Legibility of texts: The influence of blur

Abstract

This work studies the inter-relation between the legibility of texts, adaptation luminance and the efficiency of observers in performing a reading task. The work also includes subjective evaluations by the observers about the degrees of facility, fatigue and legibility of the task. The visual task consisted of searching for two typed words in lists from copies with different grades of legibility, under different levels of adaptation luminance varying from 25-750 cd m^-2. The results from a group of observers were analysed as a function of adaptation luminance and of the subjective classification of the blur of the typewritten texts. The studies show that the influence of the latter is much greater, as much as in determining the visual performance as in the preferences of the observers, for the task chosen.