Photography – With object illumination for exposure – Having preexposure illumination
Reexamination Certificate
2002-10-03
2004-03-30
Perkey, W. B. (Department: 2851)
Photography
With object illumination for exposure
Having preexposure illumination
Reexamination Certificate
active
06714734
ABSTRACT:
INCORPORATION BY REFERENCE
The disclosure of the following priority application is herein incorporated by reference:
Japanese Patent Application No. 2001-307625 filed Oct. 3, 2001.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a camera that performs a flash photographing operation by utilizing an auxiliary illumination device.
2. Description of the Related Art
In a camera that performs a photographing operation by employing an auxiliary illumination device such as an electronic flash unit in the related art, a flash control system that determines the correct flash output to be achieved during a main light emission by executing a preliminary light emission prior to the main light emission as disclosed in, for instance, Japanese Laid-Open Patent Publication No. H 9-53452 is adopted. The preliminary light emission is executed through a so-called focal plane light emission during which a light emission is sustained over a predetermined length of time with an almost constant intensity by repeatedly turning the flash unit on and off at high speed. Then, the quantity of light reflected from the subject is detected through a method similar to that adopted when measuring the ambient light and the correct flash light output to be achieved during the photographing operation is determined based upon the results of the detection.
During a preliminary light emission achieved through a continuous light emission as described above, light is emitted by dividing up the light emission energy achieved through a single charge at the capacitor and thus using the light emission energy over a plurality of times and, for this reason, the intensity level of the light emitted through each light emission is lowered. As a result, if the brightness level of the ambient light is high or if the distance to the subject is great, the quantity of reflected light resulting from the preliminary light emission becomes lower than the quantity of the reflected ambient light, which makes it difficult to detect the quantity of the reflected light resulting from the preliminary light emission
SUMMARY OF THE INVENTION
The present invention is to provide a camera capable of accurately determining the correct flash output to be achieved during a flash photographing operation by reducing the influence of the ambient light.
A camera according to the present invention comprises a storage-type photometering sensor that detects some of light from a subject; a control device that controls an auxiliary illumination device so as to perform a preliminary light emission through a single-shot light emission and controls the storage-type photometering sensor so as to detect the subject light stored over a storage period matching a length of time over which light is emitted during the preliminary light emission; and a setting device that sets a light emission condition under which the auxiliary illumination device is to emit light during a flash photographing operation based upon detection results obtained at the storage-type photometering sensor.
It is preferable that the camera further comprises a decision-making device that makes a decision whether a detection value obtained at the storage-type photometering sensor through the preliminary light emission is equal to or smaller than a predetermined value, and that if the detection value is determined to be equal to or smaller than the predetermined value by the decision-making device, (a) the control device controls the auxiliary illumination device so as to execute an additional preliminary light emission with a greater flash output than in the preliminary light emission and controls the storage-type photometering sensor so as to detect subject light stored over a storage time matching a length of time over which light is emitted during the additional preliminary light emission and (b) the setting device sets the light emission condition under which the auxiliary illumination device is to emit light for the flash photographing operation based upon detection results obtained at the storage-type photometering sensor during the additional preliminary light emission.
It is desirable that the detection value obtained at the storage-type photometering sensor represents a received light quantity with regard to reflected light from the subject attributable to the light emitted through the preliminary light emission. The received light quantity with regard to the reflected light from the subject attributable to the light emitted through the preliminary light emission may be obtained by eliminating reflected light from the subject attributable to ambient light from the detection results obtained at the storage-type photometering sensor.
It is possible that the setting device sets the light emission condition under which the auxiliary illumination device is to emit light during the flash photographing operation based upon the predetermined value if the detection value obtained by the storage-type photometering sensor through the additional preliminary light emission is determined to be equal to or smaller than the predetermined value by the decision-making device.
It is preferable that the setting device allows the auxiliary illumination device to execute the preliminary light emission when a shutter release switch is pressed. It is possible that the camera further comprises a command switch that outputs a command for an execution of the preliminary light emission, and that the setting device allows the auxiliary illumination device to execute the preliminary light emission when the command is output through the command switch.
It is preferable that the storage-type photometering sensor detects some of the subject light guided to a view finder optical system.
REFERENCES:
patent: 6240252 (2001-05-01), Yamaguchi et al.
patent: 6272292 (2001-08-01), Iwasaki et al.
patent: 6560412 (2003-05-01), Iwasaki
patent: 0 949 809 (1999-10-01), None
patent: A 9-54352 (1997-02-01), None
patent: A 11-298793 (1999-10-01), None
Nikon Corporation
Oliff & Berridge
Perkey W. B.
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