Why does optimization of VDP jobs matter?

Would you fill your brand-new Ferrari with cheap and inferior fuel? It’s a question posed by Martin Bailey in his new guide: ‘Full Speed Ahead – how to make variable data PDF files that won’t slow your digital press’. It’s an analogy he uses to explain the importance of putting well-constructed PDF files through your DFE so that they don’t disrupt the printing process and the DFE runs as efficiently as possible. 

Here are Martin’s recommendations to help you avoid making jobs that delay the printing process, so you can be assured that you’ll meet your print deadline reliably and achieve your printing goals effectively:

If you’re printing work that doesn’t make use of variable data on a digital press, you’re probably producing short runs. If you weren’t, you’d be more likely to choose an offset or flexo press instead. But “short runs” very rarely means a single copy.

Let’s assume that you’re printing, for example, 50 copies of a series of booklets, or of an imposed form of labels. In this case the DFE on your digital press only needs to RIP each PDF page once.

To continue the example, let’s assume that you’re printing on a press that can produce 100 pages per minute (or the equivalent area for labels etc.). If all your jobs are 50 copies long, you therefore need to RIP jobs at only two pages per minute (100ppm/50 copies). Once a job is fully RIPped and the copies are running on press you have plenty of time to get the next job prepared before the current one clears the press.

But VDP jobs place additional demands on the processing power available in a DFE because most pages are different to every other page and must therefore each be RIPped separately. If you’re printing at 100 pages per minute the DFE must RIP at 100 pages per minute; fifty times faster than it needed to process for fifty copies of a static job.

Each minor inefficiency in a VDP job will often only add between a few milliseconds and a second or two to the processing of each page, but those times need to be multiplied up by the number of pages in the job. An individual delay of half a second on every page of a 10,000-page job adds up to around an hour and a half for the whole job. For a really big job of a million pages it only takes an extra tenth of a second per page to add 24 hours to the total processing time.

If you’re printing at 120ppm the DFE must process each page in an average of half a second or less to keep up with the press. The fastest continuous feed inkjet presses at the time of writing are capable of printing an area equivalent to over 13,000 pages per minute, which means each page must be processed in just over 4ms. It doesn’t take much of a slow-down to start impacting throughput.

If you’re involved in this kind of calculation you may find the digital press data rate calculator at https://blog.globalgraphics.com/tag/data-rate/ useful:

Global Graphics Software’s digital press data rate calculator.
Global Graphics Software’s digital press data rate calculator.

This extra load has led DFE builders to develop a variety of optimizations. Most of these work by reducing the amount of data that must be RIPped. But even with those optimizations a complex VDP job typically requires significantly more processing power than a ‘static’ job where every copy is the same.

The amount of processing required to prepare a PDF file for print in a DFE can vary hugely without affecting the visual appearance of the printed result, depending on how it is constructed.

Poorly constructed PDF files can therefore impact a print service provider in one or both of two ways:

  • Output is not achieved at engine speed, reducing return on investment (ROI) because fewer jobs can be produced per shift. In extreme cases when printing on a continuous feed (web-fed) press a failure to deliver rasters for printing fast enough can also lead to media wastage and may confuse in-line or near-line finishing.
  • In order to compensate for jobs that take longer to process in the DFE, press vendors often provide more hardware to expand the processing capability, increasing the bill of materials, and therefore the capital cost of the DFE.

Once the press is installed and running the production manager will usually calculate and tune their understanding of how many jobs of what type can be printed in a shift. Customer services representatives work to ensure that customer expectations are set appropriately, and the company falls into a regular pattern. Most jobs are quoted on an acceptable turn-round time and delivered on schedule.

Depending on how many presses the print site has, and how they are connected to one or more DFEs this may lead to a press sitting idle, waiting for pages to print. It may also delay other jobs in the queue or mean that they must be moved to a different press. Moving jobs at the last minute may not be easy if the presses available are not identical. Different presses may require different print streams or imposition and there may be limitations on stock availability, etc.

