Why would anyone today care about what the Bentons were doing with metal type more than 100 years ago? (These days I’m in the last stages of tweaking my book about them, and I must confess that sometimes this question still haunts me.) But in fact, I’ve found that plenty of people do care, especially those involved with designing or improving digital type.
Just the other day a group of digital type designers came to RIT who were pursuing the train of thought begun in a 1912 type legibility study, one that Morris Benton worked on!
Type designers today have to deal with what came naturally to the punchcutter when he cut punches by hand. [For anyone new to the subject, the punch was a raised, reversed (“wrong-reading”) image that determined the shape of a letter. It was pounded into a brass bar which became the matrix, with a sunken, right-reading image. The matrix, fixed in a type mold, was then used to cast individual types, again wrong-reading so that they would appear right-reading when printed.] What came naturally to the punchcutter was that letters must be slightly distorted as they become larger or smaller. Today we call this phenomenon optical scaling.
In my book I explain the term like this:
Briefly put, because of the inherent limitations of the human visual system, as the size of a letterform gets smaller it needs to be expanded, and as it gets larger it needs to be condensed. “Traditional punchcutters and scribes made such proportional changes in order to optimize legibility,” RIT Professor Charles Bigelow wrote. “Recent research in visual perception suggests that such proportional changes are necessary because the human visual system has non-linear sensitivity to visual features of different spatial frequencies.”
Benton understood that slightly distorting the characters as they went up or down in size enabled the basic design to retain its integrity, and so he built this capability into the matrix engraving machine. For example, according to a hand-written ATF reference book, each size of Morris Benton’s Wedding Text was expanded or condensed relative to the pattern for the typeface. Many years later, ATF’s successor, the Kingsley/ATF Type Corp., coined the term “optical scaling” to describe this phenomenon of distorting letters.
 Charles Bigelow, “On Type: Form, Pattern, & Texture in the Typographic Image,” Fine Print 15, no. 2 (April 1989): 77.
Optical scaling is as important today as it ever was. Digital type on a computer screen especially needs to be as legible and comfortable to read as possible.
Type designers may ask: Can we systematize optical scaling? Is there an algorithm that we can use to tweak the letters at various sizes for optimum results? This is the same question Benton faced in the early 1880s in Milwaukee as he worked on his pantographic matrix engraving machine. Theo Rehak told me this past February (see my 2/14 and 2/22 posts) that he was sure there was such an algorithm. But, as he explained in Practical Typecasting, Benton’s “Engraving Factor Tables” were lost after he died. Today Rehak is not in the business of producing the full range of sizes of his metal type offerings at the Dale Type Foundry, so he can manage without such an algorithm.
When I Google “optical scaling Benton,” there are about 183,000 results in 0.28 seconds; it’s not a dead subject. It seems to me that anyone who admires Morris Benton’s optically scaled typefaces would do well to study how his father’s matrix engraving machine actually distorted the letterforms on the patterns it used for making type in different point sizes. My book would be a very good starting point for such a study.