Above: Unfolded ready for action.
Below: The camera in its folded position.
1938: The Zeca-Flex
Only three companies made a folding twin lens reflex. Welta made the Perfekta and Superfekta, KW made the Pilot. The Zeca-flex was made in 1938 by Zeh-Camera-Fabrik in Germany. What makes it different from most other TLRs, folding or not, is that the viewing lens has a shorter focal length than the shooting lens. So although the camera shoots 6x6cm images on 120 film, the viewfinder screen measures only 4x4cm. That allows the camera to fold to a more compact size. (See pic below.)
Shutter speeds of 1-1/250 second, using a rim-set Compur shutter, and apertures of f/3.5-/f22 are set conventionally top and bottom of the taking lens. As the lenses are focused by turning a knurled wheel beside the viewfinder, the upper viewing lens moves in and out on a tube while the lower taking lens moves back and forth on bellows.
But here’s the clever bit. The two lenses are mechanically linked in such a way that the upper lens moves by a smaller amount than the lower lens, ensuring the images on the viewfinder screen and on the film, from two different focal length lenses, are correspondingly sharp.
It’s a lovely camera - and just a little bit rare!