We present a systematic algorithm capable of searching for optimal colors for any lightness L * (between 0 and 100), any illuminant (D65, F2, F7, F11, etc.), and any light source reported by CIE. Color solids are graphed in some color spaces (CIELAB, SVF, DIN99d, and CIECAM02) by horizontal (constant lightness) and transversal (constant hue angle) sections. Color solids plotted in DIN99d and CIECAM02 color spaces look more spherical or homogeneous than the ones plotted in CIELAB and SVF color spaces. Depending on the spectrum of the light source or illuminant, the shape of its color solid and its content (variety of distinguishable colors, with or without color correspondence) change drastically, particularly with sources whose spectrum is discontinuous and/or very peaked, with correlated color temperature lower than 5500 K. This could be used to propose an absolute colorimetric quality index for light sources comparing the volumes of their gamuts, in a uniform color space.

A reduced set of measurement geometries allows the spectral reflectance of special effect coatings to be predicted for any other geometry. A physical model based on flake-related parameters has been used to determine nonredundant measurement geometries for the complete description of the spectral bidirectional reflectance distribution function (BRDF). The analysis of experimental spectral BRDF was carried out by means of principal component analysis. From this analysis, a set of nine measurement geometries was proposed to characterize special effect coatings. It was shown that, for two different special effect coatings, these geometries provide a good prediction of their complete color shift.

Please cite this article as: P. Sanmartín, E. Chorro, D. Vázquez-Nion, F.M. Martínez-Verdú, B. Prieto, Conversion of a digital camera into a non-contact colorimeter for use in stone cultural heritage: the application case to Spanish granites, Measurement (2014), doi: http://dx.doi.org/10. 1016/j.measurement.2014.06.023 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. In this study, a digital CMOS camera was calibrated for use as a non-contact 2 colorimeter for measuring the color of granite artworks. The low chroma values of the 3 granite, which yield similar stimulation of the three color channels of the camera, 4 proved to be the most challenging aspect of the task. The appropriate parameters for 5 converting the device-dependent RGB color space into a device-independent color 6 space were established. For this purpose, the color of a large number of Munsell 7 samples (corresponding to the previously defined color gamut of granite) was measured 8 with a digital camera and with a spectrophotomer (reference instrument). The color data 9 Conversion of a digital camera into a nonwere then compared using the CIELAB color formulae. The best correlations between 10 measurements were obtained when the camera works to 10-bits and the 11 spectrophotometric measures in SCI mode. Finally, the calibrated instrument was used 12 successfully to measure the color of six commercial varieties of Spanish granite. 13 14

A representation of the color gamut of special effect coatings is proposed and shown for six different samples, whose colors were calculated from spectral bidirectional reflectance distribution function (BRDF) measurements at different geometries. The most important characteristic of the proposed representation is that it allows a straightforward understanding of the color shift to be done both in terms of conventional irradiation and viewing angles and in terms of flake-based parameters. A different line was proposed to assess the color shift of special effect coatings on a*,b*-diagrams: the absorption line. Similar to interference and aspecular lines (constant aspecular and irradiation angles, respectively), an absorption line is the locus of calculated color coordinates from measurement geometries with a fixed bistatic angle. The advantages of using the absorption lines to characterize the contributions to the spectral BRDF of the scattering at the absorption pigments and the reflection at interference pigments for different geometries are shown.

Purpose: To report visual, refractive, and corneal aberrations after implantation of a new asymmetric intracorneal ring segment (ICRS). Methods: This was a prospective, multicenter clinical study including 30 eyes of 26 patients with keratoconus. All cases were implanted with an ICRS, named the VISUMRING (VR), which had an arc length of 353 degrees and 2 asymmetric sections that can be customized in base width, length, and thickness. Ophthalmic evaluation included uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), refraction, topography, and anterior corneal aberrations using the Sirius System (CSO, Firenze, Italy). Mean follow-up period was 14.7 ± 7.9 months. Results: Significant improvement of both UDVA and CDVA was observed after 1 year. UDVA improved from 0.08 ± 0.22 to 0.22 ± 0.16 and CDVA from 0.24 ± 0.29 to 0.43 ± 0.18 (P = 0.01). A significant reduction of more than 7 D in the spherical equivalent from −12.38 ± 3.77 D to −5.00 ± 3.26 D (P < 0.05) was noted 1 year after the procedure. In terms of higher-order aberrations, a slight reduction that was not statistically significant in the higher-order and coma-like aberrations was noted at 1 year from 4.32 and 3.82, to 4.12 and 3.55, respectively. Regarding complications, 5 of the 30 cases needed to have the VR explanted throughout the follow-up period due to severe corneal melting. Conclusions: VR ICRS improves vision and refraction and induces major corneal flattening in patients with keratoconus. Further design enhancement is needed to increase the reduction of the asymmetric corneal aberrations and reduce the extrusion rate.

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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

Received XX Month XXXX; revised XX Month, XXXX; accepted XX Month XXXX; posted XX Month XXXX (Doc. ID XXXXX); published XX Month XX Most real surfaces and objects show variation in appearance with viewing and illumination directions. Besides angular dependency, they also show spatial variation in color; i.e. they exhibit some sort of texture. Of the surfaces we see, surfaces colored by special-effect pigments produce several complex visual effects, like change in color and lightness with viewing and illumination angles, and effects like sparkle and gloss on other textures.In the last two decades, different commercial devices have appeared to help ensure the proper characterization of materials with special-effect pigments. However, the instrumental characterization of sparkle is currently available only by a commercial device integrated into a multi-angle spectrophotometer. As it is difficult to find complete open original studies about the sparkle effect for designing and calibrating this commercial instrument, the main objective of this work was to check whether a good visual and instrumental correlation exists between the sparkle that the observer perceives and the sparkle value provided by the device using some subsets of goniochromatic samples with different types of special-effect pigments and colors. Visual assessments were made by a conventional magnitude estimation method in a directional lighting booth, which belonged to the same company owner of the sparkle instrument, in different geometries and at distinct illuminance levels.The results revealed that there was a good visual correlation of the sparkle-grade value. By separately analyzing the factors used in its instrument algorithm, such as sparkle intensity and sparkle-area values, it was clearly shown that the correlation was not good or simply did not exist. Consequently, and perhaps as regards choice of new special-effect pigments, such as synthetic mica and other future ones, we generated herein even more questions about current mathematical algorithms, and only recognized calculating this texture effect at the industrial level.