Abstract: A lens barrel has an aperture ring adapted to be positioned adjacent a camera when the lens barrel is mounted to the camera, and has on the aperture ring an interlocking pawl for transmitting the lens-side information to the exposure meter of the camera. An aperture scale usable for display within the camera viewfinder is formed on the aperture ring between the interlocking pawl and that end of the lens barrel which is adjacent to the camera. A light passing portion is provided in the interlocking pawl for passing therethrough light for illuminating the aperture scale for display within the viewfinder.