Legibility of video display units during off-angle viewing

Abstract

This research examined how off-angle or oblique viewing of a VDU screen and the physical location of a message on the screen influenced message legibility. Eight trained subjects viewed five-character long common words, number strings, and alphanumeric messages presented at 15 different combinations of oblique viewing angle and location of message on the VDU screen for 2–5 seconds. It was found that common words and number strings showed little overall loss in legibility except when oblique viewing angle exceeded ± 32^°. Alphanumeric messages were found to have a significantly lower legibility than the common words and number strings. It was recommended that for best overall legibility of the three types of messages studied here, that oblique viewing angles be less than ± 32^°. Predictor equations were also developed to aid in predicting loss of accuracy based on the type of message and physical features of the viewing task.