The Contaflex was the flagship camera from Zeiss-Ikon and the first camera with a built-in photo-electric exposure meter, it further boasted interchangeable lenses and, novel on a focal-plane camera, delayed action.

It is, though, an odd and not very successful design. Combing the successful 35 mm format with the ease-of-use of a twin-lens reflex e.g. Rolleiflex, was a nice idea; pretty soon the practicalities should have caused a rethink, but once Zeiss engineers have settled on a course no design issue is so great that it can't be fixed by another gear train (preferably bevel). The result was a very heavy cumbersome camera packed full of mechanism. The focal-plane shutter (based on the Contax I) is in the lower half of the camera, the knob that tensions the shutter, sets the speed and advances the film is in the top half, requiring a lot of movement and setting information to be transmitted between the two.

The small size of the 35 mm image ruled out the simple option of providing interchangeable lenses in pairs as used on the later Mamiya TLR cameras. The focusing screen had to be made larger and so the viewing lens had to be a longer focal length, one of 8 cm was chosen, this also had the advantage of reducing the depth-of-focus making critical focusing easier. The coupling between the viewing and taking lens is by a metal block at the bottom of the taking lens throat. A lever around the viewing lens is used to focus the 5 cm lenses, when this is rotated the block moves around the throat. The block engages a socket in each lens, this rotates and engages the helical focusing thread of the lens. Long-focus lenses work in the opposite way, they are focused by turning the lens which in turn moves the viewing lens.

A condenser lens is incorporated into the focusing screen giving a bright screen especially at the edges. A huge Albada finder forms the front of the viewing hood, this showed the field of view for 5 and 8.5 cm lenses. The mirror surface of the Albada was also for use in self-portraits in conjunction with the delayed action timer. The focusing screen is marked for the two telephoto fields of view. Looking into the focusing hood the user would be able adjust the exposure meter needle shown in a window to the left of the hood.

The meter is uncoupled and works in a similar way to the Contax III. The controls are placed around the viewing lens, first an index is set against the film speed, the 'shutter' dial is then used to line up the meter needle against a mark in the meter window, the shutter/aperture pairs can then be read and transferred to the camera controls.

There is a separate shutter release when the delayed action timer is in use.

Early versions have a lever to raise the magnifier in the hood, later this was replaced by a catch, other variations are the film speed numbers which are in DIN or Scheiner. The table on the focusing hood near the shutter release showing speed settings for the exposure meter multiplier indices was not present on very early models.

The weight of the camera with the f2.8 Tessar was 50 oz. and the cost £64.12.6. The camera and lenses shown would have cost £150.

The accessory lenses are not always easy to fit to the camera; the long sunk mount tends to bind in the camera throat. The 13.5 cm is a particular heavy lens and requires only a short movement to extend the lens for focus to 6 feet, making critical focusing difficult.

Lenses available:

• f1.5 5 cm Sonnar.
• f2 5 cm Sonnar.
• f2.8 5 cm Tessar.
• f2 8.5 cm Sonnar (1936).
• f4 8.5 cm Triotar (1936).
• f4 13.5 cm Sonnar (1936).
• f2.8 3.5 cm Biogon (1937).
• f4.5 3.5 cm Orthometer (1938).

Accessories available included:

• View-finder for 3.5 cm lenses, this fits on the bayonet around the taking lens.
• Attachment to fit Contameter (1343) of Contax I and II. This is a metal plate that fits to the tripod socket and carries a fixing for the Contameter, the camera was used upside down.
• Plate Back.
• Leather focusing hood.
• Flash bulb synchroniser.
• Mirror for focusing hood. This is for use at eye-level and gives an upside down laterally reversed image.
• Lens hoods, these have a rectangular opening and fit the bayonet surrounding the lens, two were produced for the 5 cm Tessar or 5 cm Sonnars.
• Focusing screen adapter, this fits onto the lens.
• Reproduction stands.
• Microscope attachment.
• Outfit cases.
• Adapter to fit lens to the Ikomat enlarger.