ASSESSMENT OF THE INFLUENCE OF PAPER FORMATION ON THE FLUORESCENCE CONTRIBUTION TO BRIGHTNESS

Paper was produced under controlled conditions with a range of resultant formation and a constant level of fluorescent dye. Brightness and CIE-Whiteness and the fluorescent contribution to brightness or whiteness were measured by directional and diffuse illuminations. Brightness, whiteness, and fluorescence variability were evaluated as the illuminated sample aperture diameter was varied from a maximum of 12.7 mm to a minimum of 6.0 mm over a broad range of paper formation. An increase in the variance of CIE-Whiteness both including and excluding fluorescence is observed as formation degrades. The variance of the fluorescent contribution also increased, but not in a manner to suggest it is independent of the whiteness including or excluding fluorescence measurements. A higher level of instrument noise prevented a similar definitive conclusion for the fluorescent contribution to directional brightness, even though similar trends were observed An increase in variance was observed for all whiteness and brightness measurements as viewing aperture size diminished. This suggests an opportunity to understand subjective appearance as a function of viewing aperture size. (C) 1995 John Wiley & Sons, Inc.