It is not very often one comes across what could be termed industry changing or breakthrough products. I believe what I am writing about today could be such a product. One subject that has exercised the brains of many of the best technical experts in the industry is that of screening. It is also a subject that has generated a great degree of income for the patent lawyers who work with this industry’s suppliers. In the ongoing development of screening we have moved from analog conventional screening using believe it or not, screens to break up the continuous tone photographic images where the screens were either in contact with the film or were mounted in the process camera to generate halftone dots. In that time we only had conventional screens with each color separation’s dots at a specific angle defined by the screen being used. With the arrival of digital color scanning the first computer generated screens came on the scene. The battle then was fought between rational and irrational screening that depended upon the size of the cell in which the screen dot was generated, and the screening angle that could be achieved. Various patents were around the most significant one being from Dr Ing Rudolf Hell for irrational screening.

With arrival of PostScript the screening battle became intense with the different PostScript RIP suppliers each producing their own versions of rational or irrational screening. Each of these approaches would show the typical rosette pattern of screening when looked at under a loop, and most of them in certain circumstances would show moiré and color shifts. In these approaches screen dots were of different sizes and laid out in a fixed pattern. This type of screening is referred to as AM screening.

The next move introduced stochastic or frequency modulated screening where screen dots were of a limited number of sizes and laid out in what appeared a random pattern. Again all suppliers had their own versions to endeavor to get around the different patents. The best known of these and the one that was most heavily promoted was Stoccato from Creo (now Kodak). This software that is essentially a modified version of Harlequin’s HDS screening is offered in different versions based upon the imaging dot size used, the highest quality being Stoccato 10 with a 10 micron spot, however this requires extremely critical controls to print.