Abstract: A photographic or cinematographic objective, bodily displaceable between an object plane and an image plane, has a lens mount slidably supported on a base which may be inclined at an acute angle to the generally horizontal optical axis. Two setting rings, one for adjusting the magnification ratio and the other for controlling a diaphragm, are mechanically connected by a spring-loaded linkage with a pair of cam-follower rollers bearing upon respective edges of two camming strips secured to the base whereby the two rings are counterrotated upon a movement of the objective mount in either direction. The roller-engaging strip edges advantageously are so oriented, in the case of a sloping base, as to oppose the spring force upon a downward movement of the lens mount so as to exert a braking action.