Photography – Flash system responsive to focal length or distance
Reexamination Certificate
1999-09-13
2001-05-29
Perkey, W. B. (Department: 2851)
Photography
Flash system responsive to focal length or distance
C396S106000, C396S123000, C396S157000, C396S159000, C396S266000
Reexamination Certificate
active
06240252
ABSTRACT:
This application is based on applications Nos. H10-259866 and H10-260130 filed in Japan on Sep. 14, 1998, the entire content of which is hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a camera that has a plurality of distance measurement regions for obtaining information used for focusing of the taking lens, and performs light adjustment control in which the emission of subject illuminating light is ended when the quantity of reflected light from the subject reaches a predetermined quantity.
2. Description of the Prior Art
With a camera provided with multi-point distance measurement means having a plurality of distance measurement regions, the accuracy of focus detection can be improved. This is because in the multi-point distance measurement means, the probability that the subject is not present in any of the distance measurement regions is low and by selecting the distance measurement region in which the subject is present, focus detection can be performed based on the distance measurement information of the region.
Moreover, a camera is known that performs the light adjustment control by use of distance information from a plurality of distance measurement regions in flash shooting. This camera has multi-segment light adjustment means comprising a plurality of light adjustment regions including regions corresponding to a plurality of distance measurement regions. In flash shooting, the reflected light of the emitted light is detected by the multi-segment light adjustment means, and when the sum total of the light reception quantities of the light adjustment regions reaches a reference value, the light emission is stopped. The contribution percentages of the light adjustment regions and the reference value in obtaining the sum total of the light reception quantities can be changed, for example, according to the position of the subject and the distance to the background. As described above, by performing the light adjustment control based on the distance measurement information obtained by the multi-point distance measurement means, the subject can be illuminated at an appropriate brightness.
In the multi-point distance measurement means having a plurality of distance measurement regions, focus detection can be controlled when the distance measurement information of the region in which the subject is present is obtained. When distance measurement information of the multi-point distance measurement means is used in the light adjustment control as described above, it is desirable that the distance measurement information of all the distance measurement regions be obtained. However, under low-light conditions in which flash shooting is frequently performed, correct distance measurement information of all the distance measurement regions cannot be obtained in many cases because of low contrast, so that it is difficult to correctly perform the light adjustment control.
In the light adjustment control of a camera, as information for deciding the contribution percentages and the reference value, photometric information in preliminary light emission performed prior to the real light emission shooting is effective as well as the distance measurement information. This is because the light adjustment control can be performed with reference to the brightness of the subject. Which of the distance measurement information and the photometric information in preliminary light emission performed prior to the real light emission shooting is more reliable differs according to the focal length in flash shooting and various shooting conditions. There are cases where one of these pieces of information is completely invalid according to shooting conditions.
The photometric information in preliminary light emission is more reliable, for example, in the following shooting conditions:
when the distance information is invalid like in manual focusing;
when the image magnification is low and sufficiently accurate distance information is not obtained; and
when the main subject and the background are near to each other.
The distance measurement information obtained by the multi-point distance measurement means is more reliable, for example, in the following shooting conditions:
when the focal length is extremely short and the light emission angle in preliminary emission is exceeded;
when the shooting distance is too short and preliminary light emission cannot correctly be performed because of an effect of parallax; and
when photometric information by correct preliminary light emission cannot be obtained because bounce setting is made or a diffuser is attached.
Moreover, in the following shooting conditions, appropriate control is performed by calculating the contribution percentages and the reference value by combining the above-mentioned two pieces of information:
when excellent distance accuracy is not obtained and correct photometric information in preliminary light emission is not obtained (for example, when the focal length is short, the image magnification is low, and the subject and the background are near to each other).
As described above, between the distance measurement information obtained by the multi-point distance measurement means and the photometric information in preliminary light emission performed prior to the real light emission shooting, the reliability as the information used in calculating the contribution percentages and the reference value in light adjustment control differs according to the focal length in the real light emission shooting and various shooting conditions. This is not considered in conventional cameras. Therefore, inappropriate contribution percentages and reference value are calculated according to the focal length in the real light emission shooting and shooting conditions. As a result, there are cases where the subject cannot be illuminated at a desired brightness.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a flash control apparatus and a camera capable of appropriate light adjustment control even in low light. Another object of the present invention is to provide a camera capable of appropriate light adjustment control irrespective of the focal length and shooting conditions.
To achieve the above-mentioned objects, according to an aspect of the present invention, a flash control apparatus comprises: a distance measurement device having a plurality of distance measurement regions and for outputting distance measurement information of each distance measurement region; a light adjustment device having a plurality of light adjustment regions including regions substantially coinciding with the distance measurement regions; an auxiliary light emitting device for emitting auxiliary light at the time of distance measurement; and a controller for controlling a flash light emission quantity based on distance measurement information in auxiliary light emission, and an output from the light adjustment device.
According to another aspect of the present invention, a camera controlling a flash apparatus for illuminating a subject comprises: a distance measurement device for outputting distance measurement information to a subject; a first calculator for calculating a first light emission quantity control value of the flash apparatus based on the distance measurement information; a first controller for performing preliminary light emission with the flash apparatus; a photometric device for performing photometry of light reflected from the subject in the preliminary light emission and outputting photometric information; a second calculator for calculating a second light emission quantity control value of the flash apparatus based on the photometric information; a third calculator for deciding allocation percentages of the first light emission quantity control value and the second light emission quantity control value; a fourth calculator for calculating a third light emission quantity control value of the flash apparatus based on the first light emission quantity control valu
Ichikawa Tsutomu
Nakamaru Akio
Ohmori Shigeto
Suzuki Tatsuya
Tsujimura Ichiro
Burns Doane , Swecker, Mathis LLP
Minolta Co. , Ltd.
Perkey W. B.
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