A design-oriented approach for managing colored light sources in lighting design software

In the last decade, the extensive introduction of LED lighting sources has brought elements of innovation to interior lighting design in terms of color. Besides the new tunable white LED source, lighting is no longer exclusively white; indeed, colored lighting has entered the design practice thanks to the positive effects on people's health and mood. Unfortunately, this element of lighting innovation, color, cannot be computed correctly in commercial lighting design software. These computations are based on the assumption that light is only white or defined in terms of RGB triplets in the relative digital color space of computer graphics, which does not have a physically correct relationship with the actual spectral power distribution (SPD) of luminaires. In this paper, attention is focused on a practical design-oriented approach for describing luminaires in lighting design software that also considers the real SPD and the luminous intensity distribution. The focus is on information available to lighting designers who do not have a laboratory to measure light sources and luminaires. This information could be available in online datasheets or as a Cartesian graph from luminaires and light sources manufacturers. Following this approach, a set of functions is proposed that can be easily implemented in lighting design software to improve light sources' color management and allow lighting designers to add SPD data to luminaires.     

网络出版中文字背景色的优化

网络出版的阅读基于屏幕显示,不同于纸质出版,显示屏幕上呈现文字信息可不拘泥于白色背景。实验针对不同字体和字号的黑色文字,设计了亮白和红、黄、绿、蓝、品红、灰等不同色相的背景颜色,并在一定范围内改变其明亮度和彩度。视觉观测结果表明,因屏幕自发光的亮度很大,其最亮的白色并不适于黑色文字的显示,适合的白色背景是明亮度降低后的一定范围内的灰色。类似地,其他所实验的彩色,适于作为背景色的明度和彩度也都有一定的范围。就适于的范围大小比较而言,包括灰色在内,灰色、黄色、绿色和蓝色的明度范围明显大于红色和品红色;绿色、黄色和蓝色的彩度范围也明显大于红色和品红色,其中绿色的彩度范围尤为宽泛。     

Designing white‐light LED lighting for the display of art: A feasibility study

When displaying art, several criteria must be balanced when designing illumination including the artist's intention, damage, energy efficiency, viewing experience and understanding, and for commercial galleries and sales. The most common lighting for art includes natural daylight and incandescent spotlights. Neither source is optimal for all criteria; thus there is considerable interest in the use of white‐light light‐emitting diode (LED) lighting. A feasibility study was conducted to address two questions. First, was it possible to design a three‐primary LED source that yielded the same color rendering as common museum lighting? Second, could one design the lighting to achieve specific color appearance attributes? Three‐primary lights using a Gaussian function were optimized matching the chromaticity of D65 and minimizing color differences for a set of acrylic dispersion paints. The optimal wavelengths depended on bandwidth. Lights were also optimized that either maximized or minimized average chroma. A set of real LEDs was selected that produced similar results when evaluated computationally. A source that increases chroma may be useful when used to illuminate works of art with high light sensitivity: very low illuminances are necessary and such a source will compensate for the reduction of colorfulness and visual clarity. A source that decreases chroma may be used to render art in similar fashion to low‐light conditions such as churches and caves. In general, white LED lighting is advantageous for art conservation because they do not emit UV and IR radiation and their visible radiation is reduced when compared with their continuous spectrum equivalent. © 2010 Wiley Periodicals, Inc. Col Res Appl, 2011     

Effect of text‐background lightness combination on visual comfort for reading on a tablet display under different surrounds

Many tablets are designed to change display brightness or color with surround for enhancing visual comfort. Although both color and brightness of a surround may vary a lot, few studies investigated how text‐background lightness combination of a tablet display and surround jointly affect visual comfort, and how display white point affects visual comfort. In this study, 20 observers evaluated visual comfort of 20 text‐background lightness combinations of a 9.7‐inch tablet display through paired comparisons under five surrounds—a dark surround and four ambient lighting conditions comprising two levels of correlated color temperature (CCT)—3500 and 6500 K—and illuminance—300 and 3000 lx. The combination of a black text and a light‐gray background (i.e., L^*_background = 75.33; L^*_text = 1.6) was evaluated the most comfortable when there was ambient light regardless of CCT and illuminance. It was also evaluated the third most comfortable under the dark surround. The observers also evaluated the visual comfort of a dark text on five different white backgrounds under 3500 and 6500 K at 1000 lx. The color of the background that was judged as the most comfortable neither had the whitest appearance nor matched the color of the ambient light. The simultaneous adjustment of the display white point and the text‐background lightness combination merits further investigations.     

