An extension tube inserted between a single lens reflex camera body and an interchangeable objective lens barrel to extend the photographable range intrinsic to the camera is provided with an aperture value transmitting device through which the diaphragm on the lens barrel side is presettable as the aperture value is determined on the camera body side, thereby it being made possible to effect automatic exposure aperture control when making an exposure at a camera-to-object distance shorter than the lower limit of the photographable range. A transmitting device, for coupling the lens and camera, is also provided for achieving manual exposure control.
An interchangeable lens assembly including an adapter member which is held in a predetermined position relative to a camera when the lens assembly is mounted on the camera and a lens barrel structured to be rotatable relative to the adapter member during mounting of the lens assembly on the camera, the lens barrel having affixed thereto coupling means for coupling the lens assembly with the camera. The invention is directed particularly to the support structure of the lens barrel for rotatably supporting by means of the adapter member the signal transmission mechanism for transmitting exposure control signals between the lens assembly and the camera and an operation member for operating the diaphragm device of the lens assembly in accordance with operational parameters developed from the camera side of the lens assembly.
In an intermediate lens barrel mountable between an interchangeable lens having on the mount thereof means for generating a minimum F-number signal and a camera having means for detecting the signal on the mount thereof on which the interchangeable lens is mountable and including a circuit for receiving as inputs the detected signal and an output based on the light passed through the interchangeable lens and effecting an exposure operation, there is provided means capable of being coupled to each of the signal generating means and the detecting means during said mounting. The transmitting means includes correcting means for shifting the signal obtained from the signal generating means by an amount corresponding to the difference of the minimum F-number obtained as the result of the coupling of the interchangeable lens and the intermediate lens barrel from the minimum F-number of the interchangeable lens and transmitting the signal to the detecting means.
An intermediate lens tube to be mounted between an interchangeable lens and a camera body is provided with means for transmitting an information signal from the interchangeable lens to the camera body. Said information transmission means includes correction means for transmitting a corrected information signal to the camera body only when vignetting takes place in the intermediate lens tube.
A camera lens assembly adapted to be attached in operative engagement with a camera by rotative coupling therebetween including components, such as an aperture signal transmission member and a diaphragm actuating member, which may be retracted away from the camera during attachment operation, with these components being returned to a position in effective cooperative engagement with complementary control members in the camera after attachment of the lens assembly on the camera.
A lens is provided with first and second coupling means which are arranged at both ends of the lens barrel of the lens in the direction of the optical axis thereof so that the lens can be turned round and mounted in a reversed posture on a camera to permit macro-photography.
