Printing Quality » www.ifra-nt.com December 2007 newspaper techniques

Minor investment, major effectFour-colour printing is standard today in newspaper production and every produc-tion manager is interested in both optimis-ing colour printing quality and minimising consumption of costly colour printing inks. Mannheimer Morgen is using new software with which, it reports, it is obtaining highly interesting results in both respects.

Potentials of GCR and FM screeningThe use of GCR permits the share of

colour inks to be reduced, without adverse-ly affecting the colour quality of the image. That is long known and was dealt with in depth in the Ifra Special Report 2.16 (“Po-tentials and Restrictions of Grey Compo-nent Replacement in Newspaper Printing”) which was published in 1996. The process standard DIN/ISO 12647-3 specifi es a (moderate) GCR.

Likewise, the application of FM screening in newspaper printing was tested years ago – though it did not manage to gain a foothold. The reason for this is sim-ple: Whereas it was possible to clearly im-prove the image quality and sharpness with the fi ner frequency-modulated screening, the FM screen had a negative effect on col-our areas (irregular image) and gradations (tonal differentiations).

However, the irregular dot distribu-tion of the FM screen has one major advan-tage for four-colour images: the disturbing

rosette patterns that regularly occur in newspaper halftone screening (AM screen) belong to the past. Therefore, ideally differ-ent types of screens should be used in order to optimally reproduce all elements on a page – and that is exactly what is being tested under practical operating conditions in Mannheim.

New software undergoing testsSince the beginning of July, Mannhe-

imer Morgen has been testing software that uses the FM screening process exclusively on images and otherwise allows the reten-tion of the customary halftone screen. Be-sides this, the process carries out colour op-

timisation by the GCR principle which – as the theoretically calculated consumption values indicate – could permit reduced col-our ink consumption.

The software concerned is called Duo-Screen Pro and was developed by MMS in Heidelberg. It works as follows:

In a fi rst step, the image data is ex-tracted from the Postscript fi le produced by the alfa editorial system, processed by Duo-Screen Pro (including colour optimisation and tonal correction) and FM screened. This

screened data is then transmitted together with the remaining page data to the RIP of the plate imager. The RIP recognises the FM-screened image areas and exposes them directly on to the plate, while all other in-formation that was not processed by Duo-Screen Pro is transmitted as before in the AM screen to the plate. Therefore the exist-ing workfl ow was not fundamentally changed, simply enhanced by an intermedi-ate step.

By the end of the year, in a test conducted under practical operating conditions, Germany’s Mannheimer Morgen is setting out to prove how the use of FM screening and Grey Com-ponent Replacement (GCR) can improve printing quality and reduce ink consumption.

Test partner: Harald

Blendowski (left), technical

manager at Germany’s

Mannheimer Morgen, and

Georg Fütterer, director of

MMS in Heidelberg, are very

satisfied with the test

results obtained. By the end

of the year, the theoretically

calculated savings for

colour ink consumption

should be verified: 20

percent is considered to be

realistic.

What GCR means and doesGCR (Grey Component Replacement) is a process in which the grey components of CMY are replaced by black. GCR thus not only reduces the share of colour ink in the image (and slightly increases the share of black), but it also helps reduce colour fl uctuations in print. The grey balance is optimised. The visual impression of the thus adjusted image is barely affected. In certain cases, the colours even become a lot clearer. – But users must be careful not to overdo GCR, as otherwise the positive effect is reversed, i.e. the images appear dirty.

GCR and ISO standardThe ISO 12647-3 printing standard incorporates GCR. In this case, a moderate Grey Component Replacement is specifi ed as opposed to an extreme version in order to permit a certain image manipulation (colour correction). The applied values repre-sent a compromise to suit the production requirements of the newspaper con-cerned.

“I was initially sceptical. The fact that the FM screening in this case only affected the images caught my attention, so I wanted to try it and see.”

