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Esther Perales Romero

Country of Birth : Spain
Resident : France
Title : PhD Student, Department of Optics, Pharmacology and Anatomy, University of Alicante, Spain
Statement and research interests:
Esther Perales received her BS in Physics (Optics branch) from the University of Valencia at Valencia in 2003 and her MSc Dissertation on Physics from the Department of Physics, Systems Engineering and Signal Theory at the University of Alicante (Alicante, Spain) in 2006. Since 2004 she works with the Colour and Vision Group of the University of Alicante. Her work has primarily focused on Industrial Colorimetry, Colour Vision and Colour Imaging.

The research is focused on the optimal colours and their applications at vision colour and colour technology:
A colour solid includes all colours perceived by the human visual system associated to a physical colour stimuli set. The optimal colours define its external surface. An optimized algorithm allows searching optimal colour stimuli for any lightness, hue angle and illuminant. Unlike the irregularly shaped colour solid obtained in CIELAB, the colour solids associated to the most recent perceptual colour spaces, DIN99d and CIECAM02, appear more spherical or homogeneous.

Colour solid shape depends on illuminant spectrum, in particular for discontinuous (and/or very peaked) spectrum sources with correlated colour temperature less than 5500 K. At the same time it can be stated that there is a direct relationship between the colour gamut volume and the number of distinguishable colours. Then, we can apply several methods to estimate the gamut volume (content) for any colour solid associated to any illuminant or light source taking into account several packing methods (squares, ellipses, tetrahedron, spheres) in uniform colour spaces and other computing techniques like convex hull. With this preliminary methodology we propose an absolute colorimetric quality index for any illuminant/light source based on the computation of the number of distinguishable colours inside the colour solid.

The most fascinating corollary of our research can be stated in the following way: Applying the same colour correspondence (chromatic adaptation transform) among optimal colour data for each illuminant, we have found that there are distinguishable colours under one target illuminant without perceptual correspondence under another , even though target colour solid volume was smaller. This means that the number of discernible colours by the human visual system is unlimited, because it can not be associated to a single illuminant/lamp, An additional conclusion is that colour constancy, based initially on a chromatic adaptation transform, can be considered as the product of an adaptive mechanism that reduces the number of distinguishable colours without correspondence between different illuminants.

On the other hand, from 1980 to now, new technologies of colour reproduction and new pigments have appeared to cover the commercial necessities. Due to this, the research is focused on the study about different technologies of colour reproduction following the method developed by Pointer in 1980. This method consists in plot different colour gamut, associated to different technologies of colour reproduction, at lightness and hue constant planes to be compared with the MacAdam limits (or optimal colours). It is calculated the total volume of the colour solid defined by the samples to evaluate the wider colour gamut. Therefore, it could be evaluated that technology offers better results. .

Research interests:
Industrial Colorimetry, Colour management, Colour Imaging and Colour Appearance Models

Example paper:
Perales Romero, E., Concerning the Optimal Colours and their Applications in Colour Technology and Vision; Colour and Vision Group, University of Alicante

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