Overview
ISO/TS 18621-22:2024 is an international technical specification developed by ISO for the graphic technology industry, focusing on evaluating image quality in printed matter. This part of the ISO/TS 18621 series defines a process independent measurement method for the evaluation of colour graininess in printed products. The standard outlines requirements for the test forms, measurement devices, and the calculation formulas used to derive the colour graininess score (SCG). By establishing a common reference for evaluating graininess, ISO/TS 18621-22:2024 supports consistency and comparability in print quality assessments across varying printing technologies.
Key terms: image quality, colour graininess, print evaluation, SCG score, graphic technology standard.
Key Topics
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Process-Independent Measurement:
The standard specifies methods for measuring colour graininess that are not dependent on the particular printing process or technology used, enabling cross-platform comparability.
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Test Form Requirements:
Guidelines are provided for designing test forms, including the selection and placement of colour patches to ensure representative sampling across colour gamuts.
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Measurement Devices:
Requirements focus on the use of colorimetrically characterized flatbed scanners with sufficient resolution (minimum 600 ppi), ensuring accurate and repeatable colour measurements.
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Colour Graininess Score (SCG):
The document details how to calculate the SCG value by applying visual transfer-simulating Gaussian filters, analyzing CIEDE2000 colour differences at the micro-region level, and averaging results for a quantifiable score.
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Reporting Requirements:
Clear instructions are given on how to document and report the SCG, ensuring transparency regarding the evaluated system, printing conditions, and measured colour patches.
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Interpretation Guidelines:
An annex provides practical description categories to help interpret the meaning and visual impact of specific SCG levels, aiding communication with stakeholders and customers.
Applications
ISO/TS 18621-22:2024 is invaluable for a range of stakeholders in the graphic technology and printing industries seeking reliable methods for print quality evaluation:
- Print Manufacturers & Service Providers:
Objectively assess and benchmark image quality, specifically colour graininess, to meet client requirements or industry standards.
- Quality Control Laboratories:
Integrate standardized graininess evaluation in quality assurance protocols to ensure consistent print outputs and reduce customer complaints.
- Equipment Manufacturers:
Use the standard during R&D and production stages to compare and improve the graininess performance of new printing devices or substrates.
- Print Buyers & Brand Owners:
Reference quantifiable print quality parameters when specifying or accepting printed products, helping ensure visual appeal and consistency.
- Research & Development:
Facilitate comparative studies across different printing technologies and support innovation in imaging science.
Related Standards
ISO/TS 18621-22:2024 is part of a broader suite of standards and technical specifications in the field of print and image quality evaluation:
- ISO/IEC 24790: Measurement of image quality attributes for hardcopy output
- ISO/CIE 11664-6: CIEDE2000 colour-difference formula
- ISO 12641-1 & ISO 12641-2: Colour targets for input scanner calibration
- ISO 3664: Viewing conditions for graphic technology and photography
For a full list of related standards and guidance on their application, visit ISO Graphic Technology Standards.
Implementing ISO/TS 18621-22:2024 provides a robust foundation for objective, cross-technology evaluation of colour graininess, enhancing print quality management and customer satisfaction throughout the graphic technology sector.