Within the printing and publishing industries and to a lesser extent in the online information industries, there is a wide-range of ‘standards.’ The use of the term standard is probably incorrect as a real standard is one that has been adopted and supported by an international standards body. The term standard in most cases I am discussing is more of a generic term associated with well-defined and used procedures for common working approaches. My belief is that while there are many ‘standards’ in use for getting the best printing and proofing quality I still see the need for a further standard, this one to cover transferring or communicating very high-quality color data from the creative process through all forms of output process ensuring accurate rendering and reproduction on all forms of output. I outline my reasons for this after first defining what ‘standards’ exist at this time in the creation and printing processes.
In order for work that is to be printed to be output in the manner intended or imagined by the designer, this industry has a wide range of different standards that if used correctly should allow for faithful representation of the designer’s vision. One problem with this is that there are an awful lot of standards, plus a great degree of confusion about which standards to use and also how to use them. The standards problem particularly exists in taking data created in the digital world and outputting it in what is predominantly an analogue world, namely printing. If one restricts the view of how we handle the transfer of color data for printing, and how the printer works with this data, there is still a wide-range of standards that need to be understood.
Standards in the past have tended to evolve somewhat organically and are then adopted when they become of importance. They then need to be fully documented and maintained. More recently standards have been developed and are maintained by special interest groups under the auspices of a standards body. In this situation the major such body is the International Standards Organisation (ISO). Within this organisation there are technical committees in which interested parties are asked to participate as members. Most of the standards relating to printing in color are developed and maintained by the TC130 committee. This committee looks after the following ISO standards:
- ISO 12640 Prepress digital data exchange.
- ISO 12642 Input data for characterization of 4-color process printing.
- ISO 12647 Process control for the manufacture of halftone color separations, proof and production prints.
- ISO 13655 Spectral measurement and colorimetric computation for graphic arts images.
- ISO 15076 ICC color management.
- ISO 15930 Prepress data exchange PDF/X.
As a creator of print output these however are not the standards that one normally refers to or hears about. Instead we hear more of process operational procedures or alliances built around standards. As will be defined later in this paper, many of these are in fact not procedures for handling color printing but procedures for setting up a press to allow it to work in a consistent and measureable manner. The following list identifies the most prevalent of these within the industry:
- CIP4 - The International Cooperation for the Integration of Processes in Prepress, Press and Postpress Organization (CIP4) is a not-for-profit association and is registered with the U.S. Department of Justice and the Federal Trade Commission as a Standards Development Organization. This organisation with over 300 interested party members is responsible for the specification and development of the JDF and JMF standards for job management and job messaging between devices. It evolved from the CIP3 organisation that created the Print production Format PPF for press ink key setting.
- ECI – European Color Initiative working predominantly with FOGRA (see below).
- EuroScale – An earlier standard for standardization of printing presses in Europe.
- FOGRA – The leading organisation in implementing printing standards and color print profiles in Europe. They work closely in providing tools and assistance as test suites and profiles in implementing the latest ISO 12647-2 standard under the definition of FOGRA 39 for sheet fed offset printing and FOGRA 40 for web offset printing.
- GRACoL – A procedure maintained by the IDEAlliance (see below) that stands for General Requirements for Applications in Commercial Offset. This is an old procedure that has been continuously updated and the latest version is GRACoL 7. This is a procedure to allow printers to set up their presses to print to a defined standard.
- G7 – This is simply a major technological change that has been put into the GRACoL and SWOP specifications recently to enhance their working to utilize colorimetry in addition to densitometry based upon a better understanding of gray balance in setting up a press. In this G refers to gray and 7 refers to use of the seven solid ink colors specified with the ISO 12647-2 standard. I am advised that the G7 Data Set was derived from FOGRA 39.
- ICC - International Color Consortium, an international group of interested parties that has open, cross-platform standards for the description and handling of device-independent color. The ICC specification has also been accepted as an ISO standard document. Most prepress workflow systems utilize ICC color profiling for ‘device independent color.’
- IDEAlliance – A predominantly North American members association of interested parties that maintains and supports the GRACoL and SWOP print procedures.
