ISO 2469:2024

Overview - ISO 2469:2024 (Paper, board and pulps - Measurement of diffuse radiance factor)

ISO 2469:2024 specifies the general procedure for measuring the diffuse radiance factor (also referred to as diffuse reflectance factor) of all types of pulp, paper and board. This sixth edition replaces ISO 2469:2014 and standardizes instrument characteristics, calibration procedures and ancillary requirements so measurements are comparable between laboratories and over time. The standard addresses both non‑fluorescent materials and materials containing fluorescent whitening agents, where the instrument UV content is adjusted to match a selected CIE illuminant.

Key technical topics and requirements

• Scope and definitions: clear definitions of radiance factor, diffuse radiance factor, reflectance factor and related terminology.
• Measurement principle: diffuse illumination and normal detection using instruments constructed per the standard.
• Apparatus requirements: specifications for reflectometers, reference and working standards, and black cavity components (see Annex A for instrument characteristics).
• Calibration procedures: detailed steps for photometric calibration and UV‑setting of instruments, assignment and use of working standards, cleaning, and calibration verification (see Clause 6 and Annex B).
• Fluorescence handling: procedures for UV adjustment to reproduce fluorescence equivalent to a selected CIE illuminant and preparation of fluorescent reference standards (Annex C).
• Measurement process: sampling, test piece preparation, measurement routines, calculation and expression of results, precision and reporting (Clauses 7–12).
• Uncertainty and supporting info: informative guidance on measurement uncertainty (Annex D) and bibliography for further reference.

Practical applications and users

ISO 2469:2024 is used to produce consistent, traceable diffuse radiance (reflectance) measurements that form the basis for many optical properties and quality controls:

• Measurement of ISO brightness, whiteness, opacity and luminance factors.
• Calculation of derived optical parameters (e.g., Kubelka–Munk coefficients, ERIC - effective residual ink concentration).
• Quality control in pulp, paper and board production and finishing.
• Certification and inter‑laboratory comparison led by standardizing laboratories and accreditation bodies. Primary users:
• Paper, board and pulp manufacturers and converters
• Industrial and commercial testing laboratories
• Instrument manufacturers (reflectometers, spectrophotometers)
• Research institutions and standardizing laboratories

Related standards and references

• ISO 4094 - general requirements for laboratories authorized to issue optical reference transfer standards (normative reference in ISO 2469:2024)
• Standards that define measurement of brightness, whiteness and other optical properties (referenced in ISO 2469 for fluorescence adjustment)

Keywords: ISO 2469:2024, diffuse radiance factor, diffuse reflectance factor, paper board pulps, reflectometer calibration, fluorescent whitening agents, CIE illuminant, optical reference standards.