Mamiya's budget 645 SLR — focal-plane shutter, 645 mount, interchangeable finders, 1979.
The Mamiya M645J is a late-1970s medium-format SLR, a lower-cost version of the M645 in Mamiya's 6x4.5 system. It simplified some features to reduce price, offered as an entry point into the 645 system while remaining compatible with its lenses and finders.
It is a medium-format (6x4.5) SLR producing a 56x42mm frame on 120 or 220 film. It uses a body focal-plane shutter and loads film via inserts rather than fully removable magazines. It takes interchangeable waist-level or prism finders and focusing screens and mounts Mamiya 645 bayonet lenses; a metered prism finder can add TTL metering, while the plain body has none.
The reduced cost made the M645J a practical way for students and photographers on a budget to enter medium format, keeping the lighter 645 handling and the system's lens range. It suits portrait and general work where the extra features of the 1000S are not essential.
Test the focal-plane shutter across its speeds for accuracy and even travel, and confirm the film insert and its seals hold light out. Check the mirror, screen, and finder mirror, and any metered prism against the correct battery. Foam light seals commonly perish on bodies of this age and should be checked before buying.