SMPTE color bars

Source: Wikipedia, the free encyclopedia.
Rendition of SD ECR-1-1978 color bars. Colors are only approximate due to different transfers and color spaces used on web pages (sRGB) and video (BT.601 or BT.709)

SMPTE color bars are a

luminance
information correctly.

A precursor to the SMPTE test pattern was conceived by Norbert D. Larky (1927–2018)

Technology & Engineering Emmy Award in 2002.[14]
CBS did not file a patent application on the test signal, thereby putting it into the public domain for general use by the industry.

Early concept of color bar test pattern.
Recreation of EIA-189A color bars without castellations.

An extended version of the SMPTE color bars, SMPTE RP 219:2002[15] was introduced to test HDTV signals (see subsection).[16]

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.[17]

SMPTE ECR 1-1978 (SDTV)

NTSC vectorscope display, showing 75% color bar targets and a properly adjusted signal.
Rendition of ECR-1-1978 color bars with 1kHz sine wave tone.

In a SMPTE

gray, yellow, cyan, green, magenta, red, and blue.[18] 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 in luminance mode as a downward staircase from left to right. The graticule of a vectorscope
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

gray
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

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

callsign
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:[19][20][21][22]

Color Luma Chrominance Range Chrominance Phase
IRE mV IRE p-p mV p-p °
Gray
76.9 549.1 0.0 0.0 -
Yellow 69.0 492.6 62.1 443.3 167.1°
Cyan 56.1 400.9 87.7 626.6 283.7°
Green 48.2 344.5 81.9 585.2 241.3°
Magenta 36.2 258.2 81.9 585.2 61.3°
Red 28.2 201.7 87.7 626.6 103.7°
Blue 15.4 110.1 62.1 443.3 347.1°
-I 7.5 53.6 40.0 285.7 303.0°
White 100.0 714.3 0.0 0.0 -
+Q 7.5 53.6 40.0 285.7 33.0°
Super-black 3.5 25.5 0.0 0.0 -
Black 7.5 53.6 0.0 0.0 -
4% Above Black Level 11.5 81.5 0.0 0.0 -

Note:

mV values only apply to NTSC composite video.
Values sourced from the Tektronix TSG95 test pattern generator manual[22]

Digital video

For digital video sources, the 10-bit YCbCr values for SD color bars[23] are based on the SMPTE formula for Y from the NTSC system (Y = 0.299R + 0.587G + 0.114B).[24] The following table show the expected digital values, for example when measured using a signal analyzer.[25]

10-bit YCbCr values for SD 75% color bars
Color Y Cb Cr
White 940 512 512
Yellow 646 176 567
Cyan 525 625 176
Green 450 289 231
Magenta 335 735 793
Red 260 399 848
Blue 139 848 457
Black 64 512 512

Note: Values sourced from "Leader Teleproduction Test Volume 3 Number 4 - Digital Video Levels"[24]

The colors below are presented using sRGB 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 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'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:[26][27]

COLOR 8-bit Studio
R'G'B'
10-bit Studio
R'G'B'
8-bit
Y'PbPr
10-bit Y'PbPr 12-bit Y'PbPr
40% Gray 104-104-104 414-414-414 104-128-128 414-512-512 1658-2048-2048
75% White 180-180-180 721-721-721 180-128-128 721-512-512 2884-2048-2048
75% Yellow 180-180-16 721-721-64 168-44-136 674-176-543 2694-704-2171
75% Cyan 16-180-180 64-721-721 145-147-44 581-589-176 2325-2356-704
75% Green 16-180-16 64-721-64 133-63-52 534-253-207 2136-1012-827
75% Magenta 180-16-180 721-64-721 63-193-204 251-771-817 1004-3084-3269
75% Red 180-16-16 721-64-64 51-109-212 204-435-848 815-1740-3392
75% Blue 16-16-180 64-64-721 28-212-120 111-848-481 446-3392-1925
75% Black 16-16-16 64-64-64 16-128-128 64-512-512 256-2048-2048
100% White 235-235-235 940-940-940 235-128-128 940-512-512 3760-2048-2048
+Q 72-16-118 288-64-472 35-174-152 141-697-606 564-2787-2425
+I 106-52-16 424-208-64 61-103-157 245-412-629 982-1648-2516
-I 16-70-106 64-280-424 61-153-99 244-612-395 976-2448-1580

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.[27]

Per ITU-R BT.2111-2 TABLE 2

SMPTE RP 219:2002 (HDTV version)

Rendition of HD SMPTE RP 219:2002 color bars. Colors are only approximate due to different transfer used on web pages (sRGB) and video (BT.709 is using BT.1886)

An extended version of SMPTE Color Bars signal, developed by the Japanese

SDTV
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 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.[16]

Later RP 219:2002 became RP 219-1:2014, with RP 219-2:2016

HDR
transfer functions.

