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

Two experiments were performed to investigate the effects of text‐background lightness difference on visual comfort. A panel of 21 young and 20 older observers in Taiwan participated in Experiment I, using an LCD TV (with a display luminance of 551.8 cd/m2) as the presentation media. The results show that on a light background, visual comfort increases as the lightness difference gets larger and larger. On a dark background, however, the highest visual comfort value can be obtained when there is a moderate lightness difference. There seems to be little effect of age on visual comfort using the LCD TV with regard to the lightness difference. In Experiment II, 20 young and 20 older Taiwanese observers participated, using a tablet computer (with a display luminance of 397.3 cd/m2). According to the results, the larger text‐background lightness difference, the higher visual comfort value for older observers. For young observers, however, the highest visual comfort value can be obtained when there is a moderate, rather than extremely high, lightness difference. These findings can help provide useful guidelines for graphic user interface design in modern e‐reading devices. © 2014 Wiley Periodicals, Inc. Col Res Appl, 40, 125–134, 2015

Past studies investigating the unique hues only used samples with a relatively high saturation levels under standard illuminants. In this study, 10 observers selected the four samples with unique hues from 40 V6C8 (Value 6 Chroma 8) and 40 V8C4 (Value 8 Chroma 4) Munsell samples under six light sources, comprising three levels of Duv (i.e., 0, −0.02, and −0.04) and two levels of correlated color temperature (i.e., 2700 and 3500 K). Significant differences were found between the two chroma levels for unique blue and yellow, with the hue angles of unique yellow and blue judged using the desaturated samples being significantly different from those defined in CIECAM02. The iso‐lines of unique yellow, blue, and green did not always go through the origin of the a*‐b* or a′‐b′ planes in CIELAB and CAM02‐UCS. Thus, the problems of CIECAM02, CIELAB, and CAM02‐UCS identified in this study need further investigations.

Many tablets are designed to change display brightness or color with surround for enhancing visual comfort. Although both color and brightness of a surround may vary a lot, few studies investigated how text‐background lightness combination of a tablet display and surround jointly affect visual comfort, and how display white point affects visual comfort. In this study, 20 observers evaluated visual comfort of 20 text‐background lightness combinations of a 9.7‐inch tablet display through paired comparisons under five surrounds—a dark surround and four ambient lighting conditions comprising two levels of correlated color temperature (CCT)—3500 and 6500 K—and illuminance—300 and 3000 lx. The combination of a black text and a light‐gray background (i.e., L*background = 75.33; L*text = 1.6) was evaluated the most comfortable when there was ambient light regardless of CCT and illuminance. It was also evaluated the third most comfortable under the dark surround. The observers also evaluated the visual comfort of a dark text on five different white backgrounds under 3500 and 6500 K at 1000 lx. The color of the background that was judged as the most comfortable neither had the whitest appearance nor matched the color of the ambient light. The simultaneous adjustment of the display white point and the text‐background lightness combination merits further investigations.