Assessment of color preference, purchase intention and sexual attractiveness of lipstick colors under multiple lighting conditions.

Lipstick is one of the most commonly used cosmetics, which is closely associated with female attractiveness and influences people's perception and behavior. This study aimed to investigate the impact of light sources, lipstick colors, as well as gender on the subjective assessment of lipstick color products from the prospective of color preference, purchase intention and sexual attractiveness. The correlation between color preference evaluations when applying lipstick on lips and on forearms was also explored. Sixty participants completed their visual assessment of 15 lipsticks worn by 3 models under 5 light sources, with uniformly sampled correlated color temperature (CCT) values ranging from 2,500 K to 6,500 K. The results indicated that the light source significantly influenced color preference and purchase intention, while lipstick color significantly impacted on sexual attractiveness. The interactions between gender and other factors were also observed and are discussed. Compared to men, women were found to be more sensitive to different light sources and hold different attitudes toward different lipstick colors under different CCTs. Interestingly, no significant correlation was found between lipstick color preference ratings on the lips and forearm, which conflicted with the commonly recognized way of lipstick color selection. These findings should contribute to a deeper understanding of the consumer attitude toward lipstick colors and provide a useful reference for lighting design in situations where cosmetics are specified, manufactured, retailed and generally used, both professionally and in the home.

Domain and range of the CIECAM16 forward transformation.

The domain and range of the CIECAM16 forward transformation was numerically determined and visualized for CIE standard illuminants, using a linear programming approach that provides the gamuts and colour solids for optimum colours. The effect of the surround, adapting luminance, and luminance of the background on the range of the CIECAM16 forward transformation were individually analyzed, showing that their ranges increased when the surround changed from dark to dim or average, the adapting luminance increased, or the luminance of the background decreased. The proposed methodology for the determination and visualization of the domain and range of the CIECAM16 forward transformation can be used for any illuminant, as well as for CIECAM02, CAM16, CAM02-UCS and CAM16-UCS. The findings of this paper not only solve the long-term unresolved domain and range problems of the CIE colour appearance models, but also find applications in cross-media colour reproduction. Furthermore, it was also found that some non-CIE colours are inside the International Color Consortium Profile Connection Space (ICC PCS), and some CIE colours are not included in that space.

Extending the color discrimination metric with consideration of illuminance level.

Color discrimination is a crucial dimension for the visual assessment of white light sources. In this Letter, we took full advantage of data comparability among Farnsworth-Munsell 100 Hue (FM-100) color vision tests and modified our recent proposed color discrimination metric [Opt. Lett.45, 6062 (2020)10.1364/OL.400422] to make it effective in quantifying the color discrimination capability of lighting under multiple illuminance levels. The updated metric was developed based on a meta-analysis of 100 sets of combined visual data derived from three groups of visual studies containing 29 FM-100 trials and its superiority was comprehensively validated by 140 sets of combined data from five groups of studies with 42 FM-100 trials.

Spectral Reconstruction Using an Iteratively Reweighted Regulated Model from Two Illumination Camera Responses.

An improved spectral reflectance estimation method was developed to transform captured RGB images to spectral reflectance. The novelty of our method is an iteratively reweighted regulated model that combines polynomial expansion signals, which was developed for spectral reflectance estimation, and a cross-polarized imaging system, which is used to eliminate glare and specular highlights. Two RGB images are captured under two illumination conditions. The method was tested using ColorChecker charts. The results demonstrate that the proposed method could make a significant improvement of the accuracy in both spectral and colorimetric: it can achieve 23.8% improved accuracy in mean CIEDE2000 color difference, while it achieves 24.6% improved accuracy in RMS error compared with classic regularized least squares (RLS) method. The proposed method is sufficiently accurate in predicting the spectral properties and their performance within an acceptable range, i.e., typical customer tolerance of less than 3 DE units in the graphic arts industry.

Towards an optimum colour preference metric for white light sources: a comprehensive investigation based on empirical data.

