Depth of field
A measure of how much of a picture is in focus, from the nearest point in the scene to the camera that looks sharp, to the furthermost point that looks sharp. Depth of field is dependent on the aperture used, the distance that the lens is focused at, and the focal length of the lens.
Depth of field preview
Device found on some digital SLRs that enables you to see the viewfinder image at the actual aperture you’ll be using for the exposure. This gives a visual indication as to how much depth of field there is, and which parts of the resulting picture will be sharp or blurred. This is necessary because the viewfinder normally only shows the image as it would appear if the widest aperture available was used.
Depth of field scale
A scale found on some lens barrels that can be used to work out the depth of field for particular apertures, and that can be used for manual focus adjustments to maximize or minimize the depth of field.
A program exposure mode in which the aperture and shutter speed is set automatically in order to provide the maximum depth of field while maintaining a shutter speed that’s fast enough for hand-held photography. With some cameras, the different subject distances measured by the multipoint autofocus system is also taken into account, and the focus is adjusted to suit.
Sources: Pixabay, NASA, Wikipedia, Susan Wingfield Lamar High School