Test card

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SMPTE bars—common NTSC test pattern
PM5544—common PAL test pattern

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. (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. 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 broadcasts (though the negative excursions of the colourburst signal may go below 0 IRE). 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 such as VTRs) 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[edit]

BBC test cards are identified 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.[1] It was later updated as Test Card J, and for widescreen broadcasts as Test Card W. Test Card F has often been spoofed by comedians.[2]

Decline[edit]

A 1952 Philips TD1410U television set showing the optical monochrome Telefunken test card T05.

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 their demise for this purpose:

  • Modern microcontroller-controlled analogue 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 analogue broadcasting, do not introduce colour 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 stroboscopes as used to adjust the speed of record players). On the other hand, digital test signal generators do include test signals which are intended to stress the digital interface, and many sophisticated generators allow the insertion of jitter, bit errors, and other pathological conditions that can cause a digital interface to fail.
  • Likewise, use of digital broadcasting standards such as the DVB and ATSC eliminates the issues introduced by modulation and demodulation of analogue signals.
  • Test cards including large circles were used to confirm the linearity of the set's deflection systems. As solid-state components replaced vacuum tubes 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 and the United Kingdom, the financial imperatives of commercial television broadcasting mean that air-time is now typically filled with programmes and commercials (such as infomercials) 24 hours a day, and non-commercial broadcasters have to match this.

Test cards and other semi-static programming and their use around the world today:

  • In North America, most test cards such as the famous Indian-head test pattern 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, these too have become a rare sight. Many Canadian Broadcasting Corporation stations broadcast a modified form of the SMPTE bars (with an additional modulated ramp at the top and a CBC logo animation in place of the Q block) late at night until late 2006, when the network moved to 24-hour broadcasting.
  • When there are in fact no standard programmes being broadcast on the channels that do not have 24-hour programming, other, more informative features such as educational shows, e.g. 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 Weatherwatch, a weather map accompanied by 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 previously aired Fishcam, the output of a videocamera aimed at a fish tank.
  • Some Philippine cable television channels replace test cards with an advertisement showing the product, "a reason to go to sleep" and the time when the station will sign on.
  • In Malaysia it was officially inaugurated to grand opening on 1 June 2011 by the TV Alhijrah it was officially instead of showing test cards, television channels usually air music theme "歡顏" with vocalist to singers by Nikita Willy. while showing their Astro logo at the same time.
  • In Singapore, since 2005, instead of showing test cards, television channels usually air radio channels while showing their station ident at the same time.
  • In Thailand, 24-hour broadcasting was introduced on 1 January 1997 on TV5 and the full 24-hour schedule was introduced on 1 January 2005 on TV3. Since 9 April 2011, test cards are no longer used in Thailand. Most stations broadcasts teleshopping during off-air hours, while Thai PBS broadcasts station logo and test tone. NBT broadcasts relay from 24-hour international channel, NBT World.

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 analogue infrastructure, and currently as of March 2006 analogue transmissions are still found worldwide (though the United States is currently scheduled to require broadcasters to 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 such as wave monitors and vectorscopes (most modern waveform monitors include vectorscope capability), and while digital transmission eliminates many of the "analogue" effects associated with analogue television, digital broadcasting has its own set of issues.

Terrestrial television channels continuing to broadcast test cards in Europe[edit]

Terrestrial television channels continuing to broadcast test cards in Asia[edit]

Terrestrial television channels continuing to broadcast test cards in Africa[edit]

Gallery[edit]

UK Testcard timeline[edit]

