The f2.8 18 cm Sonnar for the Contax appeared in 1936, that model was without the Flektoskop and coupled to the rangefinder. Early versions had a shoe fitted to the lens barrel. In early 1938 the lens was mounted in a Flektoskop reflex housing and the rangefinder coupled version was phased out. The image in the finder is large and reasonably bright but upside down and laterally reversed, which must have made sports photography difficult. The mirror is released by a cable release that fits to the Flektoskop a second cable runs from the Flektoskop to the shutter release on the camera. The Flektoskop could not be used on The Contax I as it would foul the film-advance knob, it could be used on the Contax III but the exposure meter would no longer function.

Three models of the Flektoskop are listed for the three lenses - 18 cm, 30 cm and 50 cm,. Each lens could be purchased without the Flektoskop (at nearly £20 less) so presumably just the lens to Flektoskop fitting was different and a different focal length lens could be adapted to an existing Flektoskop. Zeiss also introduced the Panflex reflex housing intended for close-up photography. Why Zeiss introduced so many different housings rather than a common universal device is not obvious, the Ploot from Leitz was already available as a template.

The filters were produced by Carl Zeiss rather than Zeiss-Ikon, they are listed as 77 i in size and other 77 mm filters may not fit correctly. Filters listed were yellow, green and three red densities.

The lens/Flektoskop was supplied in a small fitted case with space for the lens hood and three filters. As well as filters a close-focus ring (extension tube) was available.

After the war Carl Zeiss Jena resumed production of the lens/Flektoskop and these were listed and distributed until 1954 by Zeiss-Ikon. Jena continued to develop the Flektoskop, at first by eliminating the upside down image and later by also correcting the lateral reversal. Jena then introduced a new and improved reflex housing - the Flektometer - this had a correctly oriented image and a mechanical linkage to the shutter release rather than a cable release as previously used.

Part numbers:

• f2.8 18 cm Sonnar lens and Flektoskop IHFIZ. Some existing lens/Flektoskop combinations are engraved with the number 543/78.
• Flektoskop for f2.8 18 cm Sonnar 543/89 (for 30 cm Tele-Tessar 543/90 for 50 cm Fern 543/91).
• Close-focus ring 543/86.
• Screw-in mount for spectacle lenses 543/84.
• Case for rangefinder coupled lens, camera, riffle-butt and other accessories 1777/45 IJFID.
• Case for rangefinder coupled lens 1777/46 IJFOF.
• Riffle-butt for f2.8 18 cm Sonnar and rangefinder coupled Contax 543/75.
• Riffle-butt for f2.8 18 cm Sonnar, Contax II/III and Flektoskop IJFUG 543/85.
• Riffle-butt as above but for f2.8 18 cm Sonnar or 300 mm Tele-Tessar IJGIF.

The tripod fixing ring is missing from this example.