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Color reintegration is a restoration treatment that involves applying paint or colored plaster to an object of cultural heritage to facilitate its perception and understanding. This study examines the impact of lighting on the visual appearance of one such restored piece: a tiled skirting panel from the Nasrid period (1238–1492), permanently on display at the Museum of the Alhambra (Spain). Spectral images in the range of 380–1080 nm were obtained using a hyperspectral image scanner. CIELAB and CIEDE2000 color coordinates at each pixel were computed assuming the CIE 1931 standard colorimetric observer and considering ten relevant illuminants proposed by the International Commission on Illumination (CIE): D65 plus nine white LEDs. Four main hues (blue, green, yellow, and black) can be distinguished in the original and reintegrated areas. For each hue, mean color difference from the mean (MCDM), CIEDE2000 average distances, volumes, and overlapping volumes were computed in the CIELAB space by comparing the original and the reintegrated zones. The study reveals noticeable average color differences between the original and reintegrated areas within tiles: 6.0 and 4.7 CIEDE2000 units for the yellow and blue tiles (with MCDM values of 3.7 and 4.5 and 5.8 and 7.2, respectively), and 16.6 and 17.8 CIEDE2000 units for the black and green tiles (with MCDM values of 13.2 and 12.2 and 10.9 and 11.3, respectively). The overlapping volume of CIELAB clouds of points corresponding to the original and reintegrated areas ranges from 35% to 50%, indicating that these areas would be perceived as different by observers with normal color vision for all four tiles. However, average color differences between the original and reintegrated areas changed with the tested illuminants by less than 2.6 CIEDE2000 units. Our current methodology provides useful quantitative results for evaluation of the color appearance of a reintegrated area under different light sources, helping curators and museum professionals to choose optimal lighting. [ABSTRACT FROM AUTHOR]

Three new approximately uniform color spaces named MLUV, MLUV1, and MLUV2 were developed by modifying CIELUV lightness, u′v′ chromaticity coordinates, and u*v* color coordinates, respectively. Performance tests using the combined and four individual datasets employed at CIEDE2000 development showed that MLUV, MLUV1 and MLUV2 were significantly better than CIELUV. Using values of Standardized Residual Sum of Squares (CIE 217:2016) for predictions of the four individual datasets the ranking (from best to worst) was MLUV, MLUV2 and MLUV1, but for predictions of two ellipses datasets the ranking (from best to worst) was MLUV2, MLUV, and MLUV1. Overall, the MLUV2 space was found to be the best. Hence, it is expected that MLUV2 could be used for color specification and color difference evaluations, especially in industrial applications that depend on additive light mixing, such as color TV sets, video monitors, and lighting. [ABSTRACT FROM AUTHOR]

Recently, Ohno proposed a method for computing the correlated color temperature (CCT) of a light source and the shortest distance (with sign) between its chromaticity and that of the Planckian locus (Duv). In Ohno's method, firstly a lookup table is chosen, and then a hybrid method based on the triangular and parabolic solutions is used to predict the CCT and Duv of a given light source. In this article, we found that spline interpolation is better than the parabolic solution for predicting CCT and Duv. Therefore, we propose two new hybrid methods based on the triangular and either spline interpolation or third-order interpolation using two local function values and two local second-order derivative values. Comprehensive tests using the lookup table with both 1% and 0.25% increments relative to the current selected color temperature demonstrate that the proposed methods outperform Ohno's method. [ABSTRACT FROM AUTHOR]

We have described a number of transformations by mapping the cone signal vector C, formed by LMS, to opponent space O, formed by achromatic signal OA, red‐green signal Org, and yellow‐blue signal Oyb. Two new transformations, Γop1 and Γop2, are proposed, based on the CIE 2006 spectral luminous efficiency function, VFλ, and Hurvich's opponent spectral red‐green and yellow‐blue responses, Hrgλ and Hybλ, without and with constraints, respectively. Γop1 is better than Γop2 in terms of best fit of Hrgλ and Hybλ, and both transformations improved previously proposed ones. Finally, we discuss the neutral conditions in cone space using each of the new and some of the extant transformations, as well as choosing scaling factors so that the neutral conditions in cone space are satisfied. [ABSTRACT FROM AUTHOR]

We present a multispectral system developed and optimized for measurement of the spectral reflectance and the color of the human iris. We tested several sets of filters as acquisition channels, analyzed different reconstruction algorithms, and used different samples as training sets. The results obtained show that a conventional three-channel color camera (RGB) was enough to reconstruct the analyzed reflectances with high accuracy, obtaining averaged color differences of around 2-3 CIEDE2000 units and root mean square errors of around 0.01. The device developed was used to characterize 100 real irises corresponding to 50 subjects, 68 prostheses used in clinical practice, and 17 cosmetic colored contact lenses. OCIS codes: 110.4234, 120.5700, 330.1710, 040.1520, 170.3880.