Hue and warm‐cool feeling as the visual resemblance criteria for iso‐CCT judgment

The hue perception and ‘warm‐cool’ feelings were investigated, in response to various lighting settings, following the adaptation to either 3500K or 5000K to compare which one—between conventional iso‐Correlated Color Temperature (CCT) and a new one based on CIE u'v′ color space—is more compatible with the visual perception. Twenty participants evaluated hue and warm‐cool feelings for 48 test lighting settings, by observing an empty gray booth. The results showed that yellow‐blue and ‘warm‐cool’ feelings are closely located around the Planckian locus, while red‐green roughly follows the line orthogonal to the Planckian locus in CIE u'v′ color space, at both 3500 K and 5000 K settings. This suggests that u'v′ color space correlates better with human perception.     

A review of the effects of colour and light on non‐image function in humans

This paper reviews current knowledge on non‐image‐forming aspects of vision. Developments in the last 20 years have included the discovery of a fifth class of human visual pigment (melanopsin), in addition to the three classes of photopsin to be found in the cones and rhodopsin in the rods in the human retina. Melanopsin is found in a small number of retinal ganglion cells which then, in addition to receiving input from rods and cones, are intrinsically photosensitive. These retinal ganglion cells send their input primarily to the hypothalamus, where they help to regulate the circadian system (daily rhythms of sleep patterns, body temperature, heart rate, etc.). The discovery of the anatomical basis of non‐image‐forming vision has led to a great deal of research into the effects of light on sleep, depression and mood, retinal photodamage and well‐being, amongst other factors. Given that recent technological innovations in LED lighting now give us greater control over environmental lighting, it is timely to review the non‐visual effects of light in humans in order to inform lighting design in the future.     

Color breakup visibility thresholds for 2‐field sequential colors

Nowadays local primary desaturation has been proved to be an effective method to suppress the color breakup for field‐sequential‐color (FSC) displays. However, little attention has been focused on the interaction between various subfield colors and the color breakup visibility. In this article, a perception experiment was conducted with the help of a 120 Hz 2‐field FSC display to investigate the thresholds of color breakup visibility along different hue directions with a constant white point in the standard color space. The experimental results show that the color breakup visibility is various when using different subfield colors for temporal combination. A relative high threshold value or low sensitivity of color breakup visibility can be observed when subfield colors are chosen along the blue‐yellow direction while becoming perceptible easily along magenta‐cyan direction. The results and analysis of our experiments are promising to optimize the performance of local primary desaturation. Meanwhile, other applications using the temporal color fusion such as tunable lighting can also benefit from the conclusion of our work to suppress the color breakup effect.     

Similarities and differences between male and female novice designers on color‐concept associations for warnings,action required,and signs and equipment status messages

This research examined the male and female novice designers toward color associations for the concepts used for ‘warnings’, ‘action required’, and ‘signs and equipment status’ through a questionnaire‐based study. A total of 178 Hong Kong Chinese final year undergraduate design students (89 males and 89 females) participated in the study. The test used required the participants to indicate their choice of one of nine colors to associations with each of 38 concepts in a color‐concept table, so that any one color could be associated with any one of the concepts. For both male and female groups of novice designers, chi‐square tests revealed a strong color association for each concept tested in this study (P < .05). The results showed males and females agreed on some color‐concept association stereotypes which were therefore gender neutral. The male and female novice designers had the same color associations and similar levels of stereotype strengths for 21 concepts. The nine strongest and therefore most useful color‐concept association stereotypes for both male and female novice designers were: red‐danger, red‐fire, red‐hot, red‐stop, red‐emergency, red‐error, blue‐cold, blue‐male, and green‐exit. However, the male and female novice designers had different color association stereotypes for the standby (green vs. yellow), emergency exit (green vs. red), and toxic (purple vs. black) concepts, and the strengths of the 14 remaining associations for both groups were not at equivalent levels. Overall, it is anticipated that the findings of this study will act as a useful reference for novice designers and other design practitioners to optimize color coding in the design of ‘warnings’, ‘action required’, and ‘signs and equipment status’ messages.     

