Choosing the right font size is an important aspect of design. In fact, it’s absolutely critical for effective, readable type that harmonizes well with the other typographic elements. One might think this decision is a no brainer, but there are a number of variables that affect type size, particularly when experimenting with different fonts in the early stages of the design process.
In digital fonts, the size of any given font at a specific point size can vary from font to font. That is, fonts at the same point size can have different x-heights and sometimes varying cap heights. This can be quite frustrating.
Both the x-height as well as the cap height of a font affect its legibility, and will make different typefaces look larger or smaller at the same point size. When designers first try out different fonts, they usually look for a size that looks and works best for the demographics and requirements of the design at hand. But, when exploring different fonts at that same size (and line spacing), they can look surprisingly different.
Therefore, when finalizing a decision on a particular font, re-evaluate the size and line spacing. Be sure to make decisions optically so that the type is readable, tasteful, and achieves the result you are looking for.
See these examples.
So why does this happen? In the days of metal type, the size of the glyphs in any particular point size was determined by fitting the tallest ascender and the deepest descender in the entire character set of that particular font onto the metal type, or sort.
In digital type, these physical restraints are no longer an issue, and therefore the glyph size in relation to the digital bounding box, or design space, are assigned by the typeface designer. For this reason, type sizes and appearances can vary greatly from font to font.
Another consideration when selecting a type size is that a type design with a tall x-height and/or short ascenders and descenders will usually look larger than one with opposite traits, even at the same cap height. For this reason, the actual appearance of a typeface at a particular size varies with the size of its cap height, ascenders, descenders and x-height.
The takeaway is this: since the point size of digital type doesn’t tell you everything about how a typeface will actually look at a given size, select type size optically. Let your eye be your guide, not the numerical size. Apply this optical decision-making process any time you select or change typefaces, especially for text where readability is paramount.
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