In filmmaking and video production, a shot is a series of frames that runs for an uninterrupted period of time. Film shots are an essential aspect of a movie where angles, transitions and cuts are used to further express emotion, ideas and movement. The term "shot" can refer to two different parts of the filmmaking process: In production, a shot is the moment that the camera starts rolling until the moment it stops. In film editing, a shot is the continuous footage or sequence between two edits or cuts. The term "shot" is derived from the early days of film production when cameras were hand-cranked, and operated similarly to the hand-cranked machine guns of the time. That is, a cameraman would "shoot" film the way someone would "shoot" bullets from a machine gun. Shots can be categorized in a number of ways. The field size explains how much of the subject and its surrounding area is visible within the camera's field of view, and is determined by two factors: the distance of the subject from the camera ("camera-subject distance") and the focal length of the lens. Note that the shorter a lens's focal length, the wider its angle of view (the 'angle' in wide-angle lens, for instance, which is "how much you see"), so the same idea can also be expressed as that the lens's angle of view plus camera-subject distance is the camera's field of view. the long shot or wide shot (often used as an establishing shot), that shows the environment around the subjects, the full shot, where the entirety of the subject is just visible within the frame, the medium-long shot, where the frame ends near the knees, the medium shot, where the frame stops either just above or just below the waist, the medium close-up, where more of the shoulder is visible than in the close-up, the close-up, where the shoulder line is visible, the extreme close-up, where the frame stops at the subject's chin and forehead.