Legibility and visual fatigue affected by text direction, screen size and character size on color LCD e-reader

As a portable mobile device, the e-book reader (e-reader) facilitates text-reading. With the color LCD e-reader employed, this study was aimed to investigate how legibility and visual fatigue are affected by different text directions, screen sizes, and character sizes. Following the experimental method, 60 participants were required to read the Chinese texts in the Ming typeface and to search out the target words in the pseudo-texts. Meanwhile, they were connected to an exclusive database through the Internet. The experimental data, such as the search time, accuracy rate, critical fusion frequency (CFF), and subjective visual fatigue, were recorded in the database as well as analyzed. It was discovered that text direction, screen size, and character size all produced an effect on search time. On the 6″ or 9.7″ screen, 12 pt took the shortest search time. By contrast, the 8.1″ screen was suitable for both 12 pt and 14 pt. Furthermore, the character size exerted an influence on the accuracy rate. 12 pt and 14 pt were suitable for the e-reader on the 9.7″ screen. In addition, the small character size of the text was the main cause of visual fatigue. The results of this study can be used as a reference to design the color LCD e-reader.

► We explore the visual performance and visual fatigue caused by text direction, screen size and character size on color LCD E-reader.
► The horizontal text, the bigger screen, and the 12-pt font are combined, the resultant search time is the shortest.
► 8 pt, is suitable for the 6” screen while 12 pt or 14 pt is suitable for the e-reader on the 9.7” screen.
► The small character size of the text is the main cause of visual fatigue.