Year Notes Channel(s) Image
1936–1939 The first publicly broadcast testcard. It was a simple line and circle broadcast using Baird's 30 line system, and was used to synchronise the mechanical scanning system. BBC Television Service
1936-1939
1947–1948 The second publicly broadcast testcard. It had more specific details and was referred to as Testcard A. BBC Television Service
1947-1948
1948 Referred to as Testcard B. Used behind the scenes but never broadcast. None
1948 (behind the scenes only)
1948–1964 Testcard C is released, with more specific details than Testcard B. BBC Television Service
1948-1964
1955 The ITA broadcasts an unlabelled testcard on ITV. ITV
1955–1960 A revised version of Testcard C is broadcast on ITV. ITV
1960–1964 The ITA "Picasso" testcard is released. ITV
1960-1964
1964–1985 Testcard D is released, and is the final testcard to be released for the 405-line format. Music as well as test tones were regularly used to accompany this image on BBC1 and ITV. BBC1
ITV
1964-1985 (405-line only)
1964 Testcard E is released to comply with the 625-line format. Numerous television vendors complained that the image made on screen was unattractive – its sinusoidal frequency gratings looked soft – and was therefore only used for 5 days before being replaced. BBC1
BBC2
ITV
1964 (625-line only)
1964–1969/1976 Once Testcard E was withdrawn, the BBC released a modified version of Testcard C with more specific details on the inside circle. It was withdrawn from service in 1967 and 1967 respectively, it continued in regions that were still in black and white until 1976. BBC1
BBC2(1964–1967)
ITV
1964-1969
1967–1984 Testcard F, the most famous and used testcard, is released by the BBC to coincide with colour transmissions that started that year on 1 July on BBC2. Only limited programmes were available in colour from the start. The full output became colour on BBC2 on 2 December the same year. BBC1 and ITV started colour in 1969, and began use of this testcard, phasing out Testcard C (But some regions had to wait until in the middle seventies, so in the meantime, Testcard C remained in use until 1976). It features a picture of Carole Hersee playing noughts and crosses. BBC1 (1969–1984)
BBC2
ITV (1969–1979)
1967-1984
1970s Testcard G, a variant of the Philips PM5544 test pattern, is created. It was occasionally seen on BBC1 and BBC2 during the 1970s. BBC1
BBC2
1979–1992 The Independent Broadcasting Authority (IBA) – Independent Television Authority (ITA) prior to 1972, introduce ETP-1/Electronic Test Pattern One to replace Testcard F within the ITV regions. ETP-1 was also extensively used by Channel 4 and S4C in the run up to the launch of these channels in November 1982 — using 'IBA:CH4'/'IBA:S4C' captioning instead of the 'IBA' captioning used by ITV. ETP-1 became a common sight on British television in the 1980s up until ITV started broadcasting 24 hours a day in 1988. Channel 4/S4C continued to use ETP-1 – using 'NTL:CH4'/'NTL:S4C' captioning from 1990 after the Broadcasting Act 1990 saw the privatisation of the IBA's transmitter network and sale to National Transcommunications Limited (NTL). However ETP-1 disappeared in 1992 when Channel 4 simply broadcast its teletext service 4-Tel on View whilst off air — it later began 24 hour broadcasting in 1997, with S4C simply broadcasting black screen and tone whilst off-air. ITV (1979–1988)
Channel 4 (1982–1992)
S4C (1982–1992)
1984–1999 Testcard F is converted to an electronic format. On 4 October 1997, the BBC logo on the testcard was changed to match the current logo. It was removed from BBC One a month later due to the launch of BBC News which is now seen overnight on it. BBC1 (1984–1997)
BBC One (1997)
BBC2 (1984–1997)
BBC Two (1997–1999)
1984-1997
1999–2012/2013 Testcard J is released, replacing Testcard F. Testcard J is a modified version of F, with improvements including an improved centre picture and a dot in the white area at the top. In 2000, Testcard W is released, which is similar but formatted in 16:9 widescreen. Usage of regular testcards on BBC Two gradually started to decline during the early 2000s before regular use was discontinued in 2004. It is still seen occasionally on BBC Two, around mid-January each year. The usage of testcards in the United Kingdom had completely dropped in 2012 and then again in 2013. BBC Two
1999-2000

Test patterns for photocopiers[edit]

A lesser-known kind of test pattern is used for the calibration of photocopiers.[4][5] Photocopier test patterns are physical sheets that are photocopied, with the difference in the resulting photocopy revealing any telltale deviations or defects in the machine's ability to copy.

In numismatics[edit]

Television has had such an impact in today's life, that it has been the main motif for numerous collectors' coins and medals. One of the most recent ones is The 50 Years of Television commemorative coin minted on March 9, 2005 in Austria. The obverse of the coin shows a "test pattern", while the reverse shows several milestones in the history of television.

Monoscope[edit]

Close-up, showing test-card target

Rather than physical test cards, which had to be televised using a camera, an alternative method was to use a cathode ray tube to generate, rather than display, a video signal. Each tube was only capable of generating a single video signal, hence the name.

Essentially similar in construction to an ordinary CRT, the monoscope contained a formed metal target in place of the phosphor coating at its "screen" end and as the electron beam scanned the target, rather than displaying an image, a varying electrical signal was produced generating an image from the etched pattern.

These were fragile, but had advantages over test cards, always being properly framed and in focus. They fell out of use in the 1960s, as they were not able to produce color images.

References[edit]

  1. ^ "The History of the test card". Techwatch.co.uk. 2011-12-01. Retrieved 2011-12-01. 
  2. ^ Test card special, by Ryan Dilley, BBC News, 19 April 2001
  3. ^ http://www.bbc.co.uk/news/world-asia-pacific-13006543
  4. ^ "Samsung SF531P PCSTATS Review – Printer Test Patterns". Pcstats.com. 2007-10-15. Retrieved 2010-01-01. 
  5. ^ "Projection: Room A / Room B". Thing.net. Retrieved 2010-01-01. 

External links[edit]