JPS6243168B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides highly accurate exposure control by controlling the amount of flash light while taking into account the amount of natural light when taking photographs using a flash device. This relates to a flash photography method that aims to properly expose not only the main subject but also the background at the same time by using this together with an automatic exposure control device for natural light photography in some cases.

2. Description of the Related Art Conventionally, a so-called computer strobe flash device is known, which integrates the reflected light of a flash from a subject using a quick-response light-receiving element and an integrating circuit, and interrupts the emission of flash when the integrated value reaches a predetermined value.
However, this type of camera ignores the influence of natural light during exposure, so if the subject is relatively bright and the exposure time is long, it has the disadvantage of overexposure due to the natural light.

In addition, in order to eliminate the above drawbacks, a low-pass filter and a bypass filter are inserted in the control circuit to separate the natural light and flash light information received by the light receiving element, and then exposure time information is added to the natural light information to determine the flash light emission. A method of controlling the interruption timing, that is, the amount of light emission, is also already known. However, this method also has drawbacks, such as the control circuit being complicated and overexposure occurring if another photographer turns on another flash device during exposure.

The present invention was made in view of this point, and determines the shutter time based on the so-called average photometric output,
In addition to compensating for proper exposure to the background, an integration circuit is operated to integrate the output of the light receiving element by so-called partial photometry in synchronization with the time when the shutter is opened, and the flash tube is further triggered a predetermined time before the shutter is closed to emit a flash. , receiving the light reflected from the subject by the flash light emission with the light receiving element using partial photometry;
There is no way to obtain the sum of the daylight and flash amount for the main subject as the integrated value of the integration circuit, and when the sum reaches a predetermined level, the flash is stopped and proper exposure can be obtained for the main subject as well. Because of this, it does not have the disadvantage of overexposure due to natural light when the exposure time is relatively long as in the conventional example, and the light emission amount control circuit is simple, making it extremely practical. It's expensive.
Furthermore, if the device of the present invention is used, even if another photographer happens to fire a flash while the shutter is open, the amount of light will be automatically taken into account, and the amount of light emitted by the flash will be taken into account. is controlled (reduced), so even in such a case, proper exposure can be obtained, which is an advantage not found in other devices. This will be explained in detail below using examples.

FIG. 1 shows the relationship between the opening and closing operations of the lens shutter and the emission of flash light with respect to time. In the figure, a indicates the opening/closing operation of the shutter, and the vertical axis indicates the degree of opening of the shutter. Further, b indicates the light emitting characteristics of the flash device.

When the shutter button is pressed, the shutter is unlocked at time to, the shutter opens rapidly, and after a very short period of time has passed, the shutter is fully opened at time _t1 . After a manually set time has elapsed or after a predetermined time controlled by an automatic exposure control device,
It begins to close at t ₂ and closes at t ₃ after a very short time has elapsed. On the other hand, the flash device is not activated to emit light at t ₁ as in conventional devices, but is activated to emit light at t ₄ , which is about 1 ms (milliseconds) before t ₂ , by a light emission activation means to be described later, as shown in b. The output changes in a curved manner, but as explained later, the amount of natural light irradiated on the subject from t ₀ or t ₁ to t ₅ and the amount of natural light irradiated on the subject from t ₄ to t ₅ The light emission is stopped at the moment when the sum of the amount of flash light (corresponding to the area of the shaded area in the figure) reaches a predetermined value (ie, t ₅ ).

In this way, highly accurate appropriate exposure can be obtained that also takes into account the influence of natural light.

Figure 2 shows the R-C of the light emission amount control circuit, which will be explained in detail later.
This shows the change in the capacitor terminal voltage of . From t ₀ to t ₄ , the only light irradiating the subject is natural light, so the terminal voltage of the capacitor slowly increases as shown by c and reaches v ₁ at t ₄ . When the flash device starts emitting light at t ₄ , the subject is simultaneously illuminated by natural light and flash light (which is reflected by the subject and enters the light receiving element), so the capacitor terminal voltage rises rapidly as shown by d, and soon At _t5 , a predetermined operating level _v2 is reached and the light emission is stopped.

