EX 50mm f/1.8.
Battery: M20, PX-13 or 625 mercury cell. Today, use an Wein EPX-625. It will function without a battery without metering.
Originally launched in October 1969. Replaced by EX AUTO in February 1972.
This camera had unusual features such as shutter speed-priority AE, maximum-aperture TTL metering and AE, a bright aerial image viewfinder, and focal-plane shutter. The front lens element was also interchangeable.
Other Lenses Available
The rear half of the lens is permanently attached to the EX AUTO body, while front sections interchange. This has the advantage of making for less expensive accessory lenses, since you only have to buy the front half, and that the camera is never open to dust and dirt while changing lenses.
The camera had a built-in rear lens consisting of 3 elements in 2 groups. Besides the normal EX 50mm f/1.8 lens, two other interchangeable front lens elements were available: EX 35mm f/3.5 and EX 95mm f/3.5.
Centerweighted averaging metering was incorporated for easy operation. For lenses with different maximum apertures, the f-number could be adjusted manually to compensate.
For the benefit of the TTL meter, the maximum aperture of the lens fitted (f1.8 for the 50mm, a slow f3.5 for the others) has to be set manually on the film speed setting. Apertures are set automatically or manually by a dial on the top plate; the only indication is in the viewfinder.
Among its faults (the instruction book gave no hint of this) was that the effective aperture of the in-body diaphragm differed with the lens fitted, and unless compensated for, shots taken with the 125mm would be 2/3 stop overexposed (this was corrected in the later EX Auto model).
- EX 35mm f/3.5
- EX 95mm f/3.5
- EX 125mm f/3.5
This Flickr page contains more useful information about the lenses.