sentences:  Lenses are not labeled or sold according to their angle of view, but rather by their focal length, usually expressed in millimeters.But this specification is insufficient to compare lenses for different cameras because field of view also depends on the sensor size.For example, a 50 mm lens mounted on a Nikon D3 (a full-frame camera) provides approximately the same field of view as a 32 mm lens mounted on a Sony α100 (an APS-C camera).