ISO 5799:1991

Overview

ISO 5799:1991 - Photography: Direct-exposing medical and dental radiographic film/process systems - specifies standardized methods to determine ISO Speed and ISO average gradient for film/process combinations directly exposed to X‑rays. The standard ensures reproducible sensitometric measurements so film/process performance can be compared between products and suppliers. This second edition updates units (adopting the gray for air kerma) and aligns speed/gradient tables with other radiographic film standards.

Key topics and technical requirements

• Scope: Sensitometric procedures for films exposed directly to X‑ray radiation in medical and dental radiography (excluding mammography).
• Measurement basis: Uses air kerma (gray, Gy) as the exposure quantity and derives ISO Speed and average gradient from sensitometric curves (density vs. log10 air kerma).
• Sampling & storage:
  • Samples stored per manufacturer recommendations to simulate typical product age.
  • Test temperature: 23 °C ± 5 °C; relative humidity 50 % ± 20 %.
• Exposure & densitometry:
  • Graduated exposure series providing densities from 0.2 to 2.3 above base plus fog.
  • Log exposure step increments ≤ 0.15.
  • Densitometer requirements per ISO 5-2 and ISO 5-3; minimum aperture 7 mm, readings ≥ 1 mm from edge.
  • Base-plus-fog measured on an unexposed sample processed with test samples.
• Instrumentation & calibration:
  • Air kerma measured with an ionization chamber calibrated for the radiation quality used.
  • Ion chamber/monitoring recommendations to reduce variability and correct for fluctuations.
• Processing:
  • No single processing recipe is mandated; manufacturers’ recommended processes must be reported because Speed and gradient depend on development conditions.
  • Processing to begin within 30 minutes to 8 hours after exposure.
• Quality controls:
  • Minimize scattered radiation (scattered portion ≤ 5 % of primary).
  • Film holders designed for <2 % absorption.
• Output & designation:
  • ISO Speed and ISO average gradient are calculated from averaged sensitometric data and reported with the ISO designation (e.g., ISO X D 100 for X‑ray direct exposure techniques).
• Informative annexes: Calibration parameters and measurement reproducibility guidance.

Applications and users

ISO 5799:1991 is used by:

• Radiographic film manufacturers for product specification and labeling (ISO Speed / average gradient).
• Medical physicists and quality assurance teams establishing image receptor performance and procurement criteria.
• Dental imaging suppliers and laboratory technicians validating film/process combinations.
• Test laboratories performing comparative sensitometry and conformance testing.

Keywords: ISO 5799:1991, radiographic film, ISO Speed, ISO average gradient, air kerma, sensitometry, densitometry, medical radiography, dental radiography, X‑ray exposure.

Related standards

• ISO 5-1, ISO 5-2, ISO 5-3 (Photography - density measurements)
• ISO 4037 (X and gamma reference radiations)
• ISO 2094 (aluminium composition reference)