Overview
ISO 1189:1986 is an international standard developed by the International Organization for Standardization (ISO) that specifies the recorded characteristics for magnetic sound records on 35 mm motion-picture film, excluding striped release prints. This standard applies to films operated at nominal speeds of 24 frames per second (45.6 cm or 18 in per second) or 25 frames per second (47.5 cm or 18.7 in per second). It ensures consistent and reliable audio quality in the magnetic soundtracks used in cinematography, aligning in technical content with the CCIR’s Recommendation No. 265-2.
By defining the precise frequency response and recording characteristics for magnetic sound on 35 mm film, ISO 1189:1986 supports the production, duplication, and playback of high-quality cinematic audio, facilitating interoperability and quality control across the film industry.
Key Topics
-
Magnetic Sound Recording Standards: Specifies the nominal recorded characteristic for short circuit magnetic flux as a function of frequency, defining a curve that progressively falls with increasing frequency.
-
Frequency Response: Defines a detailed frequency response ranging from 40 Hz up to 16,000 Hz, expressed in decibels (dB) with tight tolerances for consistent sound quality.
-
Technical Specifications:
- Recorded characteristic modeled as impedance of a parallel RC circuit with a time constant of 35 µs.
- Explicit mathematical formula for the frequency-dependent level adjustment.
- Reference level normalized at 1 kHz.
-
Reproducing Characteristic: The standard establishes a reproduction response designed to yield flat audio output when playing back soundtracks recorded according to the specified characteristic, ensuring fidelity across equipment.
-
Tolerances: Defines permissible deviations in decibels to maintain recording quality consistency and compatibility with playback systems.
Applications
ISO 1189:1986 is vital for manufacturers and professionals involved in:
-
Cinematography Sound Recording: Ensuring that magnetic sound records on 35 mm film conform to a standardized frequency response and signal level, crucial for original film sound recording and archival.
-
Film Duplicating Laboratories: Maintaining fidelity when copying soundtracks, by adhering to the specified recorded characteristic and tolerances.
-
Soundtrack Reproducers and Projectors: Designing playback systems capable of delivering accurate sound reproduction for magnetic soundtracks on 35 mm motion-picture film.
-
Archiving and Preservation: Supporting consistent audio quality during film preservation efforts by providing reference parameters for sound restoration.
This standard is essential for achieving compatibility and high audio fidelity in cinematic magnetic soundtracks, especially in professional filmmaking and post-production workflows.
Related Standards
-
CCIR Recommendation No. 265-2: Shares substantial technical content with ISO 1189:1986, focusing on magnetic sound recording parameters and used as a complementary reference.
-
ISO 3664: Standard for viewing conditions in film and audio production, ensuring that playback environments meet acoustic requirements.
-
ISO 7816: Although focused on identification cards, shares procedural standards for quality and testing that can influence media standards indirectly.
-
ISO 9001: Quality management principles often employed in film production and sound recording laboratories to ensure consistent application of standards like ISO 1189.
Summary
ISO 1189:1986 provides the international baseline specification for magnetic sound recording characteristics on 35 mm motion-picture film excluding striped release prints. By defining clear frequency response curves, tolerances, and reproducibility requirements, it supports high-standard sound quality and compatibility in cinematographic soundtracks. For film professionals, laboratory technicians, and equipment manufacturers, adherence to ISO 1189:1986 helps deliver superior audio experiences in motion pictures and ensures consistency across production, duplication, and exhibition systems worldwide.