ISO/TS 18621-21:2023 PDF

Graphic technology — Image quality evaluation methods for printed matter — Part 21: Measurement of 1D distortions of macroscopic uniformity utilizing scanning spectrophotometers

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Title (English):

ISO/TS 18621-21:2023

Graphic technology — Image quality evaluation methods for printed matter — Part 21: Measurement of 1D distortions of macroscopic uniformity utilizing scanning spectrophotometers

Document status:: Active
Format:: Electronic (PDF)
Number of pages:: 7
Publication date:: March 27, 2023
Edition:: ISO TS 18621 edition 2 version 1
ICS:: 37.100.10

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Description (English):

This document defines a measurement method for the evaluation of distortions in the macroscopic uniformity of printed areas that are oriented in the horizontal and vertical direction, such as streaks and bands. It provides requirements for the layout of the test form, the use of a colour measurement device taking measurements in a 2D sampling grid, and the formula to compute the Macro-Uniformity-Score. This document does not cover any non-adjacent or non-horizontal nor vertical patterns. Due to the used spatial frequency, the Macro-Uniformity-Score does not measure high frequency (fine) patterns such as missing nozzles.

Technical details

Technical committee: ISO/TC 130 - Graphic technology
SKU: ISO/TS 18621-21:2023

Abstract

Overview - ISO/TS 18621-21:2023 (Graphic technology)

ISO/TS 18621-21:2023 defines a standardized, instrumented method to quantify 1D distortions in the macroscopic uniformity of printed areas (e.g., banding and streakiness) using scanning spectrophotometers. The method produces a single Macro‑Uniformity‑Score (0–100) based on averaged CIELAB measurements and adjacent CIEDE2000 colour differences along horizontal and vertical directions. The procedure is tailored for large, uniformly tinted areas and intentionally excludes non‑adjacent, diagonal or high‑frequency defects (for example, missing nozzles).

Key topics and technical requirements

Test form and layout
- Uniformly tinted area on an A4 test page with a minimum dimension of 156 mm.
- Typical 2D sampling matrix assuming 6 mm pitch: ~31 × 26 patches (about 806 spots); perimeter patches may be omitted for processing.
Measurement grid and device
- Use a scanning spectrophotometer or a handheld device mounted on an XY table to capture a well‑defined 2D sampling grid.
- Aperture diameter should be between 3 mm and 6 mm.
- Maximum sampling pitch: 6 mm in both directions.
Measurement conditions
- Conform to ISO 13655; white backing per ISO 13655 Annex A.
- Prefer M1 measurement condition and store results in ISO 28178‑compliant format when applicable.
Computation and scoring
- Average CIELAB values along rows and columns, compute adjacent CIEDE2000 differences, normalize and combine horizontal and vertical components.
- Macro‑Uniformity‑Score is computed using a formula (includes fitted factors 40 and 15) and rounded to zero decimals; higher is better (100 = perfect uniformity).
Reporting
- Record test page dimensions, colour encoding, measurement condition/backing, any omitted perimeter patches, and final score.

Practical applications

Objective evaluation of banding, streaks and large‑scale color non‑uniformity in digital, toner and inkjet printing systems.
Quality control and acceptance testing in print production, OEM process validation, color laboratory benchmarking, and R&D for print engine development.
Useful in process control when comparing printers, substrates or ink sets under defined test conditions.

Who should use this standard

Print service providers, OEMs of printers and presses, color quality labs, prepress engineers, and researchers working on image quality metrics and print defect characterization.

Related standards

ISO 13655 - Spectral measurement and colorimetric computation (measurement conformance).
ISO/CIE 11664‑6 - CIEDE2000 colour‑difference definition.
ISO 28178 - Data format for storing colorimetric measurements.
ISO 12647‑7 - Reference point for proofing sampling (9‑point method comparison).

Keywords: ISO/TS 18621-21:2023, Macro-Uniformity-Score, macroscopic uniformity, scanning spectrophotometers, image quality evaluation, banding, streakiness, CIEDE2000, ISO 13655.

Related standards

Standards mentioned in the description

Abstract

Overview - ISO/TS 18621-21:2023 (Graphic technology)

Key topics and technical requirements

Test form and layout
- Uniformly tinted area on an A4 test page with a minimum dimension of 156 mm.
- Typical 2D sampling matrix assuming 6 mm pitch: ~31 × 26 patches (about 806 spots); perimeter patches may be omitted for processing.
Measurement grid and device
- Use a scanning spectrophotometer or a handheld device mounted on an XY table to capture a well‑defined 2D sampling grid.
- Aperture diameter should be between 3 mm and 6 mm.
- Maximum sampling pitch: 6 mm in both directions.
Measurement conditions
- Conform to ISO 13655; white backing per ISO 13655 Annex A.
- Prefer M1 measurement condition and store results in ISO 28178‑compliant format when applicable.
Computation and scoring
- Average CIELAB values along rows and columns, compute adjacent CIEDE2000 differences, normalize and combine horizontal and vertical components.
- Macro‑Uniformity‑Score is computed using a formula (includes fitted factors 40 and 15) and rounded to zero decimals; higher is better (100 = perfect uniformity).
Reporting
- Record test page dimensions, colour encoding, measurement condition/backing, any omitted perimeter patches, and final score.

Practical applications

Objective evaluation of banding, streaks and large‑scale color non‑uniformity in digital, toner and inkjet printing systems.
Quality control and acceptance testing in print production, OEM process validation, color laboratory benchmarking, and R&D for print engine development.
Useful in process control when comparing printers, substrates or ink sets under defined test conditions.

Who should use this standard

Print service providers, OEMs of printers and presses, color quality labs, prepress engineers, and researchers working on image quality metrics and print defect characterization.

Related standards

ISO 13655 - Spectral measurement and colorimetric computation (measurement conformance).
ISO/CIE 11664‑6 - CIEDE2000 colour‑difference definition.
ISO 28178 - Data format for storing colorimetric measurements.
ISO 12647‑7 - Reference point for proofing sampling (9‑point method comparison).

Keywords: ISO/TS 18621-21:2023, Macro-Uniformity-Score, macroscopic uniformity, scanning spectrophotometers, image quality evaluation, banding, streakiness, CIEDE2000, ISO 13655.

ISO/TS 18621-21:2023 PDF

Technical details

Abstract

Overview - ISO/TS 18621-21:2023 (Graphic technology)

Key topics and technical requirements

Practical applications

Who should use this standard

Related standards

Related standards

Abstract

Overview - ISO/TS 18621-21:2023 (Graphic technology)

Key topics and technical requirements

Practical applications

Who should use this standard

Related standards

Related standards

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