JPS646444B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION TECHNICAL FIELD The present invention relates to an exposure control device for flash photography that is capable of automatically performing flash photography taking into account the brightness of stationary light.

Prior Art With this type of conventional flash photography device, it was impossible to take a picture without knowing in advance how bright the subject would be when the flash was emitted.

Furthermore, with conventional devices, it has been impossible for the photographer to arbitrarily select how much brightness to make the subject and cause the photographer to emit a flash of light in an amount corresponding to the selected value.

Purpose The present invention provides a new exposure control device for flash photography that allows the photographer to take a picture after knowing in advance how much brighter the subject will be when the flash is emitted compared to when the subject is exposed only to steady light. In addition, we have created an exposure control device for flash photography that allows the photographer to select how bright they want the camera to be and emit an amount of flash light that corresponds to the selected value. be.

Therefore, by using the device of the present invention, it becomes possible to perform flash photography that takes into account the brightness of stationary light, which was not possible with conventional devices.

One aspect of the exposure control device for flash photography according to the present invention includes an output means for outputting a signal corresponding to the amount of contribution to photography due to light emission of the set flash light emitting device;
A setting means for setting the exposure time, film sensitivity, and aperture value; a photometry means for measuring the ambient light; a calculation means for calculating the step difference in the apex system from the amount of contribution to photography with the flash added; a display means for displaying based on a signal corresponding to the step difference from the calculation means; and a signal and the flash from the output means. The present invention is characterized by comprising a control means for controlling the amount of light emitted by the flashlight emitting device based on a signal corresponding to the amount of light reflected from the subject.

Another aspect is an output means that outputs the difference in the number of steps in the apex system between the amount of contribution of constant light to photography and the amount of contribution to photography of constant light plus flash, and the exposure time or film sensitivity/aperture value. a setting means for setting, a photometering means for measuring the ambient light, a calculation means for calculating the amount of contribution to photography by light emission of the flashlight emitting device based on the signals from the output means, the setting means and the photometry means, and a calculation means. The present invention is characterized by comprising a control means for controlling the amount of light emitted by the flash light emitting device based on a signal corresponding to the amount of flash light contribution from the means and a signal corresponding to the amount of light reflected from the subject of the flash light.

Still another aspect is that the first photometering means measures the standing light from the secondary subject and outputs the first photometric signal, and the second photometering means measures the standing light from the main subject and outputs the second photometric signal. a contrast setting means for setting the contrast between a main subject and a sub-subject during flash photography and outputting a corresponding contrast signal; The present invention is characterized by comprising a calculation means for determining the amount of contribution of flash light to the main subject.

Embodiment Hereinafter, an embodiment of the present invention shown in the drawings will be described in detail.

FIG. 1 is a block diagram showing an embodiment of the present invention, and first, the respective constituent circuits will be explained.

ST is a flashlight emitting device, and internally includes a signal output circuit 2 that outputs a "High" signal when preparation for flashlight is completed, and a photometry circuit that measures the amount of flash light emitted.
LM ₂ , a comparator that compares the output of the photometric circuit LM ₂ and the signal from the camera CP ₀ , a comparator
It is equipped with a stop circuit 4, etc., which stops flash light emission when the output of CP ₀ is reversed.

SE ₀ is a setting device that sets the amount of flash light emitted, and this device outputs digital data QVf as a multi-bit signal line (in the drawings below, the signal lines with diagonal lines indicate multi-bit signals). (indicates that it is a signal line). In addition, although QVf is expressed as the amount of flash light emitted in the specification, in reality, QVf
is related to the amount of flash light emitted and indicates the amount of contribution of flash light to photography, that is, the amount of light reflected from the subject or the amount of light incident on the subject, and is not like a guide number of a flash light emitting device.

SE ₂ is a setting device that sets the amount by which you want the subject to be brightened by the apex type by firing the flash light emitting device, and hereinafter this will be referred to as step difference △ ₁ . SE ₄ is a setting device that sets the aperture value,
SE ₆ is a setting device for setting exposure time, and SE ₈ is a setting device for setting film sensitivity.

