Film format refers to the physical size of the area of film used by a camera to record a photographic image. The format has a direct influence on image quality, depth of field, the number of exposures available on a roll of film, and the overall size and weight of the camera system required to use it.
The most widely used film format is 35mm, which records an image measuring 24x36mm on the film strip. It became the dominant format for both amateur and professional photography throughout the twentieth century due to its compact size, versatility, and the wide range of cameras and lenses available for it.
Medium format cameras use 120 or 220 roll film and can record images ranging from 6x4.5cm up to 6x17cm, depending on the camera. Common medium format sizes include 6x4.5cm, 6x6cm, 6x7cm, and 6x17cm. Some photographers favour the square 6x6cm format as it offers an alternative to the conventional rectangular frame, and removes the need to consider portrait or landscape orientation when shooting - any cropping decisions can be made later at the printing stage. As a general rule, the larger the format, the greater the potential image quality, as more film area captures more detail and finer grain. However, this comes at the cost of fewer exposures per roll - a 6x4.5cm camera typically yields around 15 frames, a 6x6cm around 12 frames, a 6x7cm around 10 frames, and a 6x17cm panoramic camera as few as 4 frames per roll.
Large format photography takes this further still, using individual sheet film in sizes such as 5x4 inches or 10x8 inches, offering the highest possible image quality but requiring specialist equipment and a more considered, methodical approach to shooting.