Point (typography)

Comparison table

There have been many definitions of a "point" since the advent of typography. Traditional continental European points at about 6996375000000000000♠0.375 mm are usually a bit larger than English points at around 6996350000000000000♠0.350 mm.

French points

The Truchet point, the first modern typographic point, was 1/144 of a French inch or 1/1728 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 7003900000000000000♠9000/7004277060000000000♠27706 m or about 325 mm, which made the Truchet point equal to 7004156250000000000♠15625/7004831180000000000♠83118 mm or about 6996187986000000000♠0.187986 mm. It has also been cited as exactly 0.188 mm.

The Fournier point was established by Pierre Simon Fournier in 1737^{[10][11][12]: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 = 0.0135 inches.

The Fournier scale: two inches in total, divided into four half-inches, the medium intervals are one line (​¹⁄₁₂ inch), and the smallest intervals are ​¹⁄₃₆ inch; no intervals for the point is given, though

Fournier printed a reference scale of 144 points over two inches, however, it was too rough to accurately measure a single point.^[11]

The Didot point, established by François-Ambroise Didot in 1783,^[13] 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 1/864 of a French foot or 1/72 of a French inch, that is (by 1799) 7004156250000000000♠15625/7004415590000000000♠41559 mm or about 6996375972000000000♠0.375972 mm. Accordingly, one Didot point is exactly two Truchet points.

However, 12 Fournier points turned out to be 11 Didot points,^{[11]:142–145} giving a Fournier point of about 6996345000000000000♠0.345 mm; later sources^[12]:60–61 state it as being 6996348750000000000♠0.34875 mm. 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, nonpareille became corps 6, and so on.^[11]:143 The Didot system prevailed because the French government demanded printing in Didot measurements.^[14]

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.^[12]:66

Other European points

Approximations were subsequently employed, largely owing to the Didot point's unwieldy conversion to metric units (the divisor of its conversion ratio has the prime factorization of 3×7×1979).

In 1878 Hermann Berthold defined 798 points as being equal to 30 cm, or 2660 points equalling 1 meter: that gives around 6996376000000000000♠0.376 mm to the point.^{[15][16][17][18]} A more precise number,6996376065000000000♠0.376065 mm, sometimes is given;^[16] this is used by TeX as the dd unit. This has become the standard in Germany^[8] and Central and Eastern Europe.^[19] This size is still mentioned in the technical regulations of the Eurasian Economic Union.^[20]

Metric points

TeX also supports a new Didot point (nd) at 3/8 mm or 6996375000000000000♠0.375 mm and cites a 1978 redefinition for it. The French National Print Office adopted a point of 2/5 mm or 6996400000000000000♠0.400 mm in about 1810 and continues to use this measurement today (though "recalibrated" to 6996398770000000000♠0.39877 mm).^[21][22][23]

Japanese^[24] and German^[9][16][18] standardization bodies instead opted for a metric typographic base measure of exactly 1/4 mm or 6996250000000000000♠0.250 mm. It is called Q in Japanese after the initial letter of quarter millimeter. Due to demand by Japanese typesetters, CSS adopted Q in 2015.^[25][26]

American points

The basic unit of measurements in American typography was the pica,^[27][12][28] usually approximated as one sixth of an inch, but the exact size was not standardized, and various type foundries had been using their own.^[12]

After the American war of Independence Benjamin Franklin was sent as commissioner (Ambassador) for the United States to France (December 1776 to 1785).^[29] 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. ^{[30] [31]} 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.^[27] 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 6999996240000000000♠0.99624 standard inches. A less precise definition is one pica equals 0.166 inches (4.2 mm), and one point 0.01383 inches (0.351 mm).^[27][32] 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.^[27]

This has become known as the American point system.^[32][27] The British foundries accepted this in 1898.

In modern times this size of the point has been approximated as exactly ​¹⁄_72.27 (0.01383700013837) of the inch^[33] by Donald Knuth for the default unit of his TeX computer typesetting system and is thus sometimes known as the TeX point, which is 0.35145980 mm.

Desktop publishing point

The desktop publishing point (DTP point) or PostScript point is defined as ​¹⁄₇₂ 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.^[34][35]

In 1996, it was adopted by W3C for Cascading Stylesheets (CSS) where it was later related at a fixed 4:3 ratio to the pixel due to a general (but wrong) assumption of 96 pixel-per-inch screens.