Chromatic adaptation is an important mechanism in the human visual system, allowing a relative constant color appearance under different lighting conditions, in terms of light level and color. ...Technologies have been developed to adjust the display white point according to the ambient light color, but did not consider the ambient light level. This study was designed based on a recent study to reveal the necessity to consider ambient light level and display luminance together, which affects the viewing mode, when adjusting the adaptive display white point.
Unsatisfactory user experiences such as motion sickness, low resolution and subpar image quality prevent VR/AR headsets from being embraced by ordinary consumers. To objectively define these user ...experience metrics and align the user experience metrics with product design and objective measurement are important for solving these challenges. This paper reviews and reports our results in several critical areas: motion sickness, display resolution and system sharpness, visual ripples or orange peels, and color uniformity. Through these examples, we hope to show the direct feedback between user experience and product design, and to provide a solution for designing successful VR/AR products.
Editorial: Lighting research in China Tommy Wei, Minchen
Lighting research & technology (London, England : 2001),
04/2023, Letnik:
55, Številka:
2
Journal Article
Abstract
Conventional models (e.g., a Gain‐Offset‐Gamma model) were developed based on the assumption of channel independence. Modern displays (e.g., organic light‐emitting‐diode OLED displays), ...however, sometimes have crosstalk effects among the three channels, making these conventional models have poor performance. In this article, we propose a 3D piecewise model. It divides the display gamma encoded RGB space (i.e.,
R
′
G
′
B
′) into 27 subspaces and characterizes the crosstalk effects between two and three channels based on the measurements of the tristimulus values of 64 combinations of digital signal values. The average color difference Δ
E
00
of the 41 combinations between the model predictions and the measurements was around 0.34, in comparison to the average of 3.61 by the GOG model, across nine uncalibrated OLED displays. In addition, for displays with breakpoints on each channel, a revision is proposed to divide the subspaces for maintaining the accurate predictions. The proposed model was also validated by calibrating 94 uncalibrated OLED displays to the standard P3 RGB specifications, resulting an average color difference Δ
E
00
reduced from 3.96 to 0.72.
Display technologies have been developed to adjust the display brightness and color under different viewing conditions, providing better viewing experiences to users. Solutions have been proposed to ...adjust the display white point according to the ambient light condition, which roots into the underlying chromatic adaptation mechanism in the human visual system. This study was carefully designed to reveal the necessity to consider the ambient light level and display luminance together, which affects the viewing mode, when adjusting the adaptive display white point. The results clearly suggested that when the display luminance was greater than the ambient light diffuse white luminance, the display was viewed in the self‐luminous mode and the display white point was not significantly affected by the ambient light chromaticities. In contrast, when the display luminance was lower than the ambient light diffuse white luminance, the display was viewed in the surface mode and the ambient light chromaticities had a significant effect on the display white point, especially when the surround ratio was high.
Adaptive display shifts the display white point and other colors accordingly based on the ambient conditions. In addition to the ambient light color, it needs to consider the ambient light illuminance and also the relationship between ambient light illuminance and display luminance.
Numerous efforts have been made to investigate how light source color rendition affects color preference. Though the effect of light level on color appearance (known as the Hunt effect) was found in ...1952, most studies investigating color preference under light sources only employed a single illuminance level and the illuminance levels were typically between 200 and 1000 lux. This article reports two psychophysical experiments that were designed to investigate how light source color rendition affected color preference across a wide range of illuminance levels, from 20 to 15,000 lux. The observers compared the color appearance of an artwork under nine nearly metameric light stimuli with a correlated color temperature (CCT) of 3000 K at different illuminance levels. These light stimuli were carefully designed to have different abilities to enhance the chroma of red and green colors, so that they had different gamut areas R
g
(between 100 and 124 in Experiment 1 and between 99 and 117 in Experiment 2). It was found that the illuminance level significantly affected the observers' judgments, with a light stimulus with a greater R
g
being preferred at a lower light level. The light stimuli with an R
g
beyond 100 were preferred at the light levels from 20 to 5000 lux, whereas those with an R
g
around 100 were preferred at very high light levels (i.e., 10,000 and 15,000 lux). This suggested that the preference to the stimuli with an R
g
beyond 100, as found in many past studies, was likely due to the relatively lower illuminance levels in comparison to the daylight illuminance levels. In addition, the calculations of the color attributes of the artwork under the preferred stimuli suggested that CIECAM02 may overestimate the effect of light level on color appearance, especially when the light level was very high, which merits further investigations.
Different chromaticities for producing white appearance were found when viewing color stimuli produced by physical color samples and displays, which has been widely attributed to the different ...degrees of chromatic adaptation caused by the different viewing media. Here we carried out a pilot study to investigate whether such a difference was caused by viewing medium or viewing mode. Eight human observers adjusted a series of stimuli at six luminance levels that were produced by an iPad display to make them appear the whitest under nine different adapting conditions, with four at a low adapting luminance level and five at a high adapting luminance level. The adjusted chromaticities under the low adapting luminance conditions generally shifted along the Planckian locus toward a higher correlated color temperature (CCT), whereas those under the high adapting luminance conditions were around the chromaticities of the adapting fields. The different chromaticities for producing white appearance under the two adapting luminance levels corroborated the findings in many past studies that used two viewing media (i.e., surface color samples and displays). This suggested that the high adapting luminance level changed the viewing mode of the color stimuli produced by the iPad from the self-luminous mode to the surface mode. Therefore, the different chromaticities for producing white appearance when viewing color stimuli produced by physical color samples and displays should be attributed to the viewing modes instead of the viewing media.
Chromatic adaptation is an important mechanism in the human visual system, which affects the perceived color appearance of scenes and objects under the illumination. Recent studies, however, found ...that the degree of chromatic adaptation was significantly affected by the chromaticities of the adapting condition, which is not characterized in the existing chromatic adaptation transforms and color appearance models. This work was carefully designed to investigate how the degree of chromatic adaptation needs to be considered to reproduce the overall color tone of scenes under the illumination having a wide range of chromaticities. Human observers viewed a scene under 85 light settings, and then adjusted the color appearance of the scene image shown on a smartphone display to match that of the physical scene. The adjustment of the image color appearance was achieved by performing chromatic adaptation transform with different image white points. The results clearly showed how the degree of chromatic adaptation varied with the illuminant chromaticities, and how the image white point should be adjusted to reproduce the color tone of an illuminated scene.
We have developed a two-measure system for evaluating light sources' color rendition that builds upon conceptual progress of numerous researchers over the last two decades. The system quantifies the ...color fidelity and color gamut (change in object chroma) of a light source in comparison to a reference illuminant. The calculations are based on a newly developed set of reflectance data from real samples uniformly distributed in color space (thereby fairly representing all colors) and in wavelength space (thereby precluding artificial optimization of the color rendition scores by spectral engineering). The color fidelity score R(f) is an improved version of the CIE color rendering index. The color gamut score R(g) is an improved version of the Gamut Area Index. In combination, they provide two complementary assessments to guide the optimization of future light sources. This method summarizes the findings of the Color Metric Task Group of the Illuminating Engineering Society of North America (IES). It is adopted in the upcoming IES TM-30-2015, and is proposed for consideration with the International Commission on Illumination (CIE).
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