Specifications for Web Offset Publications

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Comparison of some RGB and CMYK colour gamuts on a CIE 1931 xy chromaticity diagram

Specifications for Web Offset Publications, invariably abbreviated to SWOP, is an organization and the name of a set of specifications that it produces, with the aim of improving the consistency and quality of professionally printed material in the United States, and of certain other products, programs and endorsements related to their work.

The SWOP specification covers many areas related to print production, complementing, extending and limiting those in other industry standards. The specification includes (but is not limited to) the following.

  • A specification for the colors of the cyan, magenta, yellow and key inks used in CMYK printing. Inks conforming to the specification can be called SWOP inks. The specifications make reference to, but are not identical to, the ISO standard ISO 2846-1:2006.
  • A specification for the colors of proofs produced by various technologies, so they are accurate representation of the SWOP inks eventually used to print. (See SWOP Certification Program below). Proofs made from systems that meet these specifications may be called SWOP Proofs.
  • Specifications for expected dot gain (caused by ink dots enlarging over absorbent papers).
  • Design constraints, such as the minimum size of type which is to printed reversed or knocked out of a background, to keep legibility.
  • Production constraints, such as a limit of 300% on the total mixture of inks (taking a mixture of 100% each of cyan, magenta, yellow and black as being 400%).

SWOP also endorse, produce or specify some other things.

  • ICC profiles for color management, based on the standard called TR001, an ANSI technical report whose full title is “CGATS TR001-1995 Graphic Technology-Color Characterization Data for Type 1 Printing.” SWOP make reference to this, and a number of profiles using this are made with SWOP in the title, such as the profile USWebCoated (SWOP), which is widely available because it is included with many Adobe applications. TR001 profiles are not universal, because they were generated and tested with specific inks, papers, and printing technologies.
  • The SWOP booklet gives the specifications mentioned above, often in reference to other industry specifications (ISO and other).
  • A SWOP Certification Program for proofing (not press) printing systems. This is used by manufacturers, rather than purchasers, of systems.

SWOP is a non-profit volunteer organisation, and concerns itself only with the United States. In some other areas, similar efforts have been made by other organisation, taking account of national variations in printing techniques, expectations, and requirements.

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