Visual and instrumental assessments of color differences in automotive coatings

The interest in gonioapparent pigments (metallic, pearlescent, interference, or diffractive) has increased in the last few years, especially for applications in the automotive industry. To assure a proper characterization of colors with gonioapparent pigments, commercial devices have appeared to characterize the color in different geometries, which are called multiangle spectrophotometers. As the gonioapparent pigments and multiangle instruments are relatively new, no studies exist regarding the instrumental‐based procedure followed in the industry, and if the results provided are in agreement with the observer perception. Consequently, the main objective of this study was to examine the correlation of the instrumental color differences with visual assessments. The instrumental color difference was calculated with the color difference formula AUDI2000 (specific for this sector) between the pairs of similar samples of three types of coated panels (solid, metallic, and pearlescent). The values measured by a telespectroradiometer in a directional lighting booth and the colorimetric values obtained by means of a multiangle spectrophotometer BYK‐mac were considered for this purpose. Additionally, a visual experiment was conducted to quantify the color difference by using the gray‐scale method. The results revealed that an acceptable instrumental correlation existed despite the visual and the instrumental correlation being worse. In particular, it was checked that observers accepted a larger number of color pairs, that is, the visual color difference was smaller than the tolerance demanded by the industry (derived from AUDI2000). © 2015 Wiley Periodicals, Inc. Col Res Appl, 41, 384–391, 2016     

Affective matches of fabric and lighting chromaticity

This study investigates the impact of lighting colors on subjective judgments of fabric: in particular, whether the influence of lighting varies depending on fabric types and color combinations. We conducted two visual assessments. In Study 1 (N = 44), eight illuminants and six types of fabric were presented as cloth stimuli. Derived from the literature review, four sets of adjectives (humble-luxurious, cool-warm, old-new, and not preferred-preferred) were used as metrics. In Study 2 (N = 41), five sets of fabric color combination swatches were assessed under lighting conditions that were identical to those of Study 1. Three bipolar scales (ordinary-characterful, classic-modern, and soft-rigid), were employed from factor analysis along with three unipolar scales (luxurious, preferred, harmonious with lighting). The results showed that hue characteristics of lighting and cloth types influenced participants' perceptions of the fabric. Overall, white lighting with 4000 K was the most preferred and luxurious lighting across various types of clothes, while a pinkish white with 4700 K (duv = −0.0127) was the best matched in every color combination. In addition, there were interaction effects between lighting colors, clothes types, and fabric color combinations with regard to each of the perceptual qualities. This study provides empirical evidence for optimally match lighting colors with fabric in the presentation of fabric goods.     

An ergonomic study of visual optimization by light color managements

Light‐emitting diodes (LEDs) have the advantage of controllable light colors and provide the optimal lighting quality against various color attributes required in different environments. However, from the humanized design point of view, beside satisfying physical demands of people, it is also important to achieve satisfaction. With a good match between the LED lighting equipment and ambient colors, the space imagery that complies with psychological needs of human beings can be found. This is expected to become a new market direction for future lighting. In this study, the LED light source feature of adjustable correlated color temperature is used to match wall colors of typical commercial spaces and for the investigation and analysis of the impact of colors of light sources and environments on human beings. The measures of mental and subjective feelings of a group of people under various circumstances have also been investigated. Multivariate analysis of variance has been conducted on three color temperatures of light sources, six wall colors, and measures of five emotion adjectives, and the correlation between these three variables has been further investigated. © 2014 Wiley Periodicals, Inc. Col Res Appl, 41, 72–84, 2016     

