The original IMAX film format: 70mm film with 15 perforations per frame, transported horizontally. With 69.6 × 48.5 mm frame area, the largest commercially available film format – ten times larger than 35mm.
What is IMAX 15/70?
IMAX 15/70 refers to the original IMAX film format: 70mm wide film stock with 15 perforations per frame. The film runs horizontally through the camera and projector – unlike standard 35mm, which runs vertically.
The designation "15/70" stands for:
- 15 = 15 perforations (holes) per frame
- 70 = 70mm film width (including soundtracks)
Actual shooting is done on 65mm film; the 70mm prints contain additional magnetic soundtracks.
Technical Specifications
| Property | IMAX 15/70 | Standard 35mm |
|---|---|---|
| Film Width | 65mm (Negative) / 70mm (Print) | 35mm |
| Perforations | 15 horizontal | 4 vertical |
| Image Area | 69.6 × 48.5 mm | 22 × 16 mm |
| Aspect Ratio | 1.43:1 | variable |
| Equivalent Resolution | ~18K | ~2-4K |
| Image Area (Factor) | 10× larger | Baseline |
Horizontal Film Transport
The horizontal transport is crucial for IMAX quality:
Advantages:
- Largest possible image area per frame
- More stable image guidance during projection
- Less film wear
Disadvantages:
- Enormous film consumption (3× faster than 35mm)
- Massive film reels (up to 500 kg)
- Special projectors required
Rolling Loop System
IMAX projectors use the patented "Rolling Loop" system:
- The film is not advanced jerkily
- A vacuum plate presses each frame flat against the image window
- Result: Absolutely stable, flicker-free projection
Film Consumption
At 24 fps, IMAX 15/70 consumes:
- 102.7 meters per minute
- 3 minutes per standard magazine
- A 2-hour film = 12 km of film stock
The film reels for "Oppenheimer" (180 min) weighed over 250 kg.
Current Availability
IMAX 15/70 film is still being produced, but the infrastructure is shrinking:
- Kodak still supplies IMAX negative material
- FotoKem (LA) is one of the last labs for IMAX processing
- Approximately 20 projectors for 15/70 film still exist worldwide
Notable 15/70 Productions
- "The Dark Knight" (2008) – First Hollywood scenes in 15/70
- "Interstellar" (2014) – Space scenes
- "Dunkirk" (2017) – 70% shot in 15/70
- "Oppenheimer" (2023) – Longest 15/70 sequences in history