Overview
ISO/TS 20791-3:2023 - Photography - Photographic reflection prints - Part 3: Evaluation of glossiness - defines standardized methods to characterize the glossiness of photographic reflection prints. The technical specification combines two complementary measurements: specular gloss (intensity of mirror-like reflection) and image clarity (distinctness or sharpness of the reflected image). It applies to all common photographic printing technologies including inkjet, thermal dye transfer, electrophotography, and silver halide processes. The goal is to provide reproducible measurement procedures for product development and comparison rather than routine production QA.
Key Topics and Requirements
- Two primary properties: specular gloss and image clarity (also called distinctness of image, DOI).
- Measurement methods: based on ISO 2813 (specular gloss) and ISO 17221 (image clarity), adapted for photographic prints.
- Instrumentation: use a calibrated glossmeter (per ISO 2813) for specular gloss; image clarity instruments follow ISO 17221 principles.
- Angles: gloss measurements are standardized at 20°, 60° and 85°; 20° is recommended for photographic prints with a wide range from high gloss to matte. 60° and 85° are used for other gloss ranges.
- Directional measurements: measure gloss both perpendicular and parallel to the printing direction and report both values plus their average.
- Sample preparation:
- Test patches: at minimum white (Dmin) and black; optional C, M, Y, R, G, B, grey patches. sRGB patch values (ISO 18944) may be used.
- Patch size: ≥ 25 mm × 25 mm; specimen size: ≥ 30 mm × 30 mm.
- Environmental conditioning: standard printing conditions 23 °C ± 3 °C and 50 % RH ± 10 % RH; inks requiring curing should be conditioned (recommendation: at least two weeks under 23 °C ± 2 °C, 50 % RH ± 5 % RH if cure duration is unknown).
- Backing: prints are recommended to be backed (black boards preferred) to keep surfaces flat; backing must be reported.
- Reporting: measurement conditions, instrument calibration, specimen backing and directional values must be documented.
Applications and Who Uses It
ISO/TS 20791-3:2023 is useful for:
- Print product designers and material developers comparing surface appearance across print technologies.
- Manufacturers and OEMs evaluating surface treatments, coatings, or paper/film substrates.
- Photographic labs and imaging specialists optimizing finish (gloss/matte) for end-use applications.
- Standards bodies and test laboratories performing objective comparisons of print appearance.
This specification helps ensure consistent, reproducible evaluation of perceived shininess and reflected image sharpness, supporting informed design and product comparisons.
Related Standards
- ISO 2813 - Paints and varnishes - Determination of gloss values (20°, 60°, 85°)
- ISO 17221 - Plastics - Determination of image clarity (degree of sharpness of reflected/transmitted image)
- ISO 18913 - Imaging materials - Permanence - Vocabulary
- ISO/TS 20791 series (other parts) for broader photographic material guidance
Keywords: ISO/TS 20791-3:2023, photographic reflection prints, glossiness, specular gloss, image clarity, glossmeter, photographic print testing.