Overview
ISO/TS 18621-31:2024 is a technical specification for assessing the perceived resolution of graphic arts printing systems using the Contrast–Resolution test chart. The document defines the test chart, the printing and scanning conditions required to reproduce and capture the chart reliably, the method to interpret digitized data, and the resolution‑score computation used to quantify perceptual resolution. It is intended for characterization of complete printing workflows rather than isolated components.
Keywords: ISO/TS 18621-31:2024, Contrast–Resolution chart, perceived resolution, printing systems, image quality evaluation, resolution‑score.
Key Topics and Requirements
- Contrast–Resolution test chart: A vector-based chart that samples contrast (modulation) and spatial frequency (line pairs per mm) across orthogonal axes with logarithmic spacing to reflect human visual response.
- Printing process requirements: Conditions and data-path constraints for faithful reproduction of the test chart on target substrates (see normative annexes for conformance details).
- High-resolution scanner requirements: Characteristics and conformance criteria for digitizing printed charts so that scanned data accurately represent printed tonal and spatial information.
- Evaluation procedure: Steps for printing, scanning, signal interpretation, spatial filtering, and element identification leading to a normalized 2‑D cross‑correlation and resolution‑score computation.
- Resolution‑Score method: A standardized processing chain that yields a quantitative measure of perceived resolution for a given printing system under defined viewing conditions.
- Reporting: Required elements for test reports so results are reproducible and comparable across facilities.
- Normative annexes include test chart files, printing/data-path prescriptions, linearization, scanner conformance, evaluation conformance, and spatial-filter specifications.
Applications and Who Uses It
- Print manufacturers and press vendors use the method to characterize and compare device performance.
- Quality managers and production engineers apply the standard for process control, acceptance testing, and troubleshooting (e.g., screening, substrate choice, or RIP settings).
- Color and imaging laboratories use the resolution‑score to validate scanning setups and to quantify perceptual detail across workflows.
- R&D and standards bodies reference the method to relate system MTF characteristics to perceived image quality.
Practical uses include process benchmarking, pre‑production validation, recipe optimization, and objective comparison of print technologies.
Related Standards
- ISO/TS 18621 series (other parts of the image quality evaluation methods for printed matter) - consult the ISO catalogue for related parts and cross‑references.
- Concepts referenced: Modulation Transfer Function (MTF) and human contrast sensitivity, which underpin the test chart design and interpretation.
For implementation details, normative annexes in ISO/TS 18621-31:2024 provide test chart files, scanner conformance criteria and the precise evaluation workflow needed for reproducible, comparable results.
Open preview (PDF)Graphic technology — Image quality evaluation methods for printed matter — Part 31: Evaluation of the perceived resolution of printing systems with the Contrast–Resolution chart
