Legibility and readability

For the uninitiated, typography is a deep field of study and practice, and its basic principles and practices are far beyond the scope of this book. This section focuses on specific accessibility concerns related to typography instead of general best practices.

Reading using eyesight

Reading requires recognition and familiarity with a language and the letters and letterforms being used to communicate.

Letters

The alphabet is made up of letters, like A, B, C, which are conceptual objects. A letter can be communicated many different ways, including via sound, hand gesture, a Unicode value or through a visual letterform like “Q”.

Letterform

A letterform is the visual manifestation of a letter. For instance, the letter “O” is indicated by a letterform made up of a stroke in the shape of a circle or oval enclosing a round negative space (counter). Variations in letterforms and spacing differentiate one font from another.

Legibility

Legibility refers to the degree to which letters can be recognized from specific letterforms.

Readability

Readability is different from legibility. It refers to the accuracy and speed with which written content can be consumed over an expanse of text. Readability is affected by numerous factors including the following.

• Typeface
• Font size
• Spacing
• Line length
• Alignment
• Styling
• Formatting

Learning to read

When individuals begin to learn to read using their eyes, they work through the text one letter at a time, gradually assembling a word out of its component letters. As their skill increases, they start to recognize common pairings of letters, such as “th,” and then larger patterns of letters, such as “tters.” Eventually this pattern recognition allows the reader to quickly parse entire sequences of words.

As reading speed increases, the eyes are looking ahead, moving in quick short jumps (called saccades) at approximately seven to nine letters at a time. In between saccades, they pause to take a snapshot called a fixation, for approximately 250 millisecond. The brain analyzes these fixations as shapes, instead of individual letterforms.

As this process accelerates, these fixations focus disproportionately on the top half of these shapes. Most people are eventually able to take in approximately 15 letters per fixation, although we are typically only able to accurately recognize the first one to seven characters at a time.