Overview
ISO 18903:2002 - "Imaging materials - Films and paper - Determination of dimensional change" specifies standardized methods for quantifying how photographic films and papers change size due to environmental and processing factors. The standard covers dimensional effects from changes in relative humidity (humidity coefficient of expansion), temperature (thermal coefficient of expansion), photographic processing, and ageing. It addresses specimen history (moisture and thermal), conditioning and preconditioning, atmospheric conditions during measurement, data treatment and reporting. (Not applicable to instant photographic film.)
Key topics and technical requirements
- Scope and definitions: precise terms such as dimensional change due to processing, dimensional hysteresis, length/width (machine/cross) directions.
- Specimen selection & handling: representative, defect-free samples; moisture-resistant gloves; avoidance of contamination and breathing on specimens.
- Conditioning & preconditioning: establishment of equilibrium moisture content and controlled thermal history to manage hysteresis effects before measurement.
- Atmospheric control: use of constant-humidity chambers and defined temperature/RH environments; reference to ISO/TR 18931:2001 for humidity measurement and control.
- Tests provided:
- Humidity coefficient of expansion (change per unit length per 1% RH)
- Thermal coefficient of expansion (change per unit length per 1 °C)
- Dimensional change due to processing
- Dimensional change due to processing plus ageing
- Data treatment & reporting: standardized calculations, reporting formats and conditioning/ageing histories to ensure traceable, comparable results.
- Informative annexes: numbering of related standards (Annex A), example measurement methods (Annex B), and discussion of dimensional hysteresis (Annex C).
Note: ISO 18903 defines the test conditions, specimen history requirements and data handling, but does not mandate specific measurement instruments; Annex B describes common approaches.
Practical applications
- Quality control for photographic film and paper manufacturers to certify dimensional stability.
- Material selection and specification for reprographics, scanning, printing and photomechanical reproduction, where dimensional changes of even 0.01% can be critical.
- Archival and conservation decision-making for storage environments and treatments of photographic collections.
- Aerial mapping and geospatial imaging where dimensional uniformity impacts accuracy.
- R&D and comparative testing for new base materials (e.g., polyester vs. cellulose acetate).
Who should use this standard
- Materials and process engineers in photographic and imaging product companies
- Conservation scientists, archivists and museum technicians
- Independent testing and calibration laboratories
- Photogrammetry, reprographics and geospatial professionals concerned with dimensional fidelity
Related standards
Keywords: ISO 18903, dimensional change, imaging materials, photographic films, photographic paper, humidity coefficient of expansion, thermal coefficient of expansion, conditioning, dimensional hysteresis, processing, ageing.
