engleski

Kubelka-Munk parametersof some printed surfaces

In this paper we have measured opacity (paper backing) sometimes called printing opacity. This method employs d/0 geometry, illuminant C (TAPPi 519) and the instrument was set to measure CIEY, 2° standard observer. From the paper technology aspect high light scattering is good since the paper then becomes more opaque and whiter. When white pigment is added to a adding dark pigment or dye which absorbs light in the green part of visible spectrum. So dye increases opacity but reduces reflectance. It has been known that one can simulate continuous tones with screening in a number of ways. In this work amplitude modulated (AM) screen with 60 lines/cm and 80 lines/cm and frequency modulated (FM) screening, fine and coarse have been chosen. In so-called amplitude modulated screening or periodic screening the individual dots are spaced the same distance apart, but have different diameters or different areas, depending on the dot shape. In the case of frequency modulated screening, the individual dots have the same diameter but the different distances apart (non periodic, random screening). When using identical dots of the smallest possible size, FM screening produces better reproduction of details in printing than AM screening (for single, color image). For multicolor image FM screening produces a higher resolution [4]. When the same screen type (same halftone printing plate) is printed on different papers, the resulting reflectance spectra or tone reproduction curves are different [5]. The main reason for this phenomenon is the scattering of light within the paper substrate, the so called Yule-Nielsen effect [8] or optical dot gain. Such reflectance spectra are consequence of interaction between electromagnetic radiation of illumination and surfaces printed by different screen types [1], [2].

reflectance; unprinted surface; printed surfaces; absorption; scattering; Kubelka-Munk parameters

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