Subtractive Color Mixing Research Articles

Multicolor-tunable biomass thermochromic dyes utilizing tea polyphenols color developer for temperature-controlled linen fabric

Linen, an important industrial crop, is commonly used in the textile field. The development of temperature-controlled linen fabrics is important for the high-value utilization of cellulose-based industrial products. The linen fabrics with color and performance changes controlled by temperature are prepared via the vacuum impregnation process utilizing biomass three-component thermochromic dyes. Currently, three-component thermochromic dyes based on the bisphenol A (BPA) color developer have received special attention due to high saturation color and reversible color-changing performance. However, the toxicity and carcinogenicity of BPA limit its applications in security inks, decorative coatings, plastics, etc. Exploiting excellent and safe biomass color developers for three-component thermochromic dyes remains a challenge. Tea polyphenols (TP) are proposed as alternatives to BPA to prepare the blue, red, yellow, and green three-component thermochromic dyes. According to the laws of subtractive color mixing, multicolor-tunable thermochromic dyes are obtained by color matching of red, yellow, and blue dyes to span multiple shades. Biomass thermochromic dyes are adopted to fabricate temperature-controlled linen fabrics by the vacuum impregnation process. Temperature-controlled linen fabrics can change color reversibly between the original color and achromatic color. The color-changing occurs due to the ring opening and closing of leuco dyes triggered by the solid-to-liquid transition of solvent. The phase transition temperature of the thermochromic dyes absorbed on the linen fabric is 46 ℃. As the temperature increases, the contact angle of temperature-controlled linen fabrics decreases from 129° to 29°, resulting in a change from hydrophobic to hydrophilic with 49 J g−1 of thermal energy stored. The linen fabrics exhibit temperature-controlled changes in color, surface wettability, strength, and thermal insulation. This eco-friendly method with biomass thermochromic dyes for the preparation of color-changing linen fabrics provides a new approach, which is contributing to the development of cellulose-based smart color-changing textiles.

Butterfly blues and greens caused by subtractive colour mixing of carotenoids and bile pigments

Butterflies often have conspicuously patterned wings, due to pigmentary and/or structurally wing scales that cover the wing membrane. The wing membrane of several butterfly species is also pigmentary coloured, notably by the bile pigments pterobilin, pharcobilin and sarpedobilin. The absorption spectra of the bilins have bands in the ultraviolet and red wavelength range, resulting in blue-cyan colours. Here, a survey of papilionoid and nymphalid butterflies reveals that several species with wings containing bile pigments combine them with carotenoids and other short-wavelength absorbing pigments, e.g., papiliochrome II, ommochromes and flavonoids, which creates green-coloured patterns. Various uncharacterized, long-wavelength absorbing wing pigments were encountered, particularly in heliconiines. The wings thus exhibit quite variable reflectance spectra, extending the enormous pigmentary and structural colouration richness of butterflies.

Subtractive colour mixing with bile pigments creates the rich wing palette of Graphium weiskei butterflies.

The wings of the purple spotted swallowtail Graphium weiskei are marked by an unusual bright colour pattern. Spectrophotometry on G. weiskei wings demonstrated the presence of a pigment with an absorption spectrum (peak wavelength λmax=676 nm) similar to that of the bile pigment sarpedobilin in the wings of the congeneric Graphium sarpedon (λmax=672 nm). Sarpedobilin alone causes cyan-blue wing areas, but the green-coloured areas of G. sarpedon wings result from subtractive colour mixing with the carotenoid lutein. Reflectance spectra of the blue-coloured areas of G. weiskei wings indicate that sarpedobilin is mixed with the short-wavelength-absorbing papiliochrome II. An enigmatic pigment, tentatively called weiskeipigment (λmax=580 nm), enhances the saturation of the blue colour. Weiskeipigment causes a purple colour in areas where the sarpedobilin concentration is low. The wings of the related papilionid Papilio phorcas contain the bile pigment pharcobilin (λmax=604 nm), as well as another sarpedobilin (λmax=663 nm). The cyan to greenish wings of P. phorcas are due to phorcabilin and sarpedobilin mixed with papiliochrome II. A survey of known subspecies of G. weiskei as well as of congeneric Graphium species of the 'weiskei' group shows various degrees of subtractive colour mixing of bilins and short-wavelength absorbers (carotenoids and/or papiliochromes) in their wings. This study illuminates the underestimated role of bile pigments in butterfly wing colouration.

