometimes called NTSC II. A second NTSC standard was adopted in 1953, which allowed color television compatible with the existing stock of black-and-white sets. The EIA defined NTSC performance standards in EIS-170 (also known as RS-170) in 1957.
The term "NTSC" has referred to digital formats with 480 active lines and a 30 or 29.97 FPS frame rate since the introduction of digital sources such as DVDs, and is a digital shorthand for System M. The NTSC-film standard has a digital resolution of pixels for DVD-Videos, pixels for Super Video CDs (SVCD, aspect ratio 4:3) and pixels for Video CDs (VCD)."" in Television Standards - formats and techniques by Raffael Amadeus Trappe, 2013. The digital video (DV)-camcorder format equivalent of NTSC is pixels.NTSC in PCMag Encyclopedia The digital television (DTV) equivalent is pixels.
History
The NTSC was established in 1940 by the United States Federal Communications Commission (FCC) to resolve conflicts between companies about the introduction of a nationwide analog television system. In March 1941, the committee issued a technical standard for black-and-white television based on a 1936 recommendation by the Radio Manufacturers Association (RMA). Technical advancements of the vestigial sideband technique provided an opportunity to increase image resolution. The NTSC selected 525 scan lines as a compromise between RCA's 441-scan line standard (used by RCA's NBC TV network) and Philco and DuMont's desire to increase the number of scan lines to between 605 and 800. The standard recommended a frame rate of 30 FPS, consisting of two interlaced fields per frame at 262.5 lines per field and 60 fields per second. Other standards in the final recommendation were an aspect ratio of 4:3 and frequency modulation (FM) of the sound signal.
In January 1950, the committee was reconstituted to standardize color television. The FCC had briefly approved a 405-line field-sequential color TV standard, developed by CBS, in October 1950.A third line-sequential system from Color Television Inc. (CTI) was also considered. The CBS and final NTSC systems were called field-sequential and dot-sequential systems, respectively. The CBS system was incompatible with existing black-and-white sets. It used a rotating color wheel, reduced the number of scan lines from 525 to 405, and increased the field rate from 60 to 144 with an effective frame rate of 24 fps. Legal action by rival RCA kept commercial use of the system off the air until June 1951, and regular broadcasts only lasted a few months before the manufacture of all color sets was banned by the Office of Defense Mobilization in October (ostensibly due to the Korean War). A variant of the CBS system was later used by NASA to broadcast pictures of astronauts in space. CBS rescinded its system in March 1953, and the FCC replaced it on December 17 of that year with an NTSC color standard developed by several companies (including RCA and Philco).
In December 1953, the FCC unanimously approved what became the NTSC color-television standard (later defined as RS-170a). The standard retained backward compatibility with existing black-and-white sets. Color information was added to the black-and-white image by introducing a color subcarrier of MHz (3.579545 MHz ± 10 Hz). This frequency was chosen so horizontal line-rate modulation components of the chrominance signal fall between the horizontal line-rate modulation components of the luminance signal; the chrominance signal could be easily filtered out of the luminance signal on new sets, and would be minimally visible on existing sets. Due to limitations of frequency divider circuits when the color standard was promulgated, the color subcarrier frequency was constructed as a composite frequency assembled from small integersin this case, 5 × 7 × 9 MHz divided by 8 × 11. The horizontal line rate was reduced to 15,734 lines per second (3.579545 MHz × 2 ÷ 455 = MHz) from 15,750 lps, and the frame rate was reduced to 30/1.001 ≈ 29.970 fps (the horizontal line rate divided by 525 lines/frame) from 30 fps. The changes amounted to 0.1 percent, and were tolerated by existing TV sets.
The first publicly-announced network television broadcast of a program using the NTSC "compatible color" system was an episode of NBC's Kukla, Fran and Ollie on August 30, 1953, viewable in color only at NBC headquarters."NBC Launches First Announced Color Television Show", Wall Street Journal, August 31, 1953, p. 4. The first nationwide viewing of NTSC color was on the following January 1 with the coast-to-coast broadcast of the Tournament of Roses Parade, viewable on prototype color receivers at special presentations nationwide. The first color NTSC television camera was the RCA TK-40, used for experimental broadcasts in 1953; an improved version, the TK-40A (introduced in March 1954), was the first commercially-available color-television camera. Later that year, an improved TK-41 became the standard camera and was used through much of the 1960s. The NTSC standard was adopted by other countries, including Japan and several in the Americas.
Digital conversion With the advent of digital television, analog broadcasts were largely phased out. NTSC broadcasters in the U.S. were required by the FCC to shut down their analog transmitters by February 17, 2009; the shutdown was later moved to June 12 of that year. Low-power and Class A stations and translators were required to shut down by 2015, although an FCC extension allowed some stations operating on Channel 6 to operate until July 13, 2021. Canadian analog TV transmitters in markets not subject to the mandatory 2011 transition were to be shut down by January 14, 2022, under a 2017 schedule from Innovation, Science and Economic Development Canada.
