Gamut Volume Research Articles

The influence of raw material changes on gamut colour volume of a matt ceramic glaze

This study aims to investigate the relationship between digital printing colour performance and the raw materials used in a matt glaze. Inkjet technology has enhanced the decorative properties of ceramic tiles in production. Improving the colour perception of the glaze is possible by optimizing the raw materials in the glaze, which results in less ink usage and thus lower costs. Investigation of the colour performance of glazes is possible by determining the L* a* b* values of the colours as well as the gamut colour volumes. Colour of the samples were evaluated by spectrophotometer and i1 profiler. Gamut volume was calculated by 3D CIE chromaticity diagrams of ICC profiles. It was observed that the colour saturation was higher in the samples where the pigment was homogeneously distributed in the glaze microstructure. SiO2 particles not embedded in the glass structure observed in the glaze microstructure disrupt the colour intensity. The low sphere temperature value of the composition made with wollastonite enabled the SiO2 particles to be embedded in the glaze. When wollastonite was used instead of dolomite as the source of calcium oxide in mat glaze, the colour gamut volume reached its highest value (11262), consequently increasing colour saturation. Conversely, the lowest colour gamut volume (6475) was obtained when dolomite was used instead of wollastonite.

8‐1: Riemannian Color Difference Metric

We developed a new Riemannian color difference metric based on Friele's line element and the results of psychophysical color discrimination experiments. Visual adaptation effects are incorporated into the model. This new color difference metric was validated against various data sets available in the literature. We found adequate agreement with experimentally determined threshold ellipsoids/ellipses and a better threshold predictability compared with other color difference metrics. The new Riemannian color difference metric was applied for the calculation of the color gamut volume and the maximum number of mutually discernible colors.

Starch‐based nanoparticles as a replacement for synthetic latex: A comprehensive assessment of printability and colorimetric characteristics

AbstractThe papermaking, packaging, and printing industry are actively seeking sustainable material alternatives to address growing concerns about environmental consciousness and finite resources. Synthetic latex, a frequently utilized binder in paper coating formulations, present difficulties due to their dependence on fossil fuel resources and their reduced recyclability in comparison to eco‐friendly sustainable products. In this study, synthetic latex was replaced with a starch‐based nanoparticle (starch NP) binder at a 1:1 ratio in a coating formulation. Printing trials to assess colorimetric characteristics was made using electrophotography (EP) printing, given the current upward trajectory and expansion of EP technology into the label, packaging, and folding carton sectors. The in‐depth investigations reveal that incorporating starch NP binder result in improved optical, color, and dot characteristics. Moreover, it maintains consistent and comparable coefficients of friction. Partial replacement of synthetic latex with the starch NP binder yields significant enhancements in surface roughness and text quality. Importantly, the starch NP binder not only improves the dielectric relaxation properties of the paper and enhances toner transfer but also accelerates the distribution of the electrical field compared to synthetic latex, optimizing toner transfer and thereby enhancing color gamut volume. The study demonstrates that employing the starch NP binder leads to substantial improvements in colorimetric performance without any drawbacks in EP printing, making it highly advantageous to replace 50% of the synthetic binder.

Colour gamut analysis of low‐cost dye‐sensitised solar cells using natural dyes

AbstractDue to the increasing effects of greenhouse gases and environmental pollution, the need for new clean energies like solar energy attracts much attention. Although the characteristics and the efficiency of green photovoltaic devices have been researched, the colour gamut achievable from those devices has not been studied. This study investigates the colour gamut of low‐cost dye‐sensitised solar cells (DSSCs). To do this, 14 natural dye extracts were obtained from herbal resources including dragon fruit, blueberry, mango, radish, yellow rose, red cabbage, sour pomegranate, beetroot, olive, green cabbage pepper, eggplant, parsley, bramble and cherry, and employed as photosensitiser in solar cells. Then, the colorimetric attributes of the photosensitisers were studied in three‐dimensional (3D)‐colour space, that is, CIELab, CIELCH and CIE1931 chromaticity diagram. Additionally, the convex hull method was employed to determine the colour gamut boundary and the corresponding colour gamut volume. Results showed that the majority of samples benefited from approximately 3°–82° of hue angle in a*b* diagram of CIELab colour space and showed the yellowish to reddish tint effects. In CIELCH colour order system, cherry and parsley showed the lowest and highest lightness attributes while the chroma property of samples varied from minimum 1.2 for eggplant to maximum 60.2 for the dragon fruit. Moreover, the results of using the convex hull method showed the volume of 7.73 × 104 that is bounded by the colour gamut of 3D colour points over the CIELab colour space.

