Deep Focus

Depth of field is the measure that can be applied to the area in focus within the frame.  Deep focus, which requires a small aperture and lots of light, means that the foreground, middleground and background of the frame remain in focus.  In the image below, from Citizen Kane (Orson Welles, 1941), the extended depth of field gives the frame a 3-dimensional quality, showing multiple planes of action at once.  It also allows the filmmaker to demonstrate the largesse of Kane’s dinner party and his personality.  The ability to achieve deep focus was the result of a technological development in the lens in the late 193os and its adoption as a discursive mode is largely attributed to Welles.