What is Legibility?

Legibility is a key factor in visual communications for the built environment. If the messages on signs, displays, screens, interpretive graphics, or other environmental/experiential graphics are not readable, they are not effective.

Significant research has been devoted to the relative legibility of typefaces and, in particular, legibility is a major factor in signs and other communications designed for public buildings and spaces. The Americans with Disabilities Act (ADA) Standards for Accessible Design (SAD) provide specific guidelines for the legibility of sign messaging. SEGD’s ADA and Accessibility Committee has helped guide the environmental graphic design community on compliance with ADA guidelines for three decades. SEGD’s latest guidelines were published in the SEGD 2012 ADA White Paper Update.

Legibility varies by viewing distance, location, typeface style, color of the text versus the background, and other physical conditions. But the basic parameters for a legible typeface include:

  • ·      Clear, easily defined letterforms
  • ·      Large x-height
  • ·      Medium weights and stroke widths
  • ·      Medium character width, with letterforms neither too condensed nor too expanded

Another consideration is the use of serif versus sans-serif typefaces. In general, the horizontal strokes of serif typefaces are considered an aid to reading large blocks of small text, such as in a book, whereas they are often considered too delicate in form for larger-scale text such as in signage applications.

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