Font size and viewing distance of handheld smart phones.
ABSTRACT The use of handheld smart phones for written communication is becoming ubiquitous in modern society. The relatively small screens found in these devices may necessitate close working distances and small text sizes, which can increase the demands placed on accommodation and vergence.
Font size and viewing distance were measured while subjects used handheld electronic devices in two separate trials. In the first study (n=129), subjects were asked to show a typical text message on their own personal phone and to hold the device "as if they were about to read a text message." A second trial was conducted in a similar manner except subjects (n=100) were asked to view a specific web page from the internet.
For text messages and internet viewing, the mean font size was 1.1 M (range, 0.7 to 2.1 M) and 0.8 M (range, 0.3 to 1.4 M), respectively. The mean working distance for text messages and internet viewing was 36.2 cm (range, 17.5 to 58.0 cm) and 32.2 cm (range, 19 to 60 cm), respectively.
The mean font size for both conditions was comparable with newspaper print, although some subjects viewed text that was considerably smaller. However, the mean working distances were closer than the typical near working distance of 40 cm for adults when viewing hardcopy text. These close distances place increased demands on both accommodation and vergence, which could exacerbate symptoms. Practitioners need to consider the closer distances adopted while viewing material on smart phones when examining patients and prescribing refractive corrections for use at near, as well as when treating patients presenting with asthenopia associated with nearwork.
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ABSTRACT: Objective: To test the display luminance hypothesis of the positive polarity advantage and gain insights for display design, the joint effects of display polarity and character size were assessed with a proofreading task. Background: Studies have shown that dark characters on light background (positive polarity) lead to better legibility than do light characters on dark background (negative polarity), presumably due to the typically higher display luminance of positive polarity presentations. Method: Participants performed a proofreading task with black text on white background or white text on black background. Texts were presented in four character sizes (8, 10, 12, and 14 pt; corresponding to 0.22, 0.25, 0.31, and 0.34 of vertical visual angle). Results: A positive polarity advantage was observed in proofreading performance. Importantly, the positive polarity advantage linearly increased with decreasing character size. Conclusion: The findings are in line with the assumption that the typically higher luminance of positive polarity displays leads to an improved perception of detail. Application: The implications seem important for the design of text on such displays as those of computers, automotive control and entertainment systems, and smartphones that are increasingly used for the consumption of text-based media and communication. The sizes of these displays are limited, and it is tempting to use small font sizes to convey as much information as possible. Especially with small font sizes, negative polarity displays should be avoided.Human Factors The Journal of the Human Factors and Ergonomics Society 08/2014; 56(5):942-51. DOI:10.1177/0018720813515509 · 1.29 Impact Factor
Conference Paper: User-adaptive mobile video streaming using MPEG-DASH[Show abstract] [Hide abstract]
ABSTRACT: We describe an implementation of DASH streaming client for mobile devices which uses adaptation to user behavior and viewing conditions as means for improving efficiency of streaming delivery. Proposed design relies on sensors in a mobile device to detect presence of the user, his proximity to the screen, and other factors such as motion, brightness of the screen and ambient lighting conditions. This information is subsequently used to select stream that delivers adequate resolution implied by viewing conditions and natural limits of human vision. We show that in a mobile environment such adaptation can result in significant reduction of bandwidth usage compared to traditional streaming systems.SPIE Optical Engineering + Applications; 09/2013
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ABSTRACT: [Purpose] Smartphone use reportedly changes posture. However, how neck posture is altered in smartphone users with neck pain is unknown. This study examined changes in the posture of young adults with and without mild neck pain (MNP) when using a smartphone. [Subjects] Thirteen control subjects and 14 subjects with MNP who used smartphones were recruited. [Methods] The upper cervical (UC) and lower cervical (LC) angles in the sagittal plane were measured using an ultrasound-based motion analysis system while the seated subjects used a smartphone for 5 min. [Results] During smartphone use, the MNP group exhibited greater UC and LC flexion angles than the control group. [Conclusion] These findings suggest that young adults with MNP are more careful and more frequently utilize a neutral neck posture than young adults without MNP when using a smartphone while sitting.Journal of Physical Therapy Science 01/2015; 27(1):15-17. DOI:10.1589/jpts.27.15 · 0.20 Impact Factor