Color Reproduction Research Articles

Lip color measurement: A new hyperspectral imaging device.

The lips are of significant interest among the facial features for self-perception and social interactions. Such perceptions could rely in part upon the contrast in color between the lips and the surrounding skin. In contrast to skin color, lip color ethnic diversity measurement provides a challenge and is less documented in the literature, most likely due primarily to challenges in measurement based upon the lip characteristics of size and contour. Accurate measurement and reproduction of lip color are essential to build strong cross-sectional knowledge about lip color. This preliminary experiment of a large-scale project on lip and skin color was designed to assess accuracy in lip color measurement and recommend instruments and protocols for good measurement practice. The study involved 19 healthy French Caucasian women. Their inferior and superior natural lip color was measured twice with three devices in order to extract the standard colorimetric parameters of lightness (L*), chroma (C*), and hue (h): the VISIA-CR® (high-resolution digital camera, Canfield Scientific Inc.); the spectrophotometer VS3200 (45°:0° spectrophotometer, MetaVue™ VS3200, X-Rite Inc.); and the SpectraFace® (new hyperspectral imaging system, Newtone Technologies). The intercomparison and color distribution between the different instruments and the measurement repeatability of each one were assessed. Our results showed a reliable and equivalent repeatability for the three tested instruments. Moreover, the three tools led to the same conclusion regarding lip color heterogeneity (lighter, redder, less yellow and more saturated inferior lip versus superior lip). Agreement between the SpectraFace® and the spectrophotometer measurements was higher, and the SpectraFace® allowed to identify three separated lip color typologies. In conclusion, the combination of imaging technology and hyperspectral measurement makes the SpectraFace® a useful tool to investigate lip color characterization and establish a large-scale cross-sectional knowledge study about lip color.

Color multilayer holographic near-eye augmented reality display

This study demonstrates a full-color near-eye holographic display capable of superimposing color virtual scenes with 2D, 3D, and multiple objects with extended depth upon a real scene, which also has the ability to present different 3D information depending on the focus of the user’s eyes using a single computer-generated hologram per color channel. Our setup makes use of a hologram generation method based on two-step propagation and the singular value decomposition of the Fresnel transform impulse response function to efficiently generate the holograms of the target scene. Then, we test our proposal by implementing a holographic display that makes use of a phase-only spatial light modulator and time-division multiplexing for color reproduction. We demonstrate the superior quality and computation speed of this approach compared with other hologram generation techniques with both numerical and experimental results.

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.

A SEMI-AUTOMATED METHODOLOGY FOR 3D IMAGING OF LARGE VAULTED CEILING PAINTINGS

Abstract. 3D imaging of large painted and vaulted historic ceilings offers many challenges, including those due to complex small and large-scale geometry, environmental conditions and limited access. In this paper we introduce CHAPI (Cultural Heritage Automated Photogrammetric Imaging), a low cost solution to these problems which provides an efficient, semi-automated method of capturing large vaulted ceiling paintings in high detail, with a consistent photogrammetric network and in limited time. We will present and examine two different case studies from the Plafond3D project, the baroque ceiling paintings of the Schloss Rheinsberg Spiegelsaal (mirror room) and the Ansbach Residence Festsaal (great hall/ballroom). The paper will examine the particular challenges of capturing large painted areas with accurate colour and geometric reproduction, and suggest how the photogrammetric recording and reconstruction process of ceilings can be optimised for large rooms. This paper also gives technical specifications and Open Access Code for the CHAPI build.

Color Reproduction by Multi-Wavelength Bragg Diffraction of White Light.

Accurate color reproduction is highly important in multiple industrial, biomedical and scientific applications. Versatile and tunable light sources with high color-rendering quality are very much in demand. In this study, we demonstrate the feasibility of multi-wavelength Bragg diffraction of light for this task. Tuning the frequencies and amplitudes of bulk acoustic waves in the birefringent crystal demonstrates high precision in setting the number, wavelengths and intensities of the monochromatic components necessary to reproduce a specific color assigned according to its coordinates in the CIE XYZ 1931 space. We assembled a setup based on multi-bandpass acousto-optic (AO) filtration of white light and verified the reproduced color balance in multiple experiments. The proposed approach delivers almost full coverage of the CIE XYZ 1931 space and facilitates building compact color reproduction systems (CRSs) for various purposes.

