Bellows (photography)

In photography, a bellows is the accordion-like, pleated expandable part of a camera, usually a large or medium format camera, to allow the lens to be moved with respect to the focal plane for focusing.

The bellows provides a flexible, dark extension between the film plane and the lens.

For large format cameras, “double extension” refers to bellows that extend to a length equal to about twice the focal length of a standard lens, e.g. 300 mm for the 4×5 inch format.

Bellows allow movements that can be used to correct distortion in a photograph and to avoid converging or diverging verticals.

[2] In some cameras, the photographer can change the angle of the film plate with respect to the optical axis of the lens, providing alterations of perspective distortion and of the object plane of focus.