Estimating a Donaldson Matrix for Commercial Papers Containing Optical Brightening Agents


Document ID: 
Brian M Gamm and David R. Wyble


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Photo, Member: 
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A method for estimating a Donaldson matrix from single-monochromator spectral reflectance measurements of optically brightened paper was derived. Optical brightening agents are excited by UV energy and fluoresce in the shortwavelength visible spectrum. Therefore, the spectral reflectance of papers containing optical brightening agents is highly dependent upon the UV content of spectrophotometer source. Fluorescent papers are ideally measured with bispectral spectrophotometers. However, bispectral spectrophotometers are unavailable to most of the graphic arts industry. This method bridges the gap between spectrophotometers and the measurement of fluorescent papers by estimating illuminant independent bispectral radiance factor matrices for fluorescent papers. The method was tested by estimating the Donaldson matrix from spectral reflectances of fifteen papers measured in a Macbeth Color-Eye 7000. In addition, spectral reflectances of the fifteen papers were measured under Incandescent, Daylight, and Cool White sources in a Macbeth Spectralight III light booth. The spectral power distribution of the three sources was imposed upon the estimated Donaldson matrices, and total radiance factors were calculated from each matrix. The mean CIEDE2000s between the measured and estimated total radiances factors for Incandescent, Daylight, and Cool White were 1.38, 1.84, and 0.90, respectively. The estimated Donaldson can be used to predict the spectral reflectance of fluorescent papers under any light source and applied to models predicting the appearance of printed images.

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