Table II. Even their respective color differences for the instruments are also listed. The color differences between the assigned values and the simulated ones, in the case of the D 65 illumination, are 0.44 D E * and 0.60 D E * for CM3630d and CT2, respectively. These values are either close or slightly bigger than the required limit defined in ASTME991, 24 namely, 0.5 D E *.
5. ISO 11475:2004. Paper and board—Determination of CIE whiteness, D65/10 degrees (outdoor daylight). Geneva: International Organization for Standardization, 2004. 6. ISO 11476:2000. Paper and board—Determination of CIE-whiteness, C/2 degree (indoor illumination conditions). Geneva: International Organization for Standardization, 2000. 7. ISO 13655:2009. Graphic technology—Spectral measurement and col- orimetric computation for graphic arts images. Geneva: International Organization for Standardization, 2004. 8. ISO 14981. Graphic technology—Process control—Optical, geometrical and metrological requirements for reflection densitometers for graphic arts use. Geneva: International Organization for Standardization, 2004. 9. Bristow JA. The calibration of instruments for the measurement of paper whiteness. Color Res Appl 1994;19:475–483. 10. Yang L. Probabilistic spectral model of color halftone incorporating substrate fluorescence and interface reflections. J Opt Soc Am A 2010; 27:2115–2122. 11. Yang L. The probability model for color tone reproduction. In: Kriss M, editor. Handbook of Digital Imaging. New York: Wiley; 2015. p 1165–1197. 12. ISO 2470-1:2009. Paper, board and pulps—Measurement of diffuse blue reflectance factor, Part 1: Indoor daylight conditions (ISO brightness). Geneva: International Organization for Standardization, 2009. 13. ISO 2470-2:2008. Paper, board and pulps—Measurement of diffuse blue reflectance factor, Part 2: Outdoor daylight conditions (D65 brightness). Geneva: International Organization for Standardization, 2008. 14. ISO 2469:2007. Paper, board and pulps—Measurement of diffuse radi- ance factor. Geneva: International Organization for Standardization, 2007. 15. ISO 5631-1:2009. Paper and board—Determination of colour by diffuse reflectance, Part 1: Indoor daylight conditions (C/2 degrees). Geneva: International Organization for Standardization, 2009. 16. ISO 5631-2:2008. Paper and board—Determination of colour by diffuse reflectance, Part 2: Outdoor daylight conditions (D65/10 degrees). Geneva: International Organization for Standardization, 2009. 17. ISO 5631-3:2014. Paper and board—Determination of colour by diffuse reflectance, Part 3: Indoor illumination conditions (D50/2 degrees). Geneva: International Organization for Standardization, 2004. 18. Gay JK, Melo CC, Hirschler R. Instrumental whiteness evaluation: Practical results of inter-instrument agreement tests. In: Proceedings of the AIC Color and Paints, Interim Meeting of the International Color Association, Porto Alegre, Brazil, November 3–5, 2004. 19. G € artner F, Griesser R. Eine Vorrichtung zur Messung von optischen Aufhellern mit konstanter UV-Anregung. Die Farbe 1975;24:199–207. 20. Imura K, Imai K, Kawabata T, Makino M. Measuring apparatus for measuring an optical property of a fluorescent sample. US Patent US5636015-A, 1997. 21. Zwinkels JC, Gignac DS, Nevins M, Powell I, Bewsher A. Design and testing of a two-monochromator reference spectrophotometer for high- accuracy total radiance factor measurements. Appl Opt 1997;36:892–902. 22. Zwinkels JC, Gauthier F. Instrumentation, standards and procedures used at the NRCC for high-accuracy fluorescence measurements. Anal Chem Acta 1999;38:193–209. 23. Yang L. Spectral model of halftone on a fluorescent substrate. J Imaging Sci Technol 2005;49:179–184. 24. ASTM E991: Standard practice for color measurement of fluorescent specimens using the one-monochromator method. West Conshohockem, PA: ASTM International.
SUMMARY
The objective of this work is to examine the efficiency and the accuracy of the UV content adjustment methods adapted in the ISO standards, relying on the so-called one-point-matching technique. We present a method that quantitatively evaluates the accuracy of the UV- adjustment technique, through comparing the total spec- tral radiance factors obtained from the UV adjustment with the assigned ones. This method enables one to per- form UV content adjustment in exactly the same manner as with a physical spectrometer. This study involves three second-level international reference transfer standards (IR2s) illuminated by three standard illuminants, D 65 , C, and D 50 , and two commercial instruments using the repre- sentative UV adjusting techniques. The CT2 uses the con- ventional UV-adjusting technique with an adjustable (GG395) UV filter, and the CM3630d uses numerical UV-filtering. We found that the major differences between the assigned spectra and those obtained from the UV adjustments occur in the blue band where fluores- cence is the strongest. At a few number of wavelengths, the differences may be up to 4–5%. Nevertheless, their color differences corresponding to the assigned spectra and those obtained from the UV adjustments are still smaller than unity. Although the results obtained in this study are based on the fluorescent IR2 standards, the conclusions are valid even for fluorescent IR3s as they are made of papers from the same batch. As a part of the harmonizing proce- dures, all the Authorized Laboratories who issue the IR3s use papers from the same batch since 2012. 1. Pauler N. Paper Optics—Optical and Colour Science in the Pulp and Paper Industry. Kista, Sweden: AB Lorentzen & Wettre; 2012. p 81– 96. 2. Coppel L. Whiteness and fluorescence in paper, Mid Sweden Univer- sity, Lic Thesis; 2010. p 47. 3. Authorn WJ. Chemicals additives: Optical brightening agents–fluores- cent whitening agents. In: Herbert Holik, editor. Handbook of Paper and Board. Weinheim: Wiley-VCH Verlag; 2006. 4. Jordan B, Zwinkels J, McGarry P. The influence of the illuminant on the luminescent radiance factor spectrum of a reference fluorescent paper. In: TAGA, Rochester, New York. 2003. p 420–434.
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COLOR research and application
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