Addition of fibers derived from paper mill sludge in paper coatings: impact on microstructure, surface and optical properties

Traditionally, cellulose nanofiber (CNF) production has primarily relied on virgin cellulose sources. Yet, the shift to using paper mill sludge (PMS) as a source for CNF underscores the significance of reusing and recycling industrial byproducts. PMS contains significant amounts of cellulose that can be extracted as a raw material. The purpose of present study is to provide a sustainable approach to PMS utilization as a paper coating additive in the cellulose nanofibrils (CNFPMS) form via simply scalable wire-wound rod coating method. The effect of CNFPMS additive amounts at two coating layers on microstructure and surface properties of coatings such as porosity, air permeability surface roughness and optical properties such as brightness, gloss and CIE L*a*b* is studied, which they can also provide insight for the eventual print performance. Results indicated that the obtained CNFPMS in paper coating shows 52% decrease in porosity, presenting significant improvement in the coating microstructure. The marginal increase in permeability coefficient and surface roughness, 54% and 10%, respectively, suggests improving color reproduction and preventing color density losses. Optical analysis showed slight decrease in brightness and gloss, as was expected. Notably, the lightness was improved, which also indicates increasing color gamut volume in printing applications. As a result, the current work offers a sustainable approach to manage PMS for use in paper coatings as a high-value-added material.

Color gamut volume and the maximum number of mutually discernible colors based on a Riemannian metric.

For the calculation of the color gamut volume and the maximum number of mutually discernible colors, an algorithm based on a Riemannian metric and the densest packing of spheres is proposed. With this algorithm, the color gamut volume was calculated for the conditions of experiments reported in literature. Good agreement was found with the experimental findings of the color gamut volume as a function of the peak luminance. Using the new algorithm, the color gamut volume and the maximum number of mutually discernible colors was calculated for various sets of primary colors corresponding to display standards and various dynamic ranges. Comparisons were made with state-of-the-art methods which are based on the Euclidean metric in approximately uniform color spaces and a simple cubic lattice. It was found that the state-of-the-art methods underestimate the maximum number of mutually discernible colors. However, the relative differences decrease as the primary colors are more saturated. Based on the new algorithm the maximum number of mutually discernible colors was calculated for a range of peak retinal illuminance levels and various sets of primary colors. We found that, for a given set of primary colors, the maximum number of mutually discernible colors is proportional to the logarithm of the ratio of the peak retinal illuminance level and a fitting parameter.

Research on the color gamut volume and light efficiency in four-primary laser display systems.

The color gamut volume (CGV) and light efficiency of a four-primary display system were theoretically simulated with different wavelength configuration. Given the wavelengths of the blue and red primaries, we optimized the other two primary colors; the wavelength set with the largest CGV was chosen. The maximum CGV, 2.346 × 106, was obtained at (660, 530, 507, 465) nm. The maximum light efficiency was also determined. A trade-off between CGV and light efficiency should be made according to the requirement of the devices. This study provides guidance for the construction of a four-primary laser display system and the optimization of the CGV in multi-primary display systems.

Potential application of a green fiber laser in laser display systems.

This study explores the application of optical fiber lasers in display systems by integrating a P r3+-doped green all-fiber laser into a laser projection display system. As a control group to compare the results, a 520nm semiconductor green laser diode module was integrated, similar to the experimental group. The color gamut and speckle performances were studied and compared. The results showed that the experimental group performed slightly better in the color gamut volume. The speckle contrast decreased rapidly in the experimental group when power increased. To our knowledge, this is the first study to apply a fiber laser to a laser display system. The results shed light on developing laser display systems with fewer or no speckle reduction elements.

Comparative Colour Gamut Analysis Of Piezoelectric Inkjet (PIJ) And Sheet-Fed Offset Prinitng Technologies

This paper presents a comprehensive comparative analysis of the colour gamut achieved by Piezoelectric Inkjet (PIJ) and Sheet-Fed Offset printing technologies. The colour gamut, a crucial aspect of print quality, is a measure of the range of colours a printing process can reproduce. Both PIJ and Sheet-Fed Offset printing are widely employed in various industries, including graphic arts and commercial printing. The research methodology involves the characterization of the colour gamut of PIJ and Sheet-Fed Offset printing through empirical experiments and spectral measurements. A diverse set of colour targets is used to assess the gamut volume, including standard colorimetric tests such as colour gamut volume measurements. The study also considers factors such as substrate type, ink formulations, and printing conditions to provide a comprehensive understanding of the gamut limitations and advantages of each technology. Results reveal the strengths and weaknesses of both printing methods in terms of colour reproduction, highlighting areas where one technology may outperform the other. Insights gained from this comparative analysis can inform decision-making processes for print industry professionals, helping them choose the most suitable printing technology based on specific project requirements and desired colour outcomes. Ultimately, this research contributes valuable knowledge to the ongoing discourse on print technology selection, aiding in the optimization of colour reproduction processes for diverse applications ranging from high-quality graphics to commercial printing.

