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Quantitative Analysis of Metamerism for Multispectral Image Capture

Surface metamerism is the phenomenon whereby two spectrally different reflectances induce the same response under fixed conditions (observer and illuminant) and induce different responses when recording conditions change. Metamerism arises due to the discrepancy between the degrees of freedom of the observer (usually three) and the degrees of freedom needed to represent surface spectral reflectances. In this paper we propose new ways to study the extent of this phenomenon. We consider spectral images, model their induced response for one observer and illuminant, identify sets of surfaces that are spectrally different but induce the same response and subsequently examine these sets when changing the illuminant. If the surfaces under the new illuminant cease to induce identical responses, they are metameric reflectances and we further investigate the magnitude of the mismatch under the new illuminant by means of the CIE Lab ΔE colour difference formula. Given this method we can determine the proportion of metameric surfaces within a scene as well as the degree to which metamerism in a scene is apparent.