Photography – Having wireless remote control circuit
Reexamination Certificate
1999-09-01
2002-06-11
Perkey, W. B. (Department: 2851)
Photography
Having wireless remote control circuit
C396S106000, C396S173000, C396S182000, C396S201000
Reexamination Certificate
active
06404987
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a flash system, and more particularly to a flash system in which a flash device incorporated in or connected to, for example, a camera is used as a master transmission device to control the light emission of a slave flash device located in a remote position.
2. Description of Related Art
Heretofore, there have been known the following wireless flash systems, each of which uses a wireless flash device located in a position distant from a camera.
As a first example, in Japanese Laid-Open Patent Application No. Hei 4-343341, there is disclosed a wireless flash system, in which a flash device mounted on a camera body transmits to a slave flash device a light-emission start signal composed of a plurality of light pulse signals of a predetermined interval, the slave flash device repeats intermittent light emission upon receipt of the light-emission start signal, a light control circuit of the camera integrates reflected light from an object resulting from the light emission of the slave flash device, and when the result of the integration becomes a predetermined amount of light, the flash device mounted on the camera again transmits to the slave flash device a light-emission stop signal during the absence of the light emission of the slave flash device, thereby ending the light emission.
Further, as a second example, in Japanese Laid-Open Patent Application No. Hei 6-180472, there is disclosed a wireless flash system, in which a camera makes communication with a wireless slave flash device by means of an infrared light signal from the camera, a preliminary infrared light emission is performed a predetermined number of times by an infrared light emitting diode incorporated in the wireless slave flash device, and the camera integrates reflected infrared light from an object, computes the amount of light emission for a main light emission and gives to the wireless slave flash device instructions for the amount of light emission for the main light emission and the timing of light emission for the main light emission, so that a photograph is taken with the main light emission of the wireless slave flash device.
However, in the above first example of wireless flash system, there is a drawback that it is impossible to heighten the flash synchronizing speed due to the intermittent light emission, and there is a possibility that a photograph which is to be taken with a small amount of light emission at a near distance becomes overexposed.
Further, since it is impossible to perform wireless flash photography with a long-time light emission, called “flat emission”, used for taking a photograph at a high shutter speed exceeding the flash synchronizing speed, there is a drawback that it is impossible to perform daylight wireless flash photography for which a relatively high shutter speed.
Further, there is a drawback that the guide number of the flash device is lowered by the switching loss occurring in a control circuit due to the intermittent light emission.
In the above second example of wireless flash system, light measurement is performed with the infrared preliminary light emission of the slave flash device and an actual photograph is taken with daylight. Therefore, there is a possibility that an exposure is inaccurately performed due to the difference in reflection factor of infrared ray of an object.
Further, since an infrared light emitting part is required in each of the camera and the slave flash device, there is a drawback that the production cost of the system increases.
In addition, such an infrared light emitting device that uses the infrared light emitting diode can not produce a sufficiently strong light output, and, therefore, the slave flash device can not be located in a distant position, so that a limit is set to the shooting range.
Further, in the above first and second examples of wireless flash systems, there is a description of an automatic light control mode. However, since an exposure is sometimes made uneven depending on the condition of an object if only the automatic light control mode is used in the flash photography, there are provided, other than the automatic light control mode, a manual light emission mode for setting the amount of light emission of the flash device to a fixed setting value, a multiple light emission mode for catching and photographing continuous motions of a moving object, etc., which can not be executed in the above first and second examples.
BRIEF SUMMARY OF THE INVENTION
It is an object of the invention to provide a flash system capable of changing over between a highspeed photography using a shutter speed higher than a flash synchronizing speed and a flash photography using a shutter speed lower than the flash synchronizing speed even in a wireless photography in a camera using a focal plane shutter.
It is another object of the invention to provide a flash system capable of selecting one of a plurality of flash light emission modes, including an automatic light control mode, a manual light emission mode, a multiple light emission mode, etc., and capable of concentrically managing the operation of a slave flash device by means of a master transmission device mounted on or incorporated in a camera.
It is a further object of the invention to provide a flash system capable of enabling confirmation as to whether a command from a master transmission device has been received by a slave flash device.
To attain the above objects, in accordance with one aspect of the invention, there is provided a flash system composed of a camera having a focal plane shutter and a slave flash device located at a distance from the camera, the camera comprising selection means for selecting a light emission mode from between a flash light emission mode and a flat light emission mode according to a controlled shutter speed, and transmission means for transmitting flash-device control information including the light emission mode to the slave flash device, the slave flash device comprising receiving means for receiving the flash-device control information, flash light emission means, and light emission control means for controlling the flash light emission means in the flash light emission mode or the flat light emission mode according to the received flash-device control information. The flash-device control information includes information for selecting one of the flash light emission mode and the flat light emission mode, and, if the flat light emission mode is selected, a shutter speed and a light emission time depending on a shutter blade speed.
In accordance with one aspect of the invention, there is provided a flash system composed of a camera and a slave flash device located at a distance from the camera, the camera comprising selection means for selecting a flash-device exposure mode according to a photo-taking condition, and transmission means for transmitting information on the selected flash-device exposure mode according to a photo-taking operation of the camera, the slave flash device comprising receiving means for receiving the information, flash light emission means, and light emission control means for controlling light emission of the flash light emission means according to the received information on the flash-device exposure mode.
In accordance with one aspect of the invention, there is provided a flash system composed of a camera and a slave flash device located at a distance from the camera, the camera comprising selection means for selecting a flash-device exposure mode according to a photo-taking condition, and transmission means for transmitting information on the selected flash-device exposure mode according to a photo-taking operation of the camera, the slave flash device comprising receiving means for receiving the information, flash light emission means, and display means for displaying information corresponding to the received information on the flash-device exposure mode.
In accordance with one aspect of the invention, there is provided a flash system
Perkey W. B.
Robin, BLecker & Daley
LandOfFree
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