Fabrication of a Human Skin Mockup with a Multilayered Concentration Map of Pigment Components Using a UV Printer.

In this paper, we propose a pipeline that reproduces human skin mockups using a UV printer by obtaining the spatial concentration map of pigments from an RGB image of human skin. The pigment concentration distributions were obtained by a separating method of skin pigment components with independent component analysis from the skin image. This method can extract the concentration of melanin and hemoglobin components, which are the main pigments that make up skin tone. Based on this concentration, we developed a procedure to reproduce a skin mockup with a multi-layered structure that is determined by mapping the absorbance of melanin and hemoglobin to CMYK (Cyan, Magenta, Yellow, Black) subtractive color mixing. In our proposed method, the multi-layered structure with different pigments in each layer contributes greatly to the accurate reproduction of skin tones. We use a UV printer because the printer is capable of layered fabrication by using UV-curable inks. As the result, subjective evaluation showed that the artificial skin reproduced by our method has a more skin-like appearance than that produced using conventional printing.

Colorless to black electrochromic devices using subtractive color mixing of two electrochromes: A conjugated polymer with a small organic molecule

Abstract Herein, we present a facile method for color-tuning an electrochromic device that switched between two neutral colors through simple color mixing of a conjugated polymer, poly(2,2-dimethyl-3,4-propylenedioxythiophene) and an electrochromic small molecule aromatic diester, diethyl-4,4′-biphenyldicarboxylate. The resulting device had a photopic contrast of ca. 57% across the visible spectrum. In addition, the device exhibited color uniformity and stability over 2,000 switches. Using these mixed coloring materials, a large area electrochromic device of 140 cm2 was fabricated, exceeding the size of ophthalmic lenses and small displays.

The role of gamut, intuition and engagement in colour management in a design context

AbstractColour management is ubiquitous in the digital world. However, despite the many advances in colour management over the last couple of decades, it remains an imperfect process. In the art and design community there is often a level of dissatisfaction and deep cynicism about colour management that can lead to lac of engagement with the process. This research explores colour management in a design context though three issues: the gamut issue, the intuitive issue and the engagement issue; each relates to areas where colour management could better connect with tacit design knowhow. The work focusses on the selection of colour in a digital context since for many users this is the first touch point that they have with colour management. Psychophysical studies have been carried out in both laboratory and design‐studio settings. It is shown that users can better predict the results from subtractive colour mixing than from additive colour mixing. The performance of various types of colour picker are explored and consequences for the design of user interfaces are discussed.

The Color Top and the Distinction Between Additive and Subtractive Color Mixing [Historical Corner

This article provides a brief overview of the history of the color top as a research instrument. Specific focus is given to James Clerk Maxwell's experiments, which allowed him to obtain the first colorimetric equations using this simple device, and to Hermann von Helmholtz's use of the top to exhibit, in a very simple and clear manner, the difference between additive and subtractive color mixture.

Sensing the Frictional State of a Robotic Skin via Subtractive Color Mixing

The perception of surface properties such as shape and slipperiness is crucial to ensure that the hand-held object is stable. Without touch, precise manipulation becomes difficult. Some robotic tactile sensors use cameras that observe the elastic deformation of a membrane to detect edges or slippage of the contact. The perception of the contact state drove innovative control strategies. However, previous methods on these lines do not include quantitative means of measuring the three-dimensional (3-D) deformation of the skin or suffer from a lack of spatial resolution. Here, we present a tactile sensor based on a subtractive color mixing process designed to track the 3-D displacement of an array of markers, using the information delivered by the color channel of off-the-shelf cameras. The distributed shear and normal deformation can be assessed from the spectrum of the light reflected and refracted by an array of diffusive and transmissive markers placed on two superimposed layers. The markers show various blends of colors, depending on the displacement at the surface. The color pattern of each marker can be tracked with little computation and remains robust to external lighting. The ability to sense the 3-D deformation field can improve robotic perception of frictional properties that have applications in the fields of robotic control and human-robot interactions.

