History of Depth of field

	Revision 12 . . September 7, 2001 8:31 am by Stokerm [attempted to generalize beyond motion pictures.]
	Revision 11 . . (edit) September 7, 2001 4:20 am by (logged).121.110.xxx

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Difference (from prior major revision) (no other diffs)

Changed: 1,3c1

In film and photography, depth of field refers to the distance in front of and behind the subject which appears to be in focus. For any given lens setting, there is only one distance at which a subject is in focus, but focus falls off gradually on either side of that distance, so there is a region in which the blurring is tolerable. This region is greater behind the point of focus than it is in front.

In film and photography, depth of field refers to the distance in front of and behind the subject which appears to be in focus. For any given lens setting, there is only one distance at which a subject is in focus, but focus falls off gradually on either side of that distance, so there is a region in which the blurring is tolerable. This region is greater behind the point of focus than it is in front.

Changed: 15c13

Depth of field is related to the focal length of the lens and to camera-to-subject distance. Lenses of short focal length have greater depth of field than long lenses; for any given lens, a distant point of focus creates more depth of field than a near one.

Depth of field is related to the focal length of the lens, the effective diameter of the lens opening and the camera-to-subject distance. Lenses of short focal length have greater depth of field than long lenses. For any given lens, the depth of field increases as the distance to the point of focus increases up to the hyperfocal distance (see below). As the point of focus moves beyond the hyperfocal distance the field extends to infinity, but the distance to the nearest point of acceptable clarity increases, so the total depth of field actually decreases.

Changed: 17c15

The aperture controls the effective diameter of the lens opening. Reducing the aperture size increases the depth of field, but motion pictures make only limited use of this control. Lenses almost invariably work best at medium apertures. To produce a consistent image quality from shot to shot, cinematographers usually choose a single aperture setting for interiors and another for exteriors and adjust exposure through the use of camera filters or light levels.

The aperture controls the effective diameter of the lens opening. Reducing the aperture size increases the depth of field, however, it also reduces the amount of transmitted light placing a practical limit on the extent to which the aperture size may be reduced. In photography lenses almost invariably work best at medium apertures. Motion pictures make only limited use of this control. To produce a consistent image quality from shot to shot, cinematographers usually choose a single aperture setting for interiors and another for exteriors and adjust exposure through the use of camera filters or light levels. Aperture settings are adjusted more frequently in still photography, where variations in depth of field are used to give a variety of special effects. In photolithography, where extremely shallow depths of field on the order of a few microns are common, the proper aperture setting is critical.