Li Yang

Abstract
Perfect light diffuseness inside the medium, such as a paper sheet, is the fundamental assumption when applying the Kubelka-Munk (K-M) model. In reality, this pre-condition is seldom fulfilled, which is unfortunately either not well noticed or ignored by users. Nevertheless, this is little troublesome as long as it is applied to media of similar light diffuseness. When applied to media of significantly different light diffuseness great discrepancies between theoretical predictions and measurements may occur. Besides the intrinsic optical properties, there are other factors that affect light diffuseness inside the medium, such as illumination geometries, medium thickness, etc. In this work, we proposed a solution that enables the K-M model to be applicable across media of different light diffuseness. In the proposed model, the light distribution is explicitly expressed with a parameter, b, whose value equals to unity (b=1) for a perfect diffuse light and zero (b=0) for a collimated light distribution, respectively. The proposed model was verified by applying to papers of different light diffuseness, caused by different illumination geometries and different thickness. The spectra of light reflection as well as light transmission predicted with this model agree very well with measurements.

Keywords: Extended Kubelka Munk model, Light scattering & absorption, Partial light distribution.
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Dejana Đorđević, Aleš Hladnik, Andrej Javoršek

Abstract
Unlike human visual system, image-capturing devices, such as scanners and digital cameras, are unable to accommodate to different light sources. As a consequence, in color acquisition, display and rendering processes a number of chromatic adaptation transforms (CATs) are being used. In our study, a comparison among 15 models consisting of five CATs - Bradford, von Kries, XYZ Scaling, CMCCAT97 and CMCCAT00 - and three illuminant source pairs - D50-A, D50-D65 and D65-A - was made using 8190 color patches. Results showed that colour differences obtained with the Bradford method were the lowest regardless of the implemented illuminant source pair.

Keywords: Chromatic adaptation models, Color differences, Principal components analysis
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Vicente de Garcia, Jesús Inarejos, Susana Otero, Esther Perales and Francisco Martínez-Verdú

Abstract
Colour reproduction is based on the ability to communicate colour information accurately. The different instrument manufacturers, models and conditions result in difficult colour communication due to the loose or inexistent inter-instrumental agreement between them.

With this study we have tried to develop an application to correct colour instruments by software by applying multi-dimensional polynomial transformations between pairs of instruments. This application will filter one spectrophotometer measurement, and apply a correcting factor to emulate the colorimetric response of any other spectrophotometer.

Keywords: Colorimetry, Spectrophotometer, Measurement.
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