This study investigated the benefits of a curved display compared to a flat display and proposed the optimal radius of curvature for a monitor. The study was carried out in two steps. For identifying the optimal radius, a bendable monitor prototype was used to enable subjects to adjust the display radius manually. Each subject was instructed to search for an optimal radius according to individual preference and visual comfort. Six different themes were applied for the display content. The subjects also reported the radius in which a visual distortion occurred. As a result, it was found that curvature with a radius equal to 600 mm to 700 mm is optimal for a 23-inch diagonal display, while 700 mm to 800 mm is appropriate for a 27-inch diagonal display. Moreover, when the radius of curvature was smaller than 600 mm, a majority reported distortion regardless of the display size. Next, a validation test confirmed that the subjects read the texts faster on the curved display than on the flat display. Based on the empirical results of two experiments, the excellence of a curved monitor in terms of visual comfort, preference, and immersion was verified.
The purpose of this study is to investigate the differences in the psychophysical judgment of mobile display color appearances between Europeans and Asians. A total of 50 participants, comprising 20 Europeans (9 French, 6 Swedish, 3 Norwegians, and 2 Germans) and 30 Asians (30 Koreans) participated in this experiment. A total of 18 display stimuli with different correlated color temperatures were presented, varying from 2,470 to 18,330 K. Each stimulus was viewed under 11 illuminants ranging from 2,530 to 19,760 K, while their illuminance was consistent around 500 lux. The subjects were asked to assess the optimal level of the display stimuli under different illuminants. In general, confirming the previous studies on color reproduction, we found a positive correlation in the correlated color temperatures between the illuminants and optimal displays. However, Europeans preferred a lower color temperature compared to Asians along the entire range of the illuminants. Two regression equations were derived to predict the optimal display color temperature (y) under varying illuminants (<i>x</i>) as follows: y = α + β*log(x), where α = -8770.37 and β = 4279.29 for European (R<sup>2</sup> = 0.95, p < .05), and α = -16076.35 and β = 6388.41 for Asian (R<sup>2</sup> = 0.85, p < .05). The findings provide the theoretical basis from which manufacturers can take a cultural-sensitive approach to enhancing their products’ appeal in the global markets.
This study developed a model for setting the adaptive luminance contrast between text and background for enhancing reading performance and visual comfort on smartphone displays. The study was carried out in two experiments. In Experiment I, a user test was conducted to identify the optimal luminance contrast with regard to subjects’ reading performance, measured by lines of text reading and visual comfort, assessed by self-report after the reading. Based on the empirical results of the test, an ideal adaptive model which decreases the luminance contrast gradually with passage of time was developed. In Experiment II, a validation test involving reading performance, visual comfort, and physiological stress measured by a brainwave analysis using an electroencephalogram confirmed that the proposed adaptive luminance contrast is adequate for prolonged text reading on smartphone displays. The developed model enhances both reading performance and visual comfort as well as reduces the energy consumption of a smartphone; hence, it is expected that this study will be applied to diverse kinds of visual display terminals.
This study developed dynamic backlight luminance, which gradually changes as time passes for comfortable use of a
smartphone display in a dark environment. The study was carried out in two stages. In the first stage, a user test was
conducted to identify the optimal luminance by assessing the facial squint level, subjective glare evaluation, eye blink
frequency and users’ subjective preferences. Based on the results of the user test, the dynamics of backlight luminance
was designed. It has two levels of luminance: the optimal level for initial viewing to avoid sudden glare or fatigue to
users' eyes, and the optimal level for constant viewing, which is comfortable, but also bright enough for constant reading
of the displayed material. The luminance for initial viewing starts from 10 cd/m<sup>2</sup>, and it gradually increases to 40 cd/m<sup>2</sup>
for users’ visual comfort at constant viewing for 20 seconds; In the second stage, a validation test on dynamics of
backlight luminance was conducted to verify the effectiveness of the developed dynamics. It involving users' subjective
preferences, eye blink frequency, and brainwave analysis using the electroencephalogram (EEG) to confirm that the
proposed dynamic backlighting enhances users' visual comfort and visual cognition, particularly for using smartphones
in a dark environment.
