1. Field of the Invention
This invention relates to a motor-driven diaphragm device for a camera.
2. Description of the Prior Art
Heretofore, a single-lens reflex camera using an interchangeable lens, which is provided with an automatic stop or diaphragm device of the present type, has a diaphragm driving spring charged in response to a film winding operation and stops the diaphragm aperture down to a preset value from a full or maximum open position thereof with the stored force of the driving spring. The force, which is thus charging the diaphragm driving spring, imposes a large load on the camera together with a film driving force for winding the film and a mirror driving force. This impairs the smoothness of operation in manually winding the film and necessitates use of a large motor with a large output for simultaneously charging all the loads while film winding with a motor incorporated in the camera. Furtheremore, in the event of continuous photography, it is conventional to repeat the processes of stopping down the aperture and bringing the aperture back to the full open position thereof for every photography frame. However, the driving spring charging force requires large photography time intervals for these processes. In the case of an interchargeable lens of the type permitting manual stopping, therefore, it shortens the operation time for quicker photography by shifting the automatic stopping-down operation to a manual stopping-down operation. However, since focusing on the lens is not easy when the aperture is stopped-down, the aperture must be fully opened upon completion of every continuous photography operation. This requirement greatly impairs the operability of the camera. If a lens is mounted on the camera in a stopped-down condition, it tends to cause problems, such as misplacement of an automatic stop lever, etc.
It is an object of this invention to provide a camera in which a motor is provided within the camera body especially for operating an automatic stop arrangement dispersing the winding load for smooth winding in the event of manual film winding and permitting use of a smaller output winding motor. The stopping-down motor can be easily disposed in an unused space within the camera allowing a considerable degree of latitude in its arrangement within the camera. Therefore, since the stopping-down motor permits the use of a winding motor of a reduced size, the camera as a whole can be smaller.
It is another object of the invention to provide a camera in which a stopping-down motor is actuated and stops down the diaphragm aperture of a lens by means of a switch which operates in response to the operation of a shutter release button; the lens is kept in the stopped-down condition as long as the release button is kept depressed; therefore, in the event of continuous photography, continuous photography can be carried out at an increased speed without recourse to a troublesome manual stopping-down operation required by prior art cameras.
It is a further object of the invention to provide a camera wherein a switch detects completion of a stopping-down process; and this switch is connected in series with a shutter release switch and permits a shutter release only when the aperture of the lens is correctly stopped down to a predetermined value, so that the operability of the camera can be enhanced.
These and further objects and details of the invention will become apparent from the detailed description of a preferred embodiment thereof taken in connection with the accompanying drawings.