The legibility of visual display texts

Communicating with computers is becoming increasingly important in our technological environment. Unfortunately the quality of the texts that appear on the display screen is often far from perfect. Numerous complaints — and the occasional alarming press report — testify to this. Is there any possibility of improvement? In most cases visual display texts can indeed be shown in such a way that they can be read perfectly. A lot of improvements can often be made to the layout, the typeform, and use of color. In a number of cases, however, there is still uncertainty about our visual perception capabilities. Further research is thus called for. In what follows, some basic properties of the visual reading process will first be described. Then, the separate effects of the use of layout, color and typography on legibility will be treated explicitly, followed by some illustrations of the combined effect of the three image parameters. These illustrations, as well as all others in this paper, refer to videotex pages as used to be broadcast, regularly or in experiments, by the Dutch Teletext service. Finally, some practical rules are formulated which mostly apply to multicolor text displays in general and, to a certain extent, also to the use of graphics.