The USSR produced many system rangefinder cameras.
They had the status of systemic ones for a reason. The fleet of interchangeable optics was very impressive and allowed both amateur and professional photographers to realize their ideas.
But the peculiarity of a rangefinder camera is that sighting does not occur through the lens. The photographer observes the subject through the viewfinder. Therefore, changing a lens to another, with a different focal length, radially affects the resulting image on film, but does not in any way affect the photographer’s field of view
It has one eyepiece for observation.
But at the same time, the VU is equipped with a rotating mechanism, thanks to which one of five mini-lenses can be attached to the eyepiece, thereby changing the observer’s field of view.
Thus, five focal lengths can be met: 28, 35, 50, 85 and 135 mm.