The depth of field refers to the area within the field of view which is in focus. A large depth of field means that a large percentage of the field of view is in focus, from objects close to the lens often to infinity. A shallow depth of field has only a small section of the field of view in focus. The depth of field is influenced by several factors. A wide angle lens generally has a larger depth of field than a telephoto lens. A higher F stop setting also has a larger depth of field. With auto iris lenses the automatic adjustment of the aperture also means constant variation of the depth of field. The small depth of field is most apparent at night when the lens is fully open and the depth of field is at its minimum so objects that were in focus during the day may now be out of focus.