A multiple magnification optical system has a single objective focused upon a specimen at a given working distance. A graded-index lens receives light passing through the objective from the specimen. A beam splitter splits the light exiting the gradient-index lens into a first optical axis and a second optical axis. A first lens is aligned in the first optical axis between the beam splitter and a first camera to focus a magnified image at the first camera. A second camera is situated along the second optical axis from the rear principal plane of the objective so as to obtain unity magnification when the working distance of the objective is set at twice its focal length. Multiple magnifications can be obtained with a single objective by moving the optical system axially to set different working distances from a specimen, and by using multiple beam splitters, or combinations thereof.