Methods for Evalauating Formation, Print Unevenness and Gloss Variations Developed at STFI, 1996 Process & Product Quality Conference Proceedings
Per-Åke Johansson & Bo Norman
STFI
Formation, in the sense of local variations in grammage, has been evaluated for several years at STFI using beta-- radiographic recording. This is now followed by analy-sis using a flat bed scanner and a PC is used for statis-tical analysis of the variations based on power spectrum techniques. The resulting spectra show the variation intensity in relative wavelength bands, e.g. octave bands. The reported value, the coefficient of variation in grammage in a given wavelength interval, is a physical-ly well defined entity. In an analogous approach, the local variations in print reflectance (mottle) or in gloss can also be evaluated. The spatial band approach also gives good opportunities for comparing different structu-ral features and their links to other physical parameters or the visual quality of paper or prints.
Methods for Evalauating Formation, Print Unevenness and Gloss Variations Developed at STFI, 1996 Pro