Large format describes large photographic films, large cameras,
view cameras (including
pinhole cameras) and processes that use a
film or digital sensor, generally 4 x 5 inches or larger. The most common large formats are 4x5 and 8x10 inches. Less common formats include quarter-plate, 5x7 inches, 11x14 inches, 16x20 inches, 20x24 inches, various panoramic or "banquet" formats (such as 4x10 and 8x20 inches), as well as metric formats, including 9x12 cm, 10x13 cm, and 13x18 cm.
Old studio camera.
Lens and mounting of a large-format camera
The Polaroid 20x24 inch instant camera is one of the largest format cameras currently in common usage, and can be hired from Polaroid agents in various countries. Many well-known
photographers have used the 235 pound (106 kg), wheeled-chassis Polaroid.
Most large-format cameras have adjustable fronts and backs that allow the photographer to better control rendering of perspective and depth of field.
close-up photographers in particular benefit greatly from this ability.
Aside from the focusing action common to all formats, the special movements of many large format technical and view cameras allow the front and/or back of the camera to be tilted out of parallel with each other, and to be shifted up, down, or sideways. Based on the Scheimpflug principle, these movements make it possible to solve otherwise impossible depth-of-field problems, and to change perspective rendering, and create special effects that would be impossible with a conventional fixed-plane camera.
Ansel Adams' photographs demonstrate how the use of front (lens plane) and back (film plane) adjustments can secure great apparent depth of field when using the movements available on large-format view cameras.
A number of actions need to be taken to use a typical large format camera, resulting in a slower, often more contemplative, photographic style. For example, film loading using sheet film holders requires a dark space to load and unload the film, typically a changing bag or darkroom (although users of the most common formats, 4×5, may now use ready-loaded pre-packaged films, which are more convenient than regular film holders).
A tripod is typically used for view camera work, but some models are designed for hand-held use. These "technical cameras" have separate viewfinders and
rangefinders for faster handling.
In general large format camera use, the scene is composed on the camera's
ground glass, and then a film holder is fitted to the camera back prior to exposure. A separate Polaroid back using instant film is used by some photographers, allowing previewing of the composition, correctness of exposure and depth of field before committing the image to film to be developed later. Failure to "Polaroid" an exposure risks discovery later, at the time of film development, that there was an error in camera setup.
Ansel Adams' large-format photograph, The Tetons and the Snake River (1942).
The 4x5 inch sheet film format was very convenient for press photography since it allowed for direct contact printing on the printing plate. This was done well into 1940s and 1950s, even with the advent of more convenient and compact medium format or 35 mm roll-film cameras which started to appear in the 1930s. The 35mm and
medium format SLR which appeared in the mid-1950s were soon adopted by press photographers.
Large-format photography is not limited to film; large
digital camera backs are available to fit large-format cameras. These are either medium-format digital backs adapted to fit large-format cameras (resulting in cropped images), or scanning backs, which scan the image area in the manner of a
flat-bed scanner. Scanning backs can take seconds or even minutes to capture an image. At the end of 2007, the largest scanning back available covered 72x96 mm, amounting to only 60% of the image area of 4x5 inch film.
Large format, both film-based and digital, is still used for many applications, for example: landscape photography, advertising photos,
fine-art photography, scientific applications and generally for images that will be enlarged to a high magnification while requiring a high level of detail.
In the printing industry, very large fixed cameras were also used to make large films for the preparation of lithographic plates before computer to film and computer to plate techniques were introduced.