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Film format

Roll film & sheet film are most common.


The two most common formats for film are roll film and sheet film, which is also sometimes referred to as "cut film."

Glass plates are also available for specific uses, primarily where absolute flatness is essential, but most photographers will never come across them or have a need for them.

ROLL FILM

Roll film is manufactured in strips and wound on a spool. The widths of roll film vary considerably, depending on the camera for which they are intended, from subminiature (8mm movie film) to 10 inches wide for very large cameras used in aerial photography.

The most common size of roll film is 35 mm, also sometimes referred to as 24 X 36 film because the actual size of an image frame on the film is 24 mm by 36mm. This film is manufactured with evenly-spaced perforations along both edges to enable the camera's gears to engage the film so it can be advanced from frame to frame. Its spool is most often placed inside a metal or plastic cassette or cartridge with a small amount (the leader) sticking out. A very long strip of 100 feet (30 meters) may also be wound onto a large roll for placement in a film bulk loader that the photographer employs to load his or her own individual film cartridges in whatever lengths are desired. Typical lengths provide 8, 12, 24 and 36 exposures. 35 mm film is thicker than other formats to strengthen it against the possibility of tearing occurring at the perforations.

These cartridges contain two common varieties of roll film: 35 mm (on the left) and APS
These cartridges contain two common varieties of roll film: 35 mm (on the left) and APS

APS film is always placed in a cartridge, since the cartridge itself plays an integral part in the usefulness of APS film.

For 120 and 220 size, the film is tightly wound on a spool, held in place by a glued paper strip, then wrapped in protective paper or foil package that must be removed before loading the film into the camera. Since cameras that use these films do not have a gear system like 35 mm cameras, there are no perforations on the film.

THE ADVANTAGES of roll film are that it is compact, easy to carry in large amounts, loads and unloads easily in daylight, simplifies the making of several different exposures in sequence, and is simpler to use than many other types of film.

ONE DISADVANTAGE is that the entire roll must be processed at once; individual shots cannot be processed separately. This is not a major setback for most photographers today whose cameras and expertise provide relative consistency from exposure to exposure, particularly with auto-exposure cameras. However, the photographer is still limited in that he or she cannot effect radical changes in exposure from one image to the next, such as shooting one or two frames at different film speeds since the entire roll must be processed as if every image was taken at the same film speed.

Another disadvantage of roll film is that you cannot quickly change from one emulsion type to another (color to black and white film, for instance, to shoot the same scene). If you have taken 8 pictures on a roll of 24-exposure color film, and decide you want to shoot a scene in black and white film, you must completely rewind the color film to avoid losing your exposures before you can load a new roll of black and white film.

Cameras that use interchangeable roll film magazines get around this drawback. These are mainly medium format cameras which permit you at any time to change the entire camera back that holds the film. The photographer can switch back and forth from one film to another without the need to rewind and sacrifice unexposed film. There is a technique with 35 mm film that you can employ with manual-rewind cameras to unload a partially-exposed film, then reload it later to shoot the remaining unexposed portion of the film. You rewind the partially-exposed roll of 35 mm film so as to leave the leader out (See the paragraph called “Rewinding exposed film in a manual camera” in Unloading film from a 35 mm camera), and then unload the film from the camera. Your exposed frames are protected in the film cartridge, which you must mark to show how many exposures were made. Since the film was not completely rewound into the cartridge, you can easily re-load it later, making sure to wind it past the last frame that was exposed. This is accomplished by advancing the film to the first exposure, then tripping the shutter release while leaving the lens cap on to ensure no light reaches the film, and repeating this action until you have advanced the film one frame past the final exposure that was made. For insurance purposes, advance the film one more frame, and you can resume using the roll.

Some APS cameras have built-in "mid-roll change" capability which allows their users to remove a partially-exposed film cartridge and then re-insert it to shoot the remaining unexposed film.

SHEET FILM

There is no winding on a spool for sheet film. It is flat. Each individual sheet is good for one individual exposure, and must be loaded separately into its own unique holder.

Sheet film is available in a wide variety of sizes and emulsions. It can be purchased as small as 2 1/4" by 3 1/4" and larger than 8" X 10".

ADVANTAGES: Its flatness is one of its advantages. You can also switch from one emulsion type to another at any time. Its one-picture-per-sheet characteristic is intrinsically less wasteful because the photographer will generally take the time to ensure correct composition and exposure before taking a picture, whereas roll film photographers may tend to shoot much more film simply because it is easy to do so. Another advantage is that since sheets are processed individually, there is no film wastage and any unusual processing requirements can be applied to one sheet alone without affecting other exposures made of the same scene.

DISADVANTAGES: Sheet film is less convenient to use than roll film. If you want to make a lot of quick exposures in succession, sheet film is not for you. It must be loaded in total darkness, and each holder accommodates only two sheets at a time (one on either side). Holders are bulky and relatively heavy.