Overview
ISO 17850:2015 - Photography - Digital cameras - Geometric distortion (GD) measurements - defines a standardized protocol to measure geometric distortion of digital still cameras, including camera phones. The standard addresses the total image distortion produced by a camera system (lens plus in-camera signal processing) and provides measurement methods, test-chart specifications, data-extraction algorithms, and presentation formats for reporting GD results.
Key topics and requirements
- Measurement methods: Two complementary approaches are defined - local geometric distortion (dot-chart analysis) and line geometric distortion (grid-chart analysis).
- Test charts and planarity: Requirements for dot charts and grid charts, including design characteristics and flatness/planarity constraints, to ensure accurate GD measurements.
- Apparatus, lighting, and camera settings: Specifications for test setup, controlled lighting, camera positioning, exposure, white balance, and focus to minimize measurement variability.
- Data extraction and algorithms: Procedures to locate dot centers or grid intersections, validate detections, compute ideal vs. actual positions, and derive the GD map. Annexes provide illustrative examples and practical algorithms (e.g., dot extraction, centre validation, grid sort).
- Quantification and reporting: Numerical definitions for local and line GD, calculation of peak-to-peak (maximum) distortion values, and standardized presentation of results for consistent comparison.
- Normative references and related methods: Cross-references to ISO 14524 (OECF measurements), IEC 61146-1, and EBU Tech3249 for related measurement practices.
Applications and users
ISO 17850:2015 is intended for:
- Camera and camera-phone manufacturers for design verification, production QA, and feature specification (GD performance).
- Imaging test laboratories and third-party benchmarkers performing objective, repeatable distortion measurements.
- Optical designers and systems engineers analyzing combined lens + processing distortion effects.
- Standards bodies and compliance teams comparing products or validating improvements across firmware, lens assemblies, or manufacturing tolerances.
Practical uses include performance benchmarking, troubleshooting aberrant distortion in production, validating firmware corrections (distortion correction algorithms), and documenting GD in product specifications.
Related standards
- ISO 9039 - methods for measuring distortion of a lens as a separate optical system (ISO 17850 measures the whole camera, including signal processing).
- ISO 14524, IEC 61146-1, EBU Tech3249 - referenced for complementary measurement methods and definitions.
Keywords: ISO 17850:2015, geometric distortion, GD measurements, digital cameras, camera phones, dot chart, grid chart, local geometric distortion, line geometric distortion, camera test protocol.