ВІДПОВІДНІСТЬ ВІДТВОРЕННЯ КОЛЬОРУ НА МОНІТОРІ ПРИ ПРОЕКТУВАННІ АРХІТЕКТУРНИХ ТА ДИЗАЙНЕРСЬКИХ ОБ’ЄКТІВ

The paper substantiates the importance of appropriate color reproduction when designing architectural and designer objects in computer systems. Most studies of color in architecture and design are related to its characteristics, lighting conditions, the influence of the source, environment, visual perception, etc., rather than the accuracy of its reproduction. The color selected by the designer and the customer from the standard palettes may be distorted when displayed on a monitor in the software. Color deviations from the palette samples can be significant and visually noticeable on the monitor, which is undesirable. The article compares two monitors in terms of color reproduction quality. For this purpose, was described software and tool methods for configuring monitors. The monitors were calibrated and profiled using an instrumental method using a spectrophotometer. The obtained profiles were analyzed in comparison with sRGB and the color differences of the test scale fields were analyzed by color difference ∆E 2000. The suitability of each monitor for project visualization was determined based on monitor calibration and profiling results. The authors compared the coverage of sRGB, Adobe RGB, and ProPhoto RGB and gave practical recommendations for choosing a working profile when working and controlling color by monitor. The algorithms for calculating and using unreproducible colors were analyzed when switching from a larger color gamut to a smaller one. The article also includes practical recommendations for preparing the monitor for working with color. Therefore, it is possible to improve the color reproduction accuracy and get the color close to standard palettes on the monitor by calibrating and profiling it. The process of setting up a monitor is especially relevant in the case of preparing projects in digital form with their visualization in software.

15‐4: Improvement of Gradation and Color Shift in Dark Luminance Area with Signal Correction for OLED displays

In recent years, OLED displays have been widely used in smartphones, in‐vehicle displays, and so on. Such applications require a dimming function that responds to external ambient light. It is also necessary to achieve precise gradation and color reproducibility in low luminance levels in dark environments. In this paper, we address two problems of gradation collapse in low luminance levels during low luminance dimming using PWM‐ driven duty ratio control, and color shift due to current leakage between sub‐pixels. In addition, we propose a correction method for improving gradation reproducibility and color reproducibility, using luminance correction.

전면 카메라로 촬영한 얼굴 사진의 선호도 분석 - 삼성전자 Galaxy S22 Ultra와 Apple iPhone 13 ProMax를 중심으로

The use of the front camera, or the ‘selfie camera’ is increasing among the young generation. The act of taking self-photos is not only to capture the moment, but also to enhance ones’ self-esteem and even as a way of self-branding. The current camera manufacturers are aiming for high specification and high performance of the camera. However, accurate color reproduction of the camera may not correlate with high satisfaction of the users. This study focuses on the selfie camera of the two representative smartphone brands, Samsung Galaxy S22 Ultra and Apple iPhone 13 Pro Max. The study asked the participants to take selfies under four different lighting environments with three colored backgrounds using the two smartphones. Participants evaluated preference scores for each portrait on the two smartphones in the range of 7, where 1 is the least preferred and 7 for the most preferred. The results for the preference of the selfie camera showed that the average preference score was higher for Samsung Galaxy S22 Ultra than Apple iPhone 13 Pro Max by 0.44. The preference for the two displays were very similar with difference of only 0.01. For the background color, light pink and light yellow was preferred for Samsung Galaxy S22 Ultra but dark blue was preferred for Apple iPhone 13 Pro Max. Relatively dark environment with low color temperature was referred for both smartphones. The interview revealed that the users preferred Samsung Galaxy S22 Ultra for the skin color and less detailed expression for the skin texture. Users who preferred Apple iPhone 13 Pro Max liked the captured atmosphere of the photo, especially at low luminance low color temperature environment. This study places the significance on understanding how the users evaluate the photos taken by the selfie camera.

A study of spectral reflectance reconstruction using the weighted fitting algorithm based on the Sino Colour Book

AbstractThe spectral reflectance of a colour is its most essential characteristic, and it does not change with changes of equipment or light source. Therefore, the reconstruction of spectral reflectance from parameters such as colour tristimulus value and RGB has attracted the attention of researchers. To avoid the occurrence of metamerism in the colour reproduction process and to achieve the purpose of colour spectral reproduction, the spectral reflectance and the optimal parameters of the reconstruction using the weighted fitting method were discussed experimentally with the colour data measured from the Sino Colour Book as the research object. The results show that the best results are obtained when the weighted fitting parameters are weighted by the third power and eight colour samples are involved in the fitting. The reconstructed spectral reflectance obtained by the weighted fitting method has little variation and high overlap with the actual spectral reflectance obtained at each hue and lightness, thus meets the requirements of practical applications.

Effects of MDF Substrate Surface Coating Process on UV Inkjet Print Quality

The structural properties and whiteness of the substrate surface markedly effect printing quality and are closely related to the primer coating processes. Herein, four different roller coating schemes were applied on MDF surfaces to change their structural properties and color, and the whiteness, gloss, and roughness properties of the substrate surfaces were characterized for UV inkjet printing. Data analysis was conducted to explore the effects of these variables on the color reproduction, relative contrast, and printing gloss of the MDF substrates. The results showed that, according to CMYK, L*a*b* values and spectral reflectance data, the finishing of the MDF substrate with a 40 g/m2 layer of transparent primer combined with three layers of white primer at 20 g/m2 per roll coating layer had the best color reproduction effect for UV inkjet printing. Regarding the effects of relative contrast, the correlation with whiteness and glossiness was significant, while the correlation with glossiness was minor. The inkjet printing gloss value was positively correlated with substrate primer surface whiteness, while it was negatively correlated with roughness. When the surface whiteness of the substrate was relatively high, the roughness was lower and the printing effects were glossier. We sought to optimize the printing effects of all aspects of the MDF substrate by primer coating. The results of this work provide a feasible application method to improve printing quality and enhance the added value of low-quality boards, as well as to further expand the application of UV inkjet printing in the wood decoration market.

Appearance evaluation of digital materials in material jetting

Material jetting (MJT) products have a high subjective appearance quality in additive manufacturing (AM). MJT objects are typically manufactured from multiple layers of semi-transparent photo resins to achieve the desired appearance. This study explores the optical properties of photopolymer plates in monolayer and bilayer combinations. The role of the white substrate as the background plate in bilayer configurations is discussed concerning appearance reproduction in MJT parts. For this purpose, spectral reflectance, transmittance, absorbance, color difference, and texture were investigated for MJT objects with different plate combinations. The primary digital materials in MJT were further investigated for haze, gloss, scattering variations, and their corresponding bidirectional reflectance distribution functions (BRDFs). The optical properties of the studied surfaces were then applied to three-dimensional (3D) models to illustrate the variation in visual appearance and texture. According to the results, it was inevitable to use a white background plate for color reproduction. Therefore, increasing the layer thickness did not improve color fidelity. Due to the role of microfacet normals in the surface texture, gloss, haze, and scattering, results followed the same analysis pattern but depended on the measurement direction.

Dynamic selection of visible wavelengths using resonant TiO2 nanostructures

Abstract All-dielectric nanoarrays have strong electromagnetic resonances with various interesting applications and are tuned by adjusting their geometrical parameters. However, their optical properties are permanently encoded during fabrication. This study presents robust dynamically tunable all-dielectric nanoresonators for controllable, reversible, and reproducible color filtering. Our design uses an array of TiO2 nanodiscs embedded in a transparent, stretchable polydimethylsiloxane (PDMS) membrane and exhibits a narrow spectral response due to Mie magnetic and electric dipole resonances hybridized with the TiO2 nanodiscs lattice modes. By mechanically stretching the PDMS membrane, the pitch of the TiO2 nanodiscs was increased and the spectral location of the resonances was altered. Additionally, an optically asymmetric structure was fabricated by partially embedding TiO2 nanodiscs in PDMS. Thus, the magnitude of the Rayleigh anomaly diffraction, which could interrupt the dipole resonances, was reduced. Our design has sharp, frequency-tunable resonances in the visible spectrum, and we demonstrated dynamic tunability by stretching the metasurfaces.