LM ₀ is a photometry circuit for steady light photometry, and AD ₀ is an A-D conversion circuit that converts the output of the photometry circuit LM ₀ from analog to digital. SW ₀ is a switch that is “ON” when outputting the data of the set light emission amount, and “OFF” when not outputting, SW ₂ is “ON” when outputting the data of the set number of steps difference △ ₁ , a switch that turns “OFF” when not outputting, SW ₄
is a switch connected to terminal A when in aperture priority mode and to terminal T when in exposure time priority mode,
SW ₆ is a switch that is connected to terminal AU for automatic shooting and to terminal M for manual shooting.

AG ₀ , AG ₂ , AG ₄ , AG ₆ , and AG ₈ are switches respectively.
AND gates output setting data according to the states of SW ₀ , SW ₂ , SW ₄ , and SW ₆ ; OG _{0 and} OG 2 are OR gates; NAN ₀ is a NAND circuit; IN ₀ is an inverter.

AL is AND gate AG ₀ , AG ₂ , OR gate
OG ₀ , OG ₂ , film sensitivity setting device SE ₈ , A-D
This is an arithmetic circuit that calculates the aperture value, exposure time, light emission amount, step number difference, and the difference between the set aperture value and the calculated aperture value based on data from the converter _AD0 . CA is an aperture control device that controls the aperture based on aperture value data from the arithmetic circuit AL, and CS is a shutter control device that controls the shutter based on exposure time data from the arithmetic circuit. DS is an arithmetic circuit
This is a display device that displays various data calculated by AL. DA ₀ is a DA converter that performs DA conversion of data corresponding to the amount of light emission calculated by the arithmetic circuit AL.

Next, the operation of the above circuit device will be explained. First, the case where the output of the signal output circuit 2 is "High" will be explained. In this case _, when switch SW ₀ is "ON" and switch SW ₂ is "OFF", _the light emission amount data from AND gate AG ₀ is input to the arithmetic circuit AL. When in aperture priority mode, data corresponding to the aperture value from the AND gate AG ₄ , data corresponding to the subject brightness from the A-D converter AD ₀ , and film sensitivity from the film sensitivity setting device SE ₈ are used. The corresponding data is input to the arithmetic circuit AL.

Then, the arithmetic circuit AL calculates the exposure time, step difference, and light emission amount based on these data, and the display device DS displays the exposure time and step difference △ ₁ , and the shutter control device CS displays the calculated exposure time. The aperture control device CA is further controlled based on the set aperture value. Also,
The DA converter _DA0 outputs an analog signal corresponding to the amount of light emission to the comparator _CP0 . This signal and
The output of the photometric circuit LM ₂ in the flash device is compared by the comparator CP ₀ , and when the output of the comparator CP ₀ is reversed, the stop circuit 4 is activated to stop the light emission, and the set amount of light is emitted. .

In the exposure time priority mode, the arithmetic circuit AL calculates data corresponding to the aperture value and step number difference based on data corresponding to the amount of light emitted, subject brightness, exposure time, and film sensitivity. The display device DS displays the step number difference and exposure time, and the light emitting device
ST emits light by a set amount of light, the aperture control device CA is controlled based on the calculated aperture value, and the exposure time CS is further controlled based on the set exposure time.

In manual setting mode, the aperture value is calculated in the same way as in exposure time priority mode, and data corresponding to the difference between this calculated data and the data corresponding to the set aperture value is calculated, and the camera takes care of this difference. The display DS is performed based on the data, the difference in the number of steps is displayed, and the amount of light emission, aperture, and exposure time are controlled based on the set values.

On the other hand, when switches SW ₀ and SW ₂ are both “ON”, the output of NAND circuit NAN ₀ is “Low”
Since the AND gates AG ₄ , AG ₆ , and AG ₈ are closed, data corresponding to the set exposure time and aperture value are not input to the arithmetic circuit AL. At this time, the arithmetic circuit AL stores the set light emission amount, step number difference, film sensitivity and A-D.
Data corresponding to the subject brightness is input from the conversion circuit _AD0 . Then, in the arithmetic circuit AL, data corresponding to the aperture value and exposure time is calculated, a display corresponding to these two data is performed, and the aperture and exposure time are controlled based on the calculated data, and the light emitting device ST emits only the set amount of light.

Next, switch SW ₀ is “OFF” and the switch
The case where SW ₂ is “ON” will be explained.

First, when in aperture priority mode, data corresponding to exposure time and light emission amount is calculated based on data corresponding to subject brightness, film sensitivity, step difference, and aperture value, and the calculated exposure time is displayed. The aperture is controlled based on the set value, the exposure time is controlled based on the calculated value, and the light emitting device emits light in an amount corresponding to the calculated data.

