A signal indicating that the correct exposure value has been achieved and a signal indicating the completion of flash are logically summed to provide a shutter closing signal. This ensures that the shutter will be closed even when the light emitted by the flash is insufficient to achieve the proper level of exposure.
|
13. A camera system, comprising:
a shutter mechanism which closes in accordance with a shutter closing signal; means for generating a correct exposure signal; flash means for performing a flashing operation to generate a flash of light; means for generating a flash operation signal indicative of the completion of said flashing operation; and means for forming a logical sum of said correct exposure signal and said flash operation signal to form said shutter closing signal.
24. A camera system comprising the combination of a camera and a flash unit, said camera including means for generating a correct exposure signal, and means for generating a shutter closing signal in response to one of said correct exposure signal and a flash output signal; said flash unit including an input for receiving said correct exposure signal, means for terminating a flash emission in response to said correct exposure signal and means for providing said flash output signal, said output signal being indicative of the completion of a flashing operation.
12. A camera system, comprising; means for generating a correct exposure signal indicative of a correct exposure value, flash means for emitting a flash of light, and including flash triggering means, flash stopping means, and an output, said correct exposure signal being applied as an input to said flash stopping means, means connected to said output for producing a signal indicative of the completion of a flash operation, and means for generating a shutter closing signal in response to said correct exposure signal and said flash operation completion signal.
11. A camera system, comprising; means for generating a correct exposure signal indicative of a correct exposure value, flash means for emitting a flash of light, and including flash triggering means, flash stopping means, and an output, said correct exposure signal being applied as an input to said flash stopping means, means connected to said output for producing a signal indicative of the completion of a flash operation, and logic means for forming a logical sum of said flash operation completion signal and said correct exposure signal to generate a shutter closing signal.
1. In a camera system having a shutter mechanism, a light measurement system to generate a shutter closing signal in response to a correct exposure signal indicative of a correct exposure value, an electronic flash to emit a flash of light in synchronism with the opening of the camera shutter and to suspend the flashing operation in response to a shutter closing said correct exposure signal, the improvement comprising: logic means for generating a flashing operation signal indicative of the completion of the flash operation, and for generating said shutter closing signal by a logical sum operation of the corrct correct exposure signal and the flashing operation signal.
22. A camera system, comprising, in combination, a camera having a light measurement system, and an electronic flash for emitting a flash of light; said camera including a shutter mechanism, said light measurement system generating a shutter closing signal in response to a correct exposure signal indicative of a correct exposure value, said electronic flash including an input terminal for receiving said correct exposure signal and means for terminating said flash of light in response thereto, said electronic flash further including an output terminal for delivering an output signal indicative of the completion of a flash operation, and said light measurement system further including means for generating said shutter closing signal in response to said electronic flash output signal.
23. A camera system, comprising, in combination, a camera and an electronic flash;
said camera including: means for generating a correct exposure signal indicative of a correct exposure value, an output terminal for delivering said correct exposure signal to said flash, and means for generating a shutter closing signal in response to either said correct exposure signal or a flash output signal indicative of the completion of a flash emission; said electronic flash including: an input terminal for receiving said correct exposure signal, means for terminating a flash emission in response to said correct exposure signal, means for providing said flash output signal indicative of the completion of a flash emission, and an output terminal for delivering said flash output signal to said camera.
2. The camera system of
3. The camera system of
4. The camera system of
5. The camera of
6. The camera system of
7. The camera system of
8. The camera system of
9. The camera system of
10. The camera system of
14. A camera system as claimed in
15. A camera system as claimed in
16. A camera system as claimed in
17. A camera system as claimed in
18. A camera system as claimed in
20. A camera system as claimed in
21. A camera as claimed in
|
This invention relates to a long time exposure preventing system in a focal plane shutter camera equipped with a flash generating device (hereinafter referred to as "an electronic flash" when applicable). It is particularly applicable in cameras in which the electronic flash is controlled by a light measurement circuit in the camera.
If the distance between an object and a camera varies in comprising and taking a picture of that object with an electronic flash, it is necessary to adjust or change the aperture value in accordance with the varied distance. This is because the intensity of light reflected by the object will also vary and theshutter speed is usually fixed.
In order to eliminate this inconvenience, in this technology the concept of automatic electronic flash has been proposed. In an automatic electronic flash, an electronic flash is provided with a light measurement circuit. The light measurement circuit operates to measure the quantity of light reflected by the object when the electronic flash emits a flash, and to stop the flashing operation of the electronic flash when the quantity of light measured reaches a correct exposure value. Hence a picture can be taken with the correct exposure at all times.
In general, electric-eye (EE) cameras are provided with light measurement circuits. When a picture is taken with such a camera with the automatic electronic flash described above, the light measurement circuit in the camera is not used. That is, it is in idle state and the camera is used in a manual mode of operation.