Telemedical Support Using Smartphones for Spine Surgery in Low- and Middle-Income Countries.

Objective: Low- and middle-income countries (LMICs) face many challenges compared to industrialized nations, most notably in regard to the health care system. Patients often have to travel long distances to receive medical care with few reliable transportation mechanisms. In time-critical emergencies, this is a significant disadvantage. One specialty that is particularly affected by this is spine surgery. Within this field, traumatic injuries and acutely compressive pathologies are often time-critical. Increasing global networking capabilities through internet access offers the possibility for telemedical support in remote regions. Recently, high-performance cameras and processors became available in commercially available smartphones. Due to their wide availability and ease of use, this could provide a unique opportunity to offer telemedical support in LMICs. Methods: We conducted a feasibility study with a neurosurgical institution in east Africa. To ensure telemedical support, a commercially available smartphone was selected as the experimental hardware. Preoperatively, resolution, contrast, brightness, and color reproduction were assessed under theoretical conditions using a test chart. Intraoperatively, the image quality was assessed under different conditions. In the first step, the instrumentation table was displayed, and the mentor surgeon marked an instrument that the mentee surgeon should recognize correctly. In the next evaluation step, the surgical field was shown on film and the mentor surgeon marked an anatomical structure, and in the last evaluation step, the screen of the X-ray machine was captured, and the mentor surgeon again marked an anatomical structure. Subjective image quality was rated by two independent reviewers using the similar modified Likert scale as before on a scale of 1-5, with 1 indicating inadequate quality and 5 indicating excellent quality. Results: The image quality during the video calls was rated as sufficient overall. When evaluating the test charts, a quality of 97% ± 5 on average was found for the chart with the white background and a quality of 84% ± 5 on average for the chart with the black background. The color reproduction, the contrast, and the reproduction of brightness were rated excellent. Intraoperatively, the visualization of the instrument table was also rated excellent. Visualization of the operative site was rated 1.5 ± 0.5 on average and it was not possible to recognize relevant anatomical structures with the required confidence for surgical procedures. Image quality of the X-ray screen was rated 1.5 ± 0.9 on average. Conclusion: Current generation smartphones have high imaging performance, high computing power, and excellent connectivity. However, relevant anatomical structures during spine surgery procedures and on the X-ray screen in the operating room could not be identified with reliability to provide adequate surgical support. Nevertheless, our study showed the potential in smartphones supporting surgical procedures in LMICs, which could be helpful in other surgical fields.

The Lacune of Teleneurology: Autochromatic Correction of Jaundice (P1-4.004)

<h3>Objective:</h3> To demonstrate the lack of detection of jaundice as a pitfall to teleneurology. <h3>Background:</h3> In the midst of the COVID-19 epidemic, neurology telemedicine has flourished (Patel, 2021). However, the efficacy of a physician’s diagnostic ability to detect jaundice using telemedicine technology has not been formally assessed. A patient with carotenoid-induced jaundice, easily observable in person, but absent via telemedicine, has not heretofore been described. <h3>Design/Methods:</h3> <h3>Case Study:</h3> This 66-year-old left-handed (pathological) white male without exposure history, presented with persistent headaches after head trauma. He was taking food a supplement including, a supplement composed of the carotenoid, lutein. <h3>Results:</h3> Abnormalities on physical examination via telemedicine: General: Orofacial lingual dyskinesia. Motor Examination: Drift testing: Right pronator drift. Gait examination: unstable tandem gait. Repeat follow-up visits via telemedicine on a bi-monthly basis for two years revealed similar findings. In-person examination two years after initial presentation revealed prominent jaundice particularly involving creases of the hands and the frenulum, but not the conjunctiva, but otherwise unchanged from prior examinations. Blood and urine evaluations for origins of jaundice were normal. <h3>Conclusions:</h3> This pattern of jaundice was classic for hypercarotenemia (Vakil, 1985). Whereas in hyperbilirubinemia, the jaundice is greatest in the conjunctiva and less so in the skin. On FaceTime, auto-correction of facial image distorts color, reducing yellow chromatic frequencies such that even gross jaundice will appear absent. Such has been reported associated with telemedicine visits with jaundice due to severe hepatitis (Baillie, 2022). Elements of autocorrect from a smartphone-based photo analysis using other technology for natural reproduction of skin color may eliminate such errors (Patricoski, 2009; Clarke, 2008; Ohya, 1998; Mazzu-Nascimento, 2021). Until such time as advanced technology becomes available, even in the absence of visual jaundice in telemedicine, or presence of diseases which cause jaundice or clinical suspicion of jaundice warrants in-person visitation. <b>Disclosure:</b> Dr. Shahzadi has nothing to disclose. Miss Brar has nothing to disclose. Dr. Hirsch has nothing to disclose.

