The box camera is the simplest and cheapest type of camera. It is mainly intended for people who want to take snapshots in good light and who do not know (or want to know) a lot about photography. In its traditional form, it is simply an oblong or square box fitted with a very elementary lens, shutter, and viewfinder, and some means of registering and winding a paperbacked roll film.
Modern box cameras are usually more streamlined, resembling miniature cameras in appearance. In recent years designers have made extensive use of the possibilities of styling offered by the simple design and by the utilization of moulded plastic body components.
Traditionally box cameras used to take 2 1/4 x 3 1/4 inch (6 x 9 cm) or 2 1/4 x 2 1/4 inch (6 x 6 cm) pictures on size 120 roll film. A more modern trend is the box camera taking 16 exposures 1 5/8 x 1 5/8 inches (4 x 4 cm), again on size 120 roll film, yielding greater film economy (even though part of the film area is wasted). This has become popular with reversal color films, especially as the 1 5/8 x 1 5/8 inch format is suitable for mounting in 2 x 2 inch super slide mounts.
An alternative and still popular film size is 127, yielding usually 12 exposures 1 5/8 x 1 5/8 inches (4 x 4 cm). Other sizes also exist (for example 828 for 28 x 40 mm images on unperforated 35 mm film).
The box itself is generally made of plastic or of sheet metal, covered with leather or plastic. It is made to open so that the film can be inserted. There is one chamber to hold the full spool of film and another for the empty spool. Between the two chambers the film is led behind a metal aperture that frames the picture area. A spring-loaded pressure plate fixed inside the back of the box keeps the film pressed flat against the picture aperture.
With some designs the film plane is curved, so that the film is deliberately not allowed to lie flat. This to some extent compensates for the curvature of field of the cheap lenses employed.
The film is transported by turning a key or knob on the outside of the box. There is a window (and sometimes two) located in the back of the camera through which the frame numbers on the paper backing of the film can be read when winding on from one frame to the next. This window has a red or green filter in it to stop active light from getting to the film.
The lens in the cheapest box cameras is made of a single meniscus-shaped piece of glass. It is not corrected for any of the aberrations and has a single fixed stop that confines the light rays to the center of the lens and gives it an aperture between f11 and f16. Some of the better types have doublet lenses with a maximum aperture of about f8.
The most usual type of lens fitted has only one fixed stop, but some have two or three stops consisting of holes in a movable plate in front of the lens.
Some modern box models incorporate an exposure meter coupled to the lens aperture, so that the latter is automatically set by the prevailing light. Electric eye models of this kind still have only a fixed single shutter speed, but the exposure meter system directly operates movable plates perforated in a certain way to produce larger or smaller lens openings.
There is no means of focusing on a typical box camera; the lens is set at a fixed distance from the film to give reasonably sharp negatives of everything beyond about 7 feet from the camera. More expensive types focus down to 3 feet. To do this the lens is made to slide or screw outwards in its mount.
Box camera shutters are very simple affairs; they admit light to the film through a hole in a metal disc rotated by pressure on the shutter release lever.
Nowadays the shutter incorporates a set of contacts to synchronize the firing of flash bulbs with the full open position of the shutter. In some cases special flash guns are available which plug directly into the camera, without the need for a connecting cable between the flash and the shutter.
Some box cameras have the flash gun built in, with a miniature reflector in the front of the housing (above or to one side of the lens) taking miniature flash bulbs. A special compartment of the camera then takes the batteries for firing the flash. As an alternative the reflector may rise up from the top of the camera (and be collapsible) taking the smallest types of flash bulb.
The viewfinder on the smallest box cameras is usually of the direct-vision type, either frame or optical and on larger sizes, a reflex type. In such cameras the picture in the viewfinder is often the same, size as or only slightly smaller than the negative.
In spite of its simplicity the box is capable of taking photographs of a high standard.