JPS5858529A - Flash light quantity controller for camera - Google Patents

Abstract

PURPOSE:To control optionally the quantity of emitted light in the strobe side to facilitate selection of a lighting contrast, by stopping the light emission when the integral value of the quantity of the light in the camera side reaches a reference value in the strobe side. CONSTITUTION:Photometric circuits 33 and 35 having a photodetector, which detects the object reflected light passing through the stop of a photographic lens of a camera 2, and integration circuit 36 and 37 which output an integral voltage corresponding to the integral value of the photocurrent flowed to the photodetector 30 are provided in the side of the camera 2, and a comparing circuit 21, to which the integral voltage is inputted to one input, and exposure correction value setting circuits 17-20 where a exposure reference voltage for determining a flash light quantity is set manually by a means 19 and is applied to the other input of the comparing circuit 21 are provided in the side of a flash device 1. When the quantity of the light emitted from the flash device 1 which is measured and integrated in the side of the camera 2 reaches the set reference value of exposure correction value setting circuits, the light emission of the flash light 1 is stopped by the signal outputted from the comparing circuit 21.

Description

[Detailed Description of the Invention] Technical Field The present invention provides a flash device (hereinafter referred to as a strobe) that measures the reflected light from a subject that has passed through a photographic lens using a light-receiving element provided near the film surface on the camera side during flash photography. ] A flash used in TTL strobe control cameras that sends a dimming signal to the strobe to stop the strobe from emitting light, indicating that the exposure has reached the appropriate exposure level when the integral value of the photometric value of the flash reaches a predetermined value. The present invention relates to a light emission amount control device.

Conventional technology In this type of camera, a light receiving unit that measures the reflected light from the subject is installed inside the camera, so even if the strobe is installed far from the camera and used for 1/s, the light emission can always be controlled appropriately. This makes it possible to increase the variety of flash photography. Also, by using this TTL strobe control method, even in a multi-flash strobe system where multiple strobes are connected to one camera for flash photography, one All strobe light emission can be easily controlled by dimming signals.

However, the light control signal output from this type of conventional TTL camera is either 10" or 11, or a binary signal of high or low to stop the strobe light emission. This is a light emission stop signal, and it no longer represents the photometric value itself measured by the camera.

Now, in flash photography, the amount of light emitted by the strobe is determined based on the relationship between the brightness of the main subject and the brightness of the surroundings, as described above.
than the appropriate exposure level determined by the L system camera.
There are cases where it is desired to perform photographing according to the intention of drawing by controlling by making less or more correction. On the contrary,
As mentioned above, with conventional TTT cameras, only the light emission stop signal is output to the strobe, so the flash cannot independently adjust the amount of light emitted, making it impossible to deal with the situations described above. There was a problem.

Also, for example, two strobes may be used for one camera, with one strobe used for bounce lighting to project light onto a wall or ceiling in a direction other than the main subject, and the other strobe used to direct light to the main subject. When used for frontal illumination, a bounce strobe has an isometrically longer distance to the subject than a strobe for frontal illumination. For this reason, if you stop both the bounce strobe and front illumination strobe light emission at the same time using the dimming signal sent from the camera side, the bounce strobe may not be able to produce enough light to produce the bounce effect. There is. Therefore, in order to perform flash photography with a better bounce effect, it is necessary to correct the flash output of the bounce strobe to the appropriate exposure level determined by the camera. Since the camera only outputs a light emission stop signal to the strobe, it has not been possible to meet the demand for the strobe to arbitrarily correct the amount of light emitted.

Purpose The present invention has been made in view of the above-mentioned problems.The purpose of the present invention is to transmit a voltage signal indicating an integral value of light amount according to a photometric value obtained on the camera side to the strobe side, and to transmit this voltage signal on the strobe side. A flash that can adjust the amount of light emitted at will on the strobe side by comparing the integral value with a reference value manually set by the exposure compensation value setting circuit on the strobe side and stopping the flash when the integral value reaches the reference value. An object of the present invention is to provide a light emission amount control device.