Optical Design and Simulation of Snapshot Hyperspectral Dental Imaging Spectrometer with One-Dimensional Random Coding

To achieve perfect teeth color reproduction, we propose the design of a snapshot hyperspectral imaging spectrometer that can accurately measure the teeth spectrum. In this paper, the optical system of a snapshot hyperspectral dental imaging spectrometer is designed. In particular, to encode images in both the spatial and spectral dimensions, a one-dimensional random coding mask rotated 45 degrees around the optical axis is used. The system has a spectral resolution of approximately 2.2∼10 nm in the 450∼700 nm spectral range, and the total length of the system is less than 150 mm. The whole design can be used as a miniaturized handheld instrument. To verify the feasibility of whiteness measuring, a simulation experiment is carried out. The target spectral information is reconstructed through the reconstruction algorithm. The simulation result shows that spectral imaging has the potential to improve the accuracy and precision of teeth whiteness measurements.

Comparative Analysis of Color Simulation between Offset Printing and Inkjet Printing

This paper presents an analysis of the color output capability and accuracy of an inkjet printer, specifically the Epson L1800, used for simulating offset printing. The colorimetric values of the printer's cyan, magenta, yellow, and black primaries were found to be different from those used in offset printing, and attempts to adjust the maximal output ink level and tone curve were not able to fully eliminate the differences. As a result, the Epson printer's color gamut did not completely meet the requirements of offset printing, particularly in terms of high-chroma colors. However, the printer calibration process improved the printer's capacity and overall color output accuracy within the offset color gamut, with significant color differences only occurring for colors outside the printer's gamut. This study provides insights into the challenges and limitations of using an inkjet printer for simulating offset printing and highlights the importance of printer calibration for achieving accurate color reproduction in this context. Further research may focus on developing more advanced calibration methods or exploring alternative printer technologies to improve the accuracy of offset printing simulation using inkjet printers.

Determination of the effect of noise on the image using software

In this paper, we study the influence of noise on images of different colors and determine the difference in the level of these influences. Values characterizing the signal-to-noise ratio in decibels are obtained. The comparison of the values obtained as a result of modeling with the values of mathematical calculations is made. The results of the work present the data learned empirically. Thanks to the use of software, a unique structure that was achieved as a result of its own writing, it was possible to carry out a number of simulations and obtain several groups of values. Computer colorimetry can rightly be called digital colorimetry. This article is intended for senior students of universities, graduate students and professionals working in the field of color reproduction, image processing, color measurements and other areas related to color perception.

Ultra-small Stokes shift induced thermal robust efficient blue-emitting alkaline phosphate phosphors for LWUV WLEDs

