The Mamiya 645 system was introduced in 1975 and was the first medium format SLR to use the 6x4.5cm format, allowing for 15 exposures on a single roll of 120 film. The Mamiya 645 system was released between the RB67 and RZ67 and offered a much smaller alternative to photographers than its larger 6x7cm counterparts. The Mamiya 645 went through multiple iterations and is still currently produced as a digital 6x4.5 camera under the Phase One name.
Mamiya 645 cameras have a built-in focal plane shutter, unlike the leaf shutters of the RB/RZ67 and Hasselblad cameras. This limits the flash sync speed of the system. Because of this, some leaf shutter lenses were released for flash and studio use. Mamiya 645 manual lenses will work on all manual-focus bodies and are adaptable to many other systems. One of the best known Mamiya lenses is the 80mm F1.9 which is one of the fastest medium format lenses ever released.
Handling a Mamiya 645 is very similar to a 35mm SLR. Therefore, 35mm users who want a larger negative will feel right at home with a Mamiya 645.
The first generation of Mamiya 645 cameras have interchangeable finders, focusing screens, film inserts and grips. Second generation cameras added a removable film back. The third generation is also known as the Mamiya 645 AF, which is technically a separate mount.