A switch, button, or electronic push-button that allows for preview of the depth of field of the set aperture in the viewfinder. During composition the lens is wide open, thus the depth of field in the viewfinder is always that of the maximum aperture of the lens. It is very useful for critical selective focus shots although some rightfully consider it no more than an approximation, others feel that an SLR lacking a depth of field preview function is greatly diminished as a creative tool.ritzcamera
The range of distance in a scene that appears to be in focus and will be reproduced as being acceptably sharp in an image. Depth of field is controlled by the lens aperture, and its area of acceptable focus extends for a distance in front of and behind the point on which the lens is focused (i.e. the plane of focus).
Many cameras are equipped with a preview button that, when pressed and held in, stops the lens down to the preselected aperture, allowing you to see how much foreground or background are in focus.
Markings on the barrel of a lens that show the depth of field for a particular aperture and a particular focus setting.
The zone, or range of distances within a scene that will record on film as sharp. Depth of field is influenced by the focal length of the lens in use, the f-number setting on the lens, and the distance from the camera to the subject. It can be shallow or deep, and can be totally controlled by the photographer. It is one of the most creative and profound effects available to photographers.
A zone of focus in the camera. If an image is focused on a ground glass screen in a camera,depth of focus makes it possible to move the screen slightly backward or forward and still have the image in acceptable focus.