Evaluation of colour variation of grey scales with the viewing angle
4 pags., 2 figs. -- Jeju Island of Korea from 16th to 20th of October, 2017 ; In the textile industry, grey scales for colour change are used in fastness tests. These scales consist of nine pairs of neutral grey chips representing a visual colour difference corresponding to fastness ratings from 5 (no contrast) to 1 (highest contrast). The dependence of colour differences on the illumination and viewing directions for two widely-used grey scales ("Grey Scale for Assessing Change in Colour" (SDCE), and "Gray Scale for Evaluating Change in Color" (AATCC)) was evaluated. The spectral bidirectional reflectance distribution function (BRDF) was measured at a set of geometries well distributed in the observation domain, using the goniospectrophotometer GEFE developed at CSIC. It was found that large incidence and viewing angles must be specially avoided using these scales, as providing colour difference values considerably different than those established in ISO 105-A02 and ASTM D2616-96. ; This work was supported by Ministerio de Economía y Competitividad del Gobierno de España, Research Projects FIS2013-40661-P and FIS2016-80983-P, with support from European Regional Development Fund (ERDF), by Comunidad de Madrid (project SINFOTON-CM: S2013/MIT-2790), and by the EMRP IND52 Project "Multidimensional reflectometry for industry" (xD-Reflect). The EMRP is jointly funded by the EMRP participating countries within EURAMET and the European Union ; Peer Reviewed