Harald Blendowski

Technical manager at Mannheimer Morgen»

28

» www.ifra-nt.com December 2007 newspaper techniques Printing Quality

The FM resolution depends on the im-ager resolution as well as on how many imager dots are combined to one halftone dot: In Mannheim, the resolution of the im-ager is 1270 dots/in and four imager dots are combined to one halftone dot in each case (produces a resolution in the image area of 635 dots/in). The spot size is about 17 to 20 μm.

“I was initially sceptical,” says Harald Blendowski, technical manager at Mannhe-imer Morgen, who had already tested FM screens in the past and was not convinced

by the results at that time. “The fact that the FM screening in this case only affected the images caught my attention, so that I want-ed to try it and see.” Blendowski presents sample prints, ads with highly detailed im-ages, once printed with AM and once with FM screen. The differences can be seen: “The FM screen enhances the sharpness of the images and register differences are no longer so evident,” says Blendowski.

Relevant in this connection are also the imagers. Agfa CTP imagers are installed at the printing centre of the Mannheimer Morgen. With its changeover from FD-YAG to violet laser, it was possible not only to increase the plate throughput compared to the past, but also sharper, more stable dots can be produced on the photopolymer plates, Blendowski explains.

Lower colour ink consumptionOne surprising, but most welcome

secondary effect was that ink consumption dropped. Several factors are responsible for this. “We considered that it would be logical to avail of this opportunity (meant here is the recalculation of the RIP data for FM conversion) also to carry out colour optimi-sation,” says Georg Fütterer, MMS director. For this purpose, so-called DeviceLink pro-fi les (produced with Color Solutions DeviL

software) are used that replace the grey ele-ment of the colour inks with black (GCR principle). The special feature of the Device-Link method is the input or reference pro-fi le (e.g. ISO newspaper 26v4) is converted to the colour-optimised output profi le (CMYK to CMYK), without the added step of the neutral Lab colour space. The profi les of the input and output devices are practically linked – hence the name DeviceLink.

The colour optimisation (grey ele-ments in the images are produced exclu-sively by black) lowers the colour ink con-sumption. But GCR, and that was the big surprise, is not alone responsible for the ink savings.

The various parameters were investi-gated one by one in numerous printing

Harald Blendowski with Ifra Research Director

Manfred Werfel (right) during his visit to Mannheim

in mid-August. Two of the three Agfa CTP imagers

were already converted to violet laser. Violet lasers

are not only faster (present throughput: 135 plates/h)

but also produce sharper and more stable halftone

dots. This benefits the FM screening process that

offers better detail reproduction.

“I am amazed by how it is possible to obtain clear improvements in quality and costs with relatively minor expenditure.”

Manfred Werfel

Ifra Research director and Deputy CEO»

tests. It emerged that colour optimisation alone achieved colour ink savings of about nine percent. In combination with the use of the FM screen, however, this value prac-tically doubled to 18 percent!

There are, as yet, no proven reasons why this should be so. One possible theory as to how the lower ink consumption could come about is stated by Manfred Werfel: “In the conventional AM screen, the half-tone dots are characterised by a regular ar-rangement but a different size. With the FM screen, as opposed to this, all dots are the same size (or small, respectively), but ar-ranged irregularly. To achieve the same coverage, the AM screen needs fewer, but bigger dots. The bigger a dot is, the greater the surface tension of the ink drop and therefore the bigger the amount of ink that is picked up by the halftone dot on the plate and transferred to the paper.”

For the production manager, it is above all the result that counts. The afore-mentioned 18 percent savings on colour inks, however, are not effective results but rather provisional values calculated theo-retically (by the software) that must be ver-ifi ed in practice. The test has been sched-uled to last six months; by the end of the year, the potential savings should be evi-denced by taking the average value of the actual consumption fi gures.

At the Mannheim printing centre, 21 different newspaper editions and a part of the circulation of Financial Times Deutsch-land are produced in a total print run of about 220,000 copies.

Charlotte Janischewski (janischewski@ifra.com)

29

www.tolerans.com

In-line stitching adds value to your newspaper.