Test card

Electronically generated test patterns, used for calibrating or troubleshooting the downstream signal path, were introduced in the late-1960s, and became commonly used from the 1970s and 80s.

More recently, the use of test cards has also expanded beyond television to other digital displays such as large LED walls and video projectors.

[3] Test cards typically contain a set of patterns to enable television cameras and receivers to be adjusted to show the picture correctly (see SMPTE color bars).

Most modern test cards include a set of calibrated color 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.

In preparation for the new commercial ITV service in the 1950s, the Independent Television Authority (ITA) tasked Belling & Lee, an Enfield-based British electronics company best known for inventing the Belling-Lee connector just over three decades earlier, with designing a series of Pilot Test Transmission test cards and slides[4] intended for potential viewers and DX-enthusiasts to test the ITA's new Band III VHF transmitter network that was designed with the assistance of the General Post Office (GPO), then the UK's government-run PTT agency.

[3] Test cards are as old as TV broadcasts, with documented use by the BBC in the United Kingdom in its early 30-line mechanical Baird transmissions from 1934 and later on as simplified "tuning signals" shown before startup[10] as well as in Occupied France during World War II.

A late test card design, introduced in 2005 and fully adapted for HD, SD, 16:9 and 4:3 broadcasts, is defined on ITU-R Rec.

These custom test images can also be an opportunity for the technicians to hide inside jokes for the crew to see while installing equipment for a show.

Monoscope tubes had the advantage over test cards that a full TV camera was not needed, and the image was always properly framed and in focus.

[36] The Philips Pattern and SMPTE color bars are widely recognised as one of the iconic popular culture symbols of the 1980s and 1990s in the markets where they were used.

Numerous novelty and collectible items has been patterned after the famous test card, including wall clocks, bedsheets, wristwatches, and clothing.

The character Sheldon Cooper on The Big Bang Theory wore tees with both patterns and a bloggers identified the SMPTE shirt's use in more than a dozen episodes over the life of the series.

[41] Until September 1955, the BBC used live playing 78 RPM commercial records as an audio background to the test cards.

[42] The following year, the BBC began to build up its own library of specially produced music for the half hour tapes – initially three tunes in similar style, followed by an identification sign (the three notes B-B-C played on celesta).