The 4.5×6cm picture format was first a plate film format. It became a rollfilm format in 1932 with the Ikonta, taking 16 exposures on 120 film, and has been on continuous use until today. A close rollfilm format was the 4×6.5cm on 127 film, introduced with the Vest Pocket Kodak.
The first rollfilm camera to use the 4.5×6cm format was the Ikonta by Zeiss Ikon, released in 1932. 120 film was originally meant to be used for 6×9cm pictures, and the backing paper was numbered accordingly from 1 to 8. Zeiss-Ikon had the idea to make a half frame camera, using each number twice. This company had already invented the 3×4cm format on 127 film two years before, using this same trick with the Kolibri. The rumour says that the motivations for these two half-frame formats was the economical crisis, making film more expensive to buy, and the better quality of the film emulsions that enabled enlargements. Indeed the 4.5×6 format was meant to be enlarged, while many amateur photographers using 6×9cm cameras were satisfied with contact prints.
See the Category: 4.5x6 folding for a list of 4.5×6 folders treated in camera-wiki.
The first 4.5×6 cameras were folders, following the wake of the Ikonta. Examples of early followers are the Perle by Welta (1932) and the Baldax by Balda (1933). These two makers developed a 6×6 variant from their 4.5×6 model, and this example was followed by other companies, like Beier with the Precisa (1936), while others prefered to make dual-format folders, like the Super Sport Dolly by Certo (1934). Another German 4.5×6 folder is the Duo Six-20 by Kodak AG (1933), that was one of the few 4.5×6 horizontal folders.
More expensive models, equipped with a rangefinder, were soon developed from the cameras cited above. It seems that the first was the Super Ikonta (1934), followed by the Weltur by Welta (1935, an evolution of the Perle), and two models based on the Baldax: the Roll-Op II by Plaubel (1935) and the Baldaxette by Balda (1936).
Kodak and Agfa did not show much enthusiasm for this format, and prefered to concentrate on 6×9 models, presumably because their main interest was to sell film. An exception is the Billy-Clack by Agfa (1934), an inexpensive strut-folding model.
Voigtländer entered the 4.5×6 market quite late, with the Bessa 46, launched in 1938 together with the 6×6 Bessa 66. In 1940, it made the Bessa 466, a dual-format variant with automatic film advance and exposure counter functioning for both formats, switchable in mid-roll, considered to be very rare.
The 4.5×6 format was adopted early in Japan, the two first models being the Semi Prince and Semi Minolta, appearing in 1934. This format received much interest in that country until the 1950s. See the article titled Japanese 4.5×6 folders for in depth covering.
The production of 4.5×6 folders continued for some time after the war. To be continued