Summary of the Invention A flash light emission amount control device for a camera according to the present invention includes a photometry circuit having a light receiving element that receives reflected light from a subject that has passed through an aperture of a photographing lens of the camera; The camera is equipped with an integrating circuit that outputs an integrated voltage according to the integrated value of the photocurrent flowing through the element, a comparator circuit that takes the integrated voltage as one input, and an exposure reference voltage that determines the amount of flash light emission, which is manually set. and an exposure compensation value setting circuit that applies this reference voltage to the other input of the comparator circuit is provided on the strobe side, and the amount of light emission from the strobe that is photometrically integrated on the camera side is set in the exposure compensation value setting circuit. The present invention is characterized in that when a reference value is reached, the strobe light emission is stopped by a signal output from the comparison circuit.

EXAMPLE Hereinafter, an example of the present invention will be described based on the drawings.

In FIG. 1, the upper half of dotted line A indicates a circuit 1 provided in a strobe 50 or 51 that cooperates with a camera 52 as shown in FIG. 2, and the lower half of dotted line A indicates a circuit 2 provided in camera 52. show. In the strobe side circuit l in Fig. 1,
A main capacitor 3 is connected in parallel to the output terminal of the DC booster circuit 4 via a diode 4a, and a series circuit of a power battery 5 and a power switch 6 is connected to the input side of the booster circuit 4. A negative electrode of the battery 5 is grounded via a power switch 6. Further, the connection terminal J0 with the camera side circuit 2 is grounded. A circuit including a resistor 7, a trigger 5CR8, a capacitor 9, and a transformer 10 connected in parallel with the main capacitor 3 constitutes a trigger circuit for a xenon tube 11 for strobe light emission. A xenon tube driving 5CR 16 is connected in series with the xenon tube 11. In addition, resistors 12, 13 . A circuit consisting of the commutation capacitor 14 and the 5CR 15 for stopping light emission constitutes a light emission stopping circuit that stops light emission from the xenon tube 11 by cutting off the SCR 15.

Operational amplifier 17. Constant voltage source 18. Variable resistance 19° resistance 2
The circuit consisting of 0 constitutes an exposure correction value setting circuit. Ten poles of a constant voltage source 18 are connected to ten inputs of the operational amplifier 17, and one terminal of a variable resistor 19 for exposure correction is connected to one input of the operational amplifier 17. The resistance value of the variable resistor 19 changes depending on the exposure correction value setting of the exposure correction value setting section 53 or 54 of the strobe shown in FIG. The other terminal of this variable resistor 19 and the constant voltage source 18
One pole of is connected. Further, a resistor 20 is connected between the output and the output of the operational amplifier 17.

The output of the operational amplifier 17 is further connected to one input of a comparator 21, and the output of this comparator 21 is connected to one input of an AND gate 22. Further, the output of the AND gate 22 is connected to the gate of the 5CR 15 for stopping light emission. on the other hand,
Connection terminal J3 with the camera side circuit 2 is connected to the ten input of the comparator 21.
is connected.

In this circuit configuration, when the exposure correction value is set by the exposure correction value setting section of the strobe, the operational amplifier 17
A voltage signal corresponding to the set exposure correction value is outputted from the comparator 21, and this voltage signal is input to the comparator 21.

In the comparator 21, a voltage signal corresponding to this exposure correction value is compared with a voltage signal corresponding to a later-described light amount integral value inputted from the camera side circuit 2, and a signal representing the light amount integral value from the camera is determined as the exposure value. When the signal becomes larger than the signal representing the correction value, a high level signal occurs.

The input terminal of the one-shot circuit 23 is connected via a connection terminal J2 with the camera-side circuit 2 to a switch 46 that is turned on when the camera shutter is fully opened. The output terminal of this one-shot circuit 23 is connected to the gate of the trigger 5CR8 via the resistor 24, and also connected to the gate of the trigger 5CR8.
It is connected to the other input terminal of D gate 22. The one-shot circuit 23 is activated by the closing signal of the switch 46 input from the camera-side circuit 2 through the terminal J2, and outputs a high-level pulse signal for a predetermined period of time, and this pulse turns on the trigger 5CR8. The xenon tube 11 starts emitting light. Note that the predetermined time is selected to be a time sufficient for the xenon tube 11 to completely emit light, for example, 1Qms. Note that, if the output of the comparator 21 is at a high level when the strobe is emitting light, the AND gate 22 outputs A.
The output of the ND gate 22 becomes the zero level, turning on the light emission stopper 5CR15.

