At the screen

Two new screening technologies were presented at Ipex 2006, completing Heidelberg´s family of high quality screenings. In addition to Amplitude Modulated (AM) screenings, Prinect Hybrid Screening and Prinect Stochastic Screening now offer a broad solution range for every requirement.

In conventional AM (amplitude modification) halftone screening, the size of the dots varies based on tonal values. Larger spots render darker tonal values, or more saturated colour, while smaller spots are used for lighter values. The dots are placed on a fixed grid, and the CMYK inks are applied at specified screen angles, creating the illusion of a continuous range of colours. When printing, the four separations generate the well known rosette pattern.

So-called stochastic or FM (frequency modulation) screening, on the other hand, uses smaller dots of uniform size, modifying the number of dots and their placement to achieve darker or lighter tones. FM screening is also called stochastic screening because the placement appears to be random, although dot placement is precisely controlled by sophisticated mathematical algorithms.

Prinect Hybrid Screening is a mixture of conventional AM screening in the mid-tones and a dithered AM screening in the shadows and highlights. There are two transition points changing from the AM into the "dithered" mode with defined minimum and maximum raster dot sizes. It enables photorealistic print quality with AM-screening (up to 400lpi / 160l/cm) and was developed for offset printing - making "Fine-Screening" with AM possible.

One of the benefits of Prinect Hybrid screening is its use with lower resolution plates like violet polymer plates. The colour stability of the plate on the press is much higher than FM screening so the printer will more easily achieve better results. This screening is recommended for any job where the quality needs to be better than the average.

Prinect Stochastic Screening is best described as a high-end stochastic screening and represents the second generation of FM screening developed by Heidelberg (patent pending). It replaces Satin Screening and delivers smoother results because the details are much finer due to larger mid-tone structures, compared to Satin or FM screenings from other vendors (see comparison of Satin Screening vs. Prinect Stochastic Screening). This screening is recommended for high-quality productions, where moiré issues could occur or an excellent result in detail is required. Magnified, the Stochastic Screening has a worm structure and not a defined pattern.

Both Screenings are available for Prinect Workflows with the new version 6.0 of MetaDimension.

Further Information:
Soeren Lange
Product Manager - Prepress & Workflow
Tel: +61 3 9205 4227
Email: Soeren.Lange@heidelberg.com