Barney Cox, PrintWeek, 02 October 2009

The lack of a standard for colour in digital has been troubling printers, but moves are afoot to fix the problem, finds Barney Cox

Colour accuracy and consistency are becoming increasingly important. In the offset world, the move is towards print produced to the ISO 12647 colour standard.

The problem for anyone producing digital print is that there are no standards for digital colour – neither toner nor inkjet. The ISO 12647 specification is process-specific and, while the most common part of the standard, ISO 12647-2, refers to offset reproduction, there are other parts of the standard that relate to other production processes, including gravure and flexo. Digital production was never included within the specification, so there is no part of the standard designed to reflect the realities of digital print.

“There is no official requirement for day-to-day and job-by-job consistency,” says Andreas Kraushaar head of pre-press at Fogra, the German research body that also offers colour management and technology certification. “There is no standard, and there is no research to base that standard on.”

Fogra proposes to carry out a research project into the quality and consistency of digital print, which it hopes to get the go ahead for by the end of the year.

In the meantime, although there is no digital standard, the rise of digital print and its use alongside offset means it is becoming more and more important that the output matches and is consistent, especially as strides are made in the offset market with ISO 12647-2 to introduce greater consistency.

According to Bodoni Systems managing director Ian Reid, the target people are attempting to standardise on is ISO 12647-2 for paper types 1 or 2, which are coated gloss and matt and commonly represented by the Fogra 39L dataset.
Immediately, most digital presses hit a problem because, bar the HP Indigo, they can’t use those coated stocks.

“The problem is down to paper colour and ink, but primarily where digital devices fall down is on the solid ink colours,” says Reid. “If you print a solid on toner-based presses it looks out (compared to 12647-2).”

For offset production, there is an ISO standard for inks, ISO 2846, which specifies the colour for ink needed to print to ISO 12647, there’s no equivalent in digital, the pigments in the toners and digital inks aren’t necessarily a close match to those laid down by ISO 2846.

Stumbling block
With no standard for digital press colorants, achieving a match is hampered from the off.

HP Indigo is an exception, as its inks are a close match colorimetrically to the ISO 2846 specification. Printers using Indigo technology report that ISO conformance tools, such as Bodoni PressSign and Mellow Colour ISO litho, show the Indigo conforms pretty much out of the box, as long as you practice regular maintenance and calibration.

Today, proofs are mostly produced using inkjet, but due to the rise of toner for short-run production and its lower
cost per page, it is increasingly being seen as a technology for proofing.

“With digital, you can proof and do production on the same device,” says HP Indigo product manager, strategic marketing, Lior Lewin.

Within the ISO 12647 standard, there is a specification for contract proofing, ISO 12647-7. As a proofing specification, the tolerances are much tighter than for production. As previously explained by Bodoni’s Reid, that creates a problem for proofing on toner-based printers as their colours aren’t a close enough match to litho inks.

To get around this, Fogra developed what it termed FograCert Validation Printing certification. There has been much wrangling about whether to incorporate this within ISO 12647-7 or to implement it as a separate part of the standard as ISO 12647-8. This is due to concerns about its broader tolerances and the potential for confusion in the proofing market.

Filling the void
Despite the potential to confuse the market, Validation Printing certification has been leapt on by digital press manufacturers in the absence of a standard for digital colour as a guide for printers looking to invest in digital technology.
“Since there is no standard for digital, the vendors are appropriating Validation Printing,” says Kraushaar. “It’s not dedicated for production machines – it’s missing specification for consistency on the run and from job-to-job.”

So, it’s not a guarantee that what you print will hit the standard, but it is an indication that the system you buy (and it needs to be considered as a system – it’s particular to the workflow and substrates as well as the press) is able to get quite close to the ISO specification.

While some experts question the relevance of the scheme, vendors have got behind it. “Printers don’t have money to spend on equipment that can’t hit the target,” says Xerox Europe graphic art marketing manager Job Rombout. “So they need tools that show their equipment can hit the target. Products that have this certification meet that benchmark.”
Canon European marketing manager Mark Lawn adds: “There is an increasing demand for quality and the issue is how you measure quality. Validation Printing is one of those tools.”

