Cosina CSM

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By the mid-1970s, the advantages of bayonet lens mounts with open-aperture metering were clear; and even Pentax had moved on from the M42 screw mount. The Cosina CSM and its siblings the CSR and CSL from Cosina circa 1978[1] were interesting late attempts to keep screw-mount SLRs viable.

A half-press on the shutter release stops down the lens for metering,[2] with over/correct/under indicated with LEDs at the top of the viewfinder. The lens can be reopened to its brightest aperture again with a button on the camera front.

The CSM was only sold in black, contrasting with its silver near-twin the Cosina CSL. The same camera appears as the Petri MF-2 and the Vivitar XC-3; and German retailer Porst distributed it as the Porst Compact-reflex.

It has a cloth focal-plane shutter with speeds from 4s to 1/1000, and B. There is also a mechanical shutter speed of 1/50 sec. available. Flash sync is at 1/60 sec. or lower. A self-timer feature with a winking light is also provided and has a delay of approx. 10 sec.

The built-in exposure meter uses two CdS cells. Film speeds are set in a window on the shutter dial, to speeds from 25 to 3200 ASA. The camera is powered by two 1.5v silver oxide batteries.

The viewfinder screen features a central horizontal split-image focusing spot surrounded by a micro-prism to ease focusing. The film transport uses a single stroke film advance lever with a automatic reset film counter and double exposure prevention.

The CSM and the CS-1 are among the models that can accept a quirky accessory called the Cosina AEC adapter which adds aperture-preferred automatic exposure mode, mounting onto the hot shoe and connecting to the "A" terminal above the regular PC socket. This attachment is able to twist the shutter speed dial using its own battery-powered motor.


  1. 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).
  2. This scheme was used in the innovative Cosina Hi-Lite EC from 1972.