Influence of ambient-tablet PC luminance ratio on legibility and visual fatigue during long-term reading in low lighting environment |
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| Affiliation: | 1. Department of Industrial and Systems Engineering, Chung Yuan Christian University, No. 200, Chung Pei Rd, Chung Li, TaoYuan 32023, Taiwan, ROC;2. National Chung-Shan Institute of Science and Technology, No. 481, 6th Neighborhood, Sec. Jia''an, Zhongzheng Rd., Longtan Dist., TaoYuan 32546, Taiwan, ROC;1. School of Architecture & Design, China University of Mining and Technology, Xuzhou, China;2. School of Mechanical Engineering, Southeast University, Nanjing, China;3. The Affiliated Hospital of Xuzhou Medical University, Xuzhou, China;1. Department of Systems Engineering and Engineering Management, City University of Hong Kong, Kowloon Tong, Hong Kong;2. School of Industrial Engineering, Purdue University, West Lafayette, Indiana, United States;1. State Key Laboratory of Mountain Bridge and Tunnel Engineering, Chongqing Jiao Tong University, Chongqing, China;2. Department of Electrical Engineering and Automation, Lighting Unit, School of Electrical Engineering, Aalto University, Espoo, Finland |
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| Abstract: | We examine the effect of the (luminance) ratio of ambient luminance to tablet surface luminance on text legibility and fatigue over 1 h of long-term reading with a tablet PC in low-ambient-luminance environments limited to 45 cd/m2 (illuminance ~230 lx). Four reading-pattern subject experiments are carried out at ambient-luminance-to-tablet-surface-luminance ratios of 1:1, 1:3, 1:6, and 1:9 at 15 and 45 cd/m2. As per legibility tests based on the semantic differential (SD) method, we find that subjects experience glare at luminance ratios of 1:6 and 1:9, and it is difficult to read text at the luminance ratio of 1:9 under ambient luminances of 15 and 45 cd/m2. Based on subject fatigue (determined by subjective symptom survey), we find that the feeling of fatigue, according to the change in the luminance ratio, most affects the Fuzziness group among the five subjective fatigue groups. Based on physical fatigue determined using the critical flicker fusion frequency (CFF) value, we observe significant CFF differences before and after reading for luminance ratios of 1:1 and 1:9 at the ambient luminance of 45 cd/m2 and for the ratio of 1:9 when the ambient luminance is 15 cd/m2. A larger difference between the ambient and surface luminances corresponds to higher CFF variation rates and more fatigue. |
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| Keywords: | Low-luminance environment Ambient-to-tablet luminance ratio Visual fatigue Legibility Critical flicker fusion |
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