Pentax 645 Lenses
6 interactive lens diagrams
Pentax 645 medium-format SLR mount, introduced in 1984 | 645 medium format film and digital bodies
Pentax 645 was introduced as a relatively integrated 6x4.5 medium-format SLR system. The original body used 120/220 film inserts, a built-in motor drive, TTL metering, and electronic exposure modes rather than the fully modular backs and finders common in some studio systems.
The mount evolved from manual-focus A-series 645 lenses into autofocus FA lenses and later digital 645 bodies. Compatibility is broad but generation-dependent, especially around autofocus, aperture information, and digital image-circle expectations.
In catalog terms, Pentax 645 lenses are useful for comparing medium-format SLR designs that were meant to be more field-friendly than larger studio cameras. The system balances larger-than-35 mm image quality with handling that often feels closer to a big SLR than to a modular cube.
Mount interface
Flange focal distance 70.87 mm, bayonet mount. 0° at 12 o'clock from the camera front; the lens-side view is the horizontal mirror. Dotted strokes mark photo-scaled or schematic (not-to-scale) dimensions.