Patent
1983-08-24
1985-02-05
Perkey, William B.
354443, G03B 1505
Patent
active
044975627
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a photographic camera provided with a programmed exposure control circuit which controls the diaphragm aperture and the shutter speed in accordance with a camera-to-object distance and an object brightness when the camera is set to the flash photography mode.
BACKGROUND OF THE INVENTION
In a conventional camera, the objective lens diaphragm aperture and the shutter speed for flash photography were controlled in such a manner that the diaphragm aperture is controlled depending upon the camera-to-object distance, for instance, to F 5.6 when the object is near from the camera and F 2.8 when the object is at a distance from the camera respectively, and that the shutter speed is controlled to approximately 1/60 second which is the highest flash synchronizable speed. In other known flash photography exposure control system, a range finding device incorporated in the camera measures the camera-to-object distance prior to the exposure and the diaphragm aperture is controlled in accordance with the mesured distance, with the shutter speed being adjusted to the highest flash synchronizable speed.
However, in such exposure control systems, the ambient light and the brightness condition of the portions other than the principal target object in the objective scenery were not taken into account. When a picture is taken for a scene where a person to be photographed stands in a dark scenery, although a proper amount of exposure is given to the person as the principal object which is illuminated by the flash light, the diaphragm aperture and the shutter speed at that time can not give sufficient exposure for the surroundings of the principal object because they are ordinarily further away from the camera than the principal object and receives little amount of flash light. As the result, the surrounding are reproduced dark in the resultant picture with the principal object having been photographed with a proper exposure.
DISCLOSURE OF THE INVENTION
The present invention has been made to dissolve the above described problem and its object is to provide an exposure control device for a camera which can provide, even in the case of flash photography, pictures showing the brightness of the object and its background that have a relationship virtually the same as that of the actual scenes.
Another object of the present invention is to provide an exposure control device for a camera which selects diaphragm aperture value for the exposure control, depending upon the relationship between the diaphragm aperture value for use in the flash photography determined based on the light measurement and the full aperture value of the objective lens and the diaphragm aperture value determined by the maximum or minimum available amount of flash light of the flash device and the camera-to-object distance.
The present invention comprises: for indicating a combination of a first diaphragm aperture value and a shutter speed calculated from the data of the light measurement of the ambient light an the full aperture value and adapted to provide a required exposure level for the ambient light; for indicating a combination of a second diaphragm aperture value and a shutter speed calculated from the maximum amount of light to be emitted from the flash device, the camera-to-object distance and the light measurement and adapted to provide a required exposure level for the ambient light; combination of a third diaphragm aperture and a shutter speed combination calculated from the minimum amount of flash light to be emitted from the flash device, the camera-to-object distance and the light measurement and adapted to provide a required exposure level as mentioned above for the ambient light.
Upon determination of a diaphragm aperture value and a shutter speed for flash photography the present invention compares the above first, second, and third diaphragm aperture values with one another for selecting an optimum combination from the above three kinds of combinations of the diaphragm aperture and
REFERENCES:
patent: 3601022 (1971-08-01), Langnau
patent: 3836920 (1974-09-01), Uchiyama et al.
patent: 4047194 (1977-09-01), Nakamura et al.
patent: 4367023 (1983-01-01), Ishida et al.
patent: 4367932 (1983-01-01), Ishikawa et al.
patent: 4423936 (1984-01-01), Johnson
IBM Technical Disclosure Bulletin, vol. 12, No. 6, Nov., 1969, p. 853.
Minolta Camera Kabushiki Kaisha
Perkey William B.
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