|Unit system||typographic unit|
|metric (SI) units||0.3528 mm|
In typography, the point is the smallest unit of measure. It is used for measuring font size, leading, and other items on a printed page. The size of the point has varied throughout the history of printing. Since the 18th century, the point's size has varied from 0.18 to 0.4 millimeters. Following the advent of desktop publishing in the 1980s and 1990s, digital printing has largely supplanted the letterpress printing and has established the DTP point (desktop publishing point) as the de facto standard. The DTP point is defined as of an international inch (about 0.353 mm) and, as with earlier American point sizes, is considered to be of a pica.
In metal type, the point size of the font described the height of the metal body on which the typeface's characters were cast. In digital type, letters of a font are designed around an imaginary space called an em square. When a point size of a font is specified, the font is scaled so that its em square has a side length of that particular length in points. Although the letters of a font usually fit within the font's em square, there is not necessarily any size relationship between the two, so the point size does not necessarily correspond to any measurement of the size of the letters on the printed page.
The point was first established by the Milanese typographer, Francesco Torniella da Novara (c.1490 - 1589) in his 1517 alphabet, L'Alfabeto. The construction of the alphabet is the first based on logical measurement called "Punto," which corresponds to the ninth part of the height of the letters or the thickness of the principal stroke.
A measurement in points can be represented in three different ways. For example, 14 points (1 pica plus 2 points) can be written:
||1982||= 0.351 459 80||?||=|
||1984||= 0.3527||= 0.0138||=|
|German actual, TeX
|L'Imprimerie Nationale||1810||= 0.400||?|
|German, Japanese, CSS
There have been many definitions of a "point" since the advent of typography. Traditional continental European points at about are usually a bit larger than English points at around .
The Truchet point, the first modern typographic point, was of a French inch or of the royal foot. It was invented by the French clergyman Sébastien Truchet. During the metrication of France amid its revolution, a 1799 law declared the meter to be exactly 443.296 French lines long. This established a length to the royal foot of m or about 325 mm, which made the Truchet point equal to mm or about . It has also been cited as exactly 0.188 mm.
The Fournier point was established by Pierre Simon Fournier in 1737:60-66 The system of Fournier was based on a foot, 1 foot equals 12 inches, 1 inch (pouce) was divided into 12 lines (lignes) and 1 line was further divided into 6 typographic points (points typographiques). 1 point Fournier = .0135 inch
Fournier printed a reference scale of 144 points over two inches, however, it was too rough to accurately measure a single point.
The Didot point, established by François-Ambroise Didot in 1783, was an attempt to improve the Fournier system. He did not change the subdivisions (1 inch = 12 lines = 72 points), but defined it strictly in terms of the royal foot, a legal length measure in France: the Didot point is exactly of a French foot or of a French inch, that is (by 1799) mm or about . Accordingly, one Didot point is exactly two Truchet points.
However, 12 Fournier points turned out to be 11 Didot points,:142-145 giving a Fournier point of about ; later sources:60-61 state it as being . In Belgium the Fournier system was used until the 1970-ties and later. It was called the "mediaan"-system. To avoid confusion between the new and the old sizes, Didot also rejected the traditional names, thus parisienne became corps 5, nompareille became corps 6, and so on.:143 The Didot system prevailed because the French government demanded printing in Didot measurements.[better source needed]
The Fournier point did not achieve lasting popularity despite being revived by the Monotype Corporation in 1927. It was still a standard in Belgium, in parts of Austria, and in Northern France at the beginning of the 20th century.:66
In 1878 Hermann Berthold defined 798 points as being equal to 30 cm, or 2660 points equalling 1 meter: that gives around to the point. A more precise number,, sometimes is given; this is used by TeX as the
dd unit. This has become the standard in Germany and Central and Eastern Europe. This size is still mentioned in the technical regulations of the Eurasian Economic Union.
TeX also supports a new Didot point (nd) at mm or and cites a 1978 redefinition for it. The French National Print Office adopted a point of mm or in about 1810 and continues to use this measurement today (though "recalibrated" to ).