Many jobs have tight deadlines on delivery schedules; they may need to be ready for a specific time, with penalties for late delivery, or the potential for reduced return for the marketing department behind a direct mail campaign. Brand owners may be ordering labels or cartons on a just in time (JIT) plan, and there may be consequences for late delivery ranging from an annoyed customer to penalty clauses being invoked.

Those problems for the print service provider percolate upstream to brand owners and other groups commissioning digital print. Producing an inefficiently constructed PDF file will increase the risk that your job will not be delivered by the expected time.

You shouldn’t take these recommendations as suggesting that the DFE on any press is inadequate. Think of it as the equivalent of a suggestion that you should not fill your brand-new Ferrari with cheap and inferior fuel!


Full Speed Ahead: how to make variable data PDF files that won't slow your digital press edited by Global Graphics Software

The above is an excerpt from Full Speed Ahead: how to make variable data PDF files that won’t slow your digital press. The guide is designed to help you avoid making jobs that disrupt and delay the printing process, increasing the probability of everyone involved in delivering the printed piece; hitting their deadlines reliably and achieving their goals effectively.

DOWNLOAD THE FREE FULL GUIDE HERE: https://bit.ly/fsa-pdf

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About the author:

Martin Bailey, CTO, Global Graphics Software
Martin Bailey, CTO, Global Graphics Software

Martin Bailey first joined what has now become Global Graphics Software in the early nineties, and has worked in customer support, development and product management for the Harlequin RIP as well as becoming the company’s Chief Technology Officer. During that time he’s also been actively involved in a number of print-related standards activities, including chairing CIP4, CGATS and the ISO PDF/X committee. He’s currently the primary UK expert to the ISO committees maintaining and developing PDF and PDF/VT.

Full Speed Ahead: How to make variable data PDF files that won’t slow your digital press

The use of variable data has increased exponentially over the past five years and is emerging in new applications such as industrial inkjet. Yet poorly designed variable data PDF files disrupt production and reduce ROI.

Watch the recent webinar with Global Graphics Software’s CTO Martin Bailey, the author of Full Speed Ahead, a new guide to offer advice to anyone with a stake in variable data printing, including graphic designers, print buyers, production managers, press operators, composition tool developers and users.

In the webinar Martin presents an overview of the guide and highlights some of the key tips and tricks for graphic designers, prepress and print service providers, showing how, when they all work together, VDP jobs can fly through digital presses.

Sponsored by Delphax Solutions, Digimarc, HP Indigo, HP PageWide Industrial, HYBRID Software, Kodak, Racami and WhatTheyThink, the guide is a practical format for easy reference and includes:

• Tips and tricks for making fast, efficient PDF files for variable data printing
• Helpful illustrations, photos and explanatory diagrams
• Real examples from industry

You can download your copy here: https://www.globalgraphics.com/full-speed-ahead

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Improve inkjet output quality with PrintFlat™

If you print on an inkjet press you’ll know that the problem of non-uniformity or banding is a particularly difficult one to resolve. It’s especially acute on areas of flat tints with the result that printed output is unacceptable to you and to your customers. This means you either don’t run certain jobs on your inkjet press or, in some sectors of the market, are forced to sell your output at a discount.

The good news is that with PrintFlat you have a solution that is quick to deploy and cost-effective, and it can be applied to any workflow with or without a RIP. With more press vendors adopting this technology, watch our new explainer video to see how you might benefit.

Find out more about PrintFlat here.


Where is screening performed in the workflow?

In my last post I gave an introduction to halftone screening. Here, I explain where screening is performed in the workflow:


Halftone screening must always be performed after the page description language (such as PDF or PostScript) has been rendered into a raster by a RIP … at least conceptually.

In many cases it’s appropriate for the screening to be performed by that RIP, which may mean that in highly optimized systems it’s done in parallel with the final rendering of the pages, avoiding the overhead of generating an unscreened contone raster and then screening it. This usually delivers the highest throughput.

