overfull hbox: Computer Phototypesetting, Part I

Many in the fields of computer science, mathematics, and physics have a strange affection for a typesetting system called LaTeX. Unlike word processors and typesetting software that operate on a “what you see is what you get” (WYSIWYG) basis, LaTeX takes plaintext input files with a variety of odd-looking markup and compiles them into print-ready postscript or PDF output. While certainly less user friendly and more difficult to learn than WYSIWYG software, LaTeX is known for the high quality of its output (particularly because it largely adheres to late-19th century typesetting conventions, giving its output a kind of “quaint” appearance that many find endearing or professional) and its ability to typeset complex notation like mathematics with relative ease.

The fact that LaTeX is still in use today is rather fascinating, as it is in many ways an incredible relic of a past age. It is not alone in this regard, though. The groff typesetting system is also still used as the dominant input format for Linux manpages, and is a descendant of even older software. Both of these typesetting systems are interesting in that they predate both modern printing and graphical computer displays, and output not to PDFs or office printers but to phototypesetters.

Placing phototypesetting in context requires a bit of discussion of the history of printing itself, so I will spend this article on that topic. In the next part, we will get into the details of computer phototypesetting itself.

You may have learned that documents were originally duplicated by human printers of a sort, usually titled as scribes. These individuals would hand-copy a handwritten manuscript into a second handwritten manuscript. This was obviously labor-intensive, and so generally only religious texts and legal texts were ever duplicated in any real quantity.

The development of the mechanical printing press is often considered one of the greatest single points in the history of not just typesetting or engineering but also culture as a whole. The first printing press, invented by Gutenburg in the 15th century, was a direct or letter press in which metal plates with letters projecting from them were first coated in ink and then pressed against a page, transferring the ink as well as a impressing the shapes of the letters into the paper itself, giving a slight 3D texture. This latter property was unintentional but is the main reason that letter presses are still used today, as the effect is often desired for aesthetic reasons on certain important and decorative documents like wedding announcements.

Obviously, it was not particularly practical to have a printer carefully engrave a lead plate into a perfectly formed page of text. Instead, Gutenburg devised an ingenious scheme in which individual letters were carved into narrow metal blocks which were then arranged in strips to form sentences and then grids to form entire columns of text. When figures, decorated headings, and other special sections of print were needed, they would be hand-carved into larger blocks that were added to the composition. Once arranged, these blocks were clamped tightly together and used for printing. The individual lead letters were referred to as type and the process of arranging them as setting, thus the term typesetting which is still used today.

This remained the state of the art in printing for a remarkably long time. Typesetters were able to work reasonably quickly under this scheme, particularly since most of the typesetting being done was of books, which did not change particularly often and were printed in large quantities. The long setup time required became much more frustrating, though, in the case of newspapers. Largely to serve the newspaper industry, which needed to compose multiple large pages daily, inventor Ottmar Morganthaler developed the first hot-metal typesetting machine in the late 19th century. This machine, which he dubbed the Linotype, automatically cast lead strips containing entire sentences as an operator typed them out on a large keyboard.

The following years brought many innovations on this model, including competing systems introduced by competitors. While these were fascinating in their own right, including many aspects that resemble later computing systems, I will largely gloss over them to get to the actual point of this article. Put short, while hot-metal systems became impressively advanced and continued to be used by some operations into the 1990s, they operated at limited speed and still required a great deal of manual effort to compose the strips produced into a final page. A major evolution of printing technology started to replace hot-metal casting because of improvements in two areas: first, photographic processes and film, and second, lithographic printing, in which a carved metal printing plate is replaced with a film chemically treated so that it repels ink everywhere that there should not be ink on the final page.

A number of inventors, probably simultaneously and independently, realized that photographic exposure could be used with certain light-sensitive chemicals to produce lithographic printing plates very quickly. In its earlier applications, paper originals would be produced using typewriters, hand-writing, and other direct methods and would then be photographed to produce printing plates for duplication. This was often used for printing periodicals including academic journals, because it produced lower quality print but was faster than lead typesetting particularly for specialized notation, which is why in academic publishing the term “camera-ready” is still used to refer to a final version of a paper ready to be printed. If you ever encounter an old math text in which the body appears to be typewritten but the equations written by hand, it was most likely printed by this process. Publishers would employ draftsmen with excellent handwriting and technical illustration skill to produce these originals for books, a job that anyone who knows me can tell you I would never be able to obtain.

The next technical step from here seems somewhat obvious. Might it be possible to combine an automatic typesetting system like Linotype with phototypesetting, so that photographic film of page layouts can be directly typed? This is indeed possible, and during the 1950s it became a major focus of the typesetting equipment industry.

Join us again for part 2 to look at some of these machines and how they lead to the creation of typesetting systems that are still with us today.

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