Half-frame cameras make 18x24mm exposures, fitting twice as many pictures onto a roll of film: two portrait shots for every full-frame landscape, or, as in this case, two landscapes for every portrait.
The name 35mm film comes from the physical width of the film and has nothing to do with the size of the image format(s) recorded on the film.
For regular full-frame cameras using 35mm film, the image format is 36x24mm, with room for either 36 or 24 exposures per roll (this correspondence is purely coincidental, however).
A half-frame camera uses an ordinary 135 film cartridge but fits two images in the place of one full-frame image. Half-frame cameras make 18x24mm exposures, effectively two portrait shots for every full-frame landscape, fitting twice as many pictures onto the film, i.e., 72 exposures on a 36-exposure roll, or 48 on a 24-exposure roll. The viewfinders are therefore portrait orientation as opposed to the landscape orientation of a full-frame camera.
The half-frame format allowed manufacturers to build more compact cameras and offered consumers an alternative to other less common sub-miniature formats. Getting two shots for the price of one also provided consumers with an attractive economical option when the costs of using color film were still very high.
Half-frame cameras make 18x24mm exposures, fitting twice as many pictures onto a roll of film: two portrait shots for every full-frame landscape, or, as in this case, two landscapes for every portrait.