Evaluation of gamut enhancement in yellow regions and a choice of optimal wavelength for a RGBY four-primary laser display system.

To improve the color rendering ability in yellow color regions, the inclusion of yellow among the primary colors is commonly proposed. In this study, an algorithm for evaluating gamut enhancement in yellow regions is developed. The performance of different wavelength sets of RGBY four-primary system is studied theoretically in terms of various aspects, including the color gamut volume, gamut coverages, and gamut enhancement ratio in yellow regions. The optimal wavelength set and its optimal luminance ratio are then determined. This research provides strong guidance for the construction of practical four-primary-laser display systems.

Upper limit of gamut volumes in multi-primary display systems.

Based on the difference between multi-primary displays (MPDs) and three-primary displays, we propose a new definition for evaluating the color gamut volume (CGV) to explore the upper limit of MPDs, which could theoretically represent all colors that MPDs can display. The proposed definition corrects the defects in the L*a*b* color space that arise when calculating the CGV of MPDs. In view of the high computational complexity of this method, we propose a simplified scheme with a small margin of error. Additionally, we verify the new definition with experiments on a six-primary projector. This method is helpful in guiding the selection of light sources and the evaluation of MPDs, and also has great reference value to calculate the target gamut for gamut mapping in MPDs.

Perceived Color Gamut in Images: From Boundary to Difference.

A larger display color gamut volume (CGV) is expected to produce higher perceived brightness and colorfulness of the images displayed. However, display control algorithms such as gamut mapping and color conversion need to be carefully controlled to fully take advantage of the higher luminance and more saturated display primaries. Using RGBW displays (RGB plus a white channel) as a special case in contrast to RGB displays, it is demonstrated that a larger RGB display gamut enclosed by the boundary did not guarantee a larger color gamut perceived in images. Five gamuts with different white channel contributions were simulated, and seven different image contents were curated and rendered on each display. Using a paired comparison experiment with 33 observers, the perceived scales of color gamut as perceived brightness and colorfulness were derived. The results show more correlation with the image-wise than display-wise CGV and can be explained with image color differences. Our findings highlight the importance of considering image contents when optimizing display gamut volume, which can be guided by such image-wise analysis.

23‐1: Invited Paper: Visualization of Color‐Gamut Coverage‐Gamut Ring Intersection

The D50 CIELAB gamut volume was standardized as a suitable and unified gamut size measurement methodology. The color gamut volume is visualized using proportionate gamut rings in a two‐dimensional diagram. Gamut ring intersection assists the visual comparison of the size and shape of the color gamut coverage between a display and a reference. This paper introduces a desktop application with an intuitive graphical interface for visualizing the gamut rings and describes the algorithm of the gamut ring intersection.

39‐1: Distinguished Paper: Gamut Rings of Reflective ePaper Displays with Combined Frontlight and Ambient Illumination

Gamut Rings visualize CIELAB gamut volumes of color ePaper in ambient light. Integrated frontlights provide illumination in darkness and compensate ambient light reflection loss. CIELAB requires a different reference white for self‐luminant and reflective display modes. Color interpolation based on additivity assumption will give erroneous gamut volumes of color ePaper.

Impact of color temperature on the color gamut volume of a six-primary-laser display system

ObjectiveColor temperature (CT) is closely related to the color gamut of a display system. It is important to investigate how the color gamut volume and gamut coverage vary with the CT. MethodsThe effects of the CT on gamut volume and coverage in a six-primary-laser display system (in which color was achieved through a fixed mixture of two sets of three-primary) were investigated, both theoretically and experimentally. ResultsThe results indicated that the gamut volume increased rapidly from 64.19% to 139.99% Rec. 2020 when the CT increased from 2000 K to 12,500 K and then increased gradually to 142.4% at 20,000 K. The gamut coverage first increased to the maximum at 5000 K and then decreased. At 5000 K, the gamut volume was moderate, but the gamut coverage was the highest. Between 10,000 and 12,500 K, the gamut volume increased significantly, and the gamut coverage remained relatively high. At 20,000 K, the gamut volume was the largest, whereas the gamut coverage was relatively low. Accordingly, in the six-primary-laser display system, from the perspectives of improved gamut coverage and color management, D50 could be a safer recommendation; for better rendering ability, the CTs between 10,000 K and 12,500 K could be adopted.

