Overview
ISO 7004:2002 - "Photography - Industrial radiographic films - Determination of ISO speed, ISO average gradient and ISO gradients G2 and G4 when exposed to X- and gamma-radiation" defines standardized test methods for measuring the sensitometric behavior of industrial radiographic film systems (film + processing) exposed directly to X‑ and γ‑radiation. The standard covers how to obtain a sensitometric curve and derive ISO speed, ISO average gradient, and point gradients G2 and G4. It does not apply to film systems used with fluorescent intensifying screens.
Key topics and requirements
- Scope and definitions - film system, system type, radiation quality, net and minimum density, gradients, etc.
- Sampling and storage - evaluate representative batches and store samples per manufacturer recommendations to reflect typical consumer use.
- Handling - films must be handled in complete darkness (no safelight exposure) during exposure and processing.
- Environmental conditions - samples exposed at 23 °C ± 5 °C and 50% ± 20% relative humidity.
- Exposure and radiation quality - four representative sources (two X‑ray, two γ‑ray) are specified to reflect practical use. X‑ray generator requirements (per ISO 4037‑1) include constant-voltage operation and high-voltage stability within ±1%.
- Filtration and tube specs - example X‑ray filtration requirements: low‑potential source with total filtration equivalent to 2.0 mm ± 0.1 mm Cu and half‑value layer adjustment (approx. 120 kV); high‑potential source with 8.00 mm ± 0.05 mm Cu equivalent (approx. 220 kV). (See standard for full radiation-quality details.)
- Processing and densitometry - film development must be defined when reporting results; density measurements follow ISO density standards (ISO 5‑2, ISO 5‑3).
- Evaluation and calculations - procedures to derive ISO speed, ISO average gradient, point gradients (G2, G4), uncertainty assessment, product classification, and marking/labeling requirements.
- Informative annexes - units of measured energy, scattered radiation measurement, ionization chamber calibration, and radiation quality codes.
Applications and users
ISO 7004:2002 is intended for practical use in:
- Radiographic film manufacturers reporting standardized film characteristics (ISO speed, contrast metrics).
- Non‑destructive testing (NDT) laboratories validating film performance for industrial radiography.
- Quality assurance and procurement teams specifying film systems for X‑ray and gamma radiography.
- Calibration and test laboratories performing sensitometric evaluations and comparative studies.
- Standards committees and regulatory bodies aligning national test methods with international practice.
When publishing ISO speed or gradient values, users must specify the radiation quality and film processing used, since results depend on both.
Related standards
- ISO 4037‑1: X and gamma reference radiation (radiation characteristics and production)
- ISO 5579: Radiographic examination - basic rules
- ISO 5‑2 / ISO 5‑3: Density measurements (geometric and spectral conditions)
Keywords: ISO 7004:2002, industrial radiographic films, ISO speed, ISO average gradient, G2 G4 gradients, X‑ray radiography, gamma‑ray radiography, sensitometric curve, film processing, NDT.