Photography – With object illumination for exposure – Having preexposure illumination
Reexamination Certificate
2000-09-22
2003-05-13
Mathews, Alan A. (Department: 2851)
Photography
With object illumination for exposure
Having preexposure illumination
C396S233000
Reexamination Certificate
active
06564014
ABSTRACT:
INCORPORATION BY REFERENCE
The disclosures of the following priority applications are herein incorporated by reference:
Japanese Patent Application No. 11-270730 filed Sep. 24, 1999;
Japanese Patent Application No. 11-271626 filed Sep. 27, 1999.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a flash control device which suitably controls a flash emission amount.
2. Description of the Related Art
With regard to a method for controlling a flash emission device (a strobe) of a single lens reflex camera, in the prior art, a flash control device which controls a flash emission amount has usually been of the TTL flash control type. Further, a type is known in which preliminary light emission is performed before the main light emission during photography and photometry is performed upon the light reflected back from the photographic subject, so as to obtain information for the main light emission.
For example, Japanese Laid-Open Patent Publication No. H3-68928 discloses an automatic light adjustment device which performs photometry by subdividing the light reflected from the photographic subject during preliminary light emission, derives the reflection ratio distribution of the photographic subject based upon this result, and there by obtains information for the main light emission.
Further, there is also a device which determines the light emission amount which is required during the main light emission based upon the results of photometry during the preliminary light emission, and which causes the flash emission section to perform the main light emission using this required emission amount as a target.
However, with the above described prior art flash control device, it sometimes happens that the amount of reflected light during the preliminary light emission falls outside the range over which the flash photometric section can perform photometry because it is too small or is too large, so that the photometric value which is obtained is not sufficiently reliable.
In particular, in the method in which the emission amount for the main light emission at the time of photography is determined in advance based upon the photometric output during the preliminary light emission, it sometimes happens that sufficient exposure accuracy cannot be obtained because the photometric accuracy at the time of the preliminary light emission directly affects the light emission accuracy during the main light emission.
Further, there is a case in which the photometry for the preliminary light emission is performed with TTL on the side of the camera, the direct photometry is performed on the side of the flash unit (the flash device or the strobe unit), and the main emission amount is calculated,at the flash unit based upon the value indicated from the camera and the value of the direct photometry in the flash unit. In this case, since on the side of the camera the photometry is not performed on the beginning of the preliminary light emission to be regarded as warming up of an emission tube, it can happen that the preliminary emission amount which is measured within the camera and the preliminary emission amount which is measured within the flash unit come to differ. In such a case the problem arises that it becomes impossible to calculate an accurate main emission amount for the value indicated from the camera.
SUMMARY OF THE INVENTION
The objective of the present invention is to propose a flash control device which can enhance the accuracy of exposure during flash photography by ensuring the photometric accuracy during preliminary light emission, even when the amount of light reflected during preliminary light emission is too small or is too large, and which as a result thereof can accurately calculate the main light emission amount.
Further, the present invention proposes a flash control device which can accurately calculate the main light emission amount, also in the case that the main light emission amount is calculated based upon photometric results for preliminary light emission both on the camera side and also on the flash unit side.
In order to attain the above objective, a flash control device according to the present invention comprises: a flash emission section that performs main light emission at photography and preliminary light emission before photography; a flash photometric section on that divides a photographic field into a plurality of photometric areas and performs photometry of reflected light from a photographic subject due to the preliminary light emission; and a flash control section that performs control by, if an output from at least one photometric area of the plurality of photometric areas is outside a predetermined range, resetting a gain related to photometry for the at least one photometric area, and performing again a preliminary light emission by the flash emission section and a preliminary light emission photometry by the flash photometric section.
Another flash control device according to the present invention comprises: a flash emission section that performs main light emission at photography and preliminary light emission before photography; a flash photometric section that divides a photographic field into a plurality of photometric areas and performs photometry of reflected light from a photographic subject due to the preliminary light emission; and a flash control section that performs control by, if an output from at least one photometric area of the plurality of photometric areas is outside a predetermined range, replacing the output from the at least one photometric area by a predetermined value that is set in advance.
Another flash control device according to the present invention comprises: a flash emission section that performs main light emission at photography and preliminary light emission before photography; a flash photometric section that divides a photographic field into a plurality of photometric areas and performs photometry of reflected light from a photographic subject due to the preliminary light emission; a main light emission amount calculation section that performs calculation for controlling the main light emission based upon an output of the flash photometric section; and a flash control section that performs control by, if the output from at least one photometric area of the plurality of photometric areas is outside a predetermined range, ensuring that the output from at least one photometric area is not used for calculation by the main light emission amount calculation section.
Another flash control device according to the present invention comprises: a flash emission section that performs main light emission at photography and preliminary light emission before photography; a flash photometric section that divides a photographic field into a plurality of photometric areas and performs photometry of reflected light from a photographic subject due to the preliminary light emission; a valid area determination section that determines one or more photometric areas to be used for main light emission control based upon an output of the flash photometric section; and a flash control section that performs control by, if outputs from the photometric areas of the flash photometric section that have been determined as valid by the valid area determination section are outside predetermined ranges, performing again a preliminary light emission by the flash emission section and a preliminary light emission photometry by the flash photometric section.
Another flash control device according to the present invention comprises: an ambient light photometric section that divides a photographic field into a plurality of ambient light photometric areas and performs photometry of light intensity of the photographic field due to ambient light; a flash emission section that performs main light emission at photography and preliminary light emission before photography; a flash photometric section that divides a photographic field into a plurality of photometric areas and performs photometry of reflected light from a photographic su
Iwasaki Hiroyuki
Takeuchi Hiroshi
Mathews Alan A.
Nikon Corporation
Smith Arthur A
LandOfFree
Flash control device does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Flash control device, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Flash control device will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3027083