Definition that contains focal length
- speed the ratio of the focal length to the diameter of a (camera) lens system
- accommodation (physiology) the automatic adjustment in focal length of the natural lens of the eye
- bifocals (plural) eyeglasses having two focal lengths, one for near vision and the other for far vision
- wide-angle lens a camera lens having a wider than normal angle of view (and usually a short focal length); produces an image that is foreshortened in the center and increasingly distorted in the periphery
- closeup lens a photographic lens with a short focal length used to take pictures at short ranges
- focal ratio the ratio of the focal length to the diameter of a (camera) lens system
- dioptre a unit of measurement of the refractive power of a lens which is equal to the reciprocal of the focal length measured in meters; used by oculists
- fresnel lens lens composed of a number of small lenses arranged to make a lightweight lens of large diameter and short focal length
- diopter a unit of measurement of the refractive power of a lens which is equal to the reciprocal of the focal length measured in meters; used by oculists
- f number the ratio of the focal length to the diameter of a (camera) lens system