Laurel Brunner examines the ISO 12647 colour management standard, looking at how printers can best achieve this beneficial certification

Like it or not, standards are a way of life. The Internet works everywhere, screws fit, tools function, electricity flows and trains travel from country to country, all because of standards. Standards are vital to every aspect of life, and in recent years great strides have been made to develop digital data standards for the printing industry. Most of the best known of these were originally de facto market driven standards such as PostScript and PDF. But some important quality control standards are now gaining recognition as a rising number of printers adopt them, especially ISO 12647, the Graphic Technology Process Control for the Production of Half-tone Colour Separations, Proofs and Production Prints.

Certification is an important part of business, whether it's to prove compliance with a specific standard or to demonstrate competence. In competitive markets such as printing, it can also provide a competitive edge. The use of digital processes for print production has changed expectations for print buyers, and standards compliance is a measure of protection for their print media investments particularly for high quality work.

The latest edition of the ISO 12647 standard reflects the increasingly complex nature of digital colour management and reproduction, and it's relevant throughout the international print market. The objective for ISO 12647 is to provide a minimum set of parameters that define the technical properties and visual characteristics of a piece of print. It provides printers with a means of setting up their presses to match each other. Measurement data from these presses can be used to create ICC profiles, for producing proofs that match the press.

The assumption is that data files which meet the minimum specification will be suitable for producing accurate colour separations. This means that it will be possible to produce accurate proofs from this data, either on or off press. The standard specifies the minimum values for specifying a digital prepress job, in order to quantify the appearance of a printed product.  In this respect ISO 12647 is about facilitating information interchange between printers, prepress departments and print buyers.

It sounds simple enough but there is rather more to ISO 12647, for this is a standard of many parts: ISO 12647 is built on other standards including those for ink, paper, measurement and viewing conditions. There are several parts to the standard. Within each ISO 12647 part, the minimum values are defined for each of the process parameters included in the standard, for different print processes. This could include specific details based on common practise in a particular sector, such as the use of FM screening and direct to plate output in newspapers, or testing methods for checking the properties of digital proofs.

For printers keen to get into standards based production, ISO 12647 Part 1 is obviously the place to start. ISO 12647-1 outlines the methodology to easing information interactions between printers, prepress people and print buyers. It describes the parameters and measurement methods to use and specifies the minimum values for each parameter relevant for a digitally produced job.

There are two classes of parameters defined in ISO 12647, primary and secondary. Primary parameters are those which have a direct influence on the visual characteristics of an image. Primary parameters are all those factors directly influencing colour appearance such as substrate colour and gloss, dot gain, screening, solid ink and intermediate colours, and so on. Secondary parameters are those which might indirectly influence the image's visual characteristics because they might change a primary parameter's values.

The 12647 standard explains how colour production ought to work in the context of the standard. It defines what is meant for example, by grey balance and includes a family of TVI curves referring to six different printing conditions. Colour is defined colorimetrically in ISO 12647 (CIELa*b*, CIEXYZ and by hue, saturation and lightness), in line with ICC (ISO 15076) based workflows. For example, it's important to keep in mind that colour separations are subject to the manner in which colour transforms have been done. As long as colour reproduction takes into account the 12647 process parameters and values throughout the production process and the process parameters for the printing condition, it should be accurate. These are the substrate properties (paper is the single most important factor in colour management), the optical properties of process inks once they are printed, and the TVI (Tone Value Increase) or dot gain. Keeping values consistent throughout the production process is, of course, key.

Secondary parameters include such things as film or plate thickness, whether the plate or film is negative or positive, for film right or wrong reading, its surface texture and the print order. The standard covers all of the parameters relating to the production of the CMYK tone values required for print readiness, as they relate to a multicoloured continuous tone original, be that analogue or digital.

In addition to defining all the parameters that must be managed, ISO 12647 also includes a process vocabulary with definitions for all of the technical terms included in the standard. It assumes breaking images into halftone screens but is nonetheless relevant for all forms of print. Even for printers who don't really want to adopt the full specification, such as printers using inkjet technology and want to ignore the screening parameters, this standard is still useful and relevant.

Where to Begin

For general commercial sheet fed offset printers, ISO 12647-1 is the place to start. All the other parts of 12647 define the minimum sets of process parameters for producing print using a specific production technology. So ISO 12647-2, which is the next step for most printers, describes the process parameters for offset lithography. ISO 12647-3 is for coldset offset on newsprint and for publication gravure printing we have ISO 12647-4, for screen ISO 12647-5, for flexography ISO 12647-6 and for proofing processes (and digital printing) ISO 12647-7.

With all parts the objective is to provide a minimum set of parameters that define the technical properties and visual characteristics of a piece of print. The assumption is that data files which meet the minimum specification will be suitable for producing accurate colour separations and that it will be possible to produce accurate proofs from this data, either on or off press.

Proofing is the most stringent part of the printing and publishing process and proofing technology has to produce characterisation data sets that define the content's appearance for a given printing condition. ISO 12647-7 is the part of the standard that deals with proofing processing and is the most relevant for digital printers. Digital printing technologies each use their own bespoke combinations of ink and media, so it is currently not possible to come up with process parameters that can be applied for all digital press technologies. In the meantime ISO 12647 is a reasonable alternative

Without standards, printers and print buyers must rely either on a common understanding of what they will get coming off press, or on trial and error. Neither approach is wholly acceptable in a commercial environment, and both impede process and workflow automation. ISO 12647 is a starting point for printers who want to minimise the number of halts in the workflow and maximise process automation. ISO 127647 may look intimidating but a growing community of printers worldwide is already reaping the financial, throughput and quality control benefits that it can help yield.

About ISO

The International Standards Organisation, ISO, is an organisation made up of national standards bodies. It is responsible for preparing international standards, work which is done by technical committees. Each national standards organisation can be represented on these committees and international organisations can also contribute to the work. The idea of ISO is to be as open to contributions from interested parties as possible, although in practise it tends to be limited to the people who know most about a given subject, and of course who are willing to put in the time as this work is voluntary. At least 75% of member bodies casting a vote must approve an international standard before it can be published.

About Laurel Brunner

Laurel Brunner started her career in 1978 as an accountant for a printing company. Since then she has worked exclusively in the prepress and publishing industries, with a particular specialisation in prepress production and newspaper technologies. She is managing director Digital Dots (www.digitaldots.org) an international consulting group, and publisher of Spindrift an independent, subscriber supported newsletter for the graphic arts, printing and publishing industries.

Laurel Brunner provides private consulting and editorial services to a wide cross section of publishers and industry associations. Her work regularly appears in newspapers and magazines around the world, and she is a regular speaker at industry conferences in Europe, the United States and Asia.