In photography and optics, a plane is an imaginary flat surface on which image points lie or a surface that passes at right angles through a set of points perpendicular to the optical axis. It is a fundamental concept in understanding focus, perspective, and depth of field in photographic imaging.
Planes are used to describe how light rays converge to form a sharp image on a sensor or film. Concepts such as the focal plane and image plane rely on this idea, helping photographers control composition, focus, and the three-dimensional representation of a scene in two-dimensional images.