Rudi Bartels is a software engineer and researcher working at Agfa Offset B.V. He graduated at the Belgian KU Leuven university in 1987 with a Master of Science degree of Electrical Engineering. At the same university, he obtained his PhD in 1999. In 1996 he joined Agfa. Within this company, Rudi is in charge of the Color and Screening research managing a team of color experts while exploring new ideas to improve color and quality at our customers, the printers. Since 1998, he is the main developer of Agfa’s halftoning algorithms, which are used in Agfa’s Apogee PrePress, Amfortis Production and Asanti workflow systems. Rudi’s creative mind led to development of a groundbreaking screen technology called: SPIR@L.
SPIR@L Screening: Agfa’s New Breakthrough Technology Defining a New Reference
Rudi Bartels, Els Van Cauwenberghe, Paul Gestels, and Christophe Cleeren, Agfa
In 2020, Agfa introduced SPIR@L screening, an innovative technology with major advantages over conventional and other more modern screening technologies. Just like Agfa’s Sublima™, SPIR@L screening is an XM screen that allows for highlights and shadows to be reproduced to their full extent but with the additional benefit that substantially less ink is required to achieve the same reproduction.
As in conventional screening, darker tones are created by enlarging small highlight dots into larger AM dots. However, contrary to the conventional ways, the small highlight dots are now enlarged in the form of a spiral instead of a solid round dot. The spiral curve has a certain thickness, which we call the ‘curve’. The pitch defines the empty space between two windings, which is called ‘groove’. In order to produce the best output for a particular combination of printing process, ink and paper, it is possible to adjust the curve and groove dimensions, giving this technology a very large latitude. The relation between these two parameters is key to press stability.
By making the AM dot grow as a spiral, fine details in the mid tones are rendered with more contrast. The lattice of the screen is less visible, in fact allowing to achieve similar or higher image quality, while printing at lower screen rulings – increasing latitude for printers.
Last but not least, by using this technology, less ink is needed in order to get the same density, as the ink is spread more efficiently. Consequently, a significant amount of ink is saved – on average 10%, evaluated in hundreds of cases and on top of already installed ink save techniques like e.g. GCR.
This paper contains a technical description of how the screen is built as well as some figures of the tests we have done. Currently, SPIR@L has been installed and shown to be operational for commercial heatset, coldset newspaper, offset packaging and commercial sheetfed. More than 100 splitruns (comparing SPIR@L to other screening technologies, by printing half of the job with SPIR@L screening and half of the job with the incumbent screening) – have been performed and have proven that SPIR@L does indeed account for significant ink-saving, while keeping image quality and color gamut/density.
In print, both conventional AM screening and FM screening are used. In most cases FM screens give sharper images but are seen as more noisy, have a slightly lower ink consumption yet are much more difficult and instable to print. AM screening on the other hand is less noisy and much stabler in print. Agfa’s new SPIR@L screening combines the advantages of both. Flat tints are rendered less noisy than with FM, ink consumption is considerably lower than with conventional AM and FM screening and the good print stability of conventional screening is maintained.
In this paper Agfa’s SPIR@L screening is explained.