화학공학소재연구정보센터
Color Research and Application, Vol.36, No.3, 169-178, 2011
Goniocolorimetry: From Measurement to Representation in the CIELAB Color Space
The classical definitions of color are well adapted to diffusing objects, whose color is almost independent of the viewing angle, and to very glossy object observed in the specular direction in respect to the light source. For glossy or iridescent objects, the color is difficult to characterize due to its dependence on the viewing direction. In order to cope with such objects and to represent their angle-dependent colors in a colorimetric space, we adapt the CIELAB space to "goniocolorimetric" measurements. A crucial point when defining this space is the statement of the viewing solid angle. First, we suggest performing a BRDF measurement at high angular resolution in order to characterize the gloss of the specimen. Then, since for the definition of colors the CIE recommends cones of half-angle of 2 degrees or 10 degrees, we propose to convert the measured BRDF into a reflectance factor defined in respect to these solid angles. This procedure is eased by a planar multispectral image of the BRDF, where solid angles are specified by the pixel size. At last, the reflectance factors are converted into CIELAB coordinates. By using this procedure, the perfect white diffuser but also the perfect mirror can be represented in this colorimetric space. (C) 2010 Wiley Periodicals, Inc. Col Res Appl, 36, 169 - 178, 2011; Published online 29 April 2010 in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/col.20605