Test Cards

A test card, also known as a test pattern, is a television test signal, typically broadcast at times when the transmitter is active but no program is being broadcast (often at startup and closedown).
Used since the earliest TV broadcasts, test cards were originally physical cards at which a television camera was pointed, and such cards are still often used for calibration, alignment, and matching of cameras and camcorders. Test patterns used for calibrating or troubleshooting the downstream signal path are these days generated by test signal generators, which do not depend on the correct configuration (and presence) of a camera. Digitally generated cards allow vendors, viewers and television stations to adjust their equipment for optimal functionality.

The test card usually has a set of line-up patterns to enable television cameras and receivers to be adjusted to show the picture correctly. Most modern test cards include a set of calibrated colour bars which will produce a characteristic pattern of “dot landings” on a vectorscope, allowing chroma and tint to be precisely adjusted between generations of videotape or network feeds. SMPTE bars—and several other test cards—include analogue black, full white, and a “sub-black”, or “blacker-than-black”, which represents the lowest low-frequency transmission voltage permissible.
Between the colour bars and proper adjustment of brightness and contrast controls to the limits of perception of the first sub-black bar, an analogue receiver (or other equipment) can be adjusted to provide impressive fidelity. The most famous Test Card shown in the UK since 1967 and also shown in some other countries is Test Card F, which features a little girl (Carole Hersee) and a clown doll in a circle in the centre of the picture.
Test cards are also typically broadcast with library music (see below), a sine wave reference tone, or the relayed broadcasting of a radio station owned by the same broadcaster. There is now a cult following for test card music.

BBC Test Cards
Tuning Signals
Probably the first ever television test card, this test pattern was broadcast by the BBC in 1934 using Baird’s 30 line TV system.
2 Test Card A
3 Test Card B
4 Test Card C
5 Test Card D
6 Test Card E (later Test Card C)
7 Test Card F
8 Test Card G
9 Test Card H
10 Test Card J
11 Test Card W
12 Test Card X

 

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