Can ISO 15339 deliver on cross-process promise?

Simon Eccles
Monday, June 30, 2014

Colour is the lifeblood of any self-respecting printer. And so any opportunity to further assure all colour is exactly as it should be –particularly where the printer is dealing with highly sensitive brand-matching jobs – will hopefully be gratefully snapped up.

Printers may well, then, have had their interest piqued of late by talk of a new colour management standard ISO 15339, due to be launched later this year. Colour management is also often a fiendishly complicated area though and, as such, not as well understood in the industry as perhaps it should be. So PrintWeek has delved into the details of what this standard will mean for the industry.

What is ISO 15339?

ISO 15339 is a proposed new international colour management standard for specifying the final appearance of printed CMYK colours, regardless of press, printing process or substrate. It will also enable print buyers and printers to agree on levels of tolerance, ie how close the colours need to come to the ideal, with presumably a range of price scales to go with this. 

It may be published as a standard later this year. However, there’s still quite a lot of dissension in the standards committee ranks, with the US members pushing for early publication and the UK, German and Japanese members in particular arguing for further revision so it will be fully compatible with the existing ISO 12647 process control standard for print. It’s due to go to a final vote.

What’s the requirement?

Elie Khoury, the founder of colour consultancy and colour management software developer Alwan Color Expertise in Lyon, France, is an ISO TC130 graphics standard committee member and an advocate of both ISO 12647 and 15339. There’s a strong requirement for cross-process colour standardisation, he says: “Brand owners today may have between 10 and 50 different printed parts in their packaging, all of them needing the same colours – the box, the can, the film, the label, etc. In a Johnnie Walker whisky pack, for example, there are 47 different print operations, with flexo, gravure, offset and digital. 

“It’s impossible to match all these print processes with 12647. So 15339 is necessary to match the colours across processes. We recommend it for any workflow, but when it comes to matching colours across two or more different processes, then you absolutely need it.”

When 15339 does arrive the intention is that it will be followed over the following 12 months or so by the complementary standards ISO 17972-4, which will define special (ie non-process) colours in a new and more flexible way for printing on a range of media, and ISO 16761, which will set a standard certified workflow for colour measurement.

According to Khoury: “For the first time ISO standards will enable us to standardise workflows (16761) and communicate colour without ambiguity between brand owners, print buyers and printers (15339 and 17972), in order for these colours to be accurately reproduced on any process.”

What does it do?

ISO 15339 is a way to characterise colour results, with the intention being to provide a way to get the same colour appearance regardless of print process or substrate media. The precision of the match will be catered for by three tolerance levels. 

There are two parts to ISO 15339. Part 1 defines the characterisation data that a printer has to reproduce, with the necessary steps in order to colour manage the data. It takes into account some parameters that today’s standards don’t, including substrate correction.

Part 2 defines seven colour gamuts called Characterised Reference Printing Conditions (CRPC) that can be achieved by various processes. As the diagram opposite shows, they are hexagons with the points representing the primary colours that are achieved by CMY inks (black is not chromatic so doesn’t affect gamut). 

The smallest data set, CRPC1, is the gamut achievable on offset newsprint. CRPC6 is what offset presses can achieve on the best coated papers. CRPC7 can only be achieved by some digital presses and other especially wide-gamut CMYK processes. Profiles have already been registered with the International Color Consortium (ICC) for converting images to all of these gamuts. 


ISO 15339: the seven proposed CRPC gamut maps

crpc-gamut-map

 

 

 

 

 

 

 

 


 

This is where some of the international committee members’ doubts start to creep in. Juergen Seitz, senior technical advisor at GMG, is a German member of the ISO TC130 Working Group 3 committees. He says that the first six CRPC gamut sets are all based on offset presses and papers, and only CRPC7 is something else, being based on GMG’s own ColorMaster wide-gamut colour space for ‘process-neutral’ RGB workflows. However, he says that he has made comparative proofs between CRPC and the corresponding GRACol or ISO 12647 settings: “The difference was really minor. On the one hand the standard is a precise description of the target, but on the other I think the process controls that printers are using today are enough to control into the future as well.”

An important part of the standard is the provision for different tolerances of colour accuracy. With ISO 12647 there’s one tolerance and you either pass or fail. Printers often offer their own informal tolerance levels, but strictly speaking they are then non-standard. 

