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The whiteness level of a printing paper is considered as an important quality measure. High paper whiteness improves
the contrast to printed areas providing a more distinct appearance of printed text and colors and increases the number of
reproducible colors. Its influence on perceived color rendering quality is however not completely explained. The intuitive
interpretation of paper whiteness is a material with high light reflection for all wavelengths in the visual part of the color
spectrum. However, a slightly bluish shade is perceived as being whiter than a neutral white. Accordingly, papers with
high whiteness values incline toward bluish-white. In paper production, a high whiteness level is achieved by the use of
highly bleached pulp together with high light scattering filler pigment. To further increase whiteness levels expensive
additives such as Fluorescent Whitening Agents (FWA) and shading dyes are needed. During the last years, the CIE
whiteness level of some commercial available office paper has exceeded 170 CIE units, a level that can only be reached
by the addition of significant amounts of FWA. Although paper whiteness is considered as an important paper quality
criterion, its influence on printed color images is complicated. The dynamic mechanisms of the human visual system
strive to optimize the visual response to each particular viewing condition. One of these mechanisms is chromatic
adaptation, where colored objects get the same appearance under different light sources, i.e. a white paper appears white
under tungsten, fluorescent and day light. In the process of judging printed color images, paper whiteness will be part of
the chromatic adaptation. This implies that variations in paper whiteness would be discounted by the human visual
system. On the other hand, high paper whiteness improves the contrast as well as the color gamut, both important
parameters for the perceived color reproduction quality. In order to quantify the influence of paper whiteness pilot papers
with different amount of FWA but in all other respects similar were produced on a small scale experimental paper
machine. The fact that only the FWA content changes reduces the influences of other properties separated from the paper
whiteness in the evaluation process. A set of images, all having characteristics with the potential to reveal the influence
of the varied whiteness level on color reproduction quality, were printed on the pilot papers in two different printers.
Prior to printing the test images in the experiment, ICC-profiles were calculated for all the used printer-substrate
combinations. A visual assessment study of the printed samples was carried out in order to relate the influence of the
paper whiteness level to perceived color reproduction quality. The results show an improved color rendering quality with
increased CIE whiteness value up to a certain level. Any further increase in paper whiteness does not contribute to an
improved color reproduction quality. Furthermore, the fact that some printing inks are UV blocking while others are not
will introduce a non uniform color shift in the printed image when the FWA activation changes. This non uniform color
shift has been quantified both for variations in illuminant as well as variations of FWA content in the paper.
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