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Test Card F
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==Technical information== {{More citations needed section|date=October 2020}} Virtually all the designs and patterns on the card have some significance. Along the top (see above) are 95% [[Colorfulness#Saturation|saturation]] [[EBU colour bars|colour bars]] in descending order of [[luminance]]—[[white]], [[yellow]], [[cyan]], [[green]], [[magenta]], [[red]], [[blue]] and [[black]].<ref name=":0">{{Cite book |last=Hersee |url=https://www.worldradiohistory.com/UK/BBC/BBC-Books/bbc_monograph_69.pdf |title=BBC Engineering Division - MONOGRAPH - No. 69 |date=September 1967 |publisher=BBC |pages=13}}</ref><ref name=":1">{{Cite web |last=Pemberton |first=Alan |date=2016-03-03 |title=Not just a pretty face... Technical descriptions of UK test cards |url=http://www.pembers.freeserve.co.uk/Test-Cards/Test-Card-Technical.html |url-status=dead |access-date=2024-11-05 |website=Pembers' Ponderings |archive-date=3 March 2016 |archive-url=https://web.archive.org/web/20160303165836/http://www.pembers.freeserve.co.uk/Test-Cards/Test-Card-Technical.html }}</ref> There are triangles on each of the four sides of the card to check for correct [[overscan]]ning of the picture. Standard greyscale and [[frequency response]] (1.5, 2.5, 3.5, 4, 4.5 and 5.25 MHz) tests are found on the left and right respectively of the central picture.<ref name=":0" /><ref name=":1" /> On the updated version known as Test Card J (including widescreen and HD versions), the X on the [[noughts-and-crosses]] board is an indicator for aligning the centre of the screen. The blocks of colour on the sides would cause the picture to tear horizontally if the [[Composite video|sync]] circuits were not adjusted properly.<ref name=":1" /> The closely spaced lines in various parts of the screen allowed focus to be checked from centre to edge; mistuning would also blur the lines. All parts of the [[grayscale|greyscale]] would not be distinct if contrast and brightness (both internal preset settings and user adjustments) were not set correctly. The black bar on a white background revealed [[ringing (signal)|ringing]] and signal reflections.<ref name=":1" /> The castellations along the top and bottom also revealed possible setup problems. In the centre image, a child was depicted so that wrong skin colour would be obvious and not subject to changing [[make-up]] fashions. The juxtaposed garish colours of the clown were such that a common [[transmission (telecommunications)|transmission]] error called chrominance/luminance delay inequality would make the clown's yellow [[Button (clothing)|buttons]] turn white. Use of centre images in test cards were however not a new idea; [[Radiodiffusion-Télévision Française|RTF]] and [[Office de Radiodiffusion Télévision Française|ORTF]] in France used the [[Marly Horses]] as the central motif of its [[monochrome]] [[Analog high-definition television system|819-line]] test card which was used on [[TF1]] between 1953 and 1983,<ref>{{cite web|url=http://www.pembers.freeserve.co.uk/Test-Cards/Non-UK.html#France|archiveurl=https://web.archive.org/web/20160304051933/http://www.pembers.freeserve.co.uk/Test-Cards/Non-UK.html#France|archivedate=2016-03-04|title=Non-UK Television Test Cards, Tuning Signals, Clocks and Idents|date=March 4, 2016}}</ref> and the first French colour test card featuring a centre image of colourful roses was used on [[France 2]] from 1967 until sometime around the mid-1970s.<ref>{{cite web|url=https://www.vivelapub.fr/retrospective-la-mire-tv/|title=Rétrospective : la mire à la télévision (1953 – 2002)|date=January 5, 2012|website=VivelaPub}}</ref> [[Sveriges Television|SVT]] in Sweden was also later inspired by Test Card F to develop its own colour test card, based on its earlier monochrome test cards, [[:File:Sweden TV1 colour 1969.png|with a girl holding a doll in the centre image]].<ref>{{cite web|url=http://www.pembers.freeserve.co.uk/Test-Cards/Non-UK.html#Sweden|archiveurl=https://web.archive.org/web/20160304051933/http://www.pembers.freeserve.co.uk/Test-Cards/Non-UK.html#Sweden|archivedate=2016-03-04|title=Non-UK Television Test Cards, Tuning Signals, Clocks and Idents|date=March 4, 2016}}</ref> Modern circuitry using [[integrated circuit|large-scale integration]] is much less susceptible to most of these problems. Some of them are also associated with [[cathode-ray tube]]s; modern screens use [[liquid crystal display]]s (LCDs) that are not scanned at high speed. The test card was a vital tool in its day, but has become far less important. The name of the broadcasting channel usually appeared in the space underneath the letter F—a [[sans-serif]] F denoting an original optical version of the test card. Originally, Test Card F was a [[Reversal film|photographic slide]] made up of two transparencies in perfect registration—one containing the colour information ([[chrominance]]) and the other the monochrome background ([[luminance]]). The card was converted to electronic form in 1984 when electronic storage became possible.<ref>{{Cite book |url=http://www.bbceng.info/additions/2016/IBC_Brochure_1984%20(large).pdf |title=BBC Engineering at IBC-84 |publisher=BBC Research & Development |year=1984 |location=United Kingdom}}</ref><ref name=":1" />
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