Depth of Field (DOF)
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The distance between the farthest and nearest points which are in focus. This can also be identified as the zone of acceptable sharpness in front of and behind the subject, to which the lens is focused on. DOF varies according to numerous factors such as lens focal length, aperture, shooting distance, etc.
For more information, see the Nikonians guide Understanding DOF and Aperture & Shutter Speed Relationships by Digital Darrell [1]
