Tuesday, July 17, 2012

Digital Type Sizing Explained

So, why isn’t type true to its classified size? For instance, why is 24 point size type less than 24 points in height? And for that matter, why is any size or any style type font less than its classified size? And, on top of that, why do different fonts in the same point size differ in height? Understanding why, makes it a little easier to deal with the frustration of using letterforms that have to visually conform to a finite layout dimension in an illustration. 

It all has to do with historical type production and practice before the digital, and even the photographic type environments came along. Printing type was originally produced as wooden or metal letterforms that were used to print documents on a printing press. The letterforms could be arranged or “composed” into manuscripts, and then taken apart and reused. Printing presses used a considerable amount of pressure to transfer an image, or make an “impression” of the type onto printing paper. And, in order for this to occur without causing damage, the raised letterforms were affixed atop a supporting “body” of metal. An engineered “body” below the letterform was required to reduce the stress the printing press exerted on the letterform. Thinner font styles required a larger body to be used, while heavier fonts could get by with a smaller body and less support. As printing presses became more sophisticated, the relationship of size between the letterform and it’s supporting body also became a decision made by the type designer based on the intended use of the font and the aesthetic appearance the designer desired.

So, in keeping with tradition and the conception of users, printers, and designers regarding the appearance of a specific font in a particular size in both photographic and digital type, designers and transcribers, adopted a virtual approach to sizing type rather than an absolute one. In other words, even though it wasn’t needed, an imaginary bounding space was adopted for translating non-digital fonts into the digital environment.

The following letters are all set to 72 point. The rectangle around the letterform indicates the cast body the type was affixed to for usage, which shows why all the fonts shown are classified as 72 point, and in turn why although the letters vary in height, they are all classified as 72 point.

Letterforms set digitally at 72 point.
Letterforms and letterform bodies overlapped for comparison.

Comparing Type Size

Depending your size needs when applying type to an illustration, type can chosen using different standards. The three examples of typestyle comparisons below show fonts sized using three different priorities. The first example shows two fonts chosen for the same capital letter height, but having different “waist” heights, i.e., the height of the lower case letter "x". The second example shows fonts chosen for the same waist height, but differing cap heights. And the third example shows two fonts used to make equivalent ascender/descender heights, but differing cap and waist heights.

Type with equal cap heights, unequal waist height.

Type with equal waist height, unequal cap and ascender/descender heights.
Type with equal ascender/descender height, unequal cap and waist height.

So, there is more than one criterion that can be used to determine the visual size of a typestyle. Some situations require an illustrator or designer to rely on the height of capital letters to make decisions about selecting a typestyle while other uses rely on the waist height or lower case to determine the selection a font.