Details:
Summary:
With recent advancements in computer-to-plate architecture, stochastic screening is now competing with traditional amplitude modified (AM) halftone screening in a wider variety of print applications. Proponents of stochastic screening (also known as frequency modulated (FM) screening) have claimed that, in addition to better quality reproduction and more consistent color, FM screening allows for lower ink consumption due to the frequency modulated dot structure. Lower ink consumption results in faster drying times, less anti-setoff powder required, and reduced cost. This research project examined if a difference in ink mileage (consumption) exists between traditional halftone screening and stochastic screening. For this experiment, a four-color process test target with heavy ink coverage was imaged to plate twice at 175 lpi (AM) and twice at 10 microns (FM). The test form containing the AM and FM targets was constructed to eliminate variation due to lateral ink zone adjustments and inking system drop-off prior to the plate cylinder gap. The test form was printed in a single pass on the same sheetfed lithographic press using identical inks on 28 x 40 inch 80-pound basis weight (119 g/m2) gloss coated paper. Solid ink densities were carefully controlled, with the AM and FM targets printed to identical target densities. The test was repeated at two lower densities using reduced inking to determine the effect of varying densities on ink consumption. Printed sheets were analyzed for solid ink density and test targets weighed to determine ink consumption. The data showed that the test targets using 10 micron FM screening required measurably less ink than the identical target images using a 175 lpi conventional halftone screen when printed to identical standardized four-color process target ink densities. The difference in ink consumption between the AM and FM targets at reduced densities was significantly less. The findings presented will be of importance to printers, ink and paper manufacturers, and manufacturers of computer-to-plate technologies.