One factor that sets apart this new specification from earlier Ghent Workgroup specifications, is that it opens up which colour spaces can be used in a PDF file. This is important because of the number of wide-gamut output devices in use in this market. For the first time, a GWG specification allows the use of colour spaces such as calibrated RGB or L*a*b* for all elements within a PDF document.
GWG recently started a public beta test of its preflight specification for the sign and display market. The technical specification document is available now, together with preflight profiles from callas software and Enfocus. Software vendors can use this specification to prepare for standardised quality control; end-users can take advantage of the preflight profiles to improve their quality control.
‘The sign and display market segment covers everything from banners, over car wraps to billboards,’ said David van Driessche, executive director of the GWG and chief technology officer at Four Pees. ‘Each of these products has their own technical requirements and capturing all of them in one specification was no easy task. After some research, it became clear we would have to introduce two key variables – viewing distance and scaling factor – to derive one specification.’
‘After some research, it became clear we would have to introduce two key variables – viewing distance and scaling factor – to derive one specification,’ said van Driessche.
Viewing distance is the average distance between the final printed work and a typical viewer. This can be as little as 1 metre (3ft) for banners, or as much as 75 metres (250ft) for highway billboards. This concept is used because typically, the bigger the viewing distance, the lower the image resolution can be.
Scaling factor is another widely-used concept in the sign and display market. Because files can become very large, and typical editor applications are not always up to the task, many designers create their PDF file at half, 1/10th or even 1/48th of the final printed size. The rules in the Ghent Workgroup specification of course have to take this into account as well.
‘We could have created different specifications for each product type in sign and display, but that would have been very complex to create and maintain,’ continued van Driessche. ‘Instead we incorporated the concepts of viewing distance and scaling factor and end up with one set of rules for the whole market segment.’ Of course, applications that create or preflight PDF files can choose how they decide to integrate the rules and could still provide different templates or preflight profiles for different product types.
The specification and associated preflight profiles are available from the Ghent Workgroup website. They can be downloaded here.
This area also contains contact information in case you want to give feedback on the specification or preflight profiles, and a link to a webinar recording about this new specification given earlier by David van Driessche and Elli Cloots (vice-chair at the Ghent Workgroup and senior product marketing manager at EFI). Additional documentation will be added later. As everything else created by the workgroup, everything is available completely for free.
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