Gamut rings of reflective ePaper displays with combined frontlight and ambient illumination

AbstractGamut rings are two‐dimensional representations of three‐dimensional CIELAB color gamut volumes. Recently developed for visualizing gamut volumes of self‐luminant (emissive) displays in darkroom conditions, they can also be applied to reflective displays with integrated frontlighting. Frontlights provide illumination in low light conditions and also compensate for optical losses when reflecting ambient light. Since the frontlight is essentially fixed compared to the ambient illumination, this mode of operation is effectively “emissive.” Perceived CIELAB colors of reflective displays with frontlights can thus be treated as superposition of the spectral radiance from the “emissive” contribution and the reflected spectral radiance from ambient illumination. The CIELAB calculation will depend on whether the “emissive” or reflective mode is dominant for a given ambient illumination. CIELAB gamut ring diagrams of electrophoretic color ePaper were determined from laboratory measurements of the displays' “emissive” and reflective spectral characteristics, combined with specifications of realistic ambient indoor and outdoor viewing environments. Gamut ring diagrams demonstrate the benefit of color pigments instead of color filter arrays in both self‐luminant and reflective display modes. Interpolation of envelope colors from display primaries, commonly used in emissive displays, underestimate gamut volumes of color ePaper because reflective display primaries are not additive but subtractive.

General solution to the calculation of peak luminance of primaries in multi-primary display systems.

For a display system, a wide-color gamut can significantly improve the viewing experience. It is known that an ultra-wide color gamut can be achieved using more primaries. However, for multi-primary displays (MPDs), choosing the parameters of the primaries (e.g., wavelength and luminance) is not trivial because the necessary theoretical foundation is still lacking. In this study, starting from three-primary display, we proposed a method for calculating all possible peak luminances of MPDs. This is done by mathematically representing the added new primaries with the original three primaries. Of all the possible results, by optimizing the peak luminance of each primary color, the theoretical gamut volume satisfying specific requirements could be obtained. The method provided can be extended to N primaries (N > 6). Using this method, we have successfully built a six-primary display system and used it to verify the validity of the method. Combined with the calculation of color gamut volume, the theoretical framework provided can be used to guide the selection of wavelength, spectrum width, and luminances of primaries in MPDs.

Six-primary-laser projection display system: demonstration and stereo color gamut measurement

The mainstream light sources of display systems currently include LEDs, OLEDs, micro-LEDs, and lasers, primarily based on the three primary color systems with different color rendering abilities. A narrow-spectrum light source, such as laser, is typically used to enlarge the color gamut of a display system. Another approach is to add more primaries. In this regard, we develop a six-primary-laser projection display system compatible with 2D and 3D display, with wavelengths of 445 nm, 465 nm, 520 nm, 550 nm, 638 nm and 660 nm. We propose a simple, fast method to determine the luminance of each primary laser, by which the gamut volume can be calculated. We also propose a gamut measurement method for the six-primary-laser display system, describe the gamut boundary, and measure the gamut volume. The calculated maximum color gamut of the proposed system is 2347400, corresponding to 184.49% NTSC, while the measured color gamut is 2269900, corresponding to 178.4% NTSC. These results are in good agreement with the theoretical calculations, indicating the accuracy of the proposed analytical and experimental methods. Moreover, the time-multiplexed stereoscopic display technology and the spectral separation method would allow the development of a remarkable three-dimensional visual experience with high light efficiency and low crosstalk in full-field of view.

Seeking a paper for digital printing with maximum gamut volume: a lesson from artificial intelligence

Seeking a paper for digital printing with maximum gamut volume: a lesson from artificial intelligence

Synergetic effect of cationic starch (ether/ester) and Pluronics for improving inkjet printing quality of office papers

Improving the printability of paper is still a relevant challenge, despite the fast development of digital communications. While it is well-known that cationic starches enhance ink density, their commercial paper-grade forms are limited to ethers with low degree of substitution. This work addresses the underexplored potential of highly substituted cationic starch for paper coating and its combination with tri-block polymers, namely Pluronics (P123 and F127), taking advantage of their supramolecular interactions with amylose chains. For that purpose, cationic starch ether and ester (starch betainate), both with a degree of substitution of 0.3, were synthesized by alkaline etherification and by transesterification, respectively. Paper without any surface treatment was subjected to one-side bar coating with suspensions encompassing those products and Pluronics, besides other common components. Black, cyan, yellow and magenta inks were printed on all coated papers through an inkjet printer. Key properties of printing quality such as the gamut area, gamut volume, optical density, print-through, inter-color bleed and circularity were measured in a controlled temperature-humidity environment. For instance, a formulation with cationic starch (ether/ester) and P123 improved the gamut area by 16–18% in comparison to native starch-coated paper sheets. Interestingly, the individual assessment of each component showed that cationic starch ether, starch betainate and P123 only improved the gamut area by 5.6%, 8.9% and 6.8%, respectively. Finally, but not less importantly, starch betainate was found to quench optical brightening agents to a lesser extent than cationic starch ethers.