Overview
ISO 7343:1993 specifies the positions and width dimensions for two-track photographic (optical) sound records on 35 mm motion-picture release prints. It defines how the two variable-area sound tracks are located laterally on the film, how they are scanned in reproducers, and basic requirements for septa and picture–sound displacement. The standard is a technical revision of the 1983 edition and works in conjunction with ISO 2939 for picture area and other sound-recording requirements.
Key topics and requirements
- Track layout and alignment
- Two variable-area sound tracks are placed laterally on the 35 mm print; channel 2 is recorded nearest the outer edge of the film.
- Channel slit images for recording and reproduction must be in line at 90° ± 5′ to the film reference edge.
- Dimensions and positions
- The standard provides a table (Table 1) of defined lateral reference positions and widths (given in millimetres and inches) for markers labelled A–G to ensure correct spacing and compatibility between prints and reproducers.
- Septum and reproduction
- The septum between channel records shall be effectively opaque on prints to prevent cross-talk; lighter septa from certain print processes (e.g., direct positive on reversal stock) are allowable and not grounds for rejection.
- Picture–sound displacement
- The permissible picture–sound displacement follows the specifications in ISO 2939 (referenced normative standard).
- Track usage
- The two tracks may carry stereophonic-related program material or separate independent material (for example, two languages).
- For two-channel stereophonic programs, common practice is amplitude–phase matrix encoding (track 1 = left total, track 2 = right total).
- Interoperability note
- Projector and reproducer manufacturers may minimize guard bands between scanned areas to maintain compatibility with single-channel records made per ISO 2939.
Applications and users
ISO 7343 is used by:
- Film laboratories and print manufacturers to lay out optical sound tracks correctly on 35 mm release prints.
- Projector and sound-reproducer manufacturers to design scanning and photo-sensitive devices that align with standard track positions and widths.
- Film archivists, restoration engineers, and cinema sound technicians to verify print conformity and ensure accurate playback.
- Cinema and standards bodies that need interoperability across prints, reproducers, and distribution chains.
Related standards
- ISO 2939:1986 - Cinematography: picture image area and photographic sound record on 35 mm motion-picture release prints (referenced for picture–sound displacement and related requirements).
Keywords: ISO 7343, two-track photographic sound, 35 mm motion-picture prints, sound track positions, sound track dimensions, cinematography standard, optical sound tracks.
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