Evaluation of performance of various color‐difference formulae using an experimental black dataset

The objective of this study was to develop a specific visual dataset comprising black‐appearing samples with low lightness (L* ranging from approximately 10.4 to 19.5), varying in hue and chroma, evaluating their visual differences against a reference sample, and testing the performance of major color difference formulas currently in use as well as OSA‐UCS‐based models and more recent CAM02 color difference formulas including CAM02‐SCD and CAM02‐UCS models. The dataset comprised 50 dyed black fabric samples of similar structure, and a standard (L*= 15.33, a* = 0.14, b* = ?0.82), with a distribution of small color differences, in ΔE^*_ab, from 0 to approximately 5. The visual color difference between each sample and the standard was assessed by 19 observers in three separate sittings with an interval of at least 24 hours between trials using an AATCC standard gray scale for color change, and a total of 2850 assessments were obtained. A third‐degree polynomial equation was used to convert gray scale ratings to visual differences. The Standard Residual Sum of Squares index (STRESS) and Pearson's correlation coefficient (r), were used to evaluate the performance of various color difference formulae based on visual results. According to the analysis of STRESS index and correlation coefficient results CAM02 color difference equations exhibited the best agreement against visual data with statistically significant improvement over other models tested. The CIEDE2000 (1:1:1) equation also showed good performance in this region of the color space. © 2013 Wiley Periodicals, Inc. Col Res Appl, 39, 589–598, 2014     

Color‐person‐environment relationships

Although the nature of color and the person environment relationship are both well‐documented, it is posited that both domains need to be integrated to understand the active role that color plays in the relationship between a person and the surrounding environment. The color person environment relationship (COL‐PE) introduced in this article is an important theoretical concept for designers, and as a consequence, for environmental‐color researchers to investigate. The potential of color to be an active agent in the relationship between people and environments is introduced by drawing upon what is known about color and the person environment relationship from other sources. The nature of transition spaces is used to emphasize how color affects the emotional connection and disconnection between people and spaces. As an example of COL‐PE, transition spaces highlight the nature of the person who is also psychologically in‐transition and color as a potentially important aspect of the transitory experience. In addition, the connections between color and the constructs that we hold of the people who visit, work, or live in particular environments will be discussed briefly. Designers often focus on the object or artifact which is being colored (whether a building or a chair) as an end in itself, without considering in any depth how the designed objects or places can influence how people experience their daily activities and each other. COL‐PE is introduced as a means to address this omission and broaden designers' understandings of the potential impact of their work. The discussion of the aspects of environmental design (with particular reference to architecture and interior design), introduces the foundation of the COL‐PE as a particular way of addressing color in the built environment. The principles of COL‐PE are relevant for a range of disciplines involved in environmental design including urban design, landscape architecture, interior design, industrial design, and architecture. The COL‐PE aims to make explicit what is often an unrecognized or tacit understanding of the role of environmental color, and thereby, the article highlights the need for research to understand the relationship more fully. © 2008 Wiley Periodicals, Inc. Col Res Appl, 33, 312–319, 2008.     

Research on product color design decision driven by brand image

As one of the most important visual characteristics in a product system, color can arouse the user's emotional demands quickly. Due to the complexity of the user's emotional needs mining process, it can be expressed by color image adjectives. Meanwhile, product color trends that meet the user's emotional demands may help decision makers to anticipate a new market positioning and reduce the blindness in the product color design. In this study, the Gray theory combined with the Kansei engineering was used to mine the macro and microscopic factors in product color design decision process based on the product color brand image. The results showed that the constructed method could be used to guide the product color design that was to meet the user's emotional needs comprehensively and quickly. The method solved the problems that exist in the current product color trend prediction research and improved the accuracy of the correlation mining between product color design elements and brand image. Lastly, the color design of the mid-range sedan was taken as an example to prove the feasibility of the research approach. This is a new attempt to guide product color design decisions in two aspects, one is known from the results of product color trends quantitative prediction, and the other one comes from the correlation calculation between product color design elements and brand image.     