Global Graphics Software’s Harlequin RIP® is a world-leading RIP that’s used to drive some of the highest quality and highest speed digital presses today. The Harlequin RIP can apply a variety of different halftone types while rendering jobs, including Advanced Inkjet Screens™.

But an inkjet press vendor may also build their system to apply screening after the RIP, taking in an unscreened raster such as a TIFF file. This may be because:

  • An inkjet press vendor may already be using a RIP that doesn’t provide screening that’s high enough quality, or process fast enough, to drive their devices. In that situation it may be appropriate to use a stand-alone screening engine after that existing RIP.
  • To apply closed loop calibration to adjust for small variations in the tonality of the prints over time, and to do so while printing multiple copies of the same output, in other words, without the need for re-ripping that output.
  • When a variable data optimization technology such as Harlequin VariData™ is being used that requires multiple rasters to be recomposited after the RIP. It’s better to apply screening after that recomposition to avoid visible artifacts around some graphics caused by different halftone alignment.
  • To access sophisticated features that are only available in a stand-alone screening engine such as Global Graphics’ PrintFlat™ technology, which is applied in ScreenPro™.

Global Graphics Software has developed the ScreenPro stand-alone screening engine for these situations. It’s used in production to screen raster output produced using RIPs such as those from Esko, Caldera and ColorGate, as well as after Harlequin RIPs in order to access PrintFlat.

Achieve excellent quality at high speeds on your digital inkjet press: The ScreenPro engine from Global Graphics Software is available as a cross platform development component to integrate seamlessly into your workflow solution.
Achieve excellent quality at high speeds on your digital inkjet press: The ScreenPro engine from Global Graphics Software is available as a cross platform development component to integrate seamlessly into your workflow solution.

The above is an excerpt from our latest white paper: How to mitigate artifacts in high-speed inkjet printing. Download the white paper here.

Streaks and Banding: Measuring macro uniformity in the context of optimization processes for inkjet printing

Dr Danny Hall, Chief Screening Scientist, Global Graphics Software

Global Graphics Software’s chief screening scientist, Dr Danny Hall, discusses the emerging standards designed to objectively characterize directional print variations with particular reference to the ISO TS 18621.21 standard:

Directional printing artifacts like streaks and banding are commonly encountered problems in digital printing systems. For example, inkjet systems may produce characteristic density variations due to inconsistencies between printheads or intra-printhead variations between nozzles. When these variations have a high spatial frequency they can be characterized as causing ‘streaking’ in the direction of print, where the variations have a low spatial frequency this can cause the appearance of ‘banding’ in the direction of print.

Other causes of directional streaking and banding effects may be due, for example, to variations in the speed of printhead or substrate velocities resulting in density variations across the direction of printing. The ‘wow’ and ‘flutter’ of the digital printing age.

In the décor market there is a visual perceptual test sometimes referred to as a ‘porthole test’. In this test a human subject is presented with a print (e.g. wallpaper or floor covering) rotating slowly behind a round window under controlled viewing conditions. If they can determine the direction of printing then it test is a ‘fail’. One aspect of the porthole test is that it allows for the perceptual response differences between different printed images, for example the same press and conditions may be able to print one job containing a lot of graphical detail, but still fail on another job requiring flat tints.

There are currently emerging standards designed to objectively characterize this type of directional print variation.  For example, the proposed ISO TS 18621-21 standard defines a measurement method for the evaluation of distortions in the macroscopic uniformity of printed areas that are oriented in the horizontal and/or vertical direction, like streaks and bands.

Such recognized standards could be very useful for the development and maintenance of printing systems; as well as potentially allowing for the quantitative comparison of directional quality between different printing systems.

Having an objective ISO measurement of directional uniformity would therefore be a very useful step forward and something we at Global Graphics would like to encourage.

As a first step the current ISO TS 18621-21 proposal looks good and useable and provides for a robust and simple metric that can be calculated using standard equipment.

