Color Research and Application最新文献

Individual differences are a prominent feature of normal color vision and range from variations in sensitivity to perception and color naming. Corrections for differences in spectral sensitivity are common, and there is growing interest in calibrating displays for the sensitivity of an individual observer. In contrast, few studies have explored calibrations for aspects of color appearance. We developed a technique for adjusting images based directly on an individual's hue percepts and illustrate the principle of the approach using a set of hue scaling functions measured previously for a large sample of color-normal observers (Emery et al. PNAS 2023). Colors in an image are mapped onto the average scaling function to define the hue perceived by the average “standard observer.” This hue is then mapped back to the chromaticity that would elicit the same response in any individual observer. With this correction, different observers – each looking at physically different images calibrated for their own hue percepts – should in principle agree on the perceived colors. Adjustments of this kind could be easily implemented on standard displays, because they require only measures of hue percepts and not spectral sensitivity, and could lead to greater consistency in the perception and communication about color across individuals with potentially widely different perceptual experiences of color.

Just-noticeable color difference (JNCD) is important in color specification and characterization. The commonly referenced specification of JNCD (i.e., 0.004 or 0.0033 u′v′ unit) is thought to originate from the MacAdam ellipses, which were derived using 2° color stimuli and characterized using the CIE 1931 2° color matching functions (CMFs). However, there is no universally agreed or clear definition of JNCD. Also, such a specification is widely used in various ways based on an assumption that it is applicable regardless of the actual size of the stimuli and CMFs. In this study, an experiment using a constant stimuli method was carried out. The human observers evaluated a series pairs of test and reference stimuli, with a field of view (FOV) of 2° or 10°. The chromaticities of the test stimuli were carefully calibrated using four standard CIE CMFs (i.e., CIE 1931 2°, 1964 10°, 2006 2°, and 10° CMFs). The results suggested that the widely used specification of JNCD seems to be derived based on the one standard deviation ellipses, the use of these four CMFs has little effect on the specification, and the JNCD value for stimuli with an FOV of 10° is 0.0025–0.0027 u′v′ unit depending on the CMFs.

In 2022, CIE recommend the CIECAM16 color appearance model to replace the current CIECAM02 model for color management systems. In this paper we will report on how CIECAM16 was developed, describe the differences between CIECAM16 and CIECAM02, describe the phenomena CIECAM16 can predict, and show the performance of CIECAM16 in the prediction of perceptual color attributes. We will then discuss the numerical determination of the domain and range of the CIECAM16 forward transformation. Finally, the domain and ranges in various conditions are visualized. CIECAM16 is capable of the accurate prediction of color appearance under a wide range of viewing conditions and with the domain and range problems now solved, it can be effectively applied to cross-media color image reproduction. It can also be used to estimate the color rendering properties of light sources and for the establishment of a uniform color space for color difference evaluation.

Human color vision exhibits substantial variability, challenging the accurate measurement and reproduction of individual color appearances. This paper introduces a novel cross-media color-matching experiment that combines physical pigments and digital displays, providing a practical and efficient solution to measure individual color matching functions (CMFs). By using the Kubelka–Munk theory to synthesize broadband spectral pigments, optimized metameric pairs can be created to significantly differentiate categorical observers. Psychophysical experiment results reveal the superiority of specific CMFs for individual observers, surpassing standard models like the CIE 1931 2-degree CMFs. This study also underscores the significance of employing CMFs for personalized color reproduction and explores the potential benefits of using higher bit-depth displays, narrower-band displays, and increasing repetition counts to enhance the accuracy of the color matching process.

The goal of this study is to process digital images to facilitate color discrimination in dichromatic vision without changing their appearances in trichromatic vision as much as possible. Therefore, we propose a simple and effective image enhancement method using the geometric properties of the RGB color space. Concretely, a novel image representation that clarifies the relationship between dichromatic and trichromatic visions in the RGB color space, and an image enhancement method based on this representation are presented. The effectiveness of the proposed method is verified by experiments using several digital images.

An image is commonly white balanced using a white point that is considered to accurately characterize the scene illumination color (e.g., the white point estimated by the main camera on a smartphone, or the white point estimated by an ambient light sensor). Two recent studies, however, suggest that the perceived color appearance of self-luminous highlights is less affected by the ambient illumination color in a scene, with the color appearance judged using a white point between 5000 and 7000 K, especially when the stimulus luminance is much higher than the diffuse white luminance. Based on this, we hypothesized to use a D65 white point for white balancing the self-luminous highlights in images, regardless of the estimated white points. We captured a series of images containing self-luminous highlights, and processed them with three different white points (i.e., the white point estimated by the main camera, D50, and D65). The hypothesis was supported by the survey results collected from 73 observers, together with our observations, and believed to introduce better image color appearance, especially for images shown on high dynamic range displays.