Most countries using the NTSC standard and those using other analog television standards have switched (or are switching) to newer digital television standards; at least four different standards are in use worldwide. North America, parts of Central America, and South Korea are adopting (or have adopted) the ATSC standards; other countries, such as Japan, are adopting (or have adopted) standards other than ATSC. Most over-the-air NTSC transmissions in the United States ended on June 12, 2009,Digital Television. FCC.gov. Retrieved on May 11, 2014. and by August 31, 2011,DTV and Over-the-Air Viewers Along U.S. Borders. FCC.gov. Retrieved on May 11, 2014. in Canada and most other NTSC markets.Canada... PAL or NTSC?. VideoHelp Forum Retrieved on January 23, 2015.
Technical details
Colorimetry
Colorimetry refers to the colorimetric characteristics of the system and its components, including the primary colors used, the camera, and the display. NTSC color had two distinctly-defined colorimetries, shown on the chromaticity diagram as NTSC 1953 and SMPTE C. Manufacturers introduced a number of variations for technical, economic, marketing, and other reasons.
+ RGB chromaticity coordinates Color space Standard Year White point CCT Primary colors (CIE 1931 xy) Display gamma EOTF x y k Rx Ry Gx Gy Bx By NTSC ITU-R BT.470/601 (M) 1953 0.31 0.316 6774 (C) 0.67 0.33 0.21 0.71 0.14 0.08 2.2 SMPTE C SMPTE RP 145 (C), 170M, 240M 1987 0.3127 0.3290 6500 (D65) 0.63 0.34 0.31 0.595 0.155 0.07
Note: displayed colors are approximate and require a wide gamut display for faithful reproduction.
NTSC 1953 The original 1953 color NTSC specification, still part of the United States Code of Federal Regulations, defined the colorimetric values of the system as shown in the table.47 CFR § 73.682 (20) (iv) Early color-television receivers, such as the RCA CT-100, were faithful to this specification (based on prevailing motion-picture standards) which had a larger gamut than most present-day monitors. Their low-efficiency phosphors (notably in red) were weak and persistent, leaving trails after moving objects. Beginning in the late 1950s, picture-tube phosphors sacrificed saturation for increased brightness; this deviation from the standard at receiver and broadcaster was the source of considerable color variation.
SMPTE C
To ensure more uniform color reproduction, some manufacturers incorporated color-correction circuits into sets which converted the received signal—encoded for colorimetric values—and adjusted the monitor's phosphor characteristics. Since color cannot be accurately corrected on the nonlinear transmitted gamma corrected signals, the adjustment can only be approximated.
At the broadcaster stage, in 1968–69 the Conrac Corporation (working with RCA) defined a set of controlled phosphors for use in broadcast color video monitors.DeMarsh, Leroy (1993): TV Display Phosphors/Primaries — Some History. SMPTE Journal, December 1993: 1095–1098. This specification survives as the SMPTE C phosphor specification. As with home receivers, it was recommendedInternational Telecommunication Union Recommendation ITU-R 470-6 (1970–1998): Conventional Television Systems, Annex 2. that studio monitors incorporate similar color-correction circuits so broadcasters would transmit pictures encoded for the original 1953 colorimetric values in accordance with FCC standards.
In 1987, the Society of Motion Picture and Television Engineers (SMPTE) Committee on Television Technology Working Group on Studio Monitor Colorimetry adopted the SMPTE C (Conrac) phosphors for general use in Recommended Practice 145;Society of Motion Picture and Television Engineers (1987–2004): Recommended Practice RP 145–2004. Color Monitor Colorimetry. this prompted many manufacturers to modify their camera designs to encode for SMPTE C colorimetry without color correctionSociety of Motion Picture and Television Engineers (1994, 2004): Engineering Guideline EG 27-2004. Supplemental Information for SMPTE 170M and Background on the Development of NTSC Color Standards, pp. 9 as approved in SMPTE standard 170M, "Composite Analog Video Signal – NTSC for Studio Applications" (1994). The ATSC digital television standard states that for 480i signals, SMPTE C colorimetry should be assumed unless colorimetric data is included in the transport stream.Advanced Television Systems Committee (2003): ATSC Direct-to-Home Satellite Broadcast Standard Doc. A/81, pp.18
The Japanese NTSC never changed primaries and white point to SMPTE C, continuing to use the 1953 NTSC primaries and white point. The PAL and SECAM systems used the original 1953 NTSC colorimetry until 1970; unlike NTSC, the European Broadcasting Union (EBU) rejected color correction in receivers and studio monitors and called for all equipment to encode signals for EBU colorimetric values.European Broadcasting Union (1975) Tech. 3213-E.: E.B.U. Standard for Chromaticity Tolerances for Studio Monitors.
Color compatibility issues
In the gamuts on the CIE chromaticity diagram, variations among colorimetries can result in visual differences. Proper viewing requires gamut mapping via LUTs or additional color grading. SMPTE Recommended Practice RP 167-1995 refers to such an automatic correction as an "NTSC corrective display matrix." Material prepared for 1953 NTSC may look de-saturated when displayed on SMPTE C or ATSC/BT.709 displays, and may have noticeable hue shifts. SMPTE C materials may appear slightly more saturated on BT.709/sRGB displays, or significantly more saturated on P3 displays, if appropriate gamut mapping is not done.
Color encoding
NTSC uses a luminance-chrominance encoding system. Using a separate luminance signal maintained backward compatibility with contemporary black-and-white television sets; only color sets would recognize the chroma signal.