Part 1 - Answered by the experts at Agfa

Note from the editor: We believe there are many experts qualified to answer this question. Agfa's answer is the first of three answers that we will publish over the next three weeks.

Question:
Could you please explain the advantages and disadvantages of traditional screening, stochastic screening, and hybrid screening?

Answer:
Traditional AM (amplitude modulated) screening has been around since the dawn of photolithography and photoetching.

Just ten years ago, Agfa was first to market with its innovative FM (frequency modulated) screening :CristalRaster. Although tremendously capable of delivering the finest detail, FM technologies tend to appear grainy or sandy - especially in areas of flat tints.

Over the course of the next decade, both technologies had their best fit...FM for greater detail and AM for smoother flat tints, etc. Recently, as the advent of computer-to-plate technologies have enabled higher quality and control on-press, some companies have taken a closer look at the benefits of both AM and FM screening and have developed different hybrid approaches that combine the "best of both worlds".

Staccato is Creo's brand name for their implementation of Harlequin-based FM screening which is somewhat similar to Agfa's :CristalRaster. Screen's Spekta is a hybrid solution that uses a "random" dispersion of AM dots to improve upon the pit-falls of AM & FM. In a different fashion, Agfa has its XM or Cross-Modulation approach called :Sublima.

With :Sublima, the screen frequency can be nearly doubled (twice as fine), and yet it requires no extra effort on press. In the tricky extreme highlights and shadows, :Sublima uses a patented FM approach - ensuring full 1-99% tonal range and stability on press.

Since all the dots in :Sublima align along the established AM angles - even in the FM extremes - there is no cross-over noise or technology intersections as found in earlier hybrid approaches.

Regardless, companies like Screen, Agfa, Esko-Graphics, ArtWork Systems, and even Creo for the flexo market, are turning toward hybrid (or XM solutions) to combine all the positive aspects of both AM & FM, while at the same time, trying to minimize the negative aspects of these earlier technologies.

If you are interested in further information about stochastic and newer advanced screening technologies, GATF has recently published their screening study following their initial presentation given at the 2003 GATF TechAlert. This report can be purchased at www.gain.org.

For more information about Agfa, please visit www.agfa.com.