EBU colour bars

The EBU Colour Bars is a television test pattern used to check if a video signal 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 chrominance and luminance information correctly.

EBU 100/0/75/0 Colour Bars. Displayed colours are only approximate due to different transfer and colour spaces used on web pages (sRGB) and video (BT.601 or BT.709)
EBU 75/0/75/0 Colour Bars. Displayed colours are only approximate due to different transfer and colour spaces used on web pages (sRGB) and video (BT.601 or BT.709)

It is similar to the SMPTE color bars, although that pattern is typically associated with the NTSC analogue colour TV system. Many test cards, such as Philips PM5544 or Telefunken FuBK, feature elements equivalent to the EBU colour bars.

75% Colour Bars

The 75% Colour Bars or EBU 100/0/75/0 Colour Bars pattern[1][2][3] is very similar to the SMPTE colour bars pattern, although it only features the seven colour bars and the white bar is at 100% intensity.

There is a variant where the white bar is also at 75% intensity (EBU 75/0/75/0). This pattern is generated by some test equipment such as Philips PM5519.[4]

The signal values of these bars, for the PAL analogue system are:[5]

Color Luminance Chroma amplitude Chroma Φ
White 0.75 - -
Yellow 0.67 0.33 167º
Cyan 0.53 0.47 283º
Green 0.44 0.44 241º
Magenta 0.31 0.44 61º
Red 0.23 0.47 103º
Blue 0.08 0.33 347º
Black 0 - -

Displayed colors are only approximate due to different transfer and color spaces used on web pages (sRGB) and video (BT.601 or BT.709)

100% Colour Bars
EBU 100/0/100/0 Colour Bars. Displayed colours are only approximate due to different transfer and colour spaces used on web pages (sRGB) and video (BT.601 or BT.709)

An alternate form of colour bars is the 100% Colour Bars or EBU 100/0/100/0 Colour Bars pattern (specified in ITU-R Rec. BT.1729[6]), also known as RGB pattern or full field bars, which consists of eight vertical bars of 100% intensity, and does not include the castellation or luminance patterns. Like the SMPTE colour bars pattern, the colour order is white, yellow, cyan, green, magenta, red, and blue, but with an additional column of saturated black. This pattern is used to check peak colour levels and colour saturation as well as colour alignment. The 100% pattern is not as common as the SMPTE bars or the above-mentioned EBU 75% pattern, but many pieces of test equipment can be selected to generate either one. Many professional cameras can be set to generate a 100% pattern for calibration of broadcast or recording equipment, especially in a multi-camera installation where all camera signals must match.

Standard Definition

EBU colour bar values for standard-definition television systems following BT.601, as specified in ITU-R Rec. BT.1729:[7]

10-bit digital YCbCr values for 100/0/100/0 bars on SD systems
White Yellow Cyan Green Magenta Red Blue Black
Y 940 840 678 578 426 326 164 64
Cb 512 64 663 215 809 361 960 512
Cr 512 585 64 137 887 960 439 512

Calculation of Y (luminance) and CbCr (colour difference) signals from R′, G′ and B′ components according to BT.601 is as follows:[8]

Y′ = 0.299R′ + 0.587G′ + 0.114B′

CB ′ = 0.564 (B′ – Y′)

CR ′ = 0.713 (R′ – Y′)

High Definition

EBU colour bar values for high definition TV systems following BT.709, as specified in ITU-R Rec. BT.1729:[7]

10-bit digital YCbCr values for 100/0/100/0 bars on HD systems
White Yellow Cyan Green Magenta Red Blue Black
Y 940 877 754 691 313 250 127 64
Cb 512 64 615 167 857 409 960 512
Cr 512 553 64 105 919 960 471 512

Calculation of Y (luminance) and CbCr (colour difference) signals from R′, G′ and B′ components according to BT.709 is as follows:[8]

Y′ = 0.2126R′ + 0.7152G′ + 0.0722B′

CB ′ = (B′ – Y′)/1.8556

CR ′ = (R′ – Y′)/1.5748

See also

References
  1. "Channel 6 Television Denmark - Test patterns (English)". Channel6.dk. 2016-12-14. Retrieved 2022-02-17.
  2. "Photographic image of colour bars" (JPG). Channel6.dk. Retrieved 2022-02-23.
  3. "RECOMMENDATION ITU-R BT.471-1* - Nomenclature and description of colour bar signals" (PDF). Itu.int. Retrieved 2022-02-17.
  4. "Philips PM 5519 datasheet" (PDF). testequipmenthq.com.
  5. "Philips PM 5519 datasheet, p.3" (PDF). testequipmenthq.com.
  6. "BT.1729 : Common 16:9 or 4:3 aspect ratio digital television reference test pattern". Itu.int. Retrieved 2022-02-14.
  7. "BT.1729: Common 16:9 or 4:3 aspect ratio digital television reference test pattern". www.itu.int. p. 18. Retrieved 2022-04-12.
  8. "BT.1729: Common 16:9 or 4:3 aspect ratio digital television reference test pattern". www.itu.int. p. 10. Retrieved 2022-04-12.
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