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As display technology expands the color gamut, the potential of experiencing observer metamerism is more likely with narrow bandwidth stimuli displays. Hence, it is desired to investigate whether laser-based projector would introduce observer metamerism compared to halogen-based projector. In addition, it is also desired to develop a quick method to determine an observer’s color matching function category. In this study, a two-part experiment was designed and conducted. Experiment 1 was based on color patches and Experiment 2 was based on test images. The quick method was developed in Experiment 1. Comparison to CIE Standard Observer was also conducted, and the results had suggested the CIE Standard Observer was not suitable for laser-based projection system. In Experiment 2, a prediction was made to determine the image category. With the quick method, it is much easier to achieve the realization of p

E-reading devices are becoming more and more common in our daily life, and they are used under a wide range of ambient light levels, from completely dark to extremely bright conditions. In this study, a psychophysical experiment is carried out to investigate how ambient light level affects the visual comfort of an e-reading device. Human observers compare the visual comfort of pairs of different text-background lightness combinations on a tablet device under three ambient light levels (i.e., 150, 1500, and 15,000 lx). With our previous work, the experimental results show that the trend of visual comfort interval scales below 1500 lx (i.e., Dark, 150, 300, and 1500 lx) are similar to each other but not for those under illuminance above the 1500 lx (i.e., 3000 and 15,000 lx). For the same lightness difference between text and background, the observers tend to read the text with a white background compared to a black background, especially for 3000 and 15,000 lx. Moreover, a black text on a light-gray background is the most comfortable combination under these two illuminance levels. An evaluation model is proposed based on ambient illuminance, screen parameters, and visual estimation to design an optimal viewing condition when reading on the tablet display.

This article describes the development of new models for predicting four colour appearance attributes: saturation, vividness, blackness, and whiteness. The new models were developed on the basis of experimental data accumulated in the authors' previous study, in which the four colour appearance attributes were scaled by 64 Korean and 68 British observers using the categorical judgment method. Two types of models were developed: the ellipsoid-based and the hue-based. For the former, the perceived saturation, vividness, blackness, and whiteness were modeled in the form of colour-difference formulae between the test colour and a reference colour. For the latter, blackness, whiteness, and chromaticness scales were modeled by estimating hue-dependent lightness and chroma values for the “full colour” in the framework of Adams' equation. The new models were tested using NCS data and were found to outperform some of the existing colour appearance models.

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

There are many definitions and theories about colour harmony. But no consistent rules and definitions can be determined. Some previous researches show that there are many factors that influence the colour harmony. Colour harmony is highly depends on the external factors, including the context of colour besides their colour combinations. In the current research an experiment conducted by observing two colour combinations which applied in shirt and trousers. Twenty observers involved in the experiment, consist of ten male and ten female. Each observer predict colour harmony score in 58 samples of shirt and trouser pairs, the colour combination then applied upside down. Based on the experimental results, male and female group has similar tendency in colour harmony score prediction in the same colour samples (correlation coefficient, r=0.84). Upside down colour combinations will change the impression of observer about colour harmony and yields a different value of colour harmony prediction score which indicated from correlation coefficient results of 0.53.