Mamiya Prismat

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In 1961 Mamiya was largely known as a maker of medium format cameras. But internally they had prepared a number of prototype 35mm SLRs.[1] The original Prismat is one of their earliest-sold interchangeable lens 35mm SLR cameras. One of its distinctive features is a shutter release in the center of its shutter-speed setting dial.

The body does not have any marking for the model name. It uses an Exakta bayonet lens mount, modified with a sort of "reverse PAD" mechanism where firing the shutter causes a pin to emerge from the body and trip an aperture release mounted on a lens outrigger. The semi-automatic diaphragm must be manually recocked for the brightest viewing image using the nub close to the lens mount. It seems that at least four lens focal lengths were produced using this aperture mechanism.

This model seems to be the basis of the original Sears Tower 37, although with the pentaprism housing squared off. McKeown's states the Tower 37 lacked an instant-return mirror.[2] The original Prismat was replaced in 1961 with the Mamiya Prismat NP (basis for the Tower 32A & 37A).


  1. This is well-documented Ron L. Herron's site.
  2. McKeown, James M. and Joan C. McKeown's Price Guide to Antique and Classic Cameras, 12th Edition, 2005-2006. USA, Centennial Photo Service, 2004. ISBN 0-931838-40-1 (hardcover). ISBN 0-931838-41-X (softcover). Page 877.