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Film formats

What IMAX 70mm film actually is

standard 70mm and IMAX 70mm film use similar-width stock, but the pictures are not the same size or shape.

Ordinary film runs vertical and advances 5 perforations per frame. IMAX runs horizontal and advances 15, creating a much larger frame.

Look for “IMAX 70mm” or “15/70” on the individual showtime. A ticket that says only “70mm” normally means the conventional vertical format, which is not IMAX.

The frames at one physical scale

Film frame sizes at one millimetre scale35mm 4-perf has a 22 by 16 millimetre frame, area 352 square millimetres, and 4 perforations per frame. 70mm 5-perf has a 52.63 by 23.01 millimetre frame, area 1,211 square millimetres, and 5 perforations per frame. IMAX 15/70 has a 69.6 by 48.59 millimetre frame, area 3,381.9 square millimetres, and 15 perforations per frame.35mm 4-perf4 perforations · vertical travel22 × 16 mm352 mm² frame area70mm 5-perf5 perforations · vertical travel52.63 × 23.01 mm1,211 mm² frame areaIMAX 15/7015 perforations · horizontal travel69.6 × 48.59 mm3,381.9 mm² frame area
Each film aperture is drawn from the dimensions in the gauge data. The IMAX print aperture is reported rather than primary, and its record says so.

Why the negative is 65mm and the print is 70mm

Large-format photography normally exposes a 65mm camera negative. The release print is 70mm wide because the extra edge space historically carried magnetic sound stripes. Modern presentations can synchronize separate digital sound, but the public format name still follows the print.

The extra print width does not add 5 millimetres of picture. Camera and projector apertures are different measurements, and the projected image is smaller than the full camera opening.

Frame records

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35mm 4-perf Academy camera aperture

Sound-era 35mm photography intended for the Academy picture shape, with space reserved beside the image for an optical soundtrack on release prints.

Gauge: 35 mm
Perforations per frame: 4
Travel: vertical
Physical aperture: 22.00 × 16.00 mm
Physical aperture ratio: 1.38:1

The 22.00 by 16.00mm values are the SMPTE Style A camera aperture. Their physical ratio is 1.375:1. The standardized Academy projected aperture is smaller, 20.96 by 15.29mm, and is approximately 1.37:1. The dimensions here must not be used as projected-aperture dimensions.

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65mm 5-perf spherical camera negative for 70mm prints

Large-format spherical photography for 70mm roadshow release prints, usually projected near 2.20:1 after allowance for print edges, soundtrack, and projector aperture.

Gauge: 65 mm
Perforations per frame: 5
Travel: vertical
Physical aperture: 52.63 × 23.01 mm
Physical aperture ratio: 2.29:1

The values are the nominal 65mm camera aperture specified by ANSI/SMPTE 215 and reproduced in professional format references. SMPTE EG 25 independently establishes a nominal maximum scan width of 52.48mm and a 23.52mm limiting height that includes tolerance, so those transfer limits must not be substituted for the nominal camera aperture. A 70mm release print is wider than the 65mm negative. Its projectable image is smaller and normally masked to about 2.20:1.

reported

Ultra Panavision 65mm 5-perf camera negative

65mm photography with anamorphic optics. The classic Camera 65 and Ultra Panavision process used a 1.25:1 squeeze to produce a nominal 2.76:1 screen image from the standard 5-perf 65mm frame.

Gauge: 65 mm
Perforations per frame: 5
Travel: vertical
Physical aperture: 52.63 × 23.01 mm
Physical aperture ratio: 2.29:1

The physical camera aperture is the same as other 5-perf 65mm photography, so the aspect_ratio field remains 2.287266:1. The wider image exists only after optical unsqueezing. Historical Camera 65 sources specify 1.25:1 and 2.76:1, while modern Panavision material describes the revived lens set with slightly different squeeze language. The classic process value is used here and the conflict should remain visible.

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IMAX 15/65 camera negative for 15/70 presentation

Very-large-format IMAX photography. The 65mm negative runs horizontally, and release printing places the image on horizontal 70mm stock for 15/70 projection.

Gauge: 65 mm
Perforations per frame: 15
Travel: horizontal
Physical aperture: 70.41 × 51.61 mm
Physical aperture ratio: 1.36:1

SMPTE ST 417 Table 1 specifies a nominal camera aperture of 70.41 by 51.61mm for the horizontal 15-perforation 65mm negative. Its physical ratio is about 1.3643:1, not the projected 1.43:1 ratio. A reported 15/70 projectable print aperture is 69.60 by 48.59mm, or 1.4324:1. The public name 'IMAX 70mm' refers to the release print. The camera negative itself is 65mm stock, so gauge_mm is correctly 65 here.

reported

IMAX 15/70 projectable print image

The image area exposed through the projector aperture during an IMAX 15/70 film presentation.

Gauge: 70 mm
Perforations per frame: 15
Travel: horizontal
Physical aperture: 69.60 × 48.59 mm
Physical aperture ratio: 1.43:1

Unlike the other primary diagram records, these are reported projectable-aperture dimensions, not a camera aperture. The original cited measurements are 2.740 by 1.913 inches, converted to 69.60 by 48.59mm. They explain the 1.43 presentation label. This record is included so a diagram can distinguish what the camera exposes from what the projector shows, but the exact dimensions need confirmation from a directly accessible SMPTE print-aperture standard or IMAX engineering document.

Ultra Panavision is wide, not IMAX

Ultra Panavision uses anamorphic lenses, which squeeze a wider scene onto a vertical large-format frame and expand it again for projection. It can produce an extremely wide image, but it does not use horizontal IMAX transport or the tall IMAX frame.

What DMR does

DMR means Digital Media Remastering. It is IMAX's process for preparing a separate picture and sound master for its theatres. The work can improve presentation on a very large screen, but it cannot capture objects that were never inside the photographed frame.

A DMR release may preserve a taller composition if the source already contains one. It may also remain wide throughout. That is why the film lookup keeps capture type and expanded ratio as separate fields.

Sources