Overview
EN ISO 7759:2010 specifies a standardized method for measuring the reflectance characteristics of high‑gloss anodized aluminium surfaces using a goniophotometer or an abridged goniophotometer. The method characterizes visual appearance by quantifying specular and scattered reflection components from a narrow-source beam at a 30° angle of incidence. It is suitable for other high‑gloss metal surfaces but is not intended for diffuse‑finish metals and does not measure colour.
Key topics and technical requirements
- Measurement principle: Illumination at 30° incidence; reflected light measured at specific receiver angles to derive multiple appearance metrics.
- Primary appearance metrics:
- Specular reflectance (Rs) - measured at the specular angle (30°).
- Distinctness of reflected image (Ri) - derived from near‑specular measurements (30° ± 0.3°).
- Narrow‑angle haze (Hn) - measured at ±2° from specular (≈28° or 32°).
- Wide‑angle haze (Hw) - measured at ±5° from specular (≈25° or 35°).
- Diffuseness (Rd) - measurement 15° away from specular (≈45°).
- Directionality (Dh) - ratio of narrow‑angle haze measured parallel and perpendicular to surface texture (rolling/extrusion direction).
- Apparatus: Full goniophotometer or abridged type with fixed 30° incidence and defined receiver windows; rotatable clamp for specimen positioning; calibrated reflectance standards (including evaporated aluminium on glass); optional neutral density filters for very high specularity.
- Calibration & conditions: Geometric and spectral conditions, voltage regulation (instrument supply stability), and calibration against certified standards are specified. Precision and accuracy notes are provided (see Annex A).
Applications
- Quality control and acceptance testing of anodized aluminium finishes in automotive, architectural, appliance and decorative industries.
- Comparative appearance matching for components that must visually match across batches or joining parts.
- Specification and verification of surface-finish performance for suppliers, anodizers and coating laboratories.
- Research and development of surface treatments where directional reflectance and haze influence perceived gloss.
Who should use this standard
- Materials and surface‑finish engineers
- Anodizing and metal finishing laboratories
- OEMs, architects and specifiers requiring reproducible appearance metrics
- Test labs performing optical characterization of metallic finishes
Related standards and notes
- Normative reference: CIE 38:1977 for radiometric/photometric characteristics.
- EN ISO 7759:2010 supersedes earlier EN 12373‑13 editions; consult annexes for instrument precision details.
Keywords: EN ISO 7759:2010, anodizing, anodized aluminium, goniophotometer, reflectance measurement, specular reflectance, haze, distinctness of image, surface appearance.