The Contax was Zeiss-Ikon's first 35 mm camera. It was brought out after the popularity of the format had been established by the Leica introduced seven years previously. Compared to the Leica the Contax was difficult and cumbersome to use. Operability was improved by the introduction of the Contax II in 1936. The price was £27.0.0.

Versions

There were several changes made to the Contax I. The major being the introduction in 1933 of slow speeds (down to 1/2). In 1934 the body shape was changed and a little while after a rotating wedge rangefinder was used. Most likely the changes made in 1934 were seen as one design upgrade but with existing parts being used in a transitional model having the new body shape but mirror rangefinder. Non slow speed models continued to be available after the slow speed model was introduced.

There were many other minor changes and differences in fittings:

• 1932. Original semi-silvered mirrors replaced by gilt.
• 1932. Examples have none, one or two pimples on the camera front near the focusing wheel.
• 1933. After these very early models there was always no pimples, this corresponds with the rangefinder cover and the front plate carrying the Contax name being in one piece. A tripod foot was added to the camera base on late examples during this period. Kuc type 3.
• 1933. Slow speeds added. Kuc type 4.
• 1934. The rear corners of the body are rounded (a new type of plate back was required). The rangefinder window near the shutter controls is larger. Button to release infinity lock when using long focus lenses added. Accessory shoe is more substantial and has bevelled rather than straight sides. Focusing scale changed to nickel rather than black. Kuc type 5.
• 1934. Rotating wedge rangefinder replaced the previously used swing mirror. A solid glass block was used between the two ends of the rangefinder necessitating the view-finder window being moved to be outside the rangefinder. The sliding view-finder mask had also to change. The cover over the rangefinder near the shutter controls is deeper leaving a wide groove between it and the cover plate carrying the Contax name. Kuc type 6.
• 1935. Marker for setting speeds changed to an arrow, previously it was a slotted screw. There are now four screws holding the accessory shoe. Kuc type 7.

Shutter

The design criteria for the Contax shutter was that it was to work across the short dimension of the film and not to be made of rubberised cloth. The short travel of the vertically running blind had many benefits, distortion due to subject movement was lessened and the effect of blind acceleration worked in its favour as, typically, the sky would receive less exposure. Cloth blinds were dismissed as it was thought that they were too sensitive to temperature changes and over time would not remain light-tight. The result was a blind consisting of thin metal strips each loosely connected to the other by overlapping curved edges, the strips were then strung together on two silk bands. Unfortunately the shutter proved much less robust and reliable than the much simpler cloth model. A shutter based around the Miroflex would have been a much better solution.

The timing of the improved 1933 shutter with slow speeds was by a combination of slit width, tension and mechanical delay. To set the shutter, the shutter group was first selected. There were four groups: Sports, 1/1000 - 1/100; Normal, 1/100 - 1/25; Night, 1/10 - 1/5; Time, 1/2 and Z. Once the Group had been chosen the individual speed could be set. Zeiss must have felt that this complexity was a benefit as it is emphasised in their advertisements.

Cassettes & Film

Contax cassettes were metal re-usable containers consisting of two thin cylinders one inside the other. They could be loaded into the camera in daylight, locking the back of the camera opened the cassette by rotating the inner cylinder. They could be used in a pair (no re-wind was required) or singularly (the film would be re-wound after the last exposure).

Film at this time was available as:

• Contax spool - similar to roll-film with black paper leaders and trailers.
• Agfa/Perutz cassette - light-tight cardboard cartridge for one-time use. The film is re-wound into the cassette.
• Daylight Refills for Contax Cassettes - the film is protected by a paper leader which is drawn out before use. The film can be re-wound or wound to a second cassette.
• Darkroom loaded film - for Contax cassettes, available in lengths from 5 feet.

Extensible lens hood

This fits the outer bayonet of the camera, with 5 cm Tessar lenses all three sections of the hood are used, with the 5 cm Sonnar only two sections. It's not clear why this item was produced, it has a square aperture and being fitted to the outer bayonet means that it does not rotate, however, once fitted the diaphragm cannot be altered. An adapter ring (1283/11) allows the hood to be used with 8.5, 13.5 and 18 cm lenses A similar hood (1283/6) was made for the Super Nettel.

Cases

Four stiff ever-ready cases were made as well as pouches and soft cases:

• 1777/2 - For Tessar lenses.
• 1777/8 - For Sonnar lenses.
• 1777/22 - As /2 but with Albada finder fitted.
• 1777/28 - As for /8 but with Albada finder fitted.

The last two were introduced after the others. The earliest cases had the catch at the rear, later two press studs on the front were used. The number 1777/4 was originally used for the Sonnar case.

Miflex

The Miflex was produced by Carl Zeiss rather than Zeiss-Ikon. The camera adapter could be replaced by other fittings including roll-holders. On this example the tube of the ground glass screen is fixed to the shutter assembly, on other examples it can be replaced by a telescope. A moveable prism diverts light to the camera or the viewing screen.