Test Card

A test card, also known as a '''test pattern''' in North America , 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). Originally, all test cards were actually physical cards at which a Television Camera was pointed, and such cards are still often used for calibration, alignment, and matching of cameras and Camcorder s. Test patterns used for calibrating or troubleshooting the downstream signal path are nowadays generated by Test Signal Generator s, which do not depend on the correct configuration of (and presence of) a camera. Digitally-generated cards allow vendors, viewers and television stations to adjust their equipment for optimal functionality; while older camera-generated and kinescope-generated cards provided a reasonably good reference. They have been shown since the earliest TV broadcasts by all American and Canadian television networks, the BBC, Baird Television and Marconi E.M.I systems. The test card usually has a set of line-up patterns, enabling television cameras to be adjusted to show the picture correctly. (Compare with SMPTE Color Bars ). Most 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. SMPTE bars--and several other test cards --include analog black (a flat waveform at 7.5 IRE , or the NTSC setup level), full white (100IRE), and a "sub-black" or "blacker-than-black" (at 0 IRE), which represents the lowest low-frequency transmission voltage permissible in NTSC broadcast (though the negative excursions of the Colorburst signal may go below 0 IRE). Between the color bars and proper adjustment of brightness and contrast controls to the limits of perception of the first sub-black bar, an analog receiver (or other equipment like VTRs) may be adjusted to provide impressive fidelity. They would also typically be broadcast to a background of specially composed music (to avoid having to pay licensing fees for existing compositions), a tone, or the relayed broadcasting of a Radio Station also owned by the same broadcaster. There is now a cult following for test-card music. BBC TEST CARDS See Also: List of BBC test cards BBC test cards are identifed by a letter. The most famous British test card is Test Card F which incorporates a colour photograph of Carole Hersee (daughter of BBC engineer George Hersee ) playing Noughts And Crosses with a doll, used on the BBC and ITV from the beginning of colour broadcasts in the late 1960s . It was later updated as Test Card J , and for Widescreen broadcasts as Test Card W . This test card has often been spoofed by Comedian s. DECLINE Formerly a common sight, test cards are now only rarely seen outside of television studios, post-production, and distribution facilities. In particular, they are no longer intended to assist viewers in calibration of television sets. Several things have led to the demise of the test card for this purpose: Modern Microcontroller -controlled analog televisions rarely, if ever, need adjustment, so test cards are much less important than previously. Likewise, modern cameras and camcorders seldom need adjustment for technical accuracy, though they are often adjusted to compensate for scene light levels, and for various artistic effects. Use of digital interconnect standards, such as CCIR 601 and SMPTE 292M , which operate without the non-linearities and other issues inherent to analog broadcasting, do not introduce color shifts or brightness changes; thus the requirement to detect and compensate for them using this reference signal has been virtually eliminated. (Compare with the obsolescence of Stroboscope s as used to adjust the speed of a record player). On the other hand, digital test signal generators do include test signals which are known to stress the digital interface, and many sophisticated generators allow the insertion of Jitter , bit errors, and other pathological conditions which can cause a digital interface to fail. Likewise, use of digital broadcasting standards such as the DVB and ATSC standards, eliminates the issues introduced by modulation and demodulation of analog signals. Test cards including large circles were used to confirm the linearity of the set's deflection systems. As solid-state components replaced Vacuum Tube s in receiver deflection circuits, linearity adjustments were less frequently required (few newer sets have user-adjustable "VERT SIZE" and "VERT LIN" controls, for example). In LCD and other deflectionless displays, the linearity is a function of the display panel's manufacturing quality; for the display to work, the tolerances will already be far tighter than human perception. In Developed Countries such as the United States or the United Kingdom , the financial imperatives of commercial television broadcasting mean that air-time is now typically filled with programs and commercials (such as Infomercial s) 24 hours a day, and non-commercial broadcasters have to match this. In North America, most test cards such as the famous Indian Head Test Card of the 1950s and 1960s have long been relegated to history. The SMPTE Color Bars occasionally turn up, but with most North American broadcasters now following a 24-hour schedule, this too has become a rare sight. When there are in fact no standard programs being broadcast on the channels that do not have 24-hour programming, other, more informative features such as educational shows, i.e. the BBC Learning Zone , and teletext-type programmes such as Pages From Ceefax , ITV Nightscreen and 4-Tel On View are often broadcast, the latter type acting as the better test-card substitute as they just roll continuously. Australian national broadcaster SBS airs a weather map in place of a test card with music from albums sold by SBS and a ticker at the bottom of the screen during the early hours of the morning. Australian community broadcaster Channel 31 in Melbourne airs Fishcam , the output of a videocamera aimed at a fish tank. On television networks and stations in most of the Third World countries, test cards are still seen because most television networks and stations in those countries do not have 24-hour programming. Use of test patterns and test cards is still common ''within'' television production facilities. Many of these still have analog infrastructure, and currenty As Of March 2006 analog transmissions are still found worldwide (though the United States is currently scheduled to require broadcasters switch off the NTSC service in 2009 --NTSC may still be a viable transmission means for Cable Television for several more years). Many artistic settings are still made by using test cards or test patterns in conjunction with devices like Waveform Monitor s and Vectorscope s (most modern waveform monitors include vectorscope capability), and while digital transmission eliminates many of the "analog" effects associated with analog television, digital broadcasting has its own set of issues. TEST CARD MUSIC Background music often plays during the broadcast of a test card. This music is usually a composition commissioned by the station itself or "royalty-free" Stock Music in order to avoid having to pay Royalties for something that does not generate revenue. Test card music became popular in its own right when a group of enthusiasts discovered one another and realised they were not alone in enjoying the music played during the day in the 1950s , 60s and 70s while the test card was broadcast on BBC . The Test Card Circle , formed in 1989 , is a group of such enthusiasts. GALLERY
	Image:TCJjpg	"http://wwwinformationdelightinfo/encyclopedia/entry/Test_Card_J" class="copylinks">Test Card J
	Image:TCWjpg	"http://wwwinformationdelightinfo/encyclopedia/entry/Test_Card_W" class="copylinks">Test Card W
	Image:Ihtppng	"http://wwwinformationdelightinfo/encyclopedia/entry/Indian_Head_test_card" class="copylinks">Indian Head Test Card
	Image:smptecbpng	"http://wwwinformationdelightinfo/encyclopedia/entry/SMPTE_color_bars" class="copylinks">SMPTE Color Bars
	Image:Pm5544png	"http://wwwinformationdelightinfo/encyclopedia/entry/Philips_PM5544" class="copylinks">Philips PM5544
	Image:EBU Colorbarspng	"http://wwwinformationdelightinfo/encyclopedia/entry/EBU" class="copylinks">EBU Test Card

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Test Card