For cameras that use 35 mm film (or an equivalent digital sensor), a focal length between 35 mm and 50 mm is considered as “normal”. As indicated by its name, this kind of lens is the prime choice for cinematographers because it produces the least distortion of any type. The normal lens best approximates the way the human visual system experiences a scene, since lenses in the normal range reproduce the depth relationships of objects in a way close to human vision. Lenses with longer focal length are called telephoto lenses, whereas lenses with shorter focal length are designated as wide-angle lenses. Both types of lenses have certain characteristics regarding depth relationships, perspective distortions, depth of field and angle of view, which clearly set them apart from normal lenses.