As mentioned above, the time from t ₀ to t ₁ (also the time from t ₂ to t ₃ ) is extremely short, so even if the time to start charging the capacitor is t ₁ instead of t ₀ , the accuracy is sufficient for practical use. is obtained. (It rises like c') In Figures 1 and 2, the time from t ₀ to t ₁ and from t ₂ to t ₃ are extremely small and can be ignored, and from t ₄ It has already been mentioned that the time until t ₂ is about 1 ms. However, even after the flash stops firing, the shutter is still open, so the subject will be slightly more exposed due to natural light.

However, the amount of exposure during this time is extremely small and can be ignored, but if you want to compensate for this, you can either lower the operating level _v2 slightly below the level that provides proper exposure, or use the method described in the example below. t ₅
and t ₂ should be configured to match.

It is also possible to configure the shutter to start emitting light at a time when the shutter should begin to close, and then close the shutter after the light emission stops (closing a little later than a predetermined time).

In addition, the time from the start to the end of the flash in a flash device should be determined by the device's light emission characteristics, the distance to the subject, the amount of natural light, etc., as well as the film sensitivity (ASA) and the aperture of the photographic lens. The value (F) should also be taken into consideration when determining the value. Therefore, in order to simplify the device, for example, when ASA = 100, F
= 5.6, ASA = 200, F = 8, etc. If you manually adjust the aperture value of the photographing lens according to ASA (or if you want to automate this), the light emission ASA and F in the quantity control circuit
There is no longer a need to input this information.

Figure 3 shows an example of a lens shutter using a mechanical governor in which the count start signal and light emission start signal of the light emission amount control circuit can be taken out using a contact piece, and only the main parts are shown. It is shown. In the figure, 1 is the sector ring,
In the illustrated state, the shutter blades are fully open.
That is, when the shutter button (not shown) is pressed down, the engagement between the lock pawl 2 and the section 1a is broken, the sector ring 1 is rapidly rotated counterclockwise by the spring 1c, and the shutter blades are rapidly opened. The insulated supported switch _S1 is closed by contacting the protrusion 1b and being grounded. This starts charging the counting capacitor of the light emission amount control circuit.

Meanwhile, the lock pawl 3 is also released in synchronization with the lock pawl 2, and the locking portion 4b of the three-pronged lever 4 is cut off.
The two-pronged lever is about to rotate counterclockwise around the rotating shaft 4a by the spring 4e, but the other arm 4d is rotated by a part 5 of a mechanical governor composed of gears, escape wheels, pallets, etc. It has been stopped. After the predetermined time set in the mechanical governor has elapsed, the restraint by 5 is released, and the insulating pin 4c implanted in the arm of the three-pronged lever moves to the left, thereby closing the switch _S2 and turning on the flash device. is triggered and starts emitting light.

After about 1 ms has elapsed after S ₂ is closed, the arm of the three-pronged lever hits the pin 1d implanted in the sector ring 1 for the first time, pushing it further downward and rapidly closing the shutter blade. In order to secure a time of approximately 1 ms from when the switch _S2 closes until the pin 1d begins to be pressed, the governor may be configured to work slightly during this time. Details such as the charge mechanism have been omitted.

FIG. 4 shows an example in which an electronic governor is used in contrast to the example shown in FIG. 3 that uses a mechanical governor. In this example, the electronic governor device built into the camera and the camera are configured separately. It consists of a flash device and a connector (flash axis) that connects both devices.