In the exposure time priority mode, data corresponding to the aperture value and light emission amount is calculated and the aperture value is displayed, the exposure time is controlled based on the set value, the aperture is the calculated value, and the light emission is controlled based on the calculated value. In addition, when in manual setting mode, data corresponding to the aperture value and light emission amount is calculated, and data corresponding to the difference between the set aperture value and the calculated aperture value is calculated and displayed, and the aperture and exposure The time is controlled based on the set value, and the light emission is controlled based on the calculated value.

Furthermore, switches SW ₀ and SW ₂ are both “OFF”
In this case, neither the data corresponding to the amount of light emission nor the difference in the number of steps is input to the arithmetic circuit AL, so that the arithmetic circuit AL performs normal exposure calculation and controls. At this time, data corresponding to the amount of light emission is not calculated from the arithmetic circuit AL, so the output of the DA converter DA ₀ is 0, and the light emitting device ST detects this as described later. Performs normal flash emission.

Further, even when the light emission preparation completion signal is not inputted from the signal output circuit 2, the calculation circuit AL performs normal exposure calculation, and normal natural light photography is performed.

To set the flash light emission amount, that is, the contribution amount QVf of the flash light to photography, to setting device SE ₀ , for example, emit light from the flash light emitting device in advance, and set the amount of light reflected from the subject or the amount of light incident on the subject due to the light emission. It is sufficient to measure the light using some kind of photometer and set the apex value or the like based on the measured value.

FIG. 2 is a block diagram showing the calculation operation of the calculation circuit AL when data corresponding to the step number difference is input in the exposure time priority mode.

First, in order to make the explanation of the structure and operation of this type of block diagram easier to understand, the symbols shown in each drawing are defined as follows. △ ₁ is the difference in the number of steps, TVs is the apex value of the set exposure time, TVx is the apex value of the calculated exposure time, BVa is the apex value of the subject brightness with ambient light only, SV is the apex value of the set film sensitivity , AVs is the apex value of the set aperture value, AVx is the apex value of the calculated aperture value,
AVf is the apex value of the appropriate aperture that can be determined only by the flash light emission, QVf is the apex value of the flash light emission amount, and QVt is the light intensity apex value corresponding to the sum of the flash light emission amount and the steady light incident during the exposure time. ,
EVa is the exposure value under constant light, and TVa is the apex value of the exposure time determined from the constant light exposure value and the set aperture value.

The following relational expression holds between the values of these symbols.

2 ^QVf +2 ^BVa-TV = 2 ^QVt ...(1) Here, TV represents TVs and TVx.

QVf+SV=AVf...(2) QVt+SV=AV...(3) Here, AV represents AVs and AVx.

QVt - (BVa - TV) = △ ₁ ... (4) BVa + SV = EVa ... (5) BVa - AVs = TVa ... (6) In Figure 2, the set exposure time TVs and A-D conversion from OR gate OG ₂ , respectively. A pair of registers 22, 2 that capture the subject brightness BVa from the device AD ₀ .
Based on the data from 4, the subtraction circuit 30 performs the following calculation: (BVa-TVs)...(4-0). Next, based on the data from the register 20 that takes in the difference in the number of stages △ ₁ from the AND gate AG ₂ and the data from the subtraction circuit 30, the addition circuit 34 calculates △ ₁ + (BVa-TVs) = QVt... (4-1 ) is performed to calculate the total light amount QVt. The data calculated by the adder circuit 34 and the film sensitivity SV stored in the register 26
Based on the data corresponding to
AVx is calculated, and this calculated data is sent to the display device DS and the aperture control device CA.

On the other hand, the data from register 20 is stored in ROM2
8, and operates as a data converter for converting data from the ROM 28 into data corresponding to log ₂ (2Δ ₁ -1), which is fixed and stored in advance at the designated address. this
From the data corresponding to log ₂ (2△ ₁ -1) from the ROM 28 and the data corresponding to BVa - TVs from the subtraction circuit 30, (BVa - TVs) + log ₂ (2△ ₁ -1) = QVf ... (7 ), data corresponding to the light emission amount QVf of the flash only is calculated, and this data is sent to the D-A converter DA ₀
is sent to control the amount of light emitted.

