120 Roll Film
A 61 millimetre wide roll film on a spool with paper backing, the surviving standard for medium-format photography.
Measured in
mm
In depth
One roll yields a different number of frames depending on the camera: sixteen at 6×4.5, twelve at 6×6, ten at 6×7 or four at 6×17. The paper backing carries frame numbers readable through a red window on simpler cameras. Its longer sibling, 220, dropped the backing to double the length and is now largely discontinued.
Examples in practice
A 6×6 camera gives twelve square negatives per roll, each with about three and a half times the area of a 35 mm frame.