Subtractive color mixing educational tool using multiple CMY cubes

Subtractive color mixing educational tool using multiple CMY cubes

<italic>Interactive RGB Transparency</italic>: a color rendering tool for superimposed translucent layers in digital images

Interactive RGB Transparency is an open source tool dedicated to the visualization of transparency effects in digital color images. Transparency effect can be rendered as a binary color mixing between foreground and background layers, which can be uniformly colored layers or downloaded images, while the transparency rate can be modified interactively from perfectly transparent to perfectly opaque. The tool also allows the inverse operation, by removing transparency effects in an image. While most common softwares render transparency effects by additive color mixing (eventually subtractive color mixing), Interactive RGB Transparency proposes three different approaches: i) defining new color mixing laws varying continuously from additive to subtractive color mixing, ii) defining color mixing as a generalized average between the colors of the layers, iii) considering a translucent scattering layer whose thickness can be modified.

Reciprocal peer assessment as a learning tool for secondary school students in modeling-based learning

The aim of this study was to investigate how reciprocal peer assessment in modeling-based learning can serve as a learning tool for secondary school learners in a physics course. The participants were 22 upper secondary school students from a gymnasium in Switzerland. They were asked to model additive and subtractive color mixing in groups of two, after having completed hands-on experiments in the laboratory. Then, they submitted their models and anonymously assessed the model of another peer group. The students were given a four-point rating scale with pre-specified assessment criteria, while enacting the peer-assessor role. After implementation of the peer assessment, students, as peer assessees, were allowed to revise their models. They were also asked to complete a short questionnaire, reflecting on their revisions. Data were collected by (i) peer-feedback reports, (ii) students’ initial and revised models, (iii) post-instructional interviews with students, and (iv) students’ responses to open-ended questions. The data were analyzed qualitatively and then quantitatively. The results revealed that, after enactment of the peer assessment, students’ revisions of their models reflected a higher level of attainment toward their model-construction practices and a better conceptual understanding of additive and subtractive color mixing. The findings of this study suggest that reciprocal peer assessment, in which students experience both the role of assessor and assessee, facilitates students’ learning in science. Based on our findings, further research directions are suggested with respect to novel approaches to peer assessment for developing students’ modeling competence in science learning.

(Invited) Conjugated Polymers in Redox Active Devices: Electrochromism As a Case Study

Conjugated polymers provide a unique encompassing set of structurally tunable optical, electronic transport, and redox properties that allows their present and potential use in a host of applications which span, field effect transistors, light emitting diodes, solar cells and photodetectors, electrochromism, along with batteries and supercapacitors. Processing of these materials is carried out using a variety of solution methods including spin-coating, spray-coating, blade-coating, slot die coating and ink jet printing. In this lecture, we demonstrate how the optical absorbance spectra of electron-rich pi-conjugated polymers can be tuned to yield electrochromic materials of all colors that can be switched to highly transmissive forms as desired for absorptive/reflective (display type) and absorptive/transmissive (window type) devices. We will demonstrate how structural design and synthesis of fully conjugated polymers, along with mixing in polymer blends, has been used to complete the color palette of electrochromic polymers (ECPs) needed for subtractive color mixing. Colorimetric tuning (using the L*a*b* color space) using a combination of electron rich and poor units, in conjunction with employing subtle changes in steric strain or relaxation, allows for the enhancement of the neutral form color vibrancy, and the transmissivity of the oxidized forms. We have developed a set of fast switching, high contrast black and brown ECP blends. We use these brown blends to demonstrate the attractiveness of ECPs in window-type electrochromic devices (ECDs) as active materials in color changing eyewear.

802 Development of variable color filter using subtractive color mixing and gradational color

802 Development of variable color filter using subtractive color mixing and gradational color

Mapping the broad CMY subtractive primary color gamut using a dual-active electrochromic device.

