SMPTE color bars
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SMPTE color bars are a
television Television, sometimes shortened to TV, is a telecommunication medium for transmitting moving images and sound. The term can refer to a television set, or the medium of Transmission (telecommunications), television transmission. Television ...
test pattern used where the NTSC video standard is utilized, including countries in
North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...
. The Society of Motion Picture and Television Engineers (SMPTE) refers to the pattern as Engineering Guideline (EG) 1-1990. Its components are a known standard, and created by test pattern generators. Comparing it as received to the known standard gives video engineers an indication of how an NTSC video
signal In signal processing, a signal is a function that conveys information about a phenomenon. Any quantity that can vary over space or time can be used as a signal to share messages between observers. The ''IEEE Transactions on Signal Processing'' ...
has been altered by recording or transmission and what adjustments must be made to bring it back to specification. It is also used for setting a television monitor or receiver to reproduce NTSC
chrominance Chrominance (''chroma'' or ''C'' for short) is the signal used in video systems to convey the color information of the picture (see YUV color model), separately from the accompanying Luma (video), luma signal (or Y' for short). Chrominance is usua ...
and
luminance Luminance is a Photometry (optics), photometric measure of the luminous intensity per units of measurement, unit area of light travelling in a given direction. It describes the amount of light that passes through, is emitted from, or is reflecte ...
information correctly. A precursor to the SMPTE test pattern was conceived by Norbert D. Larky (1927–2018) and David D. Holmes (1926–2006) of
RCA Laboratories The RCA Corporation was a major American electronics company, which was founded as the Radio Corporation of America in 1919. It was initially a patent pool, patent trust owned by General Electric (GE), Westinghouse Electric Corporation, Westin ...
and first published in RCA Licensee Bulletin LB-819 on February 7, 1951. U.S. patent 2,742,525 Color Test Pattern Generator (now expired) was awarded on April 17, 1956, to Larky and Holmes. Later, the EIA published a standard, RS-189A, which in 1976 became EIA-189A, which described a Standard Color Bar Signal, intended for use as a test signal for adjustment of color monitors, adjustment of encoders, and rapid checks of color television transmission systems. In 1977, A. A. Goldberg, of the CBS Technology Center, described an improved color bar test signal developed at the center by Hank Mahler (1936–2021) that was then submitted to the SMPTE TV Video Technology Committee for consideration as a SMPTE recommended practice. This improved test signal was published as the standard SMPTE ECR 1-1978. Its development by
CBS CBS Broadcasting Inc., commonly shortened to CBS, the abbreviation of its former legal name Columbia Broadcasting System, is an American commercial broadcast television Television, sometimes shortened to TV, is a telecommunication m ...
was awarded a
Technology & Engineering Emmy Award The Technology and Engineering Emmy Awards, or Technology and Engineering Emmys, are one of two sets of Emmy Awards that are presented for outstanding achievement in engineering development in the television industry. The Technology and Engineer ...
in 2002. CBS did not file a patent application on the test signal, thereby putting it into the public domain for general use by the industry. An extended version of the SMPTE color bars, SMPTE RP 219:2002 was introduced to test
HDTV High-definition television (HD or HDTV) describes a television Television, sometimes shortened to TV, is a telecommunication medium for transmitting moving images and sound. The term can refer to a television set, or the medium of Trans ...
signals (see subsection). Although color bars were originally designed to calibrate analog NTSC equipment, they remain widely used in transmission and within modern digital television facilities. In the current context color bars are used to maintain accurate chroma and luminance levels in CRT, LCD, LED, plasma, and other video displays, as well as duplication, satellite, fiber-optic and microwave transmission, and television and webcast equipment. In a survey of the top standards of the organizations' first 100 years, SMPTE EG-1 was voted as the 5th-most important SMPTE standard.


