Angular Variations of Color in Turbid Media – the Influence of Bulk Scattering on Goniochromism in Paper

• The angular variations of color of a set of paper samples are  experimentally assessed using goniophotometric measurements.  The corresponding simulations are done using a radiative transfer based simulation tool, thus considering only the contribution  of bulk scattering to the reflectance. It is seen that measurements  and simulations agree and display the same characteristics, with  the lightness increasing and the chroma decreasing as the observation  polar angle increases. The decrease in chroma is larger  the more dye the paper contains. Based on previous results about  anisotropic reflectance from turbid media these findings are explained.  The relative reflectance in large polar angles of wavelengths  with strong absorption is higher than that of wavelengths  with low absorption. This leads to a loss of chroma and color information  in these angles. The increase in lightness is a result  of the anisotropy affecting all wavelengths equally, which is the  case for transmitting media and obliquely incident illumination.  The only case with no color variations of this kind is when a nonabsorbing,  non-transmitting medium is illuminated diffusely. The  measured and simulated color differences are clearly large, and  it is an open issue how angle resolved color should be handled  in standard color calculations.

Ämnesord

TEKNIK OCH TEKNOLOGIER  -- Materialteknik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Materials Engineering (hsv//eng)

Nyckelord

Materials science

Teknisk materialvetenskap

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