Lens focal length You can vary the depth of field from any viewpoint by using different focal lengths. A basic guideline to remember is this: Telephoto lenses with longer focal lengths offer inherently shallow depth of field, whereas wide-angle lenses with short focal lengths produce extensive depth of field. Keeping this in mind helps you capture your vision by selecting the right lens for any situation. If your goal is to pick out a small blossom and isolate it from a chaotic thicket, long focal length and large aperture provide a narrow zone of sharp focus to accomplish the desired result. If your plan is to emphasize a cluster of flowers against a harmonious background, short focal length and small aperture will maintain sharpness throughout.