Abstract: An objective of variable focal length affording an aperture ratio of about 1:1.0 to 1:1.4 for narrow film projectors and microscopes comprising at least six lens members separated by air spaces, characterized by the following construction and arrangement of the lens members:A. a first lens member confronting the longer conjugate or the projection screen, respectively, said first lens member having dispersing power and the surface thereof with the larger radius of curvature confronts the film or the shorter conjugate respectively;B. a second displaceably arranged lens member having collective power and containing outer surfaces of approximately the same radii of curvature;C. a third collecting lens member having differently curved outer surfaces, wherein the surface confronting the shorter conjugate or the film, respectively, possesses the larger radius of curvature and separated from the lens surface of the following fourth lens member by a small air space;D.