ISO 1188:1984

Overview

ISO 1188:1984 specifies the recorded characteristic for magnetic sound on full-coat, perforated 16 mm motion-picture film used at the nominal speeds of 24 frames/s (18.3 cm / 7.2 in) or 25 frames/s (19.05 cm / 7.5 in). This International Standard, produced by ISO/TC 36 (Cinematography), defines the nominal recording characteristic, normalized to 400 Hz, and includes numerical approximations and tolerances for practical recording and playback.

The second edition (1984) replaces the first (1974) and documents the frequency-dependent recording level (in dB) expected from magnetic sound records on full-coat 16 mm film. The standard also provides a graphical tolerance band for acceptable recorded levels.

Key Topics

• Nominal speeds: 24 fps and 25 fps for full-coat 16 mm magnetic film.
• Normalized reference: Values are normalized to 400 Hz.
• Frequency characteristic: The standard gives approximate dB values across a frequency range (low frequencies through 16 kHz) and describes how the recorded level falls off with frequency.
• Analytical representation: A logarithmic expression in the document represents the nominal characteristic as a function of frequency; the time constant referenced in the text is provided in the standard.
• Tolerances and calibration: A figure in the standard specifies tolerance bands for recorded level versus frequency to ensure interchangeability and consistent performance.

Applications

This standard is primarily relevant to professionals and organizations working with magnetic sound on 16 mm motion-picture film, including:

• Film laboratories and sound recordists calibrating magnetic recording chains.
• Post-production and duplication facilities ensuring compatible sound transfers.
• Archivists and preservation specialists validating recorded sound fidelity on historic 16 mm magnetic prints.
• Equipment manufacturers designing record/playback heads and chain components for 16 mm magnetic film.

Practical benefits include:

• Consistent frequency response across recordings, improving intelligibility and tonal balance.
• Clear calibration targets for recording and playback equipment.
• Guidance for quality control and interchangeability between labs and archives.

Related Standards

• Other ISO cinematography standards produced by ISO/TC 36 that address film formats, projection and sound practices.
• National and industry guidance on magnetic recording calibration procedures, archival handling and transfer best practices.

For precise numeric tables, the exact formula, and the graphical tolerance plot, consult the ISO 1188:1984 document. The standard contains the authoritative numerical values and figures required for implementation and equipment calibration.