liam@cs.qmc.ac.uk (William Roberts) (03/20/86)
The PostScript manual says that a printers' point is 1/72 of an inch (or possibly 1/72.27 of an inch). Does this mean that points are a UK/US unit only, or do printers everywhere use them? Where does the 72.27 come from? -- William Roberts ARPA: liam@UK.AC.qmc.cs Queen Mary College UUCP: liam@qmc-cs.UUCP LONDON, UK
jaap@mcvax.UUCP (Jaap Akkerhuis) (03/21/86)
In article <130@cs.qmc.ac.uk> liam@cs.qmc.AC.UK (William Roberts) writes: > The PostScript manual says that a printers' point is 1/72 of an > inch (or possibly 1/72.27 of an inch). Does this mean that > points are a UK/US unit only, or do printers everywhere use > them? Where does the 72.27 come from? In the UK/US the most used point system is the "Pica points". The officially value of a 72 point (or 12 Pica) in this system is 1 inch (and something small). But note that the exact size of a point can be dependent on the brand of the typesetter manufacturer, the traditional value actually used in the printer shop you ask about the size of point, or a combination of the two. In other places of the world (France, Holland etc.) the traditional value of a point comes from the Didot system. The size is different. 1 Pica point is about 0.934572 times a Didot point. And of course the note about manufacturers and printer shop is valid as well. This reminded me that when out typesetter arrived it was using Didot points, so everything came out too big (using troff). The typesetter was made in the USA, and I was sure, it was not an error in my C/A/T simulating filter. After some digging (thanks Piet) in the diagrams we found a switch to make it Pica points. As far as I can remember (and I don't have the diagrams always at home so cannot check) it changed a reference voltage for some DAC's int the X & Y deflection circuits. I think there is even a ten turn pot so you can adjust the point to the above mentioned standard of the printing shop. jaap
gh@utai.UUCP (Graeme Hirst) (03/26/86)
> The PostScript manual says that a printers' point is 1/72 of an > inch (or possibly 1/72.27 of an inch). Does this mean that > points are a UK/US unit only, or do printers everywhere use > them? Where does the 72.27 come from? > > William Roberts ARPA: liam@UK.AC.qmc.cs This question is answered at length in an article by Allan Haley on Nelson Hawks (1840-1929), "The John the Baptist of the American point system", in U&lc, 12(1), May 1985. Some excerpts: "It took a royal decree to force type founders to take the first step toward solving the problem of type sizing. This occurred in France in 1723. The monarchy decreed that the height of type be fixed, and established the relationships between various sizes of type. The shortcoming of this regulation was that it failed to specify the size of the smallest unit. "Twelve years later, Pierre Simon Fournier made the French regulation practical. He created the typographic point . . . In the Fournier system, there are exactly 72 points to an inch. "The trouble with Fournier's system was that is was not accepted by other type founders, and it did not conform to the official French measure for an inch . . . [50 years later,] another French type founder, Didot, further refined the concept. He made a few small changes to Fournier's system and one large one. Didot based his system on the legal foot measure in France. The Didot system became the standard among French type founders and even though the basis of the foot measure changed, the Didot system continued to grow in popularity. It eventually became the standard in most of Europe, and is still used today . . . [Meanwhile, typographic chaos continued to reign in the U.S. Type sizes were designated by names (Nonpareil, Minion, Brevier, . . .), but different founders had different standards.] "Hawks spent many hours struggling with the problem, and when he did arrive at a solution [in 1877], it was deceptively simple. ``Finding our own pica [size font] to be exactly one-sixth of an inch, the idea of adopting the mechanic's rule as a basis for measurement occurred to me. Then came the division of the pica parts. Nonpareil being one half the size of the pica the unit would have to be determined from the number of sizes above Nonpareil. These are Minion, Brevier, Bourgeois, Long Primer, Small Pica, and Pica -- six. Therefore, Nonpareil would be the other six, and pica would be 12 points.'' [So the fact that Hawks ended up with 72 points per inch, the same as Fournier, is partly coincidental! See below for th part that isn't.] "[Hawks then spent many years promoting his system. Although conversion was costly for founders, he was successful, and] lived to see his system become the standard for both the United States and Britain. "[But] every primer on type warns the neophyte that 72 points = .996 inch. What happened to the last four thousandths of an inch? Why didn't the creator of the American point system use a full inch as the basis for the standard? At the time Nelson Hawks developed the system, at least two picas were standard, and one of them measured exactly one-sixth of an inch. What happened? The APS is based on the ``Johnson pica''. ". . . It is believed that the standards for the molds and typecasting equipment for Binny and Ronaldson [the oldest American type founder, to whom Johnson was a successor] can be traced to equipment that Benjamin Franklin bought from Fournier early in the 18th century [and by Hawks's time] the Johnson pica served as the standard for seven major foundries [including Hawks's]. "And the missing four thousandths of an inch? It is believed that, even though Fournier's pica was based on an inch, four thousandths were lost as a result of active (and less than ideal) use of the original molds, and to the reproduction process, as new molds were made to replace that which had worn out. "To Hawks and his contemporaries, the difference of four thousandths mattered little anyway. [They] were working with metal type that was subject to expansion and contraction, and in dirty places where minute sizes were of little relevance." --------------------- If your library doesn't carry U&lc ("Upper and lower case, the international journal of typographics"), write to the publisher, International Typeface Corporation, 2 Hammarskjold Plaza, New York, NY 10017, who distribute it free of charge to bona fide workers in typography. -- \\\\ Graeme Hirst University of Toronto Computer Science Department //// utcsri!utai!gh / gh.toronto@csnet-relay / 416-978-8747