Colour preference is a critical dimension for describing the colour quality of lighting and numerous metrics have been proposed. However, due to the variation amongst psychophysical studies, consensus has not been reached on the best approach to quantify colour preference. In this study, 25 typical colour quality metrics were comprehensively tested based on 39 groups of psychophysical data from 19 published visual studies. The experimental results showed that two combined metrics: the arithmetic mean of the gamut area index (GAI) and colour rendering index (CRI) and the colour quality index (CQI), a combination of the correlated colour temperature (CCT) and memory colour rendering index (MCRI), exhibit the best performance. Qp in the colour quality scale (CQS) and MCRI also performed well in visual experiments of constant CCT but failed when CCT varied, which highlights the dependence of certain metrics on contextual lighting conditions. In addition, it was found that some weighted combinations of an absolute gamut-based metric and a colour fidelity metric exhibited superior performance in colour preference prediction. Consistent with such a result, a novel metric named MCPI (colour preference index based on meta-analysis) was proposed by fitting the large psychophysical dataset, and this achieved a significantly higher weighted average correlation coefficient between metric predictions and subjective preference ratings.

Color discrimination metric based on the neutrality of lighting and hue transposition quantification.

In this Letter, we propose a combined metric for quantifying the color discrimination capability of white light sources. This metric is based on considerations of human visual adaptation to daylight chromaticities, as well as on the concerns of the huge spectral diversity of modern light sources. Two existing metrics, Sneutral (degree of neutrality) by Smet et al. [Opt. Express22, 25830 (2014)OPEXFF1094-408710.1364/OE.22.025830] and Rd (hue transposition among color samples of the Farnsworth-Munsell 100 Hue color vision test) by Esposito and Houser [Lighting Res. Technol.51, 5 (2019)LRTEA90024-342610.1177/1477153517729200] were adopted, and their weights were determined by a meta-analysis of five groups of psychophysical data on color discrimination. The superiority of the newly proposed metric was demonstrated by 16 groups of psychophysical data from eight color discrimination studies, as well as by a comparison with 29 typical color quality metrics and their linear combinations.

Evaluating the color preference of lighting: the light booth matters.

On the topic of color preference of lighting, it is commonly believed that the neutral interior of a light booth has minimum impact on the color perception of the experimental object. Meanwhile, agreement has not been reached on which objects should be placed in the booth. In this study, based on a meta-analysis of eight groups of psychophysical data, we demonstrate that the "perceived color preference" obtained by consecutive visual judgement in a light booth is closely related to the lit neutral environment, while the use of different experimental objects does not markedly influence the results for lighting quality assessment. Such a finding might be attributed to the inherent features of the visual cognition process of light booth experiments and it should be fully recognized by future work.

Color quality evaluation of Chinese bronzeware in typical museum lighting.

A series of psychophysical experiments have been conducted to investigate the effect of light sources on the color appearance of Chinese bronzeware. Three groups of 30 observers were asked to evaluate a set of Chinese bronzeware under different light sources in three paired-comparison experiments-one group of observers for each experiment. The visual attributes of color preference, color comfort, color discrimination, and antiquity were scaled. A panel of seven light sources of 3000 K, with Duv values ranging from $ - {0}.{015}$-0.015 to 0.015, was used in Experiment 1. A second panel of seven light sources of 4000 K, with a similar range of Duv values, was used in Experiment 2. For Experiment 3, six light sources were chosen from Exps. 1 and 2, plus four lights of 2700 K, 3300 K, 3700 K, and 4300 K, with Duv values of zero. These experimental lights produced a constant illuminance of approximately 200 lux in a pair of viewing booths, and their color rendering indices were between 88 and 95. The results showed that the subjective judgments for color preference and color comfort were highly correlated while the whiteness of the lighting strongly influenced the perception of color preference, comfort, and discrimination. A light source of 4000 K with a Duv value of zero exhibited the best color preference and color comfort performance, while observers were found to show the greatest capability for color discrimination under a light source of 4000 K with a Duv value of $ - {0}.{015}$-0.015. In addition, the bronzeware appeared to have greatest antiquity when illuminated by a 3000 K light source with a Duv value equal to 0.005. Based on the psychophysical data, the performance of typical color quality metrics were also tested in relation to the four scaled visual attributes.

Spectra estimation from raw camera responses based on adaptive local-weighted linear regression.

An improved spectral reflectance estimation method is developed to transform raw camera RGB responses to spectral reflectance. The novelty of our method is to apply a local weighted linear regression model for spectral reflectance estimation and construct the weighting matrix using a Gaussian function in CIELAB uniform color space. The proposed method was tested using both a standard color chart and a set of textile samples, with a digital RGB camera and by ten times ten-fold cross-validation. The results demonstrate that our method gives the best accuracy in estimating both the spectral reflectance and the colorimetric values in comparison with existing methods.

