NBN ISO 24509:2021

This document provides a method for estimating minimum legible font size for single characters, but not
for words or sentences, in self-luminous or reflected mode, used in documents, products labels, signs,
and displays for people at any age and in any viewing condition in which viewing distance, luminance
and contrast are varied.
This document applies designing and evaluating legibility of single characters for people at any age
who have no pathological disorders in their eyes, but not for people with visual impairments such as
low vision. The application is specifically directed to, but not limited to, the cases of printed materials
where fixed font size is used.
Applicability of the method to other languages is given in Annex F.