Film cartridges

At left the KMZ cartridge, right the Fed one.
Copied from those of Leica and Contax, these cassettes allow to load in darkroom film bought "by meter". A mechanism opens the cassettes when locking the cover. The Fed 1 and 3 are not compatible, only my Zaria can use these cassettes. For KMZ, the Zorki 1 are not compatible, it works for other Zorkis and for Zenits S and 3.

A cassette in place in the Zaria.

The notch in the bulge of the cassette, just hang on the pin (screw or molded into the shell like for the Zorki 4 at right) to prevent rotation.

The particular shape of the cover latch allow to open the cassette while turning to lock (and to close it when reopening the camera).

There even is a manual!
As the Kiev cameras are Contax cameras, Contax cassettes are 100% compatible with them!

In a Kiev (Contax) camera, you can use two cassettes and remove directly the receiving one containing the exposed film without rewinding. It could allow to change film in the middle, you only lose a dozen cm (!). You can also use an ordinary take-up spool and rewind at the end.

The bulge of the cassette is not at the same place, and these cassettes are not compatible with the FED and Zorki (and vice versa).
This bulge (which has no slot for a pin) fits into a groove in the camera body.
The Leningrad is designed to also use Contax-Kiev cassettes.