Measuring Visibility and Legibility of On-Screen Text Under Varying Font and Background Conditions: An Eyetracking Study
K. Sharma (TU Delft - Mechanical Engineering)
Y. B. Eisma – Mentor (TU Delft - Human-Robot Interaction)
D Dodou – Graduation committee member (TU Delft - Medical Instruments & Bio-Inspired Technology)
J. C.F. Winter – Graduation committee member (TU Delft - Human-Robot Interaction)
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Abstract
This study investigates how font size, text-drawing style, and drop shadow affect the visibility, legibility, and comprehension of overlaid text. The purpose of this study is to better understand the role of these design factors and to offer practical guidelines for presenting information effectively on see-through displays. Twenty-five participants completed a visual search task, where they were asked to locate a target word presented under varying conditions on a complex background. A full factorial design was employed, incorporating four font sizes (0.10°, 0.15°, 0.20°, and 0.60°), six text-drawing styles (plain green text, plain white text, white text on blue billboards with 30%, 50%, 75% or 100% opacity), and the presence or absence of a drop shadow. Performance was evaluated across conditions in terms of noticeability (as a measure of visibility), processing time (as a measure of legibility), and word identification accuracy to determine significant differences. Applying a drop shadow improved legibility in plain text, while billboards lowered the upper performance threshold for font size. Although billboard conditions outperformed plain text conditions, varying billboard opacity had no significant effect on processing time, word identification, or noticeability. Overall, the findings suggest that font size, text styling, and background complexity interact to influence text visibility and legibility.