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Film cutter
35 mm → 21 mm

Some covert cameras used by the USSR during the Cold War, use the uncommon film format of 21 mm. In most cases, the 21 mm film is unperforated. As each camera required a different type of film cartridge, such cartridges had to be pre-loaded, and were commonly supplied by the USSR.

When the camera was used in the West (i.e. in a non-USSR country), supply of 21 mm film was always a problem, which is why many cameras were supplied with a small handheld film cutter, that allowed common 35 mm perforated photo film to be converted in 21 mm unperforated film.

In addition to the handheld – ad-hoc – solutions, there were also professional film cutters, such as the one shown in the image on the right. It is operated by a hand crank and readily accepts a standard 35 mm film cartridge. Furthermore, it can be mounted on another device or a table.
  

The 35 mm film is entered through a narrow gutter at the front of the device. When turning the crank, two cogwheels catch the perforated edge of the film and pushes the film through the device. Two internal razor-sharp knifes then cut away 7 mm of film at either side, including the perforated edge, leaving a clean strip of unperforated 21 mm film at the rear side of the device.

This film can be loaded directly into the desired cartridge. At the right, just behind the hand crank, is a wheel that counts the number of revolutions of the crank, before activating a knife that chops the film once the desired length has been reached. The one shown here, counts 8 turns. The device shown above was manufactured by the special workshop of the KMZ factory [1].

Film cutter seen from the front right Film cutter seen from the right rear Left rear view Rear view Mechanism detail Film passing through the gutter 35 mm film cartridge loaded into the device Film cutter in use
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Film cutter seen from the front right
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Film cutter seen from the right rear
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Left rear view
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Rear view
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Mechanism detail
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Film passing through the gutter
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35 mm film cartridge loaded into the device
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Film cutter in use

Features
The diagram below shows the various features of the fim cutter, as seen from the front right of the device. At the left, a standard 35 mm film cartridge is inserted into the metal gutter. The film is pulled/pushed through the mechanism by two cogwheels that are driven by the hand crank.


After 8 full revolutions of the hand crank, the counting wheel blocks the crank, until the counting wheel is manually repositioned, or the chopper is operated. This way, the operator can count the number of exposures whilst operating the device in a darkroom.


Known 21 mm cameras
References
  1. USSR Photo, KGB 21mm Film Splitter
    Retrieved December 2017.
Further information
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Crypto Museum. Created: Thursday 30 November 2017. Last changed: Tuesday, 05 December 2017 - 16:33 CET.
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