A printed sheet is the visible end of a long chain: file preparation, plate or cylinder making, ink mixing, press settings, drying and finishing. When a buyer, a prepress house and a pressroom discuss the same job, they need one shared reference for what acceptable means. Process control standards supply that reference. They fix measurable values for solid ink density, dot gain, gray balance, registration and substrate, and they describe how each value is measured.
The ISO 12647 family
Technical Committee TC130 of the International Organization for Standardization writes the documents that cover printing technology. Its output falls into several groups: terminology, prepress data exchange formats, process control, suitability of inks and substrates, and ergonomics or safety. Process control carries the most weight in daily production, because it sets technical requirements and test methods for the quality parameters that decide whether a sheet is acceptable.
ISO 12647 is arranged by printing method, and each part defines minimum values for the parameters of that process:
- Part 1: parameters and measurement
- Part 2: offset lithography
- Part 3: coldset web offset on newsprint
- Part 4: publication gravure
- Part 5: screen printing
- Part 6: flexography
- Part 7: digital printing and proofing
The series rests on separate standards for inks, paper, measurement and viewing conditions, so a density reading means the same thing in two different plants. In export work the standard also acts as a passport: overseas buyers increasingly expect a supplier to state which part of ISO 12647 the job will be run to, and many Chinese printers now build their process sheets around parts 2, 6 and 7, together with ISO 2846 for ink color, ISO 12646 for proofing displays and ISO 10128 for measurement and reporting.
DIN standards
The German Institute for Standardization, DIN, belongs to CEN and ISO and takes a large part in their technical work, holding several secretariats. Around 90 percent of its standards are written with international use in mind, and it publishes a yearly summary of German and international technical rules. The catalogue has reached 31,100 documents, including 2,500 issued in 2000 alone.
In print, DIN 16604 from 1973 covers newspaper and paper sizes, advertising column formats and the spacing between columns, and the A series sheet sizes used every day descend from that work. DIN 16537 from 1998 describes how to measure the gloss of a printed surface. Many of these documents were later adopted by ISO, which is why the German edition of the offset part appears as DIN ISO 12647-2.
Japan Color
Japan Color is a specification and certification system from the Japan Printing Machinery Association, created to push the national industry toward common practice. It conforms to ISO and supplies guidelines for sheetfed offset, newsprint and web offset, revised to suit the local market. The system defines standard inks, reference paper, measured values for solid patches, solid color samples and color reproduction targets. Because Japanese four-color inks follow a defined CMYK hue set, ISO referred to them when comparing ink sets from Europe and the United States, and the offset ink standard ISO 2846-1 grew out of that comparison.
PSO for offset production
Process Standard Offset was written by FOGRA in Munich for the German printing and media industry association BVDM. It builds on ISO 12647-2 and adds supplementary rules, notably a midtone priority when a digital proof and the actual substrate pull color in different directions. Related documents cover other processes, among them PSR for rotogravure, PSN for newspaper and pacSpace for packaging gravure. Their common aim is a run that stays inside tolerance from the first sheet to the last.
SWOP for web offset
The Specification for Web Offset Publications sets parameters for web offset work. It walks through each step of the workflow, from the viewing conditions for copy and proofs to digital file preparation, materials and proofing, and it speaks to advertisers, prepress providers, publishers and printers at the same time. Tolerances are revised as technology changes, and every step in the pressroom is measured and confirmed against them. That structure lets an operator follow the process with statistical tools rather than judging color by eye.
SNAP for newsprint
The Specifications for Newsprint Advertising Production were designed to improve newspaper print quality and the accuracy of information transfer. They address advertisers, agencies, publishers, prepress managers, material suppliers, commercial printers and newspaper printers. The scope is coldset printing on uncoated groundwood newsprint, including offset, letterpress and flexographic presses. Content covers the division of responsibility, a job summary with digital workflow notes and material requirements, plus prepress and press guidance built on tolerance based reference values. The committee cites ANSI and ISO documents throughout.
G7 and GRACOL
GRACOL, the General Requirements for Applications in Commercial Offset Lithography, is run under IDEAlliance in the United States and deals with color reproduction on sheetfed lithographic presses. It follows ISO 12647-2 and works from a neutral gray printing density curve, with the neutral print density curve at the center of the method. G7, released in June 2006, is the current version of that implementation method. G7 is not itself a standard. It is a body of production data and procedures that guides operators, and its measurements are used to adjust CTP plate curves or imagesetter RIP output so that tone and color reproduction improve on a repeatable base.
Other organizations write documents for narrower fields, among them the CGATS image printing standards in the United States, the JMPA work in Japan and the 3DAP standard in Australia. Each one exists to make output predictable across suppliers and across time.
What a buyer should ask for
The practical step is short. Name the standard and the part in the quotation request, ask the printer for measured values from the run, and agree on substrate and viewing conditions before plates are made. Two suppliers can then be compared on the same terms, a reprint has a number to match instead of an impression, and a dispute about color has a document to settle it.