In the camera side circuit 2, a circuit including a photovoltaic element 30, an operational amplifier 34, and a diode 35 constitutes a known photometry circuit. A photovoltaic element 30 provided near the film surface (not shown) is connected to a photographic lens 31 and an aperture 3.
2. Receives the object reflected light that has passed through 2. Photovoltaic element 3
The anode and cathode of 0 are connected to the input and input of a high input impedance operational amplifier 33, respectively. A constant voltage source 34 of about 1.2 V, for example, is further connected to the input of the operational amplifier 33. A constant voltage source 1 connected to the tenth input of the operational amplifier 17 in the above-mentioned strobe side circuit 1
The voltage value of 8 is made equal to the voltage value of this constant voltage source 34. A logarithmic compression diode 35 is connected between the output and the output of the operational amplifier 33, and a voltage obtained by logarithmically compressing the photometric value is generated at the output of the operational amplifier 33. The output of the operational amplifier 33 is connected to the base of a transistor 36, and the emitter of the transistor 36 is connected to a parallel circuit of a capacitor 37 and a count switch 38. transistor 36
A circuit consisting of a capacitor 37 and a capacitor 37 constitutes a light quantity integration compression circuit, and when the count switch 38 is opened in synchronization with the start of travel of the shutter base, integration of the output signal of the operational amplifier 33 is started.

When the amount of light received by the photovoltaic element 30 doubles, the voltage at point A, that is, the emitter of the transistor 36, becomes 18 at room temperature.
mV increases, and when the amount of received light quadruples, it increases by 36 mV.

This increased voltage is almost proportional to the absolute voice change. The voltage at point A is thermistor a9. Temperature compensation is provided by a circuit consisting of a resistor 40 and an operational amplifier 41.

The resistor 42 is a resistor for setting a reference voltage corresponding to the appropriate exposure level of the camera, and the resistor 43. Resistance 44. For example, the constant voltage source 34 and the operational amplifier 45 output 1.5V when the exposure level is appropriate, 1.4V when the exposure value EV is one step lower, and 1.6V when the EV value is one step higher. is set to output. The output voltage of the operational amplifier 45, ie, the voltage signal representing the integral value of the amount of light projected onto the main subject received by the camera, is transmitted to the strobe side circuit 1 via the terminal J3.

In the camera light emitting device configured as described above, it is assumed that the power switch 6 of the strobe side circuit 1 is now closed and the main capacitor 3 is charged to a high voltage of, for example, about 300 volts. The shutter button on the camera side is pressed,
At the same time as the shutter front curtain starts running due to the shirt release, the count switch 38 is opened and exposure is started. Next, the shutter is fully opened and the switch 46
When the terminal J2 is closed, the terminal J2 is grounded on the camera side, the one-shot circuit 23 is triggered, and the one-shot circuit 23 outputs a pulse having a width of 1Qm'sec. This pulse is applied to the gate of the trigger 5CR8, and the trigger 5CR8 is turned on. When the trigger 5CR8 is turned on, the xenon tube 11 is triggered, the xenon tube 11 starts emitting light, and the light is projected onto the subject. At the same time, a trigger voltage is applied to the gate of the xenon tube driving 5CR16, the xenon tube driving 5cit16 is turned on, and the xenon tube 11 continues to emit light.

On the other hand, on the camera side, the photographic lens 31° aperture 32
The photovoltaic element 30 receives the reflected light from the object that has passed through the photovoltaic element 30, and the photocurrent generated in the photovoltaic element 30 is logarithmically compressed by a circuit consisting of an operational amplifier 33 and a diode 35. An integral compression circuit consisting of a transistor 36 and a capacitor 37 outputs an integral compression voltage from point B according to the amount of integration of the photometric value. This integral compressed signal is transmitted to the thermistor 39. After being temperature compensated by a circuit consisting of a resistor 40 and an operational amplifier 41, the resistors 42, 43, 44° constant voltage source 3
The signal is inputted to the comparator 21 of the strobe side circuit 1 through an arithmetic circuit consisting of an operational amplifier 4 and an operational amplifier 45.

When the photometric integral value on the camera side described above reaches the exposure correction value set in the variable resistor 19 of the strobe side circuit 1, the output of the comparator 21 is inverted to a high level. At this time, since the output of the one-shot circuit 23 is still maintaining a high level, the output of the AND gate 22 is at a level of 1.
5CR15 for stopping light emission is turned on, commutating capacitor 14
The charge is discharged through the light emission stopper 5CR15. Therefore, a reverse voltage is applied to the anode of the xenon tube driving 5CR 16, the xenon tube driving 5CR 16 is turned off, and the xenon tube 11 stops emitting light.

