It’s About Legibility

by Allan Haley

Typographic clarity comes in two flavors: legibility and readability. What’s the difference? Legibility is a function of typeface design. It’s an informal measure of how easy it is to distinguish one letter from another in a particular typeface. Readability, on the other hand, is dependent upon how the typeface is used. Readability is about typography. It is a gauge of how easily words, phrases and blocks of copy can be read.

Legibility: A Trait, Not Always a Goal

First, not all typefaces are–or should be–created with legibility as a primary design function. Many faces are drawn for the purpose of creating a typographic statement, or for providing a particular spirit or feeling to graphic communication. Some typefaces are just designed to stand out from the crowd. To the degree that a typeface has personality, spirit, or distinction, however, it almost always suffers proportionally on the legibility scale.

Three Aspects of Legibility

So what makes a typeface legible? A long-standing typographic maxim is that the most legible typefaces are “transparent” to the reader–that is, they don’t call undue attention to themselves. Additionally, the most legible typefaces contain big features and have restrained design characteristics. While this may seem like a typographic oxymoron, it’s not. “Big features” refers to things such as large, open counters, ample lowercase x-heights, and character shapes that are obvious and easy to recognize. The most legible typefaces are also restrained. They are not excessively light or bold, weight changes within character strokes are subtle, and serifs, if the face has them, do not call attention to themselves.

Counters, the white space within letters such as ‘o,’ ‘e,’ ‘c,’ etc., help to define a character. Typographers believe that large counters are an aid to character recognition. A byproduct of open counters is usually a large lowercase x-height. As long as the x-height is not excessively large, this can also improve legibility in a typeface. Because over 95% of the letters we read are lowercase, larger letter proportions usually result in a more legible typeface.

While virtually any serif typeface can benefit from large open counters, “Clarendons” like Nimrod or Scherzo and contemporary interpretations of “Old Style" designs, such as Monotype Bembo and ITC Weidemann, tend to come by this trait most naturally.

Individual letter shapes can also affect typeface legibility. For example: the two-story ‘a’ such as the one found in Stellar or Exlibris is much more legible than the single-story ‘a’ found in Futura or Erbar. The lowercase ‘g’ based on Roman letter shapes is more legible then the simple ‘g’ found in Helvetica or Glypha. In Old Style typefaces such as Monotype Plantin, Galena and ITC Berkeley Oldstyle, individual characters have more personality than those in traditional “legibility” faces with virtually no loss in character legibility.

While the argument continues to rage about whether sans serifs are easier to read than serif fonts in text copy, sans serif typefaces, because their letter shapes are simpler, have been proven to be slightly more legible than their serifed cousins.

Little Serifs and Light Weights

Another potential drawback of serif typefaces is that the legibility of individual letters suffers when serifs have exaggerated shapes. Long serifs, those that are exceptionally heavy and those with unusual shapes all detract from legibility. Ideal serifs are somewhat short and slightly bracketed. They are also heavy enough to be obvious yet not conspicuous. Typefaces such as Monotype Sabon and ITC Stone have great serifs.

Lighter typefaces are usually more legible than heavier weights of type. They allow for full, open counters and unmodified character shapes. Studies have shown that the best character stroke thickness for text typefaces is about 18% of the x-height. Typefaces with weights similar to that of Albertina Regular, ITC Officina Sans Book and Cartier Book Roman fall into this general category.

Transparent Type

The metaphor of “transparent type” was coined by Beatrice Warde, Monotype Imaging's famous marketing manager of the 1930s and 40s. She once wrote in an article that good type is like “a crystal goblet” which allows content to be more important than the container. Warde contended that the best types do not get in the way of the communication process: these faces are virtually invisible and allow words to make the statement–not the type. While this is sage advice, if this principle were followed rigidly, graphic communication would be about as exciting as a head cold. This does not mean that legible typefaces can’t be distinctive in design, or that we should be using Ionic No. 5 for all typography. Some distinctive typefaces, such as Truesdell, Agfa Rotis, or Alinea, also make fine legibility fonts. The metaphor is, after all, a crystal goblet–not an empty jam jar.

Situational Typography

Specific situations or contexts can also affect typeface legibility. For example, if copy has a lot of numerals, a sans serif face may be the best choice. The reason? Sans serif numerals are simpler and have more recognizable character shapes than their roman counterparts.

Then there are times when you have a lot to say–and not much room in which to say it. In instances like these, faces with condensed proportions are the best choice. Condensed typefaces of light to medium weight also work well in cramped typographic quarters because their counters are not prone to filling in. Sans serif faces are almost always the safest choice because their individual character shapes tend to be more legible. A serif typeface such as ITC Garamond Condensed or Galena Condensed can be effective as small as 8 point or 9 point, but when smaller sizes are required, a sans serif like Generica Condensed or Abadi Condensed are better options.

Even though virtually anyone can set type today, there are still many skills that separate the typographer and graphic designer from the desktop publisher. Picking the absolute best–and sometimes the most legible–typeface is one of those skills.

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• Allan Haley is Director of Words & Letters at Monotype Imaging. Here he is responsible for strategic planning and creative implementation of just about everything related to typeface designs. He is also responsible for editorial content for the company’s type libraries and Web sites.
• Prior to working for Monotype, Mr. Haley was Principal of Resolution, a consulting firm with expertise in fonts, font technology, type and typographic communication. He was also executive vice president of International Typeface Corporation.
• Mr. Haley is ex officio Chairman of the Board of the Society of Typographic Aficionados, and past President of the New York Type Directors Club. He is highly regarded as an educator and is a frequently requested speaker at national computer and design conferences.
• Mr. Haley is also a prolific writer, with five books on type and graphic communication and hundreds of articles for graphic design publications to his credit.