Japanese and German standardization bodies instead opted for a metric typographic base measure of exactly mm or . It is called Q in Japanese after the initial letter of quarter millimeter. Due to demand by Japanese typesetters, CSS adopted Q in 2015.
The basic unit of measurements in American typography was the pica, usually approximated as one sixth of an inch, but the exact size was not standardized, and various type foundries had been using their own.
After the American war of Independence Benjamin Franklin was sent as commissioner (Ambassador) for the United States to France (December 1776 to 1785). Whilst there he had intimate contact with the Fournier family, including the father and Pierre Simon Fournier. Franklin wanted to teach his grandson printing and typefounding, and arranged him to be trained by Francois Ambroise Didot. Franklin bought also matrices and more equipment in order to set up a type-foundry for Bache and brought this with him, when he returned to Philadelphia. Around 1790 Bache published a specimen sheet with some Fournier types.  After the death of Franklin, the matrices and the Fournier mould were acquired by Binny and Ronaldson, the first permanent type-foundry in America. In 1833 this plant was merged into the firm that in 1860 was renamed in Mackellar, Smith and Jordan. The Fournier cicero mould was used by them to cast pica-sized type.
Nelson Hawks proposed, like Fournier, to divide one American inch exactly into six picas, and one pica into 12 points. However, this saw an opposition because the majority of foundries had been using picas less than one sixth of an inch. So in 1886, after some examination of various picas, the Type Founders Association of the United States approved the pica of the MacKellar, Smiths, & Jordan Co. foundry of Philadelphia (previously L. Johnson & Co., hence the Johnson pica) as the most established. The official definition of one pica is 0.166044 inches (4.2175 mm), and one point is 0.013837 inches (0.3515 mm). That means 6 picas or 72 points constitute 0.99624 of the standard inch. A less precise definition is one pica equals 0.166 inches (4.2 mm), and one point 0.01383 inches (0.351 mm). It was also noticed that 83 picas is nearly equal to 35 cm, so the Type Founders Association also suggested using a 35 cm metal rod for measurements, but this was not accepted by every foundry.
In modern times this size of the point has been approximated as exactly (0.01383700013837) of the inch by Donald Knuth for the default unit of his TeX computer typesetting system and is thus sometimes known as the , which is 0.35145980 mm.
The desktop publishing point (DTP point) or PostScript point is defined as or 0.0138 of the international inch, making it equivalent to 0.3527 mm. Twelve points make up a pica, and six picas make an inch.
This specification was developed by John Warnock and Charles Geschke when they created Adobe PostScript. It was adopted by Apple Computer as the standard for the display resolution of the original Macintosh desktop computer and the print resolution for the LaserWriter printer.
In lead typecasting, most font sizes commonly used in printing have conventional names that differ by country, language and the type of points used, see traditional point-size names.
Desktop publishing software and word processors intended for office and personal use often have a list of suggested font sizes in their user interface, but they are not named and usually an arbitrary value can be entered manually. Microsoft Word, for instance, suggests every even size between 8 and 28 points and, additionally, 9, 11, 36, 48 and 72 points, i.e. the larger sizes equal 3, 4 and 6 picas. While most software nowadays defaults to DTP points, many allow other units, especially code-based systems like TeX and CSS.
They commissioned for this purpose the well-known Berlin brass rule manufacturer, H. Berthold, who supplies brass rules not only to most of the German foundries but also to many foreign houses, and he, in conjunction with Prof. W. Fürster, the chief director of the Berlin Observatory, agreed that 2,660 typographical points of the Didot system should correspond to one metre. Accordingly the Standard Gauge Commission in Berlin in 1879 arranged a standard measure of 30 centimetres = 133 nonpareil or 798 typographical points, and gave a copy to all the German foundries, and since that time disputes about the Didot depth were unknown in Germany.
? ? ?. 0,376 .
The point in current use at the Imprimerie Nationale measures 0.39877 mm. This appears to be the result of a 'recalibration', for which no date can be given, of the point of 0.4 mm.
These latter figures give the size in the 'points millimétriques' of about 0.4 mm that are said to have been introduced at the Imprimerie impériale by Firmin Didot and which are the basis for the 'point IN' used today at the Imprimerie nationale.
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