The exact boundary between cameras and formats that are "subminiature" and those that are merely "small" is the subject of debate among enthusiasts. The term "miniature" was originally used to describe the 35 mm format, so cameras that used a format smaller than 35 mm were referred to as "sub-miniature". The smallest of the small are often referred to as "ultra-miniature". In the interest of specificity, cameras that produce an image on the film smaller than the standard 135 format (24x36 mm) are usually included in the genre, but some do not consider half-frame 135 (18x24 mm) cameras "subminiature", since the cameras can be almost as large as a regular 35 mm camera.
There are thousands of cameras that qualify as subminiature cameras, so there are too many to list here, but Minox, Tessina, Rollei, Yashica, Mamiya, and Minolta are the best known manufacturers. All made small, precision cameras and a few are still in production as of 2006. Getting film and processing for smaller cameras is a challenge. While a few are still available, most require cutting your own film, and home-processing as they are no longer supported.
The best known subminiature formats are -- in increasing size -- Minox (8x11 mm), Kodak disc (8x11 mm), 16 mm (10x14 mm), Super 16 mm (12x17 mm), 110 film (13x17 mm), Tessina (14x21 mm) and half-frame (18x24 mm). While many subminiature cameras were inexpensive and poorly manufactured (thus giving the format a bad name), many others, such as Minox, Tessina, Gami, Edixa, Rollei, Pentax and Minolta made quality cameras capable of producing fine results -- even enlarged. Because of their small size and light weight, subminiature cameras can be readily carried in a pocket or purse to be available at any time.
First making an appearance in the late 1800s, often as concealed cameras, a subminiature camera craze developed soon after WWII when many consumer markets required small, inexpensive cameras. In response, Kodak's introduction of the 110 camera in the 1970s and the Kodak disc camera in the 1980s brought the subminiature camera to the forefront of the photographic market. But the many cheap, poorly made cameras that soon appeared drove Kodak out of the market and gave subminiature cameras a bad name. Still, there are many subminiature cameras with top-quality lenses and a full range of features, such as variable apertures, selectable shutter speeds, focusing lenses, and numerous accessories.
The various formats of subminiature cameras have come and gone over the years. Several factors have played a part in this. For example, newer submini formats have replaced other, older submini formats. In addition, many larger-formatted cameras, especially 35 mm, become smaller in size and weight -- partly due to the consumer demand for submini cameras -- and were able to replace some submini formats. For example, full-frame 35 mm cameras, such as the Minox 35 and the Olympus XA, were made as small as the earlier half-frame submini cameras, such as the Olympus Pen. Still, some submini formats survive in the marketplace, such as the Minox and 110 formats. Most other submini cameras are still completely usable -- especially if the photographer has access to a darkroom.
The process of focusing a subminiature camera is the same as on any other camera: the lens or lenses are moved back and forth relative to the film plane. The small size of the camera and film require the use of a lens with short focal length, and hence a wide depth of field. This simplifies focusing to some extent. The simplest system is to use a lens set at the hyperfocal distance. This will produce images that are acceptably sharp from infinity to some near plane (usually five to eight feet away). No focus adjustments are possible. This system is used in most cheaper cameras. More complex systems allow variable focus, through a dial or slider. Many cameras with this system have distance markings on the control; it is up to the user to estimate the distance to their subject and set the focus accordingly. Most Minox cameras use this system. With practise, estimating distance becomes a relatively simple task, particularly at longer ranges (since the depth of field is greater). Some subminiature cameras may include a simple rangefinder to help the user set the distance properly. These tend to increase size and weight, and the small size of the camera reduces the maximum accuracy of an optical rangefinder. Autofocus or through-the-lens focusing systems are basically unheard-of in subminiature cameras, due to their size, weight and mechanical complexity.
Subminiature cameras are not ideally suited to macro photography. The lens selection and focusing limitations make it more difficult to carry out macro photography than with a larger camera. However, the relatively large depth of field at close distances and the light weight (helping to reduce camera shake) can be advantages. It is certainly not impossible; subminiature cameras (particularly the various Minox models) have an illustrious history as spy cameras, where they were used to photograph documents at distances shorter than two feet. Minox cameras come with a 24-inch measuring chain attached, with small markings corresponding to certain distances, to assist in focusing at these short ranges.
Few subminiature cameras have any lens other than their format's "normal" lens. Telephoto lenses for such small formats essentially do not exist, except for Steky and Gami. There have been attachments in the past to allow cameras (generally Minox) to attach to telescopes or binoculars, but these are less than ideal. The lens built into the camera is generally of higher quality than such an adapter will be able to reflect.