Canon has got FograCert for its ImagePress C1+, 6000 and 7000 series production machines.

Xerox has 13 printer and front end configurations in the 40-70ppm space that have Validation Printing certification from Fogra and aims for all machines and workflows to be certified in due course. At the higher end, the iGen4, in combination with CGS Oris workflow, has the certification and Xerox marketing manager for iGen and DocuColor Kevin O’Donnell says: “Our aim is to get compliance across all machines and all workflows.” Its latest machines, the 7002 and 8002, are currently awaiting certification as they use a new toner.

Validation Printing certification is fine as far as it goes, but it’s only part of the solution.

“It’s fine for showing what the kit is capable of doing, but there is still the issue of day-to-day operation,” says O’Donnell. “It’s just like an offset press, if you want consistency, you have to put the work in.”

Data issues
Finding precise data from manufacturers about the stability of their machines is hard, although, according to research carried out at Xerox’s Smart Centre, typically the colour consistency of a digital press varies by a delta E of two-to-three. In the worst case, there are instances where machines can show variation in some colours of 12-13 delta E. As delta E is a measure only of noticeable colour difference, it is clear a delta E of 13 represents a glaringly visible deviation.

“One of the biggest issues is good paper husbandry,” says O’Donnell. “People say a job has changed from week to week and we find they’ve printed it on a stock with a different white point, or just on the same stock but with different humidity.”
In digital, you need to find different ways of working to provide stable colour.

“With litho, you’ve got a colour bar on every sheet and in a 5,000 run you’ve got the time and the materials to take a couple of hundred sheets to get to colour,” says Bodoni’s Reid. “With digital, there’s no time or budget to adjust colour.”

“We’re trying to automate it, hence the inline spectrophotometers on our latest machines,” O’Donnell says. “With them we can measure and control consistency over time.”

The digital vendors use Validation Printing Certification as a benchmark for their machines, but acknowledge it’s shortcomings for production print. EFI sales development manager Kerry Moloney says: “Validation Print was designed for proofing, not for production, so the rules aren’t quite right. That’s where future standards will need to come in.”

BEYOND ISO 12647
Last month, the TC 130 committee – the group of experts who cover print technology for the ISO – met in Beijing to discuss the future.

Fogra’s Andreas Kraushaar chairs working group three, the group within TC 130 that is looking at the area of developing a future print standard.

As for plans for a digital production standard – nobody knows today, he says. My expectation is to start an all new print standard with a new number and, unlike ISO 12647, it won’t be a process standard. With digital printing techniques, it is impossible to differentiate by technical results. There are no longer clear sub groups by technology. Different parts of the standard won’t refer to different technology, but for usage cases with agreed criteria. Customers don’t care about the process, but about the result.

He believes that the key consideration will be achievable colour gamut, but other issues including resolution and light fastness will also be important.

It’s very early days at the moment, which means there is an opportunity for the industry to provide its feedback on what it considers to be important for the next standard.

There is no draft, there are ideas and concepts and the plan in Beijing was to get agreement to start work to create an all-new document, says Kraushaar. We’re calling for people’s thoughts and ideas.