Optimization of LED‐based light blendings for object presentation

This study looks at the perceived quality of light‐emitting diode (LED)‐based lighting of various colors. The objective was to find out whether LEDs could provide better (i.e., more relevant and acceptable) lighting than that which is obtained with standard halogen or fluorescent sources. The perception of objects was assessed under different lighting schemes. Subjects were invited to add red, cyan and/or amber to white LED‐based light to match the halogen and fluorescence rendering on specific targets: a color chart and a painting. They were also asked to rate the difference between the two, and to express their preference. The results obtained for the perception of LED‐based lighting were quite positive. Color blendings of LED light were found to provide illuminated situations similar to halogens or fluorescent sources. These blendings were well accepted, and indeed often preferred, although the color rendering index (CRI) was always low. This indicates that the CRI as it stands is inadequate to characterize the color rendering of solid‐state light sources, and needs to be updated. LED‐based lighting systems seem to have considerable potential for use in shops and display units, where they may well outperform existing lighting systems. © 2009 Wiley Periodicals, Inc. Col Res Appl, 34, 310–320, 2009     

Use of gray system theory in product‐color planning

A quantitative evaluation method for the CIE color‐planning activity within the product design cycle is proposed in this article. The questionnaire‐based process that is traditionally employed to obtain objective color psychology tends to be time‐consuming. Accordingly, this study proposes the use of gray system theory to overcome this problem. In the CIE color system, colors are defined by three primary colors, R (red), G (green), and B (blue). Using these three principal hues with fixed equigap sequences to simulate specific basic color samples is an efficient means of investigating unicolor images on a personal computer. However, a gray relational generating operation can be used to simulate colors beyond these basic samples and to predict the corresponding membership values for semantic words. In addition, the gray clustering operation is introduced to predict the overall color image evaluation of multicolored products. The predicted evaluation results of the gray system theory and a back‐propagation neural network are both compared with experimentally verified results. The results indicate that the gray forecasting model is the more effective means of predicting the image evaluation, and therefore, the method is adopted within the color‐planning activity. Although this study takes the example of the Internet‐aided color planning of a baby walker as a case study, the proposed method can also be used on other products. © 2004 Wiley Periodicals, Inc. Col Res Appl, 29, 222–231, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.20009     

Practical demonstration of the CIEDE2000 corrections to CIELAB using a small set of sample pairs

A set of 10 color pairs was proposed and produced in 2002 to show the advantages of the CIEDE2000 color‐difference formula with respect to CIELAB. These 10 color pairs illustrated each of the five corrections to CIELAB proposed by CIEDE2000. The 10 color pairs were visually assessed, under reference conditions close to those proposed by CIEDE2000, by two groups of 31 and 21 inexperienced observers, using two different gray scales. Average visual results in these experiments fitted CIEDE2000 predictions much better than CIELAB, as shown by a decrease of Standardized Residual Sum of Squares values of about 20 units. Current visual results showed only the improvement of CIEDE2000 upon CIELAB in predictions of perceived color differences, but they are not recommended for testing new advanced color‐difference formulas. © 2012 Wiley Periodicals, Inc. Col Res Appl, 38, 429–436, 2013.     

Viewerphilic nightscape based on correlated color temperature

Nowadays, many factors are involved in lighting design to achieve targeted lighting in addition to meeting the user's requirements and security to avoid energy loss. As building indexation at night is one of the main reasons for building lighting, it is necessary to make a decision to reduce energy consumption and increase observer's attention. The present study investigated the relationship between the correlated color temperature of the background and building based on the amount of visual attention and the amount of visual desirability. In this article, using a factor analysis approach, a range that attracts visual attention and visual desirability at the same time was obtained, and it is called viewerphilic perspective. The results presented in the form of a diagram show a relationship between the variables that directly and indirectly influence the formation of a viewerphilic night perspective. The results showed that the elements with a high correlated color temperature in the background and a low correlated color temperature and neutral color were in the viewerphilic range, while the elements with a low color temperature and a background with a high color temperature was in the range of viewer phobic.