Tag Archives: color spaces

Getting to know PDF 2.0 – update from Down Under

Are you ready for PDF 2.0? Register now for the PDF 2.0 interoperability workshops in the UK and USA.

Martin Bailey, CTO, Global Graphics Software

Martin Bailey, CTO, Global Graphics Software

I’ve been in the ISO PDF committee meeting in Sydney, Australia for a couple of days this week to review the comments submitted to the most recent ballot on PDF 2.0. Over 100 comments were received, including some complex issues around digital signatures, structure tagging (especially lists), optional content, document parts and soft masks. In all cases the committee was able to reach a consensus on what should be done for PDF 2.0.

The plan is now for one more ballot, the responses to which will be reviewed in Q2 next year, with an expectation that final text for PDF 2.0 will be delivered to ISO for publication shortly thereafter.

So we’re still on track for publication next year.

All of which means that it’s past time that a couple of PDF’s unsung heroes were acknowledged. The project leaders for PDF 2.0 have invested very substantial amounts of time and mental energy updating text in response to comments and ballots over the last several years. When somebody like me requests a change it’s the project leaders who help to double-check that every last implication of that change is explored to ensure that we don’t have any inconsistency.

So a big thank you to Duff Johnson of the PDF Association and Peter Wyatt of CISRA (Canon)!

It’s also worth noting that one of the significant improvements in PDF 2.0 that probably won’t get highlighted elsewhere is that the text now is much more consistent. When you’re writing a detailed technical document 1000 pages long it’s inevitable that some disconnections between different sections will creep in. PDF 2.0 illustrates the value of a broad group of people from many countries and many industries reviewing text in the ISO process: we’ve managed to stamp on many of those cases in this new version.

Getting to know PDF 2.0: rendering PDF transparency

Are you ready for PDF 2.0? Register now for the PDF 2.0 interoperability workshops in the UK and USA.

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In the middle of 2017 ISO 32000-2 will be published, defining PDF 2.0.  It’s eight years since there’s been a revision to the standard. In the second of a series of blog posts Martin Bailey, the primary UK expert to the ISO committee developing PDF 2.0, looks at the changes to rendering PDF transparency for print.
These changes are all driven by what we’ve learned in the last few years about where the previous PDF standards could trip people up in real-world jobs.
Inheritance of transparency color spaces
Under certain circumstances a RIP will now automatically apply a color-managed (CIEBased) color space when a device color space (such as DeviceCMYK) is used in a transparent object. It will do that by inheriting it from a containing Form XObject or the current page.
That sounds very technical, but the bottom line is that it will now be much easier to get the correct color when imposing multiple PDF files from different sources together. That’s especially the case when you’re imposing PDF/X files that use different profiles in their output intents, even though they may all be intended for the same target printing condition. The obvious examples of this kind of use case is placing display advertising for publications, or gang-printing.
We’ve tried hard to minimize impact on existing workflows in making these improvements, but there will inevitably be some cases where a PDF 2.0 workflow will produce different results from at least some existing solutions, and this is one case where that could happen. But we believe that the kinds of construct where PDF 2.0 will produce different output are very uncommon in PDF files apart from in the cases where it will provide a benefit by allowing a much closer color match to the designer/advertiser’s goal than could be achieved easily before.
Clarifications on when object colors must be transformed to the blend color space
The ISO PDF 1.7 standard, and all previous PDF specifications were somewhat vague about exactly when the color space of a graphical object involved with PDF transparency needed to be transformed into the blending color space. The uncertainty meant that implementations from different vendors could (and sometimes did) produce very different results.
Those statements have been greatly clarified in PDF 2.0.
This is another area where an upgrade to a PDF 2.0 workflow may mean that your jobs render slightly differently … but the up-side is that if you run pre-press systems or digital presses from multiple vendors they should now all be more similar to each other.
As a note to Harlequin RIP users, the new rules are in line with the way that Harlequin has always behaved; in other words, you won’t see any changes in this area when you upgrade.
ColorDodge & Burn
It tends to be taken for granted that the older PDF specifications must match what Adobe® Acrobat® does, but that’s not always correct. As an example, the formulae for the ColorDodge and ColorBurn transparency blending modes in the PDF specification have never matched the implementation in Acrobat. In pursuit of compatibility Harlequin was changed to match Acrobat rather than the specification many years ago. In PDF 2.0 the standard is finally catching up with reality and now both Acrobat and Harlequin will be formally ‘correct’!
The background
The last few years have been pretty stable for PDF; PDF 1.7 was published in 2006, and the first ISO PDF standard (ISO 32000-1), published in 2008, was very similar to PDF 1.7. In the same way, PDF/X 4 and PDF/X 5, the most recent PDF/X standards, were both published in 2010, six years ago.
In the middle of 2017 ISO 32000-2 will be published, defining PDF 2.0. Much of the new work in this version is related to tagging for content re-use and accessibility, but there are also several areas that affect print production. Among them are some changes to the rendering of PDF transparency, ways to include additional data about spot colors and about how color management should be applied.

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