120 Roll Film (Medium Format / ISO 732)
Direct Answer
120 Film (standardized under ISO 732, introduced by Kodak in 1901 for the Brownie No. 2) is the universal medium format roll film standard, featuring a 61.5 mm wide unperforated film strip attached to continuous light-tight backing paper wound on a plastic/metal spool. Capturing multiple frame formats including 6×4.5 cm (16 exp), 6×6 cm (12 exp), 6×7 cm (10 exp), and 6×9 cm (8 exp).
Source: ISO 732:2000 (Photography — 120-size and 220-size films — Dimensions) / ANSI PH1.21
Specs
| Film Strip Width | 61.5 ± 0.5 mm (2.42 in) |
| Total Film Strip Length | Approx. 820 mm (32.3 in) taped to backing paper |
| Spool Flange Diameter | 25.2 mm (Keyed end drive slot for camera winding mechanisms) |
| 6×4.5 cm Frame Yield (56 × 41.5 mm) | 15 or 16 exposures per roll (Mamiya 645, Pentax 645, Bronica ETR) |
| 6×6 cm Square Yield (56 × 56 mm) | 12 exposures per roll (Hasselblad 500C/M, Rolleiflex TLR, Mamiya C330) |
| 6×7 cm Ideal Format (56 × 70 mm) | 10 exposures per roll (Mamiya RB67/RZ67, Pentax 67, Plaubel Makina 67) |
| 6×9 cm Broad Format (56 × 84 mm) | 8 exposures per roll (Fuji GW690 'Texas Leica', technical cameras) |
Backing Paper and Red Window Frame Tracking
Because 120 film has no sprocket holes, early folding cameras and TLRs tracked frame numbers through a red ruby window on the camera back, reading sequential frame numbers printed directly onto the opaque black backing paper. Modern SLRs (Hasselblad, Mamiya) use mechanical geartrain counters driven by the take-up spool friction.