1982-06-14
1984-03-06
Gellner, Michael L.
354458, G03B 7083
Patent
active
044350570
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to an exposure control device for a camera, and more particularly it pertains to an exposure control device of a storage type wherein an output of a light measuring circuit, which measures the brightness of an object or scene to be photographed, is stored in a capacitor prior to a film exposure and the exposure is controlled in accordance with the stored output.
BACKGROUND OF THE INVENTION
In the storage type camera exposure control device, a storage capacitor stores an output of the light measuring circuit, or an exposure control signal which is obtained as a function of the output of the light measuring circuit and a signal commensurate with a set exposure parameter value. The exposure control signal may be the one for presenting an exposure time suitable for a measured object brightness, a set film sensitivity value and a set diaphragm aperture value, or otherwise may be the one for presenting an diaphragm aperture suitable for an object brightness, a set film sensitivity value and a set exposure time value. Further, the exposure control signal may be the one for presenting a combination of an exposure time and a diaphragm aperture relying on an object brightness and a set film sensitivity value. It should be noted that, throughout this specification, the term "an output of a light measuring circuit" or "a light measurement signal" should be understood or interpretated, unless specified otherwise, as including the exposure control signals having the forms mentioned above, since the exposure control signals are dependent on an output of the light measuring circuit.
In the storage type camera exposure control, the light measurement signal is, in general, stored automatically in conjunction with a camera release operation. An exposure control device is known wherein a light measurement signal is stored in response to a manual operation that is independent of the camera release operation, to enable exposure control in accordance with a light measurement for an area of a photographic scene different from the area which is aimed at by the light measuring means of the camera at a picture taking position. With such a manual storage means, for example, when it is desired that exposure is controlled in accordance with a light measurement for a small area in the scene to be photographed, the camera user may approach the desired area of the scene, have the camera measure the brightness of the area, make the manual operation for the storage, return back to his or her picture taking position maintaining the stored light measurement, and take a picture with a desired framing. The manual storage is also effective in the case when it is desired that a proper exposure is obtained for a corner of the scene with a camera having a light measuring system designed to measure the small central area of the scene. Such photography with the manual storage is often referred to as AE-lock photography since a light measurement signal or an exposure control signal is fixed previously.
Prior art exposure control circuitry capable of such AE-lock photography has a construction, for example, as shown in FIG. 1. Light measuring circuit LMC produces a logarithmically compressed exposure time control signal through an exposure calculation wherein a function of a set film sensitivity value and a set diaphragm aperture value is applied to the value of an output proportional to the logarithm of the object brightness being measured. The exposure time control signal is applied to storage capacitor C. Upon AE-lock photography, light measurement is effected with the camera being directed to a particular area of the scene to be photographed, the output of the light measuring circuit is stored in storage capacitor C and AE-lock switch S is opened by manual operation to fix the voltage of storage capacitor C. When the shutter is released, a switch S short-circuiting timer capacitor C' is opened with switch S' in the emitter circuit of logarithm expansion transistor Tr being closed, so tha
REFERENCES:
patent: 4325615 (1982-04-01), Yamada
Nakai Masaaki
Sahara Masayoshi
Gellner Michael L.
Minolta Camera Kabushiki Kaisha
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