Photography – With object illumination for exposure – Having preexposure illumination
Reexamination Certificate
1998-05-04
2002-02-19
Gray, David M. (Department: 2851)
Photography
With object illumination for exposure
Having preexposure illumination
C396S234000
Reexamination Certificate
active
06349175
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a camera system which performs a light emission toward a subject and adjusts the amount of light emission to automatically obtain the amount of correct exposure, and then performs an exposure operation.
2. Description of Related Art
It has heretofore been proposed to provide various camera systems of the type which performs a light emission toward a subject and adjusts the amount of light emission to automatically obtain the amount of correct exposure, and then performs an exposure operation.
It can be said that, among others, a camera system, which is arranged to perform a preliminary light emission before an exposure operation, perform light measurement of subject-reflected light of the preliminary light emission for each of a plurality of areas into which an image plane is divided, and perform control of the amount of light emission of a main light emission on the basis of the result of the light measurement, is a superior system capable of coping with various statuses appearing in a photographic image plane.
For example, Japanese Laid-Open Patent Application No. Hei 4-331935 has proposed a system which is arranged to exclude an area indicative of a measured-light value which is outside the range of particular values of the measured-light values of surface-reflected light of a preliminary light emission for a plurality of areas, from areas which are targets for a computation which determines the amount of light emission of a main light emission, a system which is arranged to add a predetermined correction value to the amount of light emission of a preliminary light emission according to the measured-light value of subject-reflected light of the preliminary light emission, and other systems.
Otherwise, it has been proposed to add a predetermined correction value to the amount of light emission of a preliminary light emission according to the measured-light value of reflected light of the preliminary light emission.
Any of the above-described systems is intended to solve the problem that if reflective matter such as window glass is opposed to the image plane, specular reflection light of flash light greatly influences a measured-light value and the amount of light of flash light is controlled by an amount which causes an underexposure, or that if the size of a main subject in the image plane is extremely small, the measured-light value of subject-reflected light of flash light becomes extremely small and the amount of light of flash light is controlled by an amount which causes an overexposure.
However, any of these systems is still insufficient, and there remain photographic scenes for which a correct amount of flash exposure cannot be obtained.
BRIEF SUMMARY OF THE INVENTION
In accordance with one aspect of the present invention, there is provided a flash photography system which performs control of the amount of light emission of a main light emission on the basis of a measured-light value obtained when a preliminary light emission is performed, and in order to realize correct control of the amount of flash light emission, the flash photography system comprises a control circuit which performs weighting of a measured-light value relative to a predetermined area and a measured-light value relative to another area, both of which are obtained through light measurement by multiple divided light measuring means for performing multiple divided light measurement of each of the areas of the image plane during a preliminary light emission, and performs control of the amount of light emission of the main light emission on the basis of the weighted measured-light values, and weighting means for performing such weighting on the basis of a size occupied by a main subject in the image plane, a subject distance or the measured-light value relative to the predetermined area during the preliminary light emission.
The above and other objects, features and advantages of the present invention will become apparent from the following detailed description of preferred embodiments of the present invention, taken in conjunction with the accompanying drawings.
REFERENCES:
patent: 5227836 (1993-07-01), Yasukawa et al.
patent: 5231447 (1993-07-01), Takagi
patent: 5892987 (1999-04-01), Ohmori
Canon Kabushiki Kaisha
Gray David M.
Robin Blecker & Daley
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