Mount device of a focal length changing auxiliary lens

摘要

An auxiliary lens capable of being mounted between an interchangeable lens having on the mount thereof means for generating a minimum F-number signal and a camera having means for detecting said signal on a mount to which the interchangeable lens may be mounted and including a circuit receiving as input the detected signal and an output based on the light passed through the interchangeable lens to effect an exposure operation. The auxiliary lens includes an optical system for changing the focal length of the interchangeable lens. The auxiliary lens is provided with transmitting means capable of being coupled to each of the signal generating means and the detecting means during said mounting and adapted to transmit the signal to the camera by said coupling, and a signal member having information corresponding to a variation in the F-number caused by the change of said focal length and capable of transmitting the information to the camera during said mounting.