The Dish on Dots

pP: What is meant by so-called transitional screening and what is driving its development? That is, how does transitional screening address the problems with conventional and stochastic screening?
GFA: Not all transitional screening solutions are created equal. The problem with many transitional screens is the visible crossover where FM and AM meet. The challenge became how to combine the two technologies seamlessly, without noticeable intersections.
XM (or cross modulation) screening provided the solution. Agfa’s :Sublima XM technology applies a common sense approach to advanced screening: match the screening to the pressroom environment, rather than changing the pressroom to match the screening requirements. XM screens take into consideration the type of paper typically used, such as coated, uncoated, or recycled; the printing architecture, such as flexography; and other variables. XM screening works within the established parameters and uses the smallest optimized and printable dot for the application. Since XM screening algorithms combine the best of both the AM world and the FM world, the matter of “best fit” depends on stock characteristics and how much flexibility one desires on press.
ARTWORK SYSTEMS: Hybrid Screening is a trademark of Artwork Systems, Inc. A Hybrid screen contains FM and AM screening within a single image (typically, FM in the highlight and AM through the rest of the scale). These screens are commonly used in flexo to achieve white highlights under conditions of extreme highlight dot gain. Their value in offset is limited.