With 15339 there are three pre-defined tolerance levels, A, B and C. Khoury explains: “This lets the printer offer different quality levels. If I as a print buyer want a very small Delta E, say 1.5, that’s level A and I must pay for it. A more relaxed Delta E, level C, may be appropriate for newspapers or freesheets where you don’t need high accuracy. So the buyer will ask for a certain gamut for print and proof, and also a certain tolerance level.”

How does it differ from ISO 12647?

In the past 10 years ISO 12647 has gained ground as a way for printers to demonstrate that they are working to consistent, independent standards. This can be independently certified if required. However, 12647 describes process standards, not final results. You may have a job produced perfectly within the ISO 12647-2 tolerances for offset, then take the same job and produce it perfectly to ISO 12647-6 for flexography, but the results will not necessarily be an exact match.

In particular, 12647 has struggled with digital print and presses, where there are many different ‘marking engine’ technologies and no standard ink or toner colour sets, with each manufacturer doing more or less its own thing. By setting the end result as the goal, rather than defining processes and consumables, ISO 15339 should make it easier to demonstrably match results within cross-process, multi-substrate and multi-country campaigns. 

Another weakness of 12647 is ‘non-standard’ papers, as Khoury explains: “The 12647 solids, tones and tolerances have been calculated on reference substrates. In real life printers don’t print on ISO defined papers. They can be different, sometimes supplied by the customer. If I am printing to ISO 12647 on a different substrate then the assessment is wrong. If I have a yellowish paper then a blue ink will print greener, but the standard is silent on this.”

However, Seitz at GMG is concerned that ISO 15339 still doesn’t compensate enough for the papers that are likely to be used (real papers are much bluer than the standard allows for, he says). “There are formulas to correct the characterisation for other papers, but it’s a really nerdy process,” he adds. 

Khoury says: “15339 does not replace 12647, as it is not about getting the inks and printing units right, it is about having the right colour on the print. The colour is the Fogra-39, GRACol or grey that you would like to see printed accurately. 

“There’s a shift in perspective. 12647 is process control, so it is process-specific. 15339 is data set controls, so it is data set-centric. This is a huge shift between the two standards. They don’t contradict each other: 12647 guarantees that your press is running to standard, while 15339 guarantees you’re printing the right colours.”

How will it be implemented?

Although ISO doesn’t concern itself directly with certification, it’s anticipated that, as with ISO 12647, there will be organisations offering certification. 

However, it also seems that self-certification will be a lot easier than for ISO 12647. As the results can be measured with standard colorimeters, it’s likely that measurement reports could simply be sent to customers to prove that the agreed colours and tolerances have been hit. 

Alwan already supports ISO 15339 parameters in its colour management and measurement software and Khoury expects all the other colour control system developers to support it in time. “All the data is colorimetric,” he says. “The spectrophotometer measurement tools are the same as today, so you don’t need to buy new equipment. It’s just that the target is 15339 aim points and tolerances.”

What’s its status?

At present ISO 15339 is at the FDIS (Final Draft International Standard) stage, which means it is ready for a final vote on publication by the international ISO committees that are responsible for creating it. 

What’s the controversy about?

Craig Revie, principal consultant at FFEI, sits on the ISO TC130 committee that’s concerned with graphic arts standards. He explains the problem that some international committee members have with ISO 15339 in its current form: “In principal, it’s a good idea, but it comes very quickly on the heels of our recent revision to ISO 12647/2 2013 and, unfortunately, it’s incompatible with it.”

Seitz at GMG is also concerned: “We have a mismatch between 12647-2 and 15339 that may lead to potential confusion at the user end. The Americans tried to push this evolution of 15339. They already made a CGAT-21-2 out of it so 15339 is basically a national standard from the US that they are trying to make into an ISO.”

Revie states: “As a consequence of that, at the moment, we on the UK committee are set to vote against 15339. 

“We will vote negatively, as will Japan and Germany and possibly some others, in the hope that this will force a revision.”

If the dissenters don’t get their way and ISO 15339 passes in its current state, then there will start to be localised versions, Revie predicts: “One possibility if the current vote fails is that we would add an extra annex for the 12647 aims, as they are currently defined in Europe and Japan. But that takes a different direction from the idea of a universal way to control printing worldwide. That’s regarded as a fall-back – if we have to go there we will, but most people would prefer not to.”

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