High power phosphor converted light emitting diodes (pc-LED) are thought to be the next generation technology for lighting and high-tech electronics applications. To achieve optimal luminous efficiency, maximal color gamut and stable color reproducibility, the discovery of high efficient phosphor materials with suitable excitation matching, narrow band emission and robust thermal stability is essential. Herein, we design and construct a new family of alkaline phosphate phosphors ANa3Mg7(PO4)6:Eu2+ (ANMP:Eu2+, A = K, Rb and Cs) with rigid diamond-like chain structure. The results indicates that ANMP:Eu2+(A = K, Rb and Cs) phosphors exhibit ultra-small Stokes shift and efficient blue emission (λmax = 444–465 nm) with high internal quantum efficiency (IQE = 83.2%, 90.6% and 93.4% for A = K, Rb and Cs), narrow full width at half maximum (FWHM∼50 nm) and low thermal quenching (87.5%, 96.5% and 84.2%@140 °C for A = K, Rb and Cs), which demonstrate to have higher colorful purity, wider color gamut and better wavelength applicability for using in long-wavelength near ultraviolet (LWUV) LEDs, compared with the traditional commercially available blue phosphor BaMgAl10O17:Eu2+ (BAM:Eu2+). The Eu2+ site preferences and thermal quenching mechanism are studied in detail. Moreover, the in situ temperature dependent Raman spectra and density function theory (DFT) are employed to get better comprehensions of the relationship between crystal-electronic structures and luminescent properties from experiment and calculation, which will provide a good guidance for develop new phosphors with high QE and excellent thermal stability. Finally, utilizing the title phosphors, white LED lamps are fabricated with high color rendering index and an appropriate correlated color temperature. Therefore, all the results demonstrate that the blue-emitting phosphor ANMP:Eu2+ (A = Cs, K, Rb) has great potential for applications in high power LWUV pumped pc-LEDs.

Developing a Quality Evaluation System for Color Reproduction of Color 3D Printing Based on MATLAB Multi-Metrics.

Color 3D printing has been widely used in many fields such as cultural, medical, industrial, and food. The color reproduction accuracy of 3D printed products in these fields is becoming increasingly demanding, which requires more reproduction methods and practical tools. At present, most color 3D printing devices use one quantitative index, that is, color difference, to directly predict the color reproduction quality. However, this single quantitative index is not optimal for the curved surface of 3D printed color objects. Based on color evaluation principles, in this study, five new quantitative metrics consisting of color gamut comparison index, color SSIM index, color FSIM index, iCID index, and subjective scaling values are proposed for comparison, and the corresponding GUI design and code implementation of new color quality evaluation system are performed by MATLAB. Moreover, the comprehensive color assessment of color 3D printed products is confirmed by utilizing standard image acquisition and microscopic imaging methods that are not limited to printing materials and sampling locations. The operation of this system is validated to provide interactivity, simplicity and high efficiency. As a result, the system can provide new valuable feedback for color separation and output calibration of color 3D printing devices.

Short wet-steaming low-carbon cleaner pad dyeing of cotton/polyamide/lyocell fabric with reactive dyes

Cotton/polyamide/lyocell three-component fabrics are usually dyed by the traditional dip dyeing technology with two kinds of dyes, which has the disadvantages of long process, high energy consumption and high cost. In this research, the short process cleaner pad dyeing technology for cotton/polyamide/lyocell fabric was developed. The optimal dyeing conditions were that the pH value of initial dye solution was 3–4, the reactive red 195 dye concentration was 10 g/L in the preliminary dye bath, the concentration of NaOH and Na2CO3 were 10 g/L in the alkaline fixing solution, and the steaming time of acid solution and alkali solution was 4 mins. The dyeing effects and fixation rate indicated that short wet-steaming technology was the optimum method. The developed short wet-steaming low-carbon cleaner pad dyeing technology of cotton/polyamide/lyocell fabric not only ensured the color yield, reproducibility, dyeing uniformity and permeability, but also saved dyes and chemicals, shortened dyeing time by 17.4 %, reduced power and heat consumption by 27.1 % and 15.1 %, and decreased carbon emission by 24.6 % compared with traditional dyeing. The K/S values of the dyed samples by short wet-steaming pad dyeing technique indicated that bifunctional reactive dyes with monochlorotriazine and vinyl sulfone sulfate groups (M-type) were superior to the other three kinds of reactive dyes. In the era of low-carbon economy, short wet-steaming low-carbon cleaner pad dyeing of cotton/polyamide/lyocell fabric with reactive dyes is an advanced short process dyeing technology worth of promotion for dyeing a variety of industrial crops and products.