SMPTE ECR 1-1978 (SDTV)

In a SMPTE
color Color (American English) or colour (British English) is the visual perception, visual perceptual Physical property, property deriving from the spectrum of light interacting with the photoreceptor cells of the eyes. Color categories and physica ...
bar
image An image is a visual representation of something. It can be two-dimensional, three-dimensional, or somehow otherwise feed into the visual system to convey information. An image can be an artifact, such as a photograph or other two-dimensiona ...
, the top two-thirds of the television picture contain seven vertical bars of 75% intensity. In order from left to right, the colors are
white White is the lightest color Color (American English) or colour (British English) is the visual perception, visual perceptual Physical property, property deriving from the spectrum of light interacting with the photoreceptor cells of th ...
or
gray Grey (more common in British English) or gray (more common in American English) is an intermediate color between black and white. It is a neutral or achromatic color, meaning literally that it is "without color", because it can be compose ...
,
yellow Yellow is the color between green and Orange (color), orange on the Visible spectrum, spectrum of light. It is evoked by light with a dominant wavelength of roughly 575585 Nanometre, nm. It is a primary color in subtractive color systems, u ...
,
cyan Cyan () is the color between green and blue on the visible spectrum of light. It is evoked by light with a predominant wavelength between 490 and 520 nanometre, nm, between the wavelengths of green and blue. In the subtractive color system, or ...
,
green Green is the color Color (American English) or colour (British English) is the visual perception, visual perceptual Physical property, property deriving from the spectrum of light interacting with the photoreceptor cells of the eyes ...
,
magenta Magenta () is a color that is variously defined as pinkish- purplish- red, reddish-purplish-pink or mauvish- crimson. On color wheels of the RGB (additive) and CMY (subtractive) color models, it is located exactly midway between red and b ...
,
red Red is the color at the long wavelength end of the visible spectrum of light, next to orange and opposite violet. It has a dominant wavelength of approximately 625–740 nanometre 330px, Different lengths as in respect to the molecula ...
, and
blue Blue is one of the three primary colours in the RYB color model, RYB colour model (traditional colour theory), as well as in the RGB color model, RGB (additive) colour model. It lies between Violet (color), violet and cyan on the optical sp ...
. The choice of white or gray depends on whether that bar's luminance is 100% or not. This sequence runs through all seven possible combinations that use at least one of the three basic color components of green, red, and blue, with blue cycling on and off between every bar, red cycling on and off every two bars, and green on for the leftmost four bars and off for the rightmost three. Because green contributes the largest share of luminance, followed by red, then blue, this sequence of bars thus appears on a
waveform monitor A waveform monitor is a special type of oscilloscope used in television production applications. It is typically used to measure and display the level, or voltage, of a video signal with respect to time. The level of a video signal usually corre ...
in luminance mode as a downward staircase from left to right. The graticule of a
vectorscope A vectorscope is a special type of oscilloscope used in both audio and video applications. Whereas an oscilloscope or waveform monitor normally displays a plot of signal vs. time, a vectorscope displays an Oscilloscope#X-Y mode, X-Y plot of tw ...
is etched with boxes showing the permissible regions where the traces from these seven bars are supposed to fall if the signal is properly adjusted. Below the main set of seven bars is a strip of
blue Blue is one of the three primary colours in the RYB color model, RYB colour model (traditional colour theory), as well as in the RGB color model, RGB (additive) colour model. It lies between Violet (color), violet and cyan on the optical sp ...
,
magenta Magenta () is a color that is variously defined as pinkish- purplish- red, reddish-purplish-pink or mauvish- crimson. On color wheels of the RGB (additive) and CMY (subtractive) color models, it is located exactly midway between red and b ...
,
cyan Cyan () is the color between green and blue on the visible spectrum of light. It is evoked by light with a predominant wavelength between 490 and 520 nanometre, nm, between the wavelengths of green and blue. In the subtractive color system, or ...