Gamut Volume Index: a color preference metric based on meta-analysis and optimized colour samples.

A novel metric named Gamut Volume Index (GVI) is proposed for evaluating the colour preference of lighting. This metric is based on the absolute gamut volume of optimized colour samples. The optimal colour set of the proposed metric was obtained by optimizing the weighted average correlation between the metric predictions and the subjective ratings for 8 psychophysical studies. The performance of 20 typical colour metrics was also investigated, which included colour difference based metrics, gamut based metrics, memory based metrics as well as combined metrics. It was found that the proposed GVI outperformed the existing counterparts, especially for the conditions where correlated colour temperatures differed.

Characterisation of the n-colour printing process using the spot colour overprint model.

This paper is aimed at reproducing the solid spot colours using the n-colour separation. A simplified numerical method, called as the spot colour overprint (SCOP) model, was used for characterising the n-colour printing process. This model was originally developed for estimating the spot colour overprints. It was extended to be used as a generic forward characterisation model for the n-colour printing process. The inverse printer model based on the look-up table was implemented to obtain the colour separation for n-colour printing process. Finally the real-world spot colours were reproduced using 7-colour separation on lithographic offset printing process. The colours printed with 7 inks were compared against the original spot colours to evaluate the accuracy. The results show good accuracy with the mean CIEDE2000 value between the target colours and the printed colours of 2.06. The proposed method can be used successfully to reproduce the spot colours, which can potentially save significant time and cost in the printing and packaging industry.

Brightness perception of unrelated self-luminous colors.

The perception of brightness of unrelated self-luminous colored stimuli of the same luminance has been investigated. The Helmholtz-Kohlrausch (H-K) effect, i.e., an increase in brightness perception due to an increase in saturation, is clearly observed. This brightness perception is compared with the calculated brightness according to six existing vision models, color appearance models, and models based on the concept of equivalent luminance. Although these models included the H-K effect and half of them were developed to work with unrelated colors, none of the models seemed to be able to fully predict the perceived brightness. A tentative solution to increase the prediction accuracy of the color appearance model CAM97u, developed by Hunt, is presented.

Overall gloss evaluation in the presence of multiple cues to surface glossiness.

Human observers use the information offered by various visual cues when evaluating the glossiness of a surface. Several studies have demonstrated the effect of each single cue to glossiness, but little has been reported on how multiple cues are integrated for the perception of surface gloss. This paper reports on a psychophysical study with real stimuli that are different regarding multiple visual gloss criteria. Four samples were presented to 15 observers under different conditions of illumination in a light booth, resulting in a series of 16 stimuli. Through pairwise comparisons, an overall gloss scale was derived, from which it could be concluded that both differences in the distinctness of the reflected image and differences in luminance affect gloss perception. However, an investigation of the observers' strategy to evaluate gloss indicated a dichotomy among observers. One group of observers used the distinctness-of-image as a principal cue to glossiness, while the second group evaluated gloss primarily from differences in luminance of both the specular highlight and the diffuse background. It could therefore be questioned whether surface gloss can be characterized with one single quantity, or that a set of quantities is necessary to describe the gloss differences between objects.

Correlation between color quality metric predictions and visual appreciation of light sources.

Over the past years there has been increasing evidence that the CIE color rendering index R(a) fails to correspond to the perceived color quality of many light sources, especially some Light-Emitting-Diodes. Several proposals to update, complement or even replace the CIE R(a) have therefore been made. The performance of thirteen color quality metrics was evaluated by calculating the average correlation of the metric predictions with the visual scaling of the perceived color quality obtained in several psychophysical studies. Two aspects of perceived color quality were investigated, appreciation (preference or attractiveness) and naturalness. The memory color quality metric (S(a)) of Smet et al. was found to correlate highly with perceived appreciation (r = 0.88). It was found to be statistically better (p<0.0001) at it than all other metrics. The CIE R(a) performed the worst. A metric that combines the gamut area index (GAI) and the CIE R(a) using an arithmetic mean correlated highly with the perceived naturalness of a light source (r = 0.85). It was found to be statistically better at predicting naturalness than all other metrics (p<0.0001). A negative correlation was found, between the capabilities of a light source's ability to predict appreciation and naturalness, indicating that a complete description of the color quality of a light source probably requires more than one metric.

