Hans F W Domnick was a camera designer in Berlin in the 1960s and '70s.
Domnick patented a design for a camera which can be loaded with two rolls of film at once. His patents refer specifically to the desirability of using colour or black-and-white film at will, without reloading the camera. His patents cite ones by Carl Drewling of Hamburg which describe the same idea but with much less detailed design.
In the camera, there are two spaces for a supply spool of film to be loaded, one at each side of the body. The patent refers to these as 'magazines', but they are not described as removable, as in Domnick's later designs. For each of these, there is also an uptake spool, which is mounted on a sliding sled mounted on a rail, which can travel across the width of the body. A thumb-handle attached to the sled projects through the back of the camera. At rest, the uptake spool for each film sits next to the supply spool. To select one of the two films for use, the user draws its sled with the uptake spool across the whole width of the camera. This action also cocks the shutter. After exposure, the sled is released, and the uptake spool rotates to accept the exposed frame of film. A ratchet on the supply spool prevents exposed film going back onto it; and another prevents exposed film being drawn back off the uptake spool. There are two flaps, which define the sides of the exposed frame of film. As the sled passes across the camera, bringing a fresh length of unexposed film into the frame, these flaps hinge into place, pressing the film against the pressure plate.
Another patent of 1966 describes a camera (or in fact, a film magazine, and those mechanisms of the camera that interact with it). These mechanisms are mostly identical to those described above. What is novel in the new design is the use of a removable magazine. This patent describes a camera with only one film, and one sled/rail mechanism, but this is more-or-less exactly that of the two-film camera, and it is clear that the purpose of the patent is to add removable magazines to the two-film camera design. The film advance control is shown as a conventional thumb-lever (at the bottom of the camera) rather than the more unwieldy sliding control of the previous patents.
Domnick's film magazine comprises two mating chambers. One of these chambers contains the supply spool with the unexposed film, and the other retains the uptake spool. When the chambers are fitted together, the whole magazine can be handled safely in daylight, and loaded to or unloaded from the camera. Once in the camera, the supply part of the magazine is drawn across to the far end of the camera, by a sled moving along a rail, as above. A retracting film frame extends on struts to hold the extended length of film correctly against the pressure plate. After tripping the shutter, the user presses a button to release the sled, which returns, driven by a spring, to the uptake side of the camera, taking the supply side of the magazine with it. Between exposures, the two parts of the film magazine are mated together, and it can be safely removed from the camera. This allows the user to switch to a different type of film at any point in the roll. Domnick's patent stresses the danger of film being exposed with existing kinds of roll film holder. This claim seems exaggerated; most users would find this danger the greatest when film is loaded into or removed from the holder, not when using it once loaded. Certainly however, his design allows the magazine to be removed without any special action to close it.
No example of a camera made according to the patents cited above has been seen. However, Domnick returned to his two-film concept in a new patent in 1971, and a prototype of this camera was sold at the 34th Leitz Photographica Auction. One magazine is loaded at each end of the body, and either can be used at the user's choice. Again, the description in the patent is limited mostly to those elements which interact with the film magazines. The magazines incorporate a film-speed indication, and this is passed to the camera's meter. Since between exposures, both film magazines will be retracted at the ends of the camera, the design allows ground-glass focusing, though no ground-glass back was provided for in the prototype. Incidentally, a virtually identical mechanism (though for one film, not two) is the basis of the design of the Palko, made much earlier (from about 1920-35), for which the ability to use ground-glass focusing in a roll-film camera was one of the main boasts.
The film magazines contain 127 or 227 film. The camera makes 4x4cm pictures (ten on a 127 roll, or twenty on a '227' roll). It is fitted with a Zeiss 60mm f/2.8 Sonnar, in a special bayonet mount, focusing down to 3.5 feet with a coupled rangefinder. The aperture and shutter speed are set with two dials to the right and left of the lens; the limits of the shutter speed cannot be seen in the auction listing. This prototype may be the only example of the camera made.
Domnick filed two other patents, not related to his two-film camera design: a cassette of film perforated to support two different frame sizes, and a card mailing folder for sheet film items such as microfiche.
- Domnick's two-film camera patents of 1962-66, at Espacenet, the patent search facility of the European Patent Office:
- The original German patent (not stored at Espacenet) is referred to by the French and Swiss ones, giving its priority date as 11 May 1962.
- Canadian Patent 693787, Camera Loading Two Films, 8 September 1964.
- French Patent 1375028, Appareil de prise de vues photographiques pouvant recevoir simulanément deux pellicules différentes utilisables à volonté, 7 September 1964, is equivalent.
- Swiss Patent 420842, Zweifilmkamera, 15 September 1966 is equivalent.
- German Patents granted to Carl Drewling: 1051632, Photokamera, filed November 1956 and granted February 1959, and 1071472, Zweifilmkamera, filed February 1959 and granted December 1959. Each is a single page of description and claims and a sketch diagram.
- US Patent 3443501, Photographic Camera and Film Magazine Therefor, filed 15 June 1966 and granted 13 May 1969 (original German Patent filed 9 March '66); at Espacenet.
- US Patent 3805277, Still Picture Camera Having Two Film Cassettes, filed 6 November 1972 and granted 16 April 1974 (original German Patent filed 2 December 1971), at Espacenet.
- Domnick 'Super 4x4' Prototype sold at the 34th Leitz Photographica Auction, on 8 June 2019; several excellent pictures of the prototype.
- This film designation has not been seen before: it is not a Kodak size, and it appears to be an invention of Domnick's, meaning film twice the length of a 127 roll (and presumably without backing paper, as with 220 in relation to 120, or the spools would be too large to use the same magazine).
- German Patent 2948851, Fotografischer Film für Stehbildkameras, filed 5 December 1979 and granted 11 June 1981 to Hans Domnick.
- East German Patent 141292, Versandtasche, insbesondere für Planfilme, filed 15 January 1979 and granted 23 April 1980.