1.37:1 aspect ratio (Academy Sound Ratio), developed in the 1930s for 35mm sound film with optical soundtrack. Slightly wider than 1.33:1, optimized for acoustic space in film perforation patterns.
History
The 1.37:1 aspect ratio was defined in the early 1930s in response to the introduction of sound film. Unlike the pure 1.33:1 format, sound film required space for an optical soundtrack on the physical film strip.
Developmental Steps:
- 1929-1931: Transition from silent film to sound film (Great Transition)
- 1930: Academy Standards are specified
- 1932: Official adoption of the Academy Sound Ratio (1.37:1) as the new standard
- 1932-1950s: Widespread use for all sound films on 35mm
- 1950s: Widescreen movement enabled a move away from this format
- 1960s: Only occasional use remained
Why this Value?
- 35mm film strip: 21 perforations per foot (for sound and image)
- Soundtrack required specific vertical space
- Image area was optimized for sound quality
- 1.37:1 was the mathematical compromise between image width and sound space
Technical Details
Aspect Ratio Specifications:
- Aspect Ratio: 1.37:1 (exact: 1.3703:1)
- Film Standard: 35mm film strip
- Image Area: 18 × 13.1mm (on 35mm)
- Perforation: 21 perforations per foot
- Soundtrack Position: Mono, optical, at the edges of the film strip
- Standard Resolution (digital): ~1452 × 1058 pixels
35mm Film Strip Layout:
[Perforation] [Image Area 18×13.1mm] [Soundtrack - Optical]Sound Quality:
- Optical mono soundtrack
- Frequency range: 50-8000 Hz (early standards)
- Signal-to-noise ratio: ~40dB
- Track width: ~2-3mm depending on standard
Usage Today
The 1.37:1 format is practically obsolete and is only used in special cases:
Archival / Restoration:
- Restored Classics: Some film classics (Chaplin, Keaton, etc.) in original 1.37:1
- Documentaries: about historical film production
- Archives: Original films in digital restoration
Rare in New Productions:
- Only for absolute historical authenticity
- Academic or artistic experiments
- Not for commercial cinema use
Digital Equivalents:
- 1.37:1 is mathematically between 4:3 (1.33:1) and 16:9 (1.78:1)
- Can be generated by cropping 16:9 material
- Occasionally used for television remasters of old content
Technical Differences to Other Standards
| Aspect | 1.33:1 Academy | 1.37:1 Sound | 1.66:1 European | 1.85:1 Standard |
|---|---|---|---|---|
| Soundtrack | Variable | Optical mono | None (or external) | Digital or Dolby |
| Image Area | 4:3 Square | 21-Perf Standard | Optimized | Widescreen |
| Cinema Era | 1932-1950 | 1930-1950 | 1960-1990 | 1970-Present |
| Width Relative | 100% | 102% | 125% | 140% |
| Height Relative | 75% | 73% | 60% | 54% |
| Sound Quality | Full | Compromise | Full | Full (Stereo+) |
Comparative Analysis
1.37:1 vs. 1.33:1:
- Only ~4% wider
- Minimal more side image
- Identical for visual composition
- Difference due to sound space requirements
1.37:1 vs. Modern Formats:
- Significantly more square than 1.85:1 (140% relative width)
- Less wide than 1.66:1 (125% relative width)
- Means less landscape space
- More headroom in portraits
Historical Examples
Major Productions in 1.37:1:
- "Citizen Kane" (1941) - Orson Welles
- "The Great Dictator" (1940) - Charlie Chaplin
- "Singin' in the Rain" (1952) - Gene Kelly
- "A Streetcar Named Desire" (1951) - Elia Kazan
(Note: Some of these films were later re-mastered in different formats)
Further Information
Relevant Standards:
- SMPTE RP 431-2: Academy Standards
- DCI Standard: Digitized Standards
- ISO Standards: Film Strip Specifications
Related Formats:
- Academy Ratio (1.33:1) - pure image format
- European Widescreen (1.66:1) - subsequent
- Cinemascope (2.35:1) - parallel widescreen development