Many normally sighted elderly and visually impaired viewers have problems in reading TV- subtitles. We have investigated the influence of character size, contrast, luminance and presentation time on the legibility of subtitles for a group of normally sighted young and elderly subjects and a group of visually impaired subjects. For that purpose pairs of text lines were presented on a TVmonitor. For the partially sighted the text lines were presented against a smooth background and with the normally sighted a comparison was made between the legibility of text lines against a smooth background and text lines presented against a TV-scene background. In the first experiment all subjects had to read the text aloud and they could determine the duration of the presentation of the text lines themselves. Reading rate was measured as a function of character size and contrast e.g. luminance. In the second experiment the text lines were presented for a fixed length of time. The subjects, while reading silently, were asked to indicate whether they had enough time to read through the text lines. The number of text lines read was determined as a function of the presentation-time and size of the characters. The experimental results clearly show that reading real subtitles as compared to reading text lines against a smooth background is slightly worse for the elderly. With the partially sighted subjects a strong influence of character size and contrast e.g. luminance on the reading rate is found.
|Title of host publication||Low vision : research and new developments in rehabilitation|
|Editors||A.C. Kooijman, P.L. Looijestijn, J.A. Welling, G.J. Wildt, van der|
|Place of Publication||Amsterdam|
|Publication status||Published - 1994|