The Dish on Dots

pP: For what applications and under what conditions would conventional, stochastic, or hybrid screening be an appropriate choice for a package printer?
AGFA: Flat tints, process-build brand colors, etc. are a perfect fit for XM screening, as FM screens tend to be grainy with flat tints. The regular orthogonal AM grid of XM screens gives a smoother appearance than grainy FM.
ARTWORK SYSTEMS: We used to have a complex decision tree to help decide between AM and stochastic. The more we learn about our Concentric Screening, the more it appears to be a logical choice for all offset printers. One thing we have learned about Concentric is that high ruling concentric screens require high-quality plate materials and a properly adjusted CtP unit. If you can’t image quality 20u stochastic screens, you won’t be able to image high-ruling (above 200 lpi) Concentric Screens with thin rings (below 16 microns). Such screens will show patterning on both plate and press. However, we have recently had a few printers lower screens (to around 180 lpi), increase ring widths (to 20 µ), and achieve results superior to conventional AM.
ESKO-GRAPHICS: Conventional AM screening is better for tints and flesh tones. FM screening is best for printing detail as well as in highlights and shadows. It can also be helpful in areas where a number of printed colors and tints could create a moiré. Transitional technologies try to resolve certain deficiencies in both, such as generating even better highlights and shadows, or providing transitions during the midtones.
FUJI/ENOVATION: We are beginning to see more implementations in this market. If printers want to use four-plus colors, stochastic is appropriate. We are seeing an interest in the flexo market in using multiple screening technologies on the same page or package. The reason for this is that tone dot gains are much higher in flexo than in commercial offset. By combining screening technologies, flexographers can balance the job better than just hitting one particular element and letting the rest fall where it may.
HEIDELBERG: Prinect AM Screening is applicable in any high-quality printing. In particular, Heidelberg Irrational Screening provides true conventional angles and its accuracy greatly reduces the potential for moiré compared to Supercell AM screening. Prinect Hybrid Screening allows the printer to produce very high screen rulings while maintaining the highlights and shadows. If color needs to be manipulated on press, both respond to density moves. Prinect Stochastic Screening is a perfect fit for greater then four-color process work. Without angles, screening moirés are eliminated and angle selection is unnecessary. It is a very stable process.
KODAK: Transitional AM screening is best for flexo packaging applications since it allows for the recovery of much of the tonal scale that would otherwise have been lost due to the lack of resolution of flexo plates. For metal offset printing, transitional AM/XM screens allow higher screen frequencies on lower resolution plate imaging systems. They do this at the expense of highlight detail and smoothness and offer no advantage in the pressroom over equivalent AM screens. Transitional FM screens can be used on all packaging substrates and eliminate the issues of first-order FM screens while preserving many of their lithographic advantages.