, and
white White is the lightest color Color (American English) or colour (British English) is the visual perception, visual perceptual Physical property, property deriving from the spectrum of light interacting with the photoreceptor cells of th ...
or
gray Grey (more common in British English) or gray (more common in American English) is an intermediate color between black and white. It is a neutral or achromatic color, meaning literally that it is "without color", because it can be compose ...
castellations. When a television receiver is set to filter out all colors except for blue, these castellations, combined with the main set of color bars, are used to adjust the color controls; they appear as four solid blue bars, with no visible distinction between the bars and the castellations if the color controls are properly adjusted. The bottom section contains a square of 100% intensity white and a rectangle of 7.5% intensity black, for use in setting the luminance range. More modern versions of the pattern feature a '' PLUGE pulse''. The white square lines up so that it is below the yellow and cyan bars, on a waveform monitor this will show up with the white bar overlapping the peak of the yellow and cyan chroma at 100 IRE units. The ''pluge'' (short for picture line-up generation equipment) pulse is positioned within the black rectangle, below the red bar (it is present in the illustration but may be hard to see). It comprises three small vertical bars, a rightmost one with intensity 4% above black level (11.5 IRE), a middle one with intensity exactly equal to black (7.5 IRE), and a leftmost one with intensity 4% below black (super-black or ''blacker than black'', 3.5 IRE). The pluge pulse aids in adjusting the bottom of the luminance range to avoid either washing out the black tones into grays or collapsing picture information into the signal clipping that occurs a small distance below the black level (known as ''crushing the blacks''). When a monitor is properly adjusted, the rightmost pluge bar should be just barely visible, while the left two should appear indistinguishable from each other and completely black. Also in the bottom section are two sections that contain -In-phase and +Quadrature signals (see YIQ), centered on black level and having the same gain as the color burst signal; these show up on the pattern as a square of very dark blue, and a square of very dark purple. On a vectorscope, they appear as two short lines ninety degrees apart. These are used to ensure that the television receiver is properly demodulating the 3.58 MHz color subcarrier portion of the signal. The vectors for the -I and +Q blocks should fall exactly on the I and Q axes on the vectorscope if the chrominance signal is demodulated properly. These bars give rise to the former portion of the casual term ''bars and tone''. Typically, a
television network A television network or television broadcaster is a telecommunications network for distribution of television program content, where a central operation provides programming to many television stations or multichannel video programming distributo ...
, TV station, or other originator of video programming transmits SMPTE color bars together with a continuous 1,000 Hz
sine wave A sine wave, sinusoidal wave, or just sinusoid is a curve, mathematical curve defined in terms of the ''sine'' trigonometric function, of which it is the graph of a function, graph. It is a type of continuous wave and also a Smoothness, smooth p ...
before sending program material, in order to assert ownership of the transmission line or medium, and so that receiving stations and intermediary telecommunications providers may adjust their equipment. Likewise, producers of television programs typically record ''bars and tone'' at the beginning of a videotape or other recording medium so that the playback equipment can be
calibrated In measurement technology and metrology, calibration is the comparison of measurement values delivered by a device under test with those of a Standard (metrology), calibration standard of known accuracy. Such a standard could be another measurem ...
. Often, the name or
callsign In broadcasting Broadcasting is the distribution (business), distribution of sound, audio or video content to a dispersed audience via any electronic medium (communication), mass communications medium, but typically one using the electromagne ...
of the TV station, other information such as a real-time clock, or another signal source is graphically superimposed over the bars.