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:

COLOR 8-bit Studio
R'G'B'
8-bit
Y'PbPr
10-bit Y'PbPr 12-bit Y'PbPr
100% White 235-235-235 235-128-128 940-512-512 3760-2048-2048
100% Yellow 235-235-16 219-16-138 877-64-553 3507-256-2212
100% Cyan 16-235-235 188-154-16 754-615-64 3015-2459-256
100% Red 235-16-16 63-102-240 250-409-960 1001-1637-3840
100% Blue 16-16-235 32-240-118 127-960-471 509-3840-1884
100% Black 16-16-16 16-128-128 64-512-512 256-2048-2048

ITU-R Rec. BT.1729[32] specified the last two 100% colors, green and magenta. It also specified all 100% colors for BT.601 matrix, not only BT.709.[22]

See also

References

  1. .
  2. ^ NTSC and NTSC/PAL/SECAM Test/Sync Generators (PDF). Leader.
  3. ^ Model 408NPS INSTRUCTION MANUAL (PDF). Leader. p. 5.2.
  4. ^ CG-931/2 - Color Pattern Generator (PDF). Kenwood. p. 16. Archived from the original (PDF) on 2022-07-27. Retrieved 2022-07-27.
  5. ^ "Norbert David Larky Obituary (1927 - 2018) Los Angeles Times". Legacy.com.
  6. ^ "The History of TV Color Bars, One of the First Electronic Graphics Ever Made". www.vice.com. 20 July 2020.
  7. ^ "David D. Holmes Obituary (2006) The Times, Trenton". Legacy.com.
  8. ^ "Email from The Inventor of Color Bars". March 30, 2009.
  9. ^ US patent 2742525, Norbert D. Larky, Somerville & David I. Holmes, New Brunswick, N.J., "Color Test Pattern Generator", issued April 27, 1956, assigned to Radio Corporation of America 
  10. ^ "CTA - EIA-189 Encoded Color Bar Signal". Standards.globalspec.com.
  11. ^ Hank Mahler, developer of the SMPTE color bars, passes away, from TVTechnology.com, October 13, 2021
  12. ^ "Danbury CT Funeral Home and Cremation Center | Danbury Memorial Funeral Home and Cremation Service LLC".
  13. ^ Goldberg, A. A. (June 30, 1977). "A Monitor Alignment Color Bar Test Signal" (PDF). Proceedings, 31st Annual Broadcast Engineering Conference, National Association of Broadcasters. 31: 84–85.
  14. ^ "Outstanding Achievement in Technical/Engineering Development Awards" (PDF). National Academy of Television Arts and Sciences. 2009-03-26. Archived from the original (PDF) on March 26, 2009. Retrieved 2018-05-25.
  15. ^ .
  16. ^ a b "TESTIMAGES". Testimages.org.
  17. ^ Howard Lukk. "Countdown to History – 100 Years of SMPTE Standards Development". Us9.campaign-archive.com.
  18. .
  19. ^ "SMPTE 170M-2004 - Television - Composite Analog Video Signal - NTSC for Studio Applications". standards.globalspec.com. SMPTE. p. 18.
  20. .
  21. ^ "Kenwood CG-960, CG-950, and CG-930 Series Color Pattern Generators" (PDF). Kenwood. p. 171. Retrieved 28 February 2022.
  22. ^ a b c "Tektronix TSG95 Pathfinder PAL-NTSC Signal Generator" (PDF). p. 39. Retrieved 28 February 2022.
  23. ^ DIGITAL VIDEO LEVELS (PDF). Leader Instruments Corporation. Archived from the original (PDF) on 2022-02-22.
  24. ^ a b Teleproduction Test Volume 3 Number 4 - DIGITAL VIDEO LEVELS (PDF). Leader Instruments Corporation. p. 6. Archived from the original (PDF) on 2022-02-22.
  25. ^ "LV 5100D/LV 5100D - COMPONENT DIGITAL WAVEFORM MONITOR" (PDF).
  26. ^ "Color Calculator". Res18h39.netlify.app. Retrieved 2021-04-15.
  27. ^ a b "Color Bars – Reference Levels – VideoQ Tech Blog". Blog.videoq.com. 28 October 2018. Retrieved 2021-05-11.
  28. .
  29. ^ "Overview of ARIB Standards (STD-B66)|Association of Radio Industries and Businesses". www.arib.or.jp. Retrieved 2023-07-21.
  30. ^ Recommendation ITU-R BT.2111-2 (PDF). ITU-R. 2020.
  31. ^ Colour Bar Test Pattern for Hybrid Log-Gamma (HLG) High Dynamic Range Television (HDR-TV) System - ARIB STD-B72 (PDF). ARIB. 2021.
  32. ^ Recommendation ITU-R BT.1729 - Common 16:9 or 4:3 aspect ratio digital television reference test pattern (PDF). ITU-R. 2005.