International Color Consortium Issues Major Spec Revision

RESTON, VA, USA—The International Color Consortium (ICC) reports it's issued a major revision of its specification. Says ICC, the revision is designed to eliminate ambiguities that have resulted in concerns about output consistency and interoperability of different profiles and color-management modules.

Comments ICC technical secretary Tony Johnson (of the London College of Printing): "The previous specification has been adopted widely by the color-imaging community and proved very important in achieving and maintaining image color fidelity. This widespread use has also identified ways in which the spec can be improved even further."

Specifically, says ICC, ambiguities in the previous version of the spec could, in some circumstances, allow color-profile producers (for specific devices) to interpret the reference space differently. Thus, some color profiles from different vendors could be inconsistent, and some color-management modules could interpret the same or similar profiles in different ways, ICC explains. "The changes in the spec's new version are designed to ensure profile builders understand the reference color space precisely as well as what is required of the profile exactly," Johnson adds.

ICC says the specification's newest revision was made available last December for a period of review and comment by interested parties. ICC finalized the revision in late February, following the conclusion of the review period. Specific changes include:

  • For perceptual rendering, the dynamic range of the PCS and the assumed level of illumination for viewing have been identified.
  • Chromatic adaptation information now is required if the actual illumination source is not D50. When data is intended for viewing in illumination conditions differing from those of ISO 3664, the transformation required for correction of the data must be specified. This change is expected to be especially important for color-monitor profiles.
  • Where profiles involve more than the usual CMYK colorants, the additional colors now can be specified by the XYZ or L*a*b* coordinates, and the printing sequence also can be specified.
  • New look-up table specifications have been provided, and additional clarifications have been made concerning such issues as rendering intents; definition of tags for three-component devices; and content and structure of monochrome profiles.
"This revision does not mean ICC sees its work as complete," says Johnson. "There still are important issues to address. Many users would like to see ICC ensure profile conformance.… Others have workflow needs that cannot be met with the existing structure easily. ICC is working on approaches to these remaining issues."

The new spec, designated ICC.1:2001-12, Format for Color Profiles, is available for free from the ICC web site color.org.



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