The clarity and comfort of printed text

Abstract

The successive lines of printed text form a pattern of ‘stripes’. The spatial characteristics of this pattern have been measured and found to be similar to those of patterns that induce discomfort, anomalous visual effects and even seizures. It is argued that reading provokes ‘eye-strain’ and seizures because of the striped properties of text, and that it is for this reason that headaches and seizures are reduced by covering the lines of text above and below those being read. In studies in which subjects are asked to judge the clarity of text it is shown that judgements of clarity are affected by the spatial characteristics of the pattern, in particular, the spacing between the lines. The average area of the page occupied by a letter (i.e. the product of the separation between the lines and the mean horizontal spacing between the centres of letters) accounts for less variance than does the separation between the lines of text. Within the constraints of conventional typography, the clarity of text could perhaps be improved without increasing costs by reducing slightly the typical spacing between the letters in order to increase the spacing between the lines.