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Filmmaking Dictionary: Number 1 / 1.43:1 IMAX (15/70)
Definition
1.43:1 is a picture shape approximately 1.43 times as wide as it is high. It is associated with the tall image of IMAX 15/70 film presentation and compatible IMAX digital presentations.
The ratio, the recording format and the projection system are separate facts. A film can include scenes prepared for a 1.43:1 presentation without every theatre or every release version showing that full image.
What 15/70 Means
In 15/70 presentation, the large-format film travels horizontally, with a frame spanning 15 perforations on 70 mm release film. IMAX film photography originates on 65 mm camera negative. The familiar 15/70 label therefore describes the film format, not a 15:70 aspect ratio.
A ratio such as 1.43:1 specifies the intended picture shape within the presentation system. Physical film width, camera aperture and projected image area are related but should not be treated as interchangeable measurements.
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Why the Taller Frame Matters
At a fixed picture width, a 1.43:1 frame includes more vertical space than 1.90:1 or 2.39:1. That can support a towering landscape, a figure within a large environment or action extending above and below the subject.
It does not automatically mean a wider horizontal view or a longer lens. The result depends on the lens, active image area and composition. A taller frame must still be designed, with attention to ceilings, floor areas, microphones and anything else that could enter the additional picture space.
Planning Different Release Versions
- Confirm which scenes are intended for an expanded image.
- Use the agreed frame lines and protect the required alternate compositions.
- Check whether each exhibition version preserves, crops or otherwise reformats the picture.
- Keep titles, visual effects and important action compatible with the planned versions.
For example, a wide theatrical version may use a central section of a taller source image. The composition must work within that intended extraction, while the taller presentation also needs a complete, intentional image.
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Frequently Asked Questions
Does every IMAX screening use 1.43:1?
No. The release version and theatre’s projection capabilities determine the presentation. Many digital IMAX presentations use a different picture shape.
Can a digital IMAX presentation show 1.43:1?
Yes, compatible systems and appropriately prepared content can. The ratio is not proof that the screening uses a film print.
Related Terms
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