Overview
ISO 7759:2010 - "Anodizing of aluminium and its alloys - Measurement of reflectance characteristics of aluminium surfaces using a goniophotometer or an abridged goniophotometer" - defines a standardized method to measure the reflectance characteristics of high-gloss anodized aluminium (and other high-gloss metal) surfaces. The standard prescribes geometry, apparatus, calibration, test procedure and reporting requirements for objective assessment of surface appearance using a goniophotometer or an abridged goniophotometer. Note: this method is not suitable for diffuse-finish metals and does not measure colour.
Key topics and technical requirements
- Measurement geometry: narrow-source beam incident at 30° to the specimen normal; viewing directions opposite the incidence at −30°, −30° ± 0.3°, −30° ± 2°, −30° ± 5° and −45°.
- Appearance parameters measured:
- Specular reflectance (Rs) - measured at 30° with narrow source/receiver angles.
- Distinctness of reflected image (Ri) - derived from slightly off‑specular readings at 29.7° and 30.3°.
- Narrow-angle haze (Hn) - measured at ±2° from specular.
- Wide-angle haze (Hw) - measured at ±5° from specular.
- Diffuseness (Rd) - measured at 45° (15° from specular).
- Directionality (Dh) - ratio of narrow-angle haze measured transverse vs longitudinal to texture.
- Apparatus and calibration: use a goniophotometer or abridged goniophotometer with specified beam and receiver window sizes; instrument warm-up and voltage regulation required; three calibrated reflectance standards (aluminium mirror, chromium mirror, diffuse white) are specified for calibration checks.
- Procedure essentials: clamp and flatten specimen, measure three areas in longitudinal and transverse orientations (rotate specimen 90°), regularly check standards to ensure calibration stability.
- Reporting: test report must reference ISO 7759:2010 and include instrument details, standards used, numeric results for Rs, Ri, Hn, Hw, Rd, Dh, any deviations and test date.
Applications and who uses it
- Quality control and production acceptance for anodized aluminium used in automotive, architectural, consumer goods and industrial products where consistent metallic appearance is critical.
- Surface engineering and coatings laboratories performing reflectance measurement, finish matching and incoming/outgoing inspection.
- OEMs, specifiers, material suppliers and testing labs that require objective metrics for specular reflectance, haze, and image distinctness to ensure parts match visually when assembled.
Related standards
- Normative reference: CIE 38:1977 (radiometric/photometric characteristics and measurement guidance).
- Prepared under ISO/TC 79 (Light metals and their alloys), subcommittee SC 2 (organic and anodic oxidation coatings on aluminium).
Keywords: ISO 7759:2010, anodizing of aluminium, goniophotometer, reflectance measurement, specular reflectance, haze, distinctness of reflected image, diffuseness, directionality, surface appearance.