The Cube Flash is a small clip-on device for use of N-type flash cubes. N-type flash cubes were widely used before electronic strobes as we know them now became common, but it's difficult to find them nowadays. Flash bulbs produce light by burning a chemical substance (a mixture of magnesium and aluminium in most cases) and are dead after use; they cannot be used a second time. Each cube contains four separate flash bulbs, the one that will be used next is brought into the front position by turning the cube in the socket. When all four flash bulbs of a cube have been used, the cube must be replaced with a new one. Ignition is done by electric current from a battery with N-type flash cubes. For power supply, a 15V Photoflash battery is necessary. The battery compartment for it is beneath the removable cover of the Cube Flash.
Beside the N-type flash cubes, which were ignited with current from a battery, there were also X-type flash cubes. These were ignited by a piezo-electrical device inside the flash cube, which was moved by a mechanical pin of the camera. These X-type flash cubes do not work with the Cube Flash.
With flash bulbs, the amount of light emitted cannot be regulated. Therefore, the Cube Flash has no control of flash power and does not control camera electronics. Duration of a flash bulb's light emission is about 1/30 s, much longer than the duration of an electronic strobe. The guide number of a N-type flash cube with ISO 21°/100 film and a shutter speed equal to or longer than duration of light emission is about 30 (metric) / 100 (feet).
Due to the long duration of light emission, using flash bulbs with fast shutter speeds beyond the X-synch time is possible – provided your camera offers M-synch. Different from the very short timespan of only about 1/1000 s that an electronic strobe is active, with flash bulbs it is not important that the shutter is not completely open at any time during exposure. The flash bulb is burning long enough to give light until the shutter's slit has moved over the entire image. Only the amount of light hitting the film during the fast shutter speed is reduced, so the guide number is becoming increasingly smaller the faster the shutter speed. Exposure can be controlled by the aperture and shutter speed set on the camera. A small table of guide numbers for several film speeds and shutter speeds is printed on the Cube Flash, on the small side opposite the flash cube socket.
The Cube Flash can be used with either the camera's hot-shoe contact or with the built-in synch cable on the camera's PC socket for M- or X-synch. If the hot-shoe contact is to be used, the built-in synch cable has to be plugged into the respective socket inside the Cube Flash, which is also located beneath the removable cover.
The Cube Flash was delivered in a matching, light gray plastic case.
It was offered until introduction of the Autoreflex T3N. As the flash cubes are difficult to obtain nowadays, the cube flash is not of much practical use now. The Cube Flash is quite rare.