There has been long running debate about the interaction of language and perception. In this context, bilingual people have often shown benefits, due to their double-active linguistic system, in cognitive functions, like inhibition, attention, and memory, which are central for visual perception. Color naming and categorization are domains for studying cross-linguistic effects, which arise from conceptual and perceptual variations across speakers of different languages. In this study, we compared the ‘blue’ lexicon of highly proficient French-Italian bilinguals to monolingual speakers of the corresponding languages. Prior studies have shown that Italian has two basic color terms for the blue area of color space: one denotes light blue hues (azzurro) and the other dark blue hues (blu), whilst French, with only one basic term bleu, lacks this distinction. We used a Stroop test to probe differences in perception and categorization of blue in bi- and monolingual speakers. We found that Italian monolinguals name the ink color more accurately and more rapidly when the word blu is rendered in dark blue ink (corresponding to the word blu) than when it is printed in light blue ink (corresponding to azzurro), since the latter represents an incongruent condition for them. This ‘category effect’ does not exist for French monolingual speakers. Our bilinguals' results demonstrate that, despite the emergence of a specific in-between perceptual behavior, bilinguals generally performed like Italian monolinguals. These outcomes confirm the hypothesis that their second language categories (Italian) dominate their native language (French), attesting that lexical distinctions influence perceptual faculties in general. However, the ratio of the interference effect (longer reaction times for incongruent stimuli compared to control stimuli) and the facilitation effect (shorter reaction times for congruent stimuli compared to control stimuli) is not the same for bilinguals and monolinguals. The highest magnitude in the facilitation effect was revealed for bilinguals, whereas the highest magnitude in the interference effect was revealed for Italian monolingual speakers. This phenomenon adds evidence to the existence of enhanced bilingual cognitive control abilities.

Color has become an essential element in our communication and our judgment on products. In textile, the formulation of any color is an essential process to ensure color continuity from the master standard to all subsequent production batches. Indeed, the objective is to normalize its reproduction all along the color reproduction procedure. In the literature, researches concerning textile color formulation are important, so this review focuses on these different techniques and methods of color matching for dye mixtures and precolored fiber blends. This step involves determining the dyes or fibers to use (alone or in mixtures) and their appropriate proportions to reproduce the wanted colors. The main techniques used for dye mixtures are based on colorimetric, spectrophotometric, and artificial intelligence techniques. While for precolored fiber mixtures the used techniques are dived into theoretical and experimental models. In addition to the review of these different techniques, a quantitative analysis was carried out.

Reproducing near-gamut colors on an emissive display often causes them to appear brighter than an achromatic color of the same luminance. This phenomenon can be explained by the Helmholtz–Kohlrausch (H–K) effect, which describes an increase in perceived brightness when increasing the chroma of a stimulus. Although recent studies have attempted to incorporate the H–K effect into their modeling, none of these studies have directly explored how the perception of chromatic stimuli changes with background luminance. In this article, we present results from a psychophysical brightness-matching experiment conducted across different levels of background luminance. The experimental results show the magnitude of the H–K effect upon simultaneous lightness contrast for high chroma colors. We, then, compare our results to CAM16 and other published models that propose modifications to CAM16 to account for the H–K effect. The findings reveal that CAM16 overestimates the perceived rate of lightness change by more than double for highly saturated, low luminance colors with increasing background luminance levels. Despite the progress made in incorporating the H–K effect into models, our study indicates the need for further data to establish a more accurate and robust modeling of this phenomenon.

Patients who undergo transcatheter aortic valve implantation (TAVI) may become pale during the early postoperative period. To clarify whether facial colors changed during the postoperative period, patients' skin color from before to 72 h after TAVI was measured spectrophotometrically. Factors associated with skin color were also investigated. Forehead skin color and vital signs were measured before TAVI and at 6, 18, and 72 h after TAVI in 11 patients scheduled for TAVI. Blood examinations were performed before and 18 and 72 h after TAVI. Skin color was assessed using a spectrophotometer and expressed as L* (lightness), a* (red/green), and b* (yellow/blue) according to the CIE1976L*a*b* color space. Skin lightness L* values increased at 6 and 18 h after TAVI and returned at 72 h after TAVI and a* values decreased at 6 h after TAVI. The b* values did not change perioperatively during TAVI. No associations were observed between the changes in skin color and changes in BP or laboratory data. The findings that the skin color became whitish and less reddish in the early postoperative period resembled that occurring during an acute inflammatory response. Observation of skin color is important to detect the possibility of postoperative complications.