The study aims to investigate the user-preferred color temperature adjustment for smartphone displays by observing the effect of the illuminant’s chromaticity and intensity on the optimal white points preferred by users. For visual examination, subjects evaluated 14 display stimuli presented on the Samsung Galaxy S3 under 19 ambient illuminants. The display stimuli were composed of 14 nuanced whites varying in color temperature from 2900 to 18,900 K. The illuminant conditions varied with combinations of color temperature (2600 to 20,100 K) and illuminance level (30 to 3100 lx) that simulated daily lighting experiences. The subjects were asked to assess the optimal level of the display color temperatures based on their mental representation of the ideal white point. The study observed a positive correlation between the illuminant color temperatures and the optimal display color temperatures (r=0.89 , p<0.05 ). However, the range of the color temperature of the smartphone display was much narrower than that of the illuminants. Based on the assessments by 100 subjects, a regression formula was derived to predict the adjustment of user-preferred color temperature under changing illuminant chromaticity. The formula is as follows: [Display T cp =6534.75 log (Illuminant T cp )−16304.68 (R 2 =0.87 , p<0.05 )]. Moreover, supporting previous studies on color reproduction, the effect of illuminant chromaticity was relatively weaker under lower illuminance. The results of this experiment could be used as a theoretical basis for designers and manufacturers to adjust user-preferred color temperature for smartphone displays under various illuminant conditions.
The purpose of this study is to achieve color consistency in smartphone displays under varying illuminants focusing on the correlated color temperature of the white point. In the two experiments, asymmetric color matching sessions were conducted, in which subjects were asked to recall a target white point among differently nuanced white colors. In Experiment I (N=58), 6 target white points varying from 5,900 K to 11,300 K, and 15 nuanced white colors varying from 2,700 K to 19,200 K were produced. The recalling test was carried out under 11 illuminants varying between 2,500 K and 19,300 K. Both display white colors and illuminants were divided into intervals of approximately 1,000 K. The study observed a shift in the recall of the target white point. The direction of the shift had a tendency toward higher color temperature. However, when the target white points were between 5,900 K and 8,000 K, the effect of the illuminants on color recall was marginal. In order to confirm the weak effect of the illuminants, Experiment II particularly focused on this color temperature range. 3 target white points were chosen which corresponded to the color temperatures of 6,600 K, 7,000 K, and 7,500 K, respectively. The visual assessment was conducted with a group of graphic design experts, and the 33 nuanced white colors used for the comparison had intervals of approximately 200 K. The study revealed that the maximum shift in color temperature was 294 K, which is in agreement with the result of Experiment I.
With the wide use of mobile devices, display color reproduction has become extremely important. The purpose of this study is to investigate the optimal color temperature for mobile displays under varying illuminants. The effect of the color temperature and the illuminance of ambient lighting on user preferences were observed. For a visual examination, a total of 19 nuanced whites were examined under 20 illuminants. A total of 19 display stimuli with different color temperatures (2,500 K ~ 19,600 K) were presented on an iPad3 (New iPad). The ambient illuminants ranged in color temperature from 2,500 K to 19,800 K and from 0 lx to 3,000 lx in illuminance. Supporting previous studies of color reproduction, there was found to be a positive correlation between the color temperature of illuminants and that of optimal whites. However, the relationship was not linear. Based on assessments by 56 subjects, a regression equation was derived to predict the optimal color temperature adjustment under varying illuminants, as follows: [<i>Display T<sub>cp</sub> = 5138.93 log(Illuminant T<sub>cp</sub>) – 11956.59</i>, p<.001, R<sup>2</sup>=0.94]. Moreover, the influence of an illuminant was positively correlated with the illuminance level, confirming the findings of previous studies. It is expected that the findings of this study can be used as the theoretical basis when designing a color strategy for mobile display devices.
An eye tracking experiment was conducted to investigate the relationship between eye gazing movements and the color attributes to support the creation of effective communication and increase aesthetic satisfaction. With consideration to the context of smart phones, the study focused on icon arrays, and thus each stimulus set was composed of 25 color square patches arrayed in the format of a 5 by 5 grid. The experiment was divided into three parts, each examining one specific attribute of color, while controlling its other attributes. Fifteen college students were recruited, among whom all partook in all three parts. In Part I, hue difference was examined. Each stimulus set contained 25 hues under a fixed tone. It was revealed that subjects were more attentive to warm colors than to cool colors, particularly when warm colors were arranged along the horizontal and vertical axes; In Part II, the experiment dealt with tone difference. 25 tone variations for red, green and blue were provided as stimulus sets. However, the result indicated that changes in tone does not have a significant influence on subjects’ initial attention; Lastly, in Part III, combinations of colors were examined to determine whether color contrast influenced participants’ attention in a manner different from that of single colors. Among them, icons with complementary contrast gained the greatest attention. Throughout the experiments, the background was applied with either black or white; however a contrast effect between background and foreground was not noticeable.