Nu mi-am propus în acest articol să intru în detaliile tehnologiei tiparului digital. De fapt urmăresc să clarific doar câteva aspecte esențiale ale acestei tehnologii aflate în prag de maturitate.
Stricto senso, tipar digital înseamnă reproducerea unei imagini digitale pe un suport fizic. De aici și până la adevăratele semnificații ale termenului de tipar digital este cale lungă.
In extenso tipar digital înseamnă orice tipărire a unei imagini folosind tehnologii de imprimare cu cerneală sau toner, fără a fi necesară realizarea unei matrițe sau a unei plăci (ca în cazul tiparului offset).
Urmând calea bătătorită deja de fotografie, tiparul se apropie din ce în ce mai mult de tehnologia digitală.
Destinat în general tirajelor foarte mici și mici sau personalizării printurilor realizate prin tehnologiile clasice, tiparul digital câștigă teren nu atât datorită scăderii prețului echipamentelor cât reducerii costului per copie.
O utilizare des întâlnită a tiparului digital este tiparul la cerere (POD – Print on Demand), destinat în special pieței de carte cu tiraj redus, este o tehnologie în care cartea se tipărește numai după ce a fost comandată de utilizatorul final. POD mai este folosită pentru tipărirea «semnalului» editorial sau pentru comenzi reduse după epuizarea tirajului inițial.
Printul cu date variabile (VDP – Variable Data Print) este un caz particular de aplicare a tehnologiei POD în care fiecare exemplar tipărit este diferit atât de precedentul cât și de următorul. Practic există două secvențe de date, una comună întregului tiraj și o alta care diferă  de la exemplar la exemplar, aflată de regulă într-o bază de date. Imposibil de realizat cu tehnologiile clasice, tiparul cu date variabile ramâne prin excelență apanajul echipamentelor digitale.
Se remarcă câteva direcții esențiale în dezvoltarea acestei tehnologiilor de tipar digital:

• Tiparul destinat pieței de tiraje mici, pe suport de hârtie și carton;
• Tiparul pe suport de material plastic, destinat pieței de ambalaje și etichete în tiraje reduse (cosmetice, parfumerie etc.);
• Tiparul de format mare, pentru planșe, hărți afișe cu aplicare indoor sau outdoor;
• Tiparul cu date variabile (VDP);
• Tiparul la cerere (POD).

În această prim articol mi-am propus să abordez doar segmentul de tipar pe hârtie și carton.
Derivate inițial din imprimantele de mare capacitate, echipamentele de tipar digital au evoluat profitând de experiența producătorilor de copiatoare. Printre cele mai întâlnite echipamente destinate pieței “Digital press” regăsim:

• iGen de la XEROX
• Indigo de la HP
• NexPress de la Kodak
• VarioPrint de la Oce
• Xeicon de la Punch Graphics Int
• Meteor de la MGI

Fie că folosesc hârtie în coală sau bobină (cut sheet sau web) tehnologiile sunt asemănătoare și constau în realizarea unui strat subțire (thin layer) de cerneală sau toner la suprafața hârtiei, lucru ce constituie deosebirea esențială față de tiparul offset (cerneala tipografică se impregnează în substrat).
O altă tendință în industria de profil este mărirea capacității copiatoarelor, multifuncționalelor și a imprimantelor departamentale în așa fel încât o mare parte din ele au ajuns să fie folosite pentru producție tipografică în zona de tiraje mici și foarte mici.
De multă vreme, în România, echipamente de tipul BH C451 sau C550 de la Konica Minolta sau multifuncționalele din seria WorkCentre 7xxx sunt folosite în copyshop-uri sau în tipografii pentru producția de materiale tipărite cu dimensiune A3 sau SRA3.
Deși sunt limitate din punct de vedere tehnologic ele acoperă o plajă destul de largă de utilizări.
Printre problemele des întâlnite la echipamentele de tip multifuncțional sau imprimantă departamentală îmi permit să enumăr câteva:

• potrivirea față-verso mai mult decât aproximativă (adesea erorile sunt de ordinul a 1–1,5  sau chiar 2 mm);
• imposibilitatea de a reproduce degradeuri și suprafețe mari de culoare uniformă;
• calibrare greoaie sau chiar imposibilă în absența unui controler de tip Creo sau Fiery;
• instabilitatea în timp a culorilor;
• probleme numeroase cu transportul hârtiei datorate în special mecanismului de preluare cu rolă;
• dificultăți în lucrul cu hârtie subțire (sub 80gmp) sau groasă (peste 250‑280 gmp)
• necesitatea imperioasă de a lucra cu hârtia recomandată de producător lucru care cel mai adesea se traduce prin dublarea sau chiar triplarea prețului hârtiei folosite.

Am să încerc mai jos o trecere în revistă a echipamentelor existente pe piață în acest moment împreună cu câteva caracteristici tehnice mai importante.

Konica Minolta, bizhub series (BH)

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