Although synthetic efforts have been fruitful in coarse color control, variations to an electrochromic polymer (ECP) backbone are less likely to allow for the fine control necessary to access the variations and shades of color needed in display applications. Through the use of thin films of cyan, magenta, and yellow ECPs, non-emissive subtractive color mixing allows the color of an electrochromic device (ECD) to be selected and tailored, increasing access to various subtle shades and allowing for a non-emissive display to exhibit a wide range of colors. Using a dual-active ECD, subtractive color mixing utilizing the cyan-magenta-yellow (CMY) primary system was examined. The bounds of the gamut, or the subset of accessible colors, using these three 3,4-propylenedioxythiophene (PProDOT)-derived materials in combination with the recently recognized 3,4-propylenedioxypyrrole-based minimally color changing polymer (MCCP) were mapped, highlighting the benefit of applying subtractive color mixing toward the development of full-color non-emissive displays. Here, we demonstrate that ECPs are suitable for the generation of a wide gamut of colors through secondary mixing when layered as two distinct films, exhibiting both vibrantly colored and highly transmissive states.

Patterning technique for expanding color variety of Jacquard fabrics in alignment with shaded weave structures

This study aimed to enhance the capability of multiple weave color reproduction for Jacquard textiles. Today, the subtractive color mixing of CMYK color system is being widely used for rendering weave patterns and assorting filling yarn colors. However, as Jacquard color creation involves optical color mixing, the direct application of pigment mixing is limited to corresponding to an artwork that involves red, green, blue and saturated solid black. Since Jacquard colors are realized by opaque and non-blended material of yarns, it requires a different approach of light and pigment mixing to simulate colors of an original image in woven forms. Therefore, in this study, the optimization of weave color reproduction was approached to properly embrace the proposed color gamut of the CMYK model in digital Jacquard textiles. Based on the ink densities of the CMYK color scope, segmentation was applied in reflection of optical thread color mixing to attain optimal weave patterns. A pair of primary color layers was merged by defining a set of rules to classify individual primary and secondary color patterns to designate colored threads in associated regions, and weave structures were designed and aligned to generate varied levels of color shades in weaving form. The correlation between shaded weave structures and the primary color-based weave patterns were matched to present a faithful color reproduction in weaving.

Inverse Opal SiO2 Photonic Crystals as Structurally‐Colored Pigments with Additive Primary Colors

AbstractPorous silica, structured as three‐dimensionally ordered macroporous (3DOM) photonic crystal particles, is investigated as a pigment material with structural color. Brightly and uniformly colored 3DOM SiO2 powders were obtained by templating of a tetraethoxysilane‐containing precursor in polymeric colloidal crystals, pyrolysis in an inert atmosphere to maintain a small amount (ca. 5–8 wt %) of residual carbon as a background absorber, and particle size reduction. The color depended on placing optical stop bands in the appropriate range of the visible spectrum. This was achieved through selection of the polymer sphere diameter in the colloidal crystal template and fine‐tuning by the pyrolysis temperature, which controls the extent of condensation and shrinkage of the 3DOM SiO2 structure. The stop bands shifted to shorter wavelengths, and the chroma of these pigments increased with increasing pyrolysis temperature in the range from 475 to 900 °C. Using this temperature control, it was possible to obtain materials with a variety of colors and chroma using a single template sphere size. In addition, the assortment of spectral colors could be extended by mixing 3DOM SiO2 pigments with primary colors (red, green, blue) via a unique additive color‐mixing mechanism, which distinguishes these pigments from most conventional pigments that rely on subtractive color mixing. These approaches enable the preparation of pigments with multiple colors using a single material composition, providing opportunities to replace potentially harmful dyes and pigments with nontoxic and relatively inert silica.