Analog NTSC

Values of 75% (75/7.5/75/7.5) SMPTE ECR 1-1978 color bars as analog NTSC signals: ''Note: IRE units apply to both NTSC
composite video Composite video is an Video#Analog video, analog video signal format that carries Standard-definition television, standard-definition video (typically at 525 lines or 625 lines) as a single channel. Video information is Video coding format, e ...
and broadcast signals while mV values only apply to NTSC composite video.
Values sourced from the Tektronix TSG95 test pattern generator manual
''


Digital video

For digital video sources, the 10-bit
YCbCr YCbCr, Y′CbCr, or Y Pb/Cb Pr/Cr, also written as YCBCR or Y′CBCR, is a family of color spaces used as a part of the color image pipeline in video and digital photography systems. Y′ is the Luma (video), luma component and CB and CR are t ...
values for SD color bars are based on the SMPTE formula for Y from the NTSC system ( Y = 0.299R + 0.587G + 0.114B). The following table show the expected digital values, for example when measured using a signal analyzer. Note: Values sourced from "''Leader Teleproduction Test Volume 3 Number 4 - Digital Video Levels''" The colors below are presented using
sRGB sRGB is a standard RGB color space, RGB (red, green, blue) color space that Hewlett-Packard, HP and Microsoft created cooperatively in 1996 to use on monitors, printers, and the World Wide Web. It was subsequently standardized by the Internation ...
transfer of CSS. Since sRGB is the standard colorspace for webpages and computer screens, this gives only an idea of the intended colors. They are not completely representative of how they look on TV displays, since these follow the ITU-R BT.1886 standard, specifying a different
gamma correction Gamma correction or gamma is a nonlinear operation used to encode and decode Relative luminance, luminance or CIE 1931 color space#Tristimulus values, tristimulus values in video or still image systems. Gamma correction is, in the simplest cases, ...
value, and thus colors below will look darker on such a display, and those darker colors will be the reference ones. The off-by-one errors (for example 254 instead of 255 and 1 instead of 0) happen because the 8 bit Y'PbPr values were used when decoding to R'G'B', if you use 10-bit Y'PbPr that does not happen. Y'PbPr (and Y'CbCr) values of 75% (100/0/75/0) SMPTE ECR 1-1978 color bars (0.75 * 219 + 16 = 180) using BT.709-2 matrix coefficients as written in RP 219:2002: The source data for 10-bit and 12-bit Y'PbPr is 8-bit Studio R'G'B', so 10-bit data is not just a bitshift operation (that means multiply by 4) from 8-bit Y'PbPr, as usually the case. For example, for 75% Blue 28-212-120 would be just 112-848-480, but it is actually 111-848-481.


SMPTE RP 219:2002 (HDTV version)

An extended version of SMPTE Color Bars signal, developed by the Japanese Association of Radio Industry and Businesses as ARIB STD-B28 and standardized as SMPTE RP 219:2002 (High-Definition, Standard-Definition Compatible Color Bar Signal) was introduced to test
HDTV High-definition television (HD or HDTV) describes a television Television, sometimes shortened to TV, is a telecommunication medium for transmitting moving images and sound. The term can refer to a television set, or the medium of Trans ...
signal with an aspect ratio of 16:9 that can be down converted to a
SDTV Standard-definition television (SDTV, SD, often shortened to standard definition) is a television system which uses a resolution that is not considered to be either high-definition television, high or enhanced-definition television, enhanced ...
color bar signal with an aspect ratio of either 4:3 or 16:9. The Color Bar signal is generated with unconventionally slow rise and fall time value to facilitate video level control and monitor color adjustments of HDTV and SDTV equipment. Digital test images generated following the SMPTE RP 219:2002 specifications and adapted to perfectly fit 114 standard and non-standard resolutions for both 16bpp and 8bpp, are freely available in the COLOR dataset of the TESTIMAGES archive. Later RP 219:2002 became RP 219-1:2014 and then RP 219-2:2016 was added for UHD (and ARIB STD-B66). Then ITU-R Rec. BT.2111 was done with PQ and HLG HDR transfer functions (like ARIB STD-B72).


Values

The values of 100% (100/0/100/0) SMPTE RP 219:2002 color bars (1.00 * 219 + 16 = 235) using BT.709 matrix coefficients (only white and black are the same using BT.601 matrix), taken from the standard:
ITU-R The ITU Radiocommunication Sector (ITU-R) is one of the three sectors (divisions or units) of the International Telecommunication Union (ITU) and is responsible for radio communications. Its role is to manage the international radio-frequency sp ...
Rec. BT.1729 specified the last two 100% colors, green and magenta. It also specified all 100% colors for BT.601 matrix, not only BT.709.


See also

* EBU color bars * China Girl (filmmaking) *
Indian-head test pattern The Indian-head test pattern is a test card A test card, also known as a test pattern or start-up/closedown test, is a television test signal, typically broadcast at times when the transmitter is active but no program is being broadcast (oft ...
* Test Card F * 2-pop * Philips PM5544


References

{{DEFAULTSORT:Smpte Color Bars SMPTE standards Test cards Television terminology Articles containing video clips de:Testbild#SMPTE-Testbild