JPS58102226A - Electronic flash device - Google Patents

Abstract

PURPOSE:To decide whether an electronic flash is necessary or not, by measuring the luminance of an object to be photographed, by use of a photodetector, calculating a measuring output and a set shutter speed signal, and displaying a calculated aperture value. CONSTITUTION:When an electric power supply switch (S) 23 is turned on, a DC electric power supply 3 is supplied to a photometric circuit 11 through a diode 2, a capacitor 1 and a constant-voltage circuit 12, and on the other hand, through a DC-DC converter 4, a main capacitor 5 is charged. In this case, a measuring mode switching circuit 13 of the circuit 11 is switched to a photographed object luminance measuring mode by a changeover S22, and light of an object to be photographed is measured by a photodetector 14 and a photoelectric current measuring circuit 15. An output of the circuit 15 is applied to a shutter speed setting circuit 21 to which a shutter speed causing no camera shake is set, is applied to an aperture value range display switching circuit 18 which is calculated and is subjected to an aperture value switching display operation, and a range of an aperture value causing no camera shake is displayed on a display part 19. Accordingly, a user can decide whether an electronic flash is necessary or not, and electric flash light photographing can be excuted by switching the S22.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electronic flash device that receives reflected light from a subject and can automatically control light emission.

2. Description of the Related Art Conventionally, cameras are known that measure the brightness of a subject and, if the brightness is less than a predetermined value, issue some sort of warning to prevent camera shake. However, if the camera does not have such a warning function, there is a risk of photographing with camera shake depending on the brightness of the subject.

Therefore, the present invention has been made to solve these problems, and will be described below with reference to drawings of embodiments.

The figure shows an electric circuit diagram of an embodiment of the electronic flash device of the present invention. In the figure, when the power switch 23 is turned on, the DC power source 3 is connected to the diode 2. Capacitor 1. Constant voltage circuit 1
2 to the photometric circuit 11, and the DC-DC converter 4 operates to start charging the main capacitor 6.

The force signal is applied to the shutter speed setting circuit 21, which is set to a shutter speed that does not cause camera shake, and is calculated here, and the aperture value distance display switching circuit 1B is operated to change the late value by switching the changeover switch. is applied to
This circuit 18 converts it into an aperture value display signal, and the display unit 1
At 9, the aperture range without camera shake is displayed. This aperture range allows the user to decide whether or not a strobe light is required.

Next, suppose that the aperture value range is the one that causes camera shake,
When strobe light is required, switching the selector switch 22 to receive the light reflected from the subject by the strobe light allows the integrating circuit 16 to operate, and at the same time, the power supply switching circuit 24 allows the photometry from the constant voltage circuit 12 to be activated. Power to the circuit is cut off.

When the trigger switch 6 is turned on and the trigger circuit 4 is operated to cause the flash tube 8 to emit light, power is supplied from the photometry circuit 1 (1 power generation circuit 10 to the photometry circuit 11 via the switching circuit 24. The light is received by the light receiving element 14 and integrated by the integrating circuit 16. When this integrated value reaches a predetermined value, the light emission control circuit 9 is activated to stop the flash tube 8 from emitting light.

Here, by switching the switch 22 to the metering mode using strobe light, the photographing information selection circuit 17 transfers photographing information such as the light control F value and film sensitivity to the calculation circuit 20.
Here, the first aperture value and distance display are sent to the camera via the switching circuit 18 to display the first aperture value and the distance display. If distance range is displayed on the display section 19.

As stated above, the electronic flash device of the present invention has a function of photometering the brightness of the subject and issuing a camera shake warning, so it is effective when combined with a camera that does not have a camera shake warning function. be able to.

[Brief explanation of drawings]

The figure is a circuit diagram of an electronic flash device according to an embodiment of the present invention. 3...DC power supply, 6...Main capacitor, 8...Flash tube, 9...Light emission control circuit, 11...Photometering circuit , 17... Shooting information setting circuit, 18... Shooting information display switching circuit,
19...Display section, 21...Shutter speed setting circuit.

Claims (3)

[Claims] (1) In an electronic flash device in which the flash tube emits light by consuming the charging energy of the main capacitor, a circuit that includes a light receiving element and measures the subject brightness, and calculates the output signal of the measurement circuit and the shutter speed signal to be set. An electronic flash device comprising: a circuit for calculating an aperture value; and a display section for displaying an aperture value in response to an output signal from the calculation circuit. (2) a circuit that stops the light emission of the flash tube; and an integration circuit that integrates the light receiving element and the photocurrent generated by this element, and applies a light emission stop signal to the light emission stop circuit when the integrated value reaches a predetermined value. 2. The electronic flash device according to claim 1, further comprising: a circuit for receiving subject light generated by flash emission; and a changeover switch for switching between the luminance measuring circuit and the light receiving circuit. (3) Distance signal generating means for setting and calculating photographic information such as film sensitivity and light control F value, emitting a TT effective distance range signal during luminescence photographing with the flash tube, and supplying the same signal to the display section. An electronic flash device according to claim 2, comprising: