New GWG Specification for Sign & Display Market


Staff member
GWG (Ghent Workgroup) has released a new specification to address the Sign & Display segment. The new specification incorporates the factors of viewing distance, scaling and wide gamut. This allows having one specification to address the big differences in printing techniques within typical sign & display jobs, and will make the delivery of PDF files for Sign & Display much easier and bring standardization to this segment.

Viewing distance
Viewing distance—the average distance between the final printed work and a viewer—can be as little as 1 meter for banners, or as much as 75 meters for highway billboards. Typically, the bigger the viewing distance, the lower image resolution can be.

Scaling is another widely used factor, because files can become very large, and many designers create PDF files at half, 1/10th or1/48th of the final printed size. The rules in the GWG specification take this into account.

Wide gamut
The new specification opens up which colour spaces can be used in a PDF file. 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.

The specification and application settings are available now—free-of-charge—from the Ghent Workgroup web site.


Well-known member
Not sure what the 'clarity' issue is?
Let me know as we have a meeting next month, we can work on it


Well-known member
Not sure what the 'clarity' issue is?
Let me know as we have a meeting next month, we can work on it

I guess it depends on who the intended audience is and my level of ignorance. It is usually good practice with technical documents to begin by stating who the intended audience is and their expected level of understanding. E.g. something like "This document is intended to be used by prepress staff charged with preflighting PDF Documents. It is expected that they have a basic understanding of PDF and color management terms as well as PDF creation from native design applications."

The stated goal is "This document describes the requirements that a PDF must comply with to follow the GWG2015 - Digital specification."
However I'm not sure that a graphic designer can use this document to create a PDF for files to be digitally printed, either on small format (cut sheet) presses or on large format devices (printers or presses) as stated.

The document mostly says what you shouldn't do and not what you should do. For example:

"4.24 Classic Delivery Method
A PDF file shall not contain any print content that uses any of the following color spaces. These color spaces shall not be used as an intended or alternate color space:
• DeviceRGB
• CalRGB
• CalGray
• ICCbased (i.e. ICC based grayscale, RGB, Lab and CMYK color spaces)
Additionally, print content shall not use the following color space as an intended color space:
• Lab
ICC based RGB"

Also "Classic Delivery Method" is the title - so I expected the contents to be about couriers, email, CDs etc. But instead it's about color spaces. Further, most of the terms like "CalRGB," "ICCbased" are not defined. Most creatives work and are familiar with sRGB or Adobe RGB neither of which are in this document.

Another one:

"3.13 Effective image resolution 
Effective image resolution is defined by the Width and Height keys of the Image dictionary combined with the current transformation matrix. If the effective image resolution differs between the Width and Height directions, the smaller of the two values applies."

Well, what should the resolution of my images be? The document never actually says this in a way that, I think, a graphic designer can understand. Most may think of dpi or dpi+lpi of the screening when it comes to resolution.

I could go on with more examples.
But the key is: who is the audience for this document? What is the intended use of the document? To create original documents? To export those document as PDFs or is it only for people that are preflighting incoming PDFs or...??
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Well-known member
The target market for the document are companies who develop preflight solutions, so Developers/QA etc.

To that goal, the terms, definitions, and requirements describe how the various checks should be created on a technical level.

The various settings for the requirements, ie resolution and the preflight level of severity are in chapter 5 at the back.

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