Readability refers to the ease with which we comprehend text by recognizing words and phrases as shapes. Readability is all about putting the reader first and leaving your ego behindor at least confining it to your early drafts. Good typography is said to be "invisible"you don't even notice it. Instead the type is a conduit for the message of the text. This might make the typographer sound undervalued, but while your readers may not notice good typography, they will certainly recognize bad typography. As the acclaimed typographer and book designer Jan Tschichold put it: "To remain nameless and without specific appreciation, yet to have been of service to a valuable work and to the small number of visually sensitive readersthis, as a rule, is the only compensation for the long, and indeed never-ending, indenture of the typographer." Humbling stuff.
Serif vs. Sans
Readability studies have found that serif typefaces are better for continuous reading. Explanations for this vary. Some experts feel that serifs function like rails, guiding your eye along the line. Others suggest that we respond to serif types better because the transition of their strokes more closely resembles calligraphy. Or perhapsand my money's on this onewe read serif type more easily, simply because we're more used to reading serif type. In the words of Zuzana Licko, cofounder of Émigré digital font foundry: "You read best what you read most."
Maybe we could get used to anything, but we've been reading serif type for centuries and the habit is pretty much in our DNA. Sans serif typefaces are the new kids on the block relatively speakingnot invented until the early 19th Century and not in common usage until the 1920s.
Readability is less of a concern when it comes to display type, which, because it is set in short bursts rather than long passages, can afford to draw much more attention to itself.
It sounds like an overly simplistic formula, but you won't go far wrong if you use serif faces for your body text and sans serif for your headings and subheads. Because sans serifs tend to be bolder and blockier, they are better at grabbing the reader's attention. Also, the absence of serifs makes it possible to track sans serif headlines tighter, adding to their solidity. To make a subhead distinct from your body text, it is enough to choose a contrasting typeface; subheads do not necessarily need to be set in a larger point size.
Other Readability Factors
Your choice of font is just one of several factors that work in sync to createhopefullyreadable type. Other factors includebut as they say in legaleseare not limited to:
Tip: Shortcuts for Sizing Type
In addition to using the Type Size control on the Control Palette, you can also size your type using keyboard shortcuts:
Cmd+Shift+>/< (Ctrl+Shift+>/<) Increase or decrease point size by the increment specified in Preferences>Units & Increments>Size/Leading.
Cmd+Shif+Option> /< (Ctrl+Shift+Alt>/<) Increase or decrease point size by five times the increment specified in Preferences>Units & Increments>Size/Leading.