- PANTONE Matching System and PANTONE GOE– These systems are more of a standard way of selecting spot colors than a standard. They permit via both analogue and digital swatch books for creative users to select spot colors to be transferred into the printing process.
- SNAP – Specification for Newspaper Advertising Production. A North American specification for the specifying and printing of newspaper advertising.
- SWOP – A procedure standing for Specification for Web Offset Publications for maintaining printing to a standard maintained by the IDEAlliance. This started in the 1980s and the most recent release has followed GRACoL in adopting the G7 calibration, printing and process control methods.
Within the above there are really two main areas for standardized ways of working. The first is the transfer of data from the creator to the printer. This comes under data transfer and today this is covered under the developments of work within the CIP4 and ICC environments and the ISO 19530 groups implementing PDF/X. The second is in the groups working around the ISO 12647 process control for printing and proofing organisations. Within this are developments including FOGRA 39 and 40, and the IDEAlliance with GRACoL 7 and SWOP. To my mind the two separate groups do not link and operate relatively independently of each other.
With both FOGRA 39/40 and the G7 element of GRACoL 7 and SWOP the standardization of printing presses has become better. Earlier versions of these systems’ routines used densitometry to measure solid ink densities and tonal value increase (previously referred to as dot gain) for press set up with no reference to color. A densitometer does not measure color. With G7 a colorimeter is used to measure gray balance on the press and to set it up to print using the CIE l.a.b. color definitions to work out neutral gray in the midtones. This ensures more consistent printing to a defined standard.
This sounds ideal however there are limitations. The following quotes are taken from the IDEAlliance G7 publication.
The G7 method controls gray balance and neutral density, but not color reproduction. A properly G7- calibrated device should produce gray tones that are extremely similar to any other G7- calibrated device, but colored areas may still be different due to variations in ink colors, ink trapping, etc. (This is also true of TVI-based calibration.) Neither G7 nor TVI calibration alone can guarantee to simulate a reference CMYK color space.
Remember that G7 calibration only controls gray scale appearance, not the appearance of colored areas. Depending on the device you are calibrating, some additional color management (for example ICC profiles) may be needed to optimize the match to a specific reference print condition.
It would appear from the above that with the new approaches for press characterization and calibration linked up with the work of standardized PDF/X file transfer with ICC color management that all the problems should now have been solved. Unfortunately I don’t think that this is the case. What we have now is a colorimetric approach where color is not really device independent as calibration of the data at time of creation is based upon knowing all about the output device and the substrates on which the data is to be printed. ICC profiles are based upon colorimetric data based upon a specific viewing condition. While in most cases the data is generated by a spectrophotometer is it not held and transferred in a spectral format but in tristimulus values of red green and blue (RGB). This causes problems if the job has to be output on a different press or substrate or in a different media. It also does not easily and accurately allow for handling spot colors and ensuring they are printed correctly.
I believe however that the answer is at hand. X-Rite is introducing the latest version of their Color Exchange Format (CxF) that transfers spectral data rather than tristimulus color data. The good thing about CxF is the data is captured at source in a spectral format by a spectrophotometer and carried through the system. It is only converted to color data at the time of output. Printed color can also be checked on certain presses in spectral format as many modern presses have spectrophotometric printed sheet scanning systems that check finished sheets. CxF can also easily be added to existing prepress and printing workflow systems as it is written in the XML format that is used by JDF. CxF files can be carried around the system as an XML attachment in a JDF driven workflow together with all the production data, in the same way that the JMF messaging format works within a JDF environment. The use of CxF would allow a designer working for example with Adobe Creative Suite CS3, to define or specify a color accurately at source and this color can then be communicated to all the various players in the workflow to ensure accurate output. I also envisage developments coming from X-Rite’s Pantone division that will package spectral data automatically as a part of selecting a color in the new PANTONE GOE system.
CxF does not mean that all the press systems I have mentioned in this paper become redundant, far from it. It is essential to have presses set up and running to a consistent standard, and this is what work evolving from the ISO 12647 standard such as FOGRA 39/40 and GRACoL and SWOP provide. I believe that CxF will be the final element that will allow truly device independent color to become a reality rather than a dream.