A multi-flash strobe system using a strobe according to the present invention, for example, as shown in FIG. The 1<lance strobe 51 whose irradiation direction is matched so as to illuminate the camera 5
It is fixed at 2.

Note that the above-mentioned signal is transmitted from the camera 52 to the strobe 50 via a part of the accessory shoe, and the same signal as above is transmitted to the strobe 51 via the bottom of the camera and the bracket of the strobe. be done. In order to emphasize that the photographed image was taken during daytime flash photography, a case will be described below in which the amount of light emitted by the strobe for the main subject is set to be a little less than the appropriate value and the amount of light due to bounce is set to the appropriate value. The front illumination strobe 50 is set to K-1# by the exposure correction value setting unit 53 so as to stop emitting light when it is one step under the appropriate exposure level, for example. On the other hand, the bounce strobe 51ζ is set to 'O1 by its exposure correction value setting unit 54 so that it stops emitting light at proper exposure. The variable resistors 19 are set accordingly. After making the settings as described above, press the shutter button on the camera to cause the strobe device to emit light. Thereby, in the same way as described above, the output voltage of the operational amplifier 45 on the camera side is applied to the input terminal of the comparator 21 of each strobe 50, 51. As mentioned above, in the strobe 50, the variable resistor 19 is set one step lower, so the output of the comparator 21 reaches a high level before the integral value of the amount of light reflected from the object measured by the camera reaches the appropriate value. The strobe 5o then stops emitting light. At this time, the strobe 51 continues to emit light. Then, when the light amount integral value of the camera reaches a proper value, the output of the comparator 21 of the strobe 51 becomes high level, and the strobe 51 stops emitting light. In this case, assuming that the catchlight strobe 50 and the bounce strobe 51 have the same light emission waveform and amount of light, the ratio of the amount of light emitted is such that the bounce strobe 51 has three times the amount of light emitted by the front lighting strobe 50. controlled by.

Effects As explained above, in the present invention, a signal corresponding to the photometric value is sent from the camera side to the strobe side, and an exposure correction value setting circuit is provided on the strobe side, and an exposure correction value setting signal from the exposure correction value setting circuit is sent to the strobe side. A comparison circuit is provided to compare the signal representing the integral value of the light intensity transmitted from the camera side to the strobe side, and when the light emission amount of the strobe reaches the manually set exposure correction value, the signal is output from the comparison circuit. Since the strobe stops firing, the strobe can control the amount of light emitted at will.
For example, when setting up a multi-flash flash system and using one flash for bounce and the other flash for front lighting, the amount of light emitted by the bounce strobe should be greater than the amount of light emitted by the front flash. Moreover, the ratio can be set freely, making it possible to take strobe photography where you can freely choose the lighting contrast with a bounce effect.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing one embodiment of the present invention, and FIG. 2 is a perspective view showing an example of use using two flash devices of the present invention. 11... Xenon tube, 17... Operational amplifier, 18.
... Constant voltage source, 19... Variable resistance, 20... Resistor,
17-20... Exposure correction value setting circuit, 21... Comparator, 30... Photovoltaic element, 31... Photographing lens,
32... Aperture, 33... Operational amplifier, 34... Constant voltage source, 35... Diode, (3Q, 33, 35...
...Photometering circuit')% 36...Transistor, 37.
... Capacitor, (36, 37... Light amount integration compression circuit). Patent applicant: Minolta Camera Co., Ltd. Agent: Patent attorney Aoyama, 2 people

Claims (1)

[Claims] a photometering circuit having a photodetector that receives reflected light from a subject that has passed through the aperture of the camera's photographing lens; and an integral that receives the output of the photometer and outputs an integrated voltage according to the integral value of the photocurrent flowing through the photodetector. A comparator circuit is provided on the camera side, the integrated voltage is used as one input, and an exposure reference voltage that determines the amount of flash light is manually set, and this reference voltage is applied to the other input of the comparator circuit. A correction value setting circuit is provided on the flash device side, and when the light emission amount of the flash device, which is photometrically integrated on the camera side, reaches a reference value set in the exposure correction value setting circuit, the signal output from the comparison circuit is used. A flash light emission amount control device for a camera, characterized in that the light emission of a flash device is stopped.