Furthermore, recently a circuit has been developed in which the flashing operation of an electronic flash is controlled by using a light measurement circuit incorporated in an electronic focal plane shutter camera. In this case a correct exposure can be readily obtained in taking a picture with an electronic flash without incorporating a light measurement circuit in the electronic flash. With this type of circuit, when the shutter top curtain is allowed to run by shutter release and the light photographing optical path is opened, the "X" contact on the camera is closed to permit the electronic flash to emit a flash. When the quantity of light reflected by the object reaches a correct exposure value, a shutter closing signal is generated by the light measurement circuit, energization of the shutter bottom curtain magnet is suspended, and the shutter bottom curtain is allowed to run. The shutter closing signal is also employed as a signal for stopping the flashing operation of the electronic flash, so that a picture is taken with the correct exposure.
However, since the quantity of light emitted by the electronic flash is limited, the correct exposure is not always obtained for the aperture value set in the camera. For instance, when a film having a sensitivity of ASA 100 is used, a correct exposure cannot be obtained with an electronic flash guide number "32" and an aperture value "F4"; that is, a picture will be underexposed. In this situation, since the correct exposure cannot be obtained, no shutter closing signal is generated by the light measurement circuit in the electronic focal plane shutter camera and as a result the bottom curtain controlling magnet is maintained energized. Therefore, the bottom curtain will not run. In other words, although the electronic flash has been operated to emit a flash of maximum duration, the exposure itself runs for a longer period of time. Such action will undoubtedly lead to poor picture quality due to camera shaking, and may lead to faulty operation and trouble a that one of the magnet deenergizing signals which occurs earlier. In the case also where no magnet deenergizing signal is provided by the light measurement circuit because the object is far away from the camera and the reflected light is therefore weak, the signal indicating the flashing operation of the electronic flash is still provided and therefore the magnet is deenergized.
Therefore, when a picture is taken with a camera having the memoryless light measurement circuit the light measurement is started in synchronization with the shutter opening operation and the shutter closing signal is generated when the quantity of light measured reaches a correct exposure value. Also, with a generating device that operates in synchronization with the completion of the shutter closing operation of the camera and stops the flashing operation in response to the shutter closing signal of the light measurement circuit, the shutter does not cause a long-time-exposure. That is, it is operated at the synchronizing speed even if no shutter closing signal is generated by the light measurement circuit because the quantity of light reflected by the object is small.
Hence an improved device is obtained that overcomes a material deficiency in the prior art. It is apparent that variations of this invention may be made without departing from the essential scope of the invention.
Kawasaki, Masahiro, Sawada, Yoshio
Patent | Priority | Assignee | Title |
Patent | Priority | Assignee | Title |
3792484, | |||
4021824, | Jun 07 1974 | Canon Kabushiki Kaisha | Flash light photographic system for camera |
4079389, | Aug 25 1975 | Olympus Optical Company, Ltd. | Daytime strobo apparatus for cameras with electric shutters |
4086582, | Aug 08 1975 | Canon Kabushiki Kaisha | Exposure control device for a camera |
4096492, | Apr 21 1975 | Polaroid Corporation | Camera with detachable electronic flash unit and exposure control system therefor |
4162426, | Sep 25 1974 | Canon Kabushiki Kaisha | Zone responsive, light-sensing circuit for controlling flash photographing |
4189219, | Jun 23 1976 | Nippon Kogaku K.K. | Control system for flash photographing apparatus |
4210849, | Jun 02 1976 | Minolta Camera Kabushiki Kaisha | Electronic control circuitry for terminating flash output |
Executed on | Assignor | Assignee | Conveyance | Frame | Reel | Doc |
Jun 22 1982 | Asahi Kogaku Kogyo Kabushiki Kaisha | (assignment on the face of the patent) | / |
Date | Maintenance Fee Events |
Date | Maintenance Schedule |
May 15 1987 | 4 years fee payment window open |
Nov 15 1987 | 6 months grace period start (w surcharge) |
May 15 1988 | patent expiry (for year 4) |
May 15 1990 | 2 years to revive unintentionally abandoned end. (for year 4) |
May 15 1991 | 8 years fee payment window open |
Nov 15 1991 | 6 months grace period start (w surcharge) |
May 15 1992 | patent expiry (for year 8) |
May 15 1994 | 2 years to revive unintentionally abandoned end. (for year 8) |
May 15 1995 | 12 years fee payment window open |
Nov 15 1995 | 6 months grace period start (w surcharge) |
May 15 1996 | patent expiry (for year 12) |
May 15 1998 | 2 years to revive unintentionally abandoned end. (for year 12) |