An algorithm is proposed for the spectral and colorimetric characterization of digital still cameras (DSC) which allows them to be used as tele-colorimeters with CIE-XYZ color output, in cd/m 2 . The spectral characterization consists in the calculation of the color-matching functions from the previously measured spectral sensitivities. The colorimetric characterization consists in transforming the raw RGB digital data into absolute tristimulus values CIE-XYZ (in cd/m 2 ) under variable and unknown spectroradiometric conditions. Thus, in the first stage, a gray balance was applied over the raw RGB digital data to convert them into RGB relative colorimetric values. In the second stage, an algorithm of luminance adaptation versus lens aperture was inserted in the basic colorimetric profile. Capturing the ColorChecker chart under different light sources, and comparing the estimated XYZ data according to the developed color model in relation to the measured XYZ data (in cd/m 2 ) using a telespectroradiometer, we verified that the proposed characterization model may be broken down into two portions. Firstly, there is the basic colorimetric profile in combination with the new luminance adaptation algorithm. Secondly, there is the linear correction term due only to the mismatch of the color matching functions of the camera. Although the linear color correction term works relatively well, despite the imposed initial conditions (unknown spectral content of the scene), the separation of the proposed characterization model into two portions (raw and corrected performance) would allow the future comparison of various commercial cameras.
Interest in applications of natural dye applications has increased because of their antibacterial properties and the possibility of extracting them from nature and residues. Using nanoclays as hosts to reinforce natural dye properties has been successfully demonstrated. However, no one has attempted to optimize the polymer matrix and hybrid pigment properties at the same time to ensure the best final properties for bio-composite applications. Using a statistical design for experiments, we propose the best combination of modifiers with the best nanoclay as the host of three natural dyes: chlorophyll, β-carotene, and betanine. Using the L9 Taguchi designs, we learned both the influence of the nanoclay structure, and the addition moment of surfactant, mordant salt, and silane modifiers. FTIR, XRD, DTG, integration sphere spectrophotometer, and UV-aging tests were used to characterize the hybrid pigments and epoxy bioresin composites. The degradation temperatures of the three natural dyes rose and the reinforcement of the stability of three natural dyes to UV–Vis radiation exposure was demonstrated, which avoided the migration of these dyes from bioresin to wet ribbing. Optimal results were obtained with hydrotalcite clay (calcined or not) by using surfactant and mordant before the natural dye, and before or after silane.
New color-measuring instruments known as multi-gonio-spectrophotometers have recently been created to measure and characterize the goniochromism of special-effect pigments in many materials with a particular visual appearance (metallic, interference, pearlescent, sparkle or glitter). These devices measure the gonio color appearance from the spectral relative reflectance factor and the L*a*b* values of the sample with different illumination and observation angles. These angles usually coincide with requirements marked in ASTM and DIN standards relating to the gonio color appearance characterization, but little is known about the extent of agreement between these new instruments. The main purpose of this study, therefore, is to compare several multi-gonio-spectrophotometers at a reproducibility level according to ASTM E2214-08 guidelines. In particular, we compared 2 X-Rite multi-gonio spectrophotometers (MA98 and MA68II), a Datacolor multi-gonio spectrophotometer (FX10) and a BYK multigonio spectrophotometer (BYK-mac). These instruments share only 5 common measurement geometries: 45ºx:-30º (as 15º), 45ºx:-20º (as 25º), 45ºx:0º (as 45º), 45ºx:30º (as 75º), 45ºx:65º (as 110º). Specific statistical studies were used for the reproducibility comparison, including a Hotelling's test and a statistical intercomparison test to determine the confidence interval of the partial color differences ∆L*, ∆a*, ∆b*, and the total color difference ∆E * ab . This was conducted using a database collection of 88 metallic and pearlescent samples, which were measured 20 times without replacement for all the instruments. The final findings show that in most measurement geometries, the reproducibility differences between pairs of instruments are statistically significant, although in general there is a better reproducibility level at certain common geometries for newer instruments (MA98 and BYK-mac). This means that these differences are due to systematic or bias errors (angle tolerances for each geometry, photometric scales, white standards, etc.), but not exclusively to random errors.However, neither of the statistical tests used is valid to discriminate and quantify the detected bias errors in this comparison between instruments.
Purpose -This research deals with a new kind of nanopigment, obtained from the combination of organic dyes and layered nanoclays, that the authors call nanoclay-colorant pigment (NCP). Whilst they have already been employed in inks and coatings, to date these nanopigments have not been used as pigments for polymers. The existing lack of knowledge surrounding them must be redressed in order to bridge the gap between current academic studies and commercial exploitation. Therefore, the main purpose of this paper is to examine the hitherto unknown aspects of the NCP, which relate specifically to their applicability as a new type of colorant for polymers. Design/methodology/approach -A blue NCP has been prepared at the laboratory according to the patented method of synthesis (patent WO0104216), using methylene blue and montmorillonite nanoclay. It has then been applied to a thermoplastic polymer (linear low-density polyethylene -LLDPE) to obtain a coloured sample. Furthermore, samples with the same polymer but using conventional blue colorants have been prepared under the same processing conditions. The mechanical, thermal and colorimetric properties of these materials have been compared. Findings -The thermal stability of the sample coloured with NCP is reduced to some extent, while the mechanical strength is slightly increased. Moreover, this sample has better colour performance than the conventionally pigmented samples. Originality/value -In this paper, a blue NCP has been synthesised and successfully employed with polyethylene and the obtained sample shows better colour performance than polyethylene with conventional pigments.
Abstract:Materials with new visual appearances have emerged over the last few years. In the automotive industry in particular, there is a growing interest in materials with new effect finishes, such as metallic, pearlescent, sparkle and graininess effects. Typically for solid colors the mean of the three measurements with repetitions it is enough for obtaining a representative measurement of the color characterization. But gonio-apparent samples are colors not homogeneous and there are not studies that recommend the minimal number of repetitions for color, sparkle and graininess characterization in this type of panels. We suppose that the color panels incorporating special-effect pigments in their color recipes will require a higher minimum number of measurements than solid color panels. Therefore the purpose of this study is to confirm this by using a multiangle spectrophotometer BYK-mac, given that it is currently the only commercial device that can measure color, sparkle and graininess values simultaneously. In addition, this paper shows a possible methodology for assessing the minimum number of measurements when characterising gonio-apparent materials using a specific instrument. Thus, we studied the minimum number of measurements needed to characterize the color, sparkle and graininess of three types of samples with solid, metallic and http://mc.manuscriptcentral.com/cte Coloration Technology
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