A neuroanatomically-based model for human color vision

Presently there are two dominant theories for human color vision: Young-Maxwell-Helmholtz's trichromatic theory and Hering's opponent-color theory. It is widely purported that the trichromatic theory holds true for retinal color processing whereas the opponent-color theory works for cortical color processing. My purposes in the present paper are threefold: to demonstrate, based on both empirical and logical grounds, that the opponent-color theory is fundamentally untenable; to extend the trichromatic theory from retinal color processing to the cortical level; and to present a computational model based on neuroanatomical data for human color vision. Empirically, the opponent-color theory is false because it runs against many lines of observational and experimental data. First of all, this theory claims that it is impossible for a human being to perceive red and green colors in the same place at the same time; now there have been several demonstrations (e.g., see [1] and [2]) clearly indicating that this assumption is unwarranted. Second, colors appearing in complementary afterimages and in color contrast conditions are complementary to stimulus colors—rather than opponent colors as the opponent theory supposes. Third, in the so-called flight-of-colors phenomenon, the predominant colors are the complementary colors of three primary colors (red, green, and blue) embraced by the trichromatic theory, not the four unique hues (red, green, yellow, and blue) as assumed by the opponent-color theory. Logically, the opponent-color theory needs to postulate a neural mechanism for mixing colors between red and green colors which in turn needs to turn off neural activities along the red and the green cardinalities—it is simply impossible to realize such a mechanism in any physical system. In contrast to the opponent-color theory, the trichromatic color theory can easily be extended to cortical color processing. In fact, such a theoretical integration had been attempted by Rollett [3] and McDougall [4] more than a century ago—It is very unfortunate that their efforts had largely been forgotten. Here I attempt to use an extended Young-Maxwell-Helmholtz trichromatic theory to explain several color perception phenomena, including co-existence of red and green colors, both positive and negative afterimages, contrast colors, and flight-of-colors. Based on the fact that many color phenomena are monocular, I further propose that, in the primate (including the humankind) visual system, lamina 4C in the primary visual cortex (V1) is the neural substrate for cortical trichromaticity—because this is the only cortical stage where neurons are predominantly monocular. I present a three-layer computational model to simulate the first three stages of human visual processing: the retina, the LGN, and layer 4C. By incorporating anatomical data of cell distributions and a scheme of neuronal population cardinality coding, the model can account for many essential features of trichromaticity: additive and subtractive color mixing, color complementarity in afterimages and in contrast colors, and color transparency. Conclusions In summary, I contend that the trichromatic theory can explain both retinal and cortical color processing and that the opponent-color theory is fundamentally erroneous. Furthermore, I suggest that the neuronal trichromatic stage directly corresponding to human color sensation is layer 4C in V1.

Colour mathematics: with graphs and numbers

The different combinations involved in additive and subtractive colour mixing can often bedifficult for students to remember. Using transmission graphs for filters of the primarycolours and a numerical scheme to write out the relationships are good exercises inanalytical thinking that can help students recall the combinations rather than justattempting to memorize them.

Experiments on subtractive color mixing with a spectrophotometer

We describe experiments on color mixing suitable for undergraduate nonscience majors. A commercial spectrophotometer is used to study the spectra of light sources, combinations of color filters, and mixtures of acrylic paints. Special emphasis is placed on teaching the fundamentals of subtractive color mixing and the complex processes that occur in mixing pigments.

Methods for Optimal Color Selection

The color characterization of digital cameras often re- quires the use of standard charts containing a fixed number of color samples. The exact choice of such characterization charts—how many (and which) known samples to include—is known to affect characterization performance. This study describes methods to se- lect optimum color samples from a set of 1269 Munsell surface col- ors. The effect of sample selection on characterization performance is evaluated and compared with performance using the standard GretagMacbeth ColorChecker and GretagMacbeth ColorChecker DC colors. The work confirms that the standard charts appear to have been well selected. However, we show that it is possible to select 24 samples from the Munsell set that outperform the Gretag- Macbeth ColorChecker and that this selection can be efficiently de- rived using an algorithm called MAXMINC. It is proposed that this al- gorithm may have general applicability; for example, to the optimal selection of samples constrained to be a subspace Munsell color solid. © 2006 Society for Imaging Science and Technology. DOI: 10.2352/J.ImagingSci.Technol.200650:5481 the ANSI IT8 charts are designed to be used in a color- management process with the aim to allow a system to re- produce colors with acceptable tolerance. These charts are typically checkerboard array targets containing a number of carefully selected and prepared squares or chips in a wide range of achromatic and chromatic colors. Many of these square patches represent the color of certain natural objects of special interest, such as human skin, foliage, and blue sky. 11,12 Primary colors for both additive and subtractive color mixing are also commonly included. A series of ach- romatic patches in the characterization charts provide a con- venient grayscale that may be used for color balance and tone-reproduction purposes. Repeated white, midgray, and black patches around the outer edge of the chart (Gretag- Macbeth ColorChecker DC, for example) allow measure- ments for spatial uniformity of illumination. Special colors, such as glossy surface colors in the GretagMacbeth ColorChecker DC and optional vendor colors in the ANSI IT8 charts, can also be included.