Overview
ISO 12642-3:2021 - Graphic technology - Input data for characterization of 4-colour process printing - Part 3: Extended data set including near neutral scale - defines a standardized data set of ink value combinations for characterizing four‑colour (CMYK) process printing. It is an alternative to ISO 12642‑2 when more neutral scale / grey scale data are required. The document provides a robust, process‑agnostic collection of ink value sets that can also be used with any three chromatic inks plus a dark ink.
Key technical topics and requirements
- Data set definition: The standard specifies ink value sets (ink value combinations) identified by ID numbers. New neutral-focused combinations were added as IDs 1618–1646; in total a valid ISO 12642‑3 data set shall include all 1617 ink value sets.
- Replacement of duplicates: 29 duplicate patches present in ISO 12642‑2 were removed and replaced by 29 new near-neutral and K‑only patches to improve grey scale characterization.
- Tone value precision: Tone values are expressed as whole integer percentages except for magenta and yellow in the CMY grey scale, which use one decimal place derived from CGATS TR 015 grey‑balance formulae - important for light greys (0–20%).
- Layout flexibility: No mandatory physical patch size or layout. Users may randomize arrangement to fit measurement equipment, but CMY and K-only grey ramps are recommended as contiguous ramps along an edge to reduce in‑line ink variation effects.
- Digital image precision: Printable target generation is typically done with 8‑bit per channel images (adequate for most uses); 16‑bit source images with LSB error diffusion are noted for higher precision when needed.
- Compatibility: ISO 12642‑3 is not a replacement for ISO 12642‑2 but provides compatibility guidance - deleted IDs and equivalents allow recreation of ISO 12642‑2 data for comparison.
Practical applications and users
ISO 12642-3 is intended for anyone involved in color characterization, profiling, and quality control of process printing:
- Prepress engineers and color management specialists creating ICC profiles
- Print service providers (offset lithography, gravure, flexography, digital)
- Packaging and publication printers requiring improved neutral scale data
- Color scientists and labs using spectrophotometers for automated scanning
- Software vendors implementing printable target generation and profiling tools
Benefits include standardized, neutral-rich reference data for more accurate grey balance measurement, improved profile computation, and consistent cross‑process comparisons.
Related standards & resources
- ISO 12642‑2 (Expanded data set) - complementary; ISO 12642‑3 is an alternative when near‑neutral data are prioritized.
- CGATS TR 015 - referenced for grey‑balance calculations.
- Downloadable layout and image files (example layouts, TIFF/PDF) and the full ID listing are available from the ISO website (standards.iso.org).