However, in exploring the potential use of this standard we also note a few limitations which may constrain the widest possible utility for a general directional measure in printing. For example, the frequency response of the proposed measurement technique may limit the response of the measure to higher frequency ‘streaking’ artifacts, this may be inevitable with the measurement devices available but this potential spatial frequency bias needs to be clearly understood and accepted.

Another challenge in standardizing such a metric across different printing platforms is the difficulty in selecting some kind of objective color tint to measure. The ‘goodness’ of the proposed ISO TS 18621-21 metric will depend on the color tint chosen for measurement; therefore making such measurements standard between systems with different color gamuts is a difficult and perhaps impossible task. Nonetheless we would like to propose a color tint selection strategy which at least a priori could have the potential to provide a selection of standardized color tints that could be used meaningfully with ISO TS 18621-21 across a range of different printers.

Frequency response

The frequency response is discussed in the ISO proposal.  There is a potential bias in the measuring methodology towards lower frequencies due to the suggested 6mm sampling cut-off. For example, in our experience the main frequency elements of ‘streakiness’ may not be captured by this methodology potentially resulting in a bias towards lower-frequency ‘banding’ effects. That’s not necessarily a problem, it just needs to be understood that this metric may be biased towards ‘banding’ over ‘streakiness’ determination.

Where any streakiness is random and un-correlated with lower frequency banding: changes in high frequency streakiness can be expected to show up statistically as variations at lower frequencies (white noise). However, there are currently printing compensation systems available (such as PrintFlat ™) which can correct for directional variations so that high and low frequency variations are no longer correlated in a gaussian way. In such a case the proposed metric could in the worst case be blind to any underlying changes in high frequency streakiness variation above the band-pass of the sampling system.

Color selection

The proposed standard does not specify the printed color to use, which may make objective comparisons between systems based on this metric difficult and the metric itself is correlated with the underlying contrast of the tint selected. For example, one can expect an apparently better metric to result from printing a 5% tint compared to a 70% tint of the same ink. Therefore, an objective method for selecting color tints could be helpful and this is something we would like to explore.

This is an abstract from Danny’s forthcoming talk at the TAGA Annual Technical Conference, March 17 – 20, 2019 in Minneapolis, MN.

Register here: https://www.taga.org/register/

ScreenPro™ with PrintFlat™ removes banding on large format posters

Watch our latest video showcasing our award-winning technology, ScreenPro with PrintFlat.

Global Graphics Software’s Technical Services team worked with Ellerhold AG, the leading poster printing house in Germany, to enhance the printing quality of its large-format posters. The result was 100% customer satisfaction and an increased market share of outdoor advertising products in digital printing.

Questions from the Inkjet Conference, Düsseldorf

The Inkjet Conference Düsseldorf has been and gone for another year and we’re already looking ahead to the 2019 events that will be organised by ESMA.

This year delegates in the audience were able to submit questions via an app for the first time. I’m grateful to the IJC for sending me the questions that we either didn’t have time to cover after my presentation, or that occurred subsequently. So here they are with my responses:

Is it possible to increase the paper diversity with software by e.g.  eliminating paper related mottling?

Yes, we have yet to come across a media/ink combination ScreenPro™ will not work well with. The major artefact we correct for is mottle. This may mean you can print satisfactory results with ScreenPro on papers where the mottle was unacceptable previously, so increasing the diversity of papers that can be used.

It sounds like ScreenPro is very good at tuning a single machine. How do you also then match that output quality among several machines?

There are two technologies in ScreenPro, the screening core itself with the Advanced Inkjet Screens (AIS), and PrintFlat™ to correct for cross web banding. ScreenPro generally improves print quality and Mirror and Pearl screens (AIS) work in the majority of screening situations. PrintFlat, however, needs to be tuned to every press and if the press changes significantly over time, if a head is changed for example, it will have to be recalibrated. This calibration actually makes subsequent ink linearization and colour profiling more consistent between machines as you have removed the cross-web density fluctuations (which are machine specific) from the test charts used to generate these profiles.