In the figure, the electronic governor device detects a time constant circuit consisting of a light receiving element CdS (e.g. cadmium sulfide) that measures the average brightness of the subject, a capacitor _C1 , and the charging voltage of the capacitor of the time constant circuit. A proper exposure control circuit consisting of a voltage detection circuit 6 that outputs a post-shutter film running signal, and a proper exposure control circuit that controls the flash device to start emitting light a certain number of seconds before the proper exposure time (for example, 1 ms before the light emission time of the flash device). It consists of a flash start signal generation circuit that commands. That is, the photodetector CdS and the capacitor C ₁
CdS−R ₁ −C ₁ with resistor R ₁ connected between
The connection points between the light receiving element and the resistor and between the resistor and the capacitor are respectively connected to a voltage detection circuit having the same detection voltage value. Therefore, if the resistance value of the photodetector CdS is R ₀ , the resistor R ₁ is the capacitance of the capacitor C ₁ is C ₁ , then the charging characteristics of each connection point are (Charging characteristics of the connection point between CdS and R ₁ ) (Charging characteristics at the connection point between R ₁ and C ₁ ). However, E
is the power supply voltage.

Therefore, let t _R and t _C be the time required for the voltage value at each connection point to reach a predetermined voltage value V ₀ from the time when switch S ₄ , which short-circuited both ends of the capacitor, is turned off from on. t _R = C ₁ (R ₀ + R ₁ ) log _e (R ₀ /R ₀ +R ₁ ) (E/E
-V ₀ ) t _C =C ₁ (R ₀ +R ₁ )log _e (E/E-V ₀ ). If the time difference between t _R and t _c is t ₀ , then t ₀
is t ₀ =t _R −t _C =C ₁ (R ₀ +R ₁ )log _e (R ₀ /R ₀ +R ₁ ). Therefore, if R ₁ is constant and R ₀ ≫ R ₁ , then t ₀
remains almost constant even if R ₀ changes. That is, t ₀ in the above equation is a monotonically increasing function that converges to −C ₁ R ₁ with respect to the variable R _0. For example, if C ₁ = 2μF and R ₁ = 1KΩ, when R ₀ is 10, 100, 1000, 10000KΩ t ₀ is −2.096822, −2.009966, −
2.000998, −2.0001 milliseconds and R ₀ is 10~
It maintains a nearly constant value within the practical range of 10,000KΩ. For this reason, the photodetector CdS and resistor R ₁
From the time constant circuit consisting of and capacitor _C1 ,
As explained above, the connection point between resistor R ₁ and capacitor C ₁ outputs a signal that measures the average brightness of the object and controls appropriate exposure, and the connection point between photodetector CdS and resistor R ₁ . A signal a certain number of seconds before the end of proper exposure can be taken out from the connection point. In the figure, the circuit surrounded by a dashed-dotted line 6 is an embodiment of the proper exposure control circuit and a flash device light emission start control circuit that outputs a signal a certain number of seconds before the end of proper exposure, and the circuit surrounded by a dashed-dotted line 7 The camera has a light-receiving element (for example, a silicon photocell) with a fast response speed, and its light-receiving angle is regulated, and the amount of flash light is controlled by the reflected light from the main subject located in the center of the screen. This is an embodiment of a so-called computer strobe type flash device, and what is surrounded by a dashed line 8 is a flash axis provided with a connection terminal for connecting the proper exposure control device and the flash device.

Next, the operation of the embodiment of this apparatus will be explained with reference to the same figure.

When the shutter release button (not shown) is pressed down, the main switch _S3 is first turned on and electricity is supplied to the electric circuit. In this state, count switch S ₄ remains on, so field effect transistor FET ₁ and transistor
The input voltage of the voltage detection circuit consisting of Tr ₁ , Tr ₂ and Tr ₅ and resistors R ₂ , R ₃ , R ₄ , R ₉ and R ₁₁ is at zero potential, and the input voltage of resistor R ₅ and the film sensitivity Since it is lower than the reference voltage V ₀ divided by the variable resistor VR ₁ for information input, the transistor TR ₆ becomes conductive and the electromagnetic magnet Mg is excited, so that film movement after the shutter is prohibited. On the other hand, the voltage V _R at the connection point between the photodetector CdS and the resistor _R1
(R ₁・E/R ₀ +R ₁ , R ₀ is the resistance value of the light receiving element CdS)
Since V is also lower than ₀ , the field effect transistor FET ₂ and
Transistors Tr ₃ , Tr ₄ and Tr ₇ and resistor R ₆ ,
The flash start signal is not generated from the voltage detection circuit composed of R ₇ , R ₈ , R ₁₀ , and R ₁₂ . Further press down on the shutter release button,
When the button is pressed all the way, the prohibition of shutter tip film travel is canceled and exposure is started, and in synchronization with this, the count switch _S4 is turned "off." As a result, the photodetector element CdS
A current corresponding to the brightness of the object passing through the resistor
The capacitor _C1 is charged through _R1 , and proper exposure control is started.

Also, when the shutter tip membrane runs and fully opens, X contact _S5 turns on in synchronization with the shutter tip membrane.
A time constant circuit consisting of a light-receiving element P with a fast response speed and a capacitor _C2 , which controls the amount of light emitted by the flash device, starts operating, and as a result, the output current of the light-receiving element P, which spot-meters the subject, is transferred to the transistor.
After being amplified by Tr ₁₀ , it is charged to capacitor C ₂ . As shown in FIG. 2, the charging waveform of the capacitor _C2 rises in response to the brightness of the subject due to natural light. In a camera's exposure control circuit, the voltage at the connection point between CdS and R ₁ of a time constant circuit consisting of a light receiving element CdS, resistor R ₁ , and capacitor C ₁ that measures the average brightness of the subject. However, when a certain number of seconds before the time required for proper exposure, the film sensitivity information input variable resistor RV ₁
When we reach the voltage V ₀ divided by and resistor R ₅ ,
The voltage detection circuit is activated and a flash start signal is sent to the flash device, causing the flash device to emit light. After the predetermined time has elapsed since the flash start signal was generated, that is, when the time required for proper exposure is reached, the voltage at the connection point between the resistor _R1 and the capacitor _C1 of the time constant circuit reaches the reference voltage _V0 . , the detection circuit is activated and the transistor Tr ₆ becomes non-conductive, so that the magnet Mg is demagnetized and the prohibition of film running after the shutter is released, and the film runs after the shutter and the exposure is completed. On the other hand, the flash amount control circuit of the flash device starts operating in synchronization with the X contact _S5 , which is turned on when the shutter tip membrane is fully opened, and receives the reflected light from the subject emitted by the flash device, as explained in Fig. 2 above. Until then, only the brightness of the subject due to natural light is measured using the spot photometry method, and after the light emission starts, the total amount of natural light and flash light is continuously measured. When a flash firing start signal is sent from the camera to the flash device, the signal is applied to the gates of silicon rectifying elements SCR ₃ and SCR ₂ via resistors R ₂₇ and R ₂₈ , and SCR ₃ and SCR ₂ become conductive. As a result, a high potential voltage is induced in the flash discharge tube _F1 by the trigger coil _Tl1 , so the gas inside the flash discharge tube _F1 is ionized and becomes conductive, and the voltage of the booster circuit A increases the voltage of the flash discharge tube _F1 . It flows rapidly and emits intense light along with heat. When this strong light hits the subject, reflects, and enters the film, it reaches the amount of light that was insufficient during natural light exposure (when the total amount reaches the appropriate amount), in other words, the response speed of the flash device is fast. Element P
The charging voltage of the time constant circuit consisting of the transistor Tr ₁₀ and the capacitor C ₂ is determined by the field effect transistor FET ₃ , the transistors Tr ₁₂ , Tr ₁₃ , Tr ₁₄ and the resistors R ₁₈ , R ₁₉ , R ₂₀ , R ₂₁ , R ₂₂ , and a resistor that is the operating voltage of the voltage detection circuit consisting of _R23 .
R ₂₀ and variable resistor VR ₁ for inputting film sensitivity information
When the voltage V ₀ ' divided by
Added to SCR ₁ gate. As a result, SCR ₁ is inverted to a conductive state, and a negative voltage is applied to the anode side of the SCR ₂ via the capacitor C ₄ , and the SCR 2 is inverted to a non-conductive state. As a result, the current passing through the interior of the flash discharge tube _F1 is cut off and the flash light emission is stopped. Thereafter, the proper exposure control circuit on the camera side is activated, the post-shutter film is run, and proper exposure is completed. As explained above, proper exposure is controlled based on the average brightness of the subject under natural light, and the amount of light emitted from the flash device compensates for the lack of light on the subject. Therefore, both the field and the subject are photographed with proper exposure.

In addition, remove the resistor R ₂₀ and variable resistor VR ₂ that create the reference voltage of the voltage detection circuit in the flash device.
By adding a connection terminal to the axis section and directly connecting the reference voltage point of the voltage detection circuit on the camera side and the reference voltage point of the voltage detection circuit on the flash device side, as shown by the dotted line, operation during flash photography is greatly simplified. It can be made easy. (There is no need to set the film sensitivity information in VR ₂ on the flash device side.) Also, some circuitry may be improved so that the film after the shutter is run by the flash light emission amount stop signal.

In the same figure, FET ₁ and FET ₃ are field effect transistors, Tr ₁ to _{Tr 14} are transistors, and SCR ₁
~SCR ₃ is a silicon rectifier, Di ₁ and Di ₂ are diodes, P is a fast response light receiving element, CdS is a photoconductive light receiving element (response speed is not very fast),
R ₁ to R ₃₀ are resistors, C ₁ to C ₈ are capacitors, F ₁ is a flash discharge tube, Tl ₁ is a trigger coil, L is a neon lamp, and B and B' are aperture devices or filters for inputting aperture value information. The amount of light passing through the lens is adjusted manually or automatically according to the aperture value of the photographic lens.

A is the booster circuit, E ₁ and E ₂ are the power batteries, S ₃ is the main switch, S ₄ is the count start switch, and S ₅ is the X
Contact point _S6 is a main switch, and _S7 is a switch that is switched depending on whether the camera used in combination with this flash device is a dedicated camera as mentioned above or a general camera.

Even when the above flash device is used in combination with a general camera other than a dedicated camera with a control circuit like the one above, the brightness of the main subject due to natural light will not be affected unless the exposure time is very short. Although this is not taken into consideration, proper exposure can be obtained by flash photography. In this case, switch switch _S7 to the opposite direction from that shown in the diagram, set the aperture value of the photographing lens in the aperture device (or filter) B' of the light receiving element P, and also set the sensitivity of the film used for VR ₂ . and use it. When the X contact (corresponding to _S5 mentioned above) of a general camera is closed, in this case, since the changeover switch _S7 has been changed, it is immediately triggered and the flash discharge tube _F1 starts emitting light. As in the case described above, when the X contact closes, the flash amount control circuit starts operating, and when the flash amount reaches an appropriate value, the flash emission is automatically stopped.

When used in conjunction with a camera other than a dedicated camera that has an appropriate exposure control device for natural light photography, the background will also be properly exposed, but the main subject will be overexposed by the amount of brightness due to the natural light of the main subject. The exposure time is long, the main subject is far away,
The brighter it is, the bigger it becomes. In the embodiment shown in FIG. 4, it is necessary to input film sensitivity information (VR ₂ ) and aperture value information (B') to the flash device, but as already mentioned, VR ₂ may also serve as VR ₁ . If it is possible, and if the configuration is configured so that the aperture value information is also added to VR ₁ and input, both B and B' become unnecessary, and therefore there is no need to set the film sensitivity information and aperture value information on the flash device side. This makes operation during flash photography extremely easy.

FIG. 5 shows, with respect to time, the relationship between the opening and closing operations of the shutter and the emission of flash light when a focal plane shutter is used, unlike the previous example. When the shutter button is pressed, the front membrane of the shutter is released at time t ₀ , and exposure begins from one end of the screen, and the opening gradually expands as shown in e and reaches t ₁ , when the entire screen is exposed. Become so.
After the time manually set in advance or the predetermined time controlled by the automatic exposure control device has elapsed, at _t2 the rear film begins to cover the opening from one end of the screen and performs the same operation as f, which is the same as e. Eventually, at _t3 , the exposure will be completed by covering the entire screen.

g indicates the light emission characteristics of the flash device, and as in the above embodiment, light emission starts at t ₄ , about 1 ms before t ₂ , and at t ₅ , the sum of natural light and flash light reaches an appropriate value. Stops emitting light. In the case of a focal plane shutter, unlike the case of a lens shutter, the time from t ₀ to t ₁ (also the time from t ₂ to t ₃ ) is around 10 ms, which is a time that cannot be ignored, so the flash The device's light emission control circuit starts counting.
It is necessary to start from t ₀ , not from t ₁ . When taking flash photography, if you always use a constant exposure time (for example, 1/60 second) and the time when the shutter is fully open, that is, the time from t ₁ to t ₂ , is about 1 ms to 3 ms. When luminescence starts
t ₄ may coincide with the full opening time t ₁ of the acromembrane. In this case, it is sufficient to start the light emission amount control circuit from t ₀ and to start the flash device to emit light using the same synchronizing contact (X contact) used in a normal camera. The rear film may be activated by the light emission stop signal at t ₅ (t ₅ and t ₂ coincide), as in the case of the lens shutter.

FIG. 6 is a mechanical diagram of the main parts showing the interlocking relationship between the rear film drum and the light emission start switch when the focal plane shutter is particularly an electronic shutter. Reference numeral 6 denotes a disk which rotates integrally with the rear film drum, and is controlled via a lock pawl 7 by a magnet M connected to an electronic shutter circuit. Further, _S8 is a switch for starting light emission. When the shutter button is pressed down, a current flows through the magnet M, which attracts the bent portion 7d of the lock pawl 7 with the rotation axis 7a.
The 6b portion of the disc 6 can be locked by the 7b portion at the other end. When the front membrane is unlocked, at the same time, another rear membrane drum locking member (not shown) is released, the drum is locked by the magnet M, and the electronic shutter circuit starts counting, and when a predetermined period of time has elapsed. After the current of the magnet Mg is cut off, the disk 6 is moved by the charged spring force (not shown).
The lock claw 7, which is biased to rotate by the weak spring 7c, is pushed away and rotated clockwise, thereby closing the rear membrane. When the disk 6 starts rotating, the rear membrane starts to move along with it, but the insulating pin 6c implanted in the disk 6 during the run-up period until its tip comes out within the effective screen.
When the switch _S8 is closed, the flash device starts emitting light. If the run-up period of the shutter film is effectively utilized in this manner, the light emission start signal can be extracted from the shutter closing signal, thereby simplifying the device. When outputting a closing signal from the electronic shutter circuit, if you want the shutter to actually close before _t2 , it is necessary to output the signal earlier than this due to the delay time of the magnet and mechanism. Appropriate measures may be taken, such as starting counting earlier than t ₀ , when t0 starts to open.

FIG. 7 is a diagram showing a shutter time control circuit and a flash device circuit for a focal plane shutter, which were explained in FIG. 5 above. As explained in FIG. 4, this shutter time control circuit causes the flash device to emit light a certain number of seconds before the proper exposure end signal, and after compensating for the insufficient amount of light during natural light photography, As shown in the figure, the amount of light emitted from the discharge tube of the flash device is controlled by the light-receiving element P, which has a fast response. In particular, the difference from FIG. 4 is that, as explained in FIG. Two points were taken: time was taken into consideration, and the method of controlling the amount of light emitted by the discharge tube of the flash device was to use a bypass discharge tube instead of controlling it with an SCR. That is, in the flash device shown in Fig. 4, the operation start signal for the light emission amount control circuit was obtained from the X contact that was turned on when the shutter was fully opened, but here it is linked to the count switch for controlling the shutter time. , from OFF
This camera differs from the embodiment shown in FIG. 4 and previous cameras in that it is provided with a switch _S9 that turns on, and does not use an X contact. As already mentioned in connection with Fig. 5, if the time from _t1 to _t2 when the shutter is fully open is shortened from 1ms to 3ms in the case of flash photography, instead of _t4 .
Even if the light is emitted from t ₁ , the error will be small. That is, there are cases where it is acceptable to start the light emission using a so-called X contact. Also, when using a focal plane shutter with a very fast film speed, t ₀
Since the time up to t ₁ can be ignored for practical purposes as in the case of the lens shutter, switch S ₉ can be replaced with a switch corresponding to S ₅ in FIG. 4.

Note that the circuit configuration and operation are the same as those shown in FIG. 4, so the explanation will be omitted. In addition, in a focal plane shutter, the mirror rises during exposure, which blocks information from the subject to the CdS installed in the viewfinder system, so this figure measures the light that passes through the lens system. This is a control circuit for external light mounting with a light receiving element located outside the lens system, but it is also possible to perform photometry in the same way using light that has passed through the lens system using a generally known storage device. In the figure, R ₁ to R ₃₀ are resistors, VR ₂ is a variable resistor, CdS is a light receiving element that measures the average brightness of the subject, P is a fast response light receiving element that measures the center part, and C ₁
~C ₉ is a capacitor, FET ₁ and FET ₂ are field effect transistors, Tr ₁ to _{Tr 14} are transistors, SCR ₁ and SCR ₃ are silicon rectifiers, L ₁ is a neon discharge tube, F ₁ is a flash discharge tube, F ₂ is a bypass discharge tube, Tl ₁ and Tl ₂ are trigger coils, Di ₁ is a diode, Mg is an electromagnetic magnet, B' is an aperture device for inputting aperture value information, E ₁ and E ₂ are power batteries, and S ₃ is a camera. S ₄ is the count switch, _{S 6} is the main switch for the flash device, S ₇ is the switch for switching between a special camera and a general camera, and S ₉ is the count switch, which starts controlling the amount of light emitted from the flash device. It is a switch that tells X, but in some cases
It may be replaced with a contact point. However, in this case, the flash amount control does not take into account the amount of natural light exposure until the shutter tip film is fully opened.

As described above, the present invention determines the shutter time based on the average photometric output, further integrates the partial photometric output for light from the subject from the time the shutter is opened, and flashes the flash tube a predetermined time before the shutter is closed. The light reflected from the subject by the flash is detected by the partial photometry, and an integral value based on the partial photometry output by the reflected light is added to the integral value before the flash is emitted, and the added value becomes a predetermined value. Since the flash is stopped at the same time, both the background and the main subject are properly exposed.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing the operating principle of the flash photography method according to the present invention, Fig. 2 is an explanatory diagram showing the time constant circuit charging characteristics, and Fig. 3 is an explanatory diagram showing the case where the method according to the present invention is applied to a lens shutter. FIG. 4 is a control circuit diagram when the shutter mechanism shown in FIG. 3 is implemented using an electric circuit. FIG. Figure 6 is a configuration diagram of the main parts of the shutter mechanism for performing the operation shown in Figure 5. Figure 7 is a control circuit diagram when the mechanism shown in Figure 6 is performed using an electrical circuit. CdS measures natural light information from the center of the subject. A light receiving element, P is a light receiving element that receives illumination reflected light from a subject, 6 is a control circuit that generates a light emission signal, and 7 is a light emission amount control circuit that generates a light emission stop signal.

Claims (1)

[Claims] 1 A photometering circuit that measures the entire photographic area, and a shutter that generates a first output after the elapse of the shutter seconds according to the luminance measured by the photometering circuit, and a second output that outputs a first output a predetermined time before the first output is generated. a shutter time control circuit containing a timer circuit that generates a second output; the second output activates a trigger circuit to trigger a flash tube, and the first output activates a shutter closing member; In a flash photography device for a camera that activates and ends the exposure,
A light-receiving element that partially meters the photographing area to receive the light flux from the main subject, an integrating circuit that integrates the output of the light-receiving element, and a stop signal when the integrated value by the integrating circuit reaches a predetermined value. a stop signal forming circuit that outputs a stop signal; a flash stop circuit that uses the stop signal to stop the flash tube from emitting flash light to a subject;
switch means for shifting from a first state to a second state in synchronization with the opening operation of the shutter, and causing the integrating circuit to respond to the shift of the switch means from the first state to the second state; A flash photography device for a camera, characterized in that an integral operation is started.