Luminance-based specular gloss characterization.

Gloss is a feature of visual appearance that arises from the directionally selective reflection of light incident on a surface. Especially when a distinct reflected image is perceptible, the luminance distribution of the illumination scene above the sample can strongly influence the gloss perception. For this reason, industrial glossmeters do not provide a satisfactory gloss estimation of high-gloss surfaces. In this study, the influence of the conditions of illumination on specular gloss perception was examined through a magnitude estimation experiment in which 10 observers took part. A light booth with two light sources was utilized: the mirror image of only one source being visible in reflection by the observer. The luminance of both the reflected image and the adjacent sample surface could be independently varied by separate adjustment of the intensity of the two light sources. A psychophysical scaling function was derived, relating the visual gloss estimations to the measured luminance of both the reflected image and the off-specular sample background. The generalization error of the model was estimated through a validation experiment performed by 10 other observers. In result, a metric including both surface and illumination properties is provided. Based on this metric, improved gloss evaluation methods and instruments could be developed.

Optimal colour quality of LED clusters based on memory colours.

The spectral power distributions of tri- and tetrachromatic clusters of Light-Emitting-Diodes, composed of simulated and commercially available LEDs, were optimized with a genetic algorithm to maximize the luminous efficacy of radiation and the colour quality as assessed by the memory colour quality metric developed by the authors. The trade-off of the colour quality as assessed by the memory colour metric and the luminous efficacy of radiation was investigated by calculating the Pareto optimal front using the NSGA-II genetic algorithm. Optimal peak wavelengths and spectral widths of the LEDs were derived, and over half of them were found to be close to Thornton's prime colours. The Pareto optimal fronts of real LED clusters were always found to be smaller than those of the simulated clusters. The effect of binning on designing a real LED cluster was investigated and was found to be quite large. Finally, a real LED cluster of commercially available AlGaInP, InGaN and phosphor white LEDs was optimized to obtain a higher score on memory colour quality scale than its corresponding CIE reference illuminant.

Memory colours and colour quality evaluation of conventional and solid-state lamps.

A colour quality metric based on memory colours is presented. The basic idea is simple. The colour quality of a test source is evaluated as the degree of similarity between the colour appearance of a set of familiar objects and their memory colours. The closer the match, the better the colour quality. This similarity was quantified using a set of similarity distributions obtained by Smet et al. in a previous study. The metric was validated by calculating the Pearson and Spearman correlation coefficients between the metric predictions and the visual appreciation results obtained in a validation experiment conducted by the authors as well those obtained in two independent studies. The metric was found to correlate well with the visual appreciation of the lighting quality of the sources used in the three experiments. Its performance was also compared with that of the CIE colour rendering index and the NIST colour quality scale. For all three experiments, the metric was found to be significantly better at predicting the correct visual rank order of the light sources (p < 0.1).

Geometry of illumination, luminance contrast, and gloss perception.

The influence of both the geometry of illumination and luminance contrast on gloss perception has been examined using the method of paired comparison. Six achromatic glass samples having different lightness were illuminated by two light sources. Only one of these light sources was visible in reflection by the observer. By separate adjustment of the intensity of both light sources, the luminance of both the reflected image and the adjacent off-specular surroundings could be individually varied. It was found that visual gloss appraisal did not correlate with instrumentally measured specular gloss; however, psychometric contrast seemed to be a much better correlate. It has become clear that not only the sample surface characteristics determine gloss perception: the illumination geometry could be an even more important factor.

Design of an instrument for measuring the spectral bidirectional scatter distribution function.

The spectral bidirectional scatter distribution function (BSDF) offers a complete description of the spectral and spatial optical characteristics of a material. Any gloss and color measurement can be related to a particular value of the BSDF, while accurate luminaire design with ray tracing software requires the BSDF of reflectors and filters. Many measuring instruments, each having particular advantages and limitations, have been reported in the literature, and an overview of these instruments is included. A measuring instrument that allows for an absolute determination of the spectral BSDF with a full three dimensional spatial coverage in both reflectance and transmittance mode, a broadband spectral coverage, a large dynamic range, a reasonable acquisition time, and a large sample illumination area is presented. The main instrument characteristics are discussed, and the measurement capabilities are illustrated.