P‐12: The Effect of Character Size and Contrast on Performance in Pseudo‐text and Letter‐search Tasks

The purpose of the study was to compare pseudo-text and lettersearch tasks in studying character sizes in different contrast conditions. Four character sizes (0.14, 0.16, 0.22, and 0.24 deg) and two contrast levels (CMichelson=0.06 and CMichelson=0.99) were used. According to the results, search performance improved with increasing character size and contrast in both tasks. Contrast had more effect on performance in the letter-search task than in the pseudo-text task. Consequently, the letter-search method may be better for investigating small displays in bright lighting conditions, which usually cause low contrast in displays. However, the use of the pseudo-text method is less timeconsuming because the results were less variable. 1. Introduction ease with which information can be read from a screen is an increasingly important issue in commercial competition of display technology. The influence of visual attributes like sharpness and contrast on displayed text is well known. Details in layout, for instance character size and type, are factors that also affect visual quality. However, the methods, variables, and criteria that should be used in order to get the most reliable results concerning quality of displayed text are not obvious. Furthermore, different requirements of varying display sizes and lighting conditions may cause a single method to be insufficient for all test configurations. In this paper we compare two methods, pseudo-text and lettersearch, that have previously been applied in examining properties of displayed text. The aim of the present study was to compare pseudo-text and letter-search tasks in studying character size effects and to evaluate the applicability of the methods in future studies concerning small displays in variable lighting conditions.