“We haven’t found ink or substrate that we couldn’t print with.” Does this include functional materials, such as metals, wood, rubber? or is it limited to cmyk-like processes?

No – with ScreenPro we have only worked with CMYK-like process colours, i.e. print that is designed to be viewed with colour matching etc. ScreenPro is designed to improve image quality and appearance. I see no reason why ScreenPro would not work with functional materials but I would like to understand what problems it is trying to solve.

What is the main innovation of the screening software in terms of how it works as opposed to what it can do?

“How it works” encompasses placing the drops differently on the substrate in order to work around common inkjet artefacts. The innovation is therefore in the algorithms used to generate the screens.

Advanced Inkjet Screens are standard in the ScreenPro screening engine


Avoiding the orange peel

When you speak frequently at industry events as I do, you can tell what resonates with your audience. So, it was very gratifying to experience the collective nodding of heads at the Inkjet Conference in Neuss, Dusseldorf this week.

I gave an on update mitigating texture artifacts on inkjet presses using halftone screens.

You see, it turns out that there is more commonality between inkjet presses than we previously thought. I’m not saying that there is no need for a custom approach, because there will always be presses with specific characteristics that will need addressing through services like our BreakThrough engineering service.

What I am saying is that we’ve discovered that what matters most is the media. And it gives rise to two distinct types of behavior.

On reasonably absorbent and/or wettable media drops tend to coalesce on the substrate surface in the direction of the substrate, causing visible streaking especially in mid and three-quarter tones. These issues are amenable to correction in a half tone.

Whereas on non-absorbent, poorly wettable media such as flexible plastics or metal, prints are characterized by a mottle effect that looks a bit like orange peel.

This effect seems to be triggered by ink shrinkage during cure. This can be corrected with a halftone with specially designed characteristics. We have one in test on real presses at the moment.

So it won’t be long now before we introduce two advanced screens for inkjet that will greatly improve quality on the majority of inkjet presses. One to counteract streaking. The other to counteract the orange peel effect. And the next project is to address non-uniformity across the web. Fixing that in software gives you the granularity to address every nozzle separately on any head/ electronics.

And for those presses aforementioned with unique properties that need special tuning? Our Chameleon design tools can create unique halftones for these cases.

I do like it when a good plan comes together!

Preparing for the Inkjet Conference 2015

Making progress in half-tone screening technology – our samples are ready to display!

We’re really looking forward to the Inkjet Conference in Düsseldorf next week. Global Graphics’ CTO, Martin Bailey, will be speaking at the conference and focusing on the problems inkjet vendors have encountered when printing on high-speed inkjets, particularly with regard to optimum image quality and droplet placement.

With this in mind, for the last few months we’ve been working with a number of inkjet press manufacturers to develop entirely new half-tone screening technology for presses that can vary the amount of ink delivered in any one location on the media. We’ve just received our sample prints to show you at the Conference and we’re really pleased with the results – you can see the improvement immediately.

The samples show typical ‘before and after’ scenarios: The ‘before’ samples are quite noisy and show mottle and puddling; the ‘after’ samples, printed with Global Graphics screening technology, show much smoother gradients where we manage the transition of droplet size in multi-level heads.

We have also prepared sample prints showing what the output looks like with no tuning on: They show noise and steps in gradients for multi-level output, then we demonstrate what happens when we use transition points of drop size when using inks such as white, orange and violet in the colour spectrum.

Look out for Martin at the Conference and drop by our table in the IJC Networking Arena to see the prints for yourself.

If you are interested in the benefits of half-tone screening on high-speed inkjets and would like to join our research programme, watch our video here for more information: https://www.youtube.com/watch?v=WNrSbb46efg.

Alternatively, contact Martin Bailey directly: martin.bailey@globalgraphics.com

Read Martin’s abstract here: