For a list of folding cameras, see Category: Folding.
A folding camera, or folder, is a camera with bellows that can be folded so that the camera occupies less space when not in use. Exceptions without bellows are a few old camera designs which were foldable due to a set of hinges, for example foldable variants of the sliding box camera by Charles Chevalier and Thomas Ottewill (more accurately described as "collapsible box camera" instead of folding camera), or other special designs with a bellows replacement like the Minolta Vest. Many folding cameras allow variations of their bellows' length, thus making the bellows also the means for focusing.
Not all bellows cameras can be called folding: a monorail view camera has bellows, but it cannot be folded (at least not "folded into itself") and instead provides greater flexibility for "movements". Other large format view cameras are foldable, known as field cameras for their portability.
Some press cameras (like the Busch Pressman Model D) allow tilts and shifts but also fold for compactness. However, the great majority of folding cameras force the lens board and image plane to be parallel (no tilts), and force the lens and image frame to centre on an axis perpendicular to these two planes (no shifts). This reduces the function of the bellows to the saving of space.
Strut folding cameras are folding cameras, but some people classify them separately, not as "folding cameras". While Folding bed cameras and self-erecting folding cameras have all or nearly all camera parts covered by itself when folded, the most strut folding cameras leave lens and some mechanical parts unprotected when folded. This disadvantage is sometimes equalised by the advantage of the extreme compactness of a folded strut folder, for example the Ensignette or the Nettix.
Putting aside strut folders (indeed they are folders), we can divide folders into two. A very small minority, exemplified by the Voigtländer Vitessa, have "barn doors": a symmetrical pair of doors. The others have a single door. A distinction is often drawn according to whether the bed hinges "vertically" or "horizontally" (that is, if the camera's longest dimension is vertical or horizontal when the bed is unfolded towards the bottom). The great majority of 6×6 folders are horizontal folders; the great majority of 4.5×6 and 6×9 folders are vertical folders.
The early folding cameras were compact amateur view cameras, plate cameras of the folding bed type and predecessors like the Lucidograph. Other than common view cameras the whole camera was securely enclosed in its body when folded.
The typical rollfilm folding camera of the 1910s/1920s is a folding bed camera like the Conley Folding Kewpie No. 2 or the No. 3A Autographic Kodak Junior. Its lens assembly needs to be pulled out along the rails on its opened hinged front door. The leaf shutter has a small lever for firing and maybe another for cocking; it also allows a cable release to be screwed in. (The screw dimensions are the same as those used in those of today's cameras.) Film is advanced with a key or knob; one stops winding when the new number appears in a red window on the back. There is no rangefinder, and the only viewfinder is a swivelling brilliant finder attached to the front of the lens. There is no pressure plate to hold the film in the right plane.
Its successor of the 1930s is self-erecting: as one unlocks the front door, the lens pops forward. (It may be necessary to pull it a little further at the lens standard, so that it clicks into position.) The brilliant finder is supplemented by some other viewfinder, many very rudimentary even by the standards of the 1930s. There may be a mask inside to allow a choice between two formats (e.g. 4.5×6 and 6×9). Sophisticated models might include a rangefinder, some even a coupled one. A sample is the Kodak Junior 620.
By the 1950s, the brilliant finder is gone and a viewfinder, perhaps with integrated rangefinder, is under a rigid housing. The shutter still needs to be cocked, but the shutter release is now on the body. There is certainly a film pressure plate; either this has one or more holes for red windows, or there are no holes and no red windows as film advance is semi-automatic. The lens is focused in one of three ways:
- the frontmost element alone is moved ("front-cell focusing"): optically the least satisfactory solution and normal in cheap cameras, but sometimes used for expensive and highly regarded cameras too
- all the elements of the lens are moved forward and backward together ("unit focusing"): this can be achieved by mounting the lens and shutter assembly on an helical ("helicoid focusing"), or on a strut that moves along a rail or is displaced in some other way
- the film is moved forward and back while the lens is kept stationary ("film-plane focusing"): the least common of the three systems
The Agfa Isolette cameras are typical 1950s folders.
By the 1970s a new kind of folder became popular among the better-off, the instant SLR camera Polaroid_SX-70. The 1980s brought a bellows-less "folding" conception represented by the Minox 35 and others, belonging more to the class of modern compact cameras than to the "folding cameras".
There have been folding cameras for a wide range of image formats, from 18×24 mm to 18×24 cm.