TEST METHOD FOR EVALUATING FAULTS ON PRINTED SHEETS AND WEBS

摘要

The specification discloses a method for evaluating faults on printed sheets and webs, more particularly slip and/or mackle, by means of a reflectance meter and of test fields. The method of evaluating fault is characterized by the metorlogical detection of the reflectance values of four test fields, one of which is a full tone field and the other three are line screen test fields. The screen line test fields exhibit different screen angles, but equal screen width and equal screen tone values in the film. The mathematical evaluation of the screen tone value in the print, deducting the influence of slip and mackle, from the four reflected values or from screen tone values in the three line screen test fields can be ascertained therefrom and by selective indication of said values.