Typeface recognition and legibility metrics

Abstract

In the digital age, people prefer digital content, but screen-related health concerns like eye strain and blue light emerge. Legibility gains importance in digital text, especially in fields like optometry and for those with low vision. Therefore, having good letter recognition ensures better readability of words and written language in general. This work focuses on defining three typeface legibility indices from the judgements of a group of 31 observers. Those indices are based on statistics, confusion matrices, and power indices from game theory. As far as we know, this is the first time that typeface legibility indices have been defined using game theory. These indices help us to globally assess how legible is a typeface. We apply them to three commonly used typefaces (Roboto, Helvetica and Georgia), and to a new one developed for the authors (Optotipica 5 v2022). This comparison helps us understand which typefaces are more legible according to the defined indices on digital screens. The major conclusions are: (1) The three indices are highly consistent pairwise; (2) Helvetica is the most legible typeface for uppercase letters, whilst Optotipica is the most legible for lowercase; (3) the two cases of Helvetica exhibit uniform high legibility metrics, ensuring optimal recognition regardless of letter case.