GWG Annouces New Specifications for Large-Format Digital & Screen Printing
GHENT, Belgium—The Ghent PDF Workgroup (GWG), the fast growing international association making it easy to produce and exchange reliable digital documents for use throughout the publishing workflow, announces four new GWG Specifications addressing two additional markets: large format digital printing and screen printing. The specifications answer the growing need for PDF best practices in these markets, which are rapidly moving to PDF workflows.
The four new specifications are additions to the GWG 2005 v3 specifications offering best practices for PDF file exchange in graphic arts and publishing applications. To download the free specifications visit www.gwg.org
According to Andy Den Tandt, technical product manager for Enfocus and co-chair of the GWG Specifications subcommittee, “As a group we are really pleased with the progress and speed with which we’ve collaborated and developed these best practice PDF specifications for practical production applications. The goal of the Ghent PDF Workgroup is to make it easy to produce reliable digital documents that can be used from creation to final print production. To accomplish this, the Ghent PDF Workgroup considers the entire workflow and all the steps that influence the final result.”
“Customers are generally well informed regarding the specifications of the litho process, but quite often don’t have an understanding of the requirements of screen or digital processes, therefore these new standards will help to deliver files appropriate to these production processes,” says Nick Stevens, technical director, SP Group, one of the largest screen and digital printers, including large format, in the UK.
GWG Serving Additional Market Applications
The new specifications added to the GWG release v3 2005 set address two new, rapidly expanding markets:
For large-format digital printing—specialized high resolution print productions using screen rulings higher than 150 lpi (60 l/cm) or using special screening technologies like FM, Stochastic, or large format printing (where the pages are created at a fraction of the final output size).
• very high resolution (without downsampling) CMYK (CmykVeryHiRes_1v3)
• CMYK+spot (SpotVeryHiRes_1v3)
In the “standard” GWG CMYK HiRes specifications, color and grayscale images shall not be below 100 dpi and should not be above 300 dpi. This is common practice for many Hi Res printing applications using traditional screening with screen rulings up to 150 lpi (60 l/cm). For special productions, the use of higher frequency screens, FM screening, Stochastic screening, or a mix of some of these technologies may require higher image resolutions in order to result in the best possible, fine detail in print. For such projects, GWG recommends using the specifications “CmykVeryHiRes” and “SpotVeryHiRes”.
Using these settings will leave the image resolution unchanged (i.e., no downsampling during PDF creation and preflighting). Image resolution for VeryHiRes applications may vary depending on the screening technology used, as well as on subject matter.
As a rule of thumb for “traditional” screening, it is recommended that image resolution should be 1.5 to 2x the screen resolution. For alternative screening technologies (such as FM, Stochastic, etc.), you may follow the instructions of your supplier or define the optimum image resolution yourself by printing test targets.