Effects of age and ambient illuminance on visual comfort for reading on a mobile device

Abstract

A psychophysical experiment was carried out to investigate visual comfort for reading on an iPad under various illuminance levels, ranging from 50 lx to 1200 lx, in order to see whether and how the following variables can influence the visual comfort: observer's age, gender, the illuminance of ambient lighting, and the background colour in a document layout. A panel of 21 young and 22 older Taiwanese observers participated in the study. The paired comparison method was used for data collection and analysis. The experimental results show that for all lighting conditions, young observers tended to prefer reading documents that had a moderate CIELAB lightness difference between text and background, while older observers tended to prefer reading those with an extremely large lightness difference. The results also show that female observers tended to feel less comfortable than male observers when reading documents with an extremely large lightness difference. These findings were found not to be affected by the ambient illuminance. Regarding the influence of document background colour on visual comfort, the observers tended to feel more comfortable reading documents that had a gray background than reading those with a background colour of either white or black. It was also found that the visual comfort was slightly higher for positive polarity than for negative polarity, but the difference between the two settings was insignificant. © 2016 Wiley Periodicals, Inc. Col Res Appl, 42, 352–361, 2017

Effect of text‐background lightness combination on visual comfort for reading on a tablet display under different surrounds

“…The visual comfort of the combinations with a white background, however, was largely affected by the ambient illuminance. As shown in Figure , the visual comfort of the combinations with a white background were judged relatively low under the conditions with an ambient illuminance of 1200 lx in our previous study, which did not happen to the conditions with an ambient illuminance of 3000 lx in this study (Figure B).…”

“…In contrast, the correlation between the two illuminance levels for each CCT was relatively lower, as shown in Figure . It was also lower than the correlation between 50 and 1200 lx in our recent study . Thus, the data collected under the 2 CCT levels were combined for the analyses below.…”

“…The higher the value, the more comfortable evaluated by the observers. The CIELAB lightness difference between the text and background, instead of Weber and Michelson contrasts that used a ratio of the text‐background luminance difference to the adaptation luminance as the contrast, was used to quantify the text‐background contrast, as neither Weber nor Michelson contrasts were found to correlate well to a perceptually uniform color space …”

“…Visual comfort interval scales of the 20 text‐background combinations evaluated by the observers under 1200 lx in our previous study . Open markers are used to differentiate the combinations with a same text‐background lightness difference but with a lower text lightness…”

“…When using the tablet, older observers preferred a larger text‐background lightness difference, while younger observers preferred a moderate lightness difference. Huang and his colleagues later carried out a similar study using a 9.7‐inch tablet (maximal luminance of 286 cd/m 2 ) under four ambient illuminance levels—50, 200, 600, and 1200 lx—and found a gray background was preferred over a white or black background regardless of the ambient illuminance level. Lin and his colleagues used a 17‐inch TFT‐LCD monitor (maximal luminance of 200 cd/m 2 ) to investigate the optimal text‐background luminance combination (background luminance was always higher) under the ambient illuminance of 200, 500, and 800 lx by asking the observers to perform an identification task on the monitor.…”