Here, we will explain why the amount of light emission QVf is determined using equation (7).

First, by transforming equation (1) using equation (4), we get 2 ^QVf = 2 ^BVa-TVs・(2△ ₁ -1) ...(1-1), and by taking the logarithm of both sides, we get QVf = BVa-TVs + log ₂ (2△ ₁ -1), and equation (7) holds true. Therefore, the light emission amount QVf of only the flash can be found from equation (7). In addition,
Set exposure time TVs from register 22 in Figure 2
The corresponding data is sent to the shutter control device CS.

FIG. 3 is a block diagram showing the arithmetic operation of the arithmetic circuit AL when the step number difference _Δ1 is input in the aperture priority mode. First, in the subtraction circuit 44, the calculation AVs-SV=QVt (3-2) is performed based on the data corresponding to the set aperture value AVs and the set film sensitivity SV from the registers 38 and 26, and the total light amount QVt is calculated. be done. On the other hand, the adder circuit 42 calculates data corresponding to (BVa+ _Δ1 ) based on the difference in the number of stages _Δ1 from the registers 20 and 24 and data corresponding to the subject brightness BVa. Then, the subtraction circuit 46 calculates the appropriate exposure time TVx by performing the following calculation based on the data from the addition circuit 42 and the subtraction circuit 44: BVa+Δ ₁ −QVt=TVx (4-2). The data calculated by this subtraction circuit 46 is sent to the display device DS and the shutter control device CS.

On the other hand, data corresponding to the difference in the number of stages _Δ1 from the register 20 is converted by the ROM 28 into data corresponding to log ₂ (2Δ ₁ -1). The subtraction circuit 30 calculates data corresponding to (BVa-TVx) based on the exposure time TVx calculated by the subtraction circuit 46 and the data corresponding to the subject brightness BVa from the register 24. Then, in the addition circuit 34, based on the data from the ROM 28 and the subtraction circuit 30, BVa−TVx+log ₂ (2△ ₁ −1)=QVf
...(7-1) is performed, data corresponding to the amount of light emission QVf is calculated, and this data is sent to the DA converter _DA0 . In addition, the aperture value set in register 38
Data corresponding to AVs is sent to the aperture control device CA.

FIG. 4 is a block diagram showing the operation of the arithmetic circuit AL when data corresponding to the step number difference _Δ1 and the light emission amount QVf are both input. first,
The ROM 50 converts data corresponding to the stage number difference _Δ1 from the register 20 into data corresponding to -log ₂ (1-2-Δ1). ROM50 is the above-mentioned
Similar to ROM28, data corresponding to △ ₁
It specifies an address in the ROM 50 and outputs data corresponding to -log ₂ (1-2-Δ1) fixedly stored at that address. This ROM
Addition circuit 52 uses the data from 50 and the data corresponding to the set light emission amount QVf from register 48.
Then, the following calculation is performed: QVt=QVf+{−log ₂ (1−2−Δ1)} (8), and the total light amount QVt is calculated. To explain the reason why the total light intensity QVt can be obtained from the above equation (8), first, BVa−TVx=QVt−△ ₁ …(4-3) holds, and the above equation (1) becomes 2 ^QVf + 2 ^{BVa -TVx} = 2 ^QVt …(1) Therefore, if we transform this using formula (4-3), we get 2 ^QVf = 2 ^QVt (1-2-△1) …(1-2), and this formula (1 -2) is transformed by taking the logarithm of both sides, QVt=QVf−log ₂ (1−2−△1) …(8). Therefore, QVt has been obtained.

In the adder circuit 42, the difference in the number of stages from the register 20 is △
Object brightness from register 24 as data ₁
Calculate data corresponding to (BVa+△ ₁ ) from the BVa data. This register 24
data and the total light amount QVt from the adder circuit 52
The subtraction circuit 46 calculates data corresponding to the exposure time TVx by performing the following calculation: BVa+Δ ₁ −QVt=TVx (4-2). The data calculated by this subtraction circuit is sent to the shutter control device CS and the display device DS.
In addition, the adder circuit 36 calculates the total light amount QVt from the adder circuit 52 and the film sensitivity from the register 26.
Based on the data corresponding to SV, calculate QVt + SV = AVx (3-1), and the data corresponding to the aperture value AVx calculated by this formula (3-1) is displayed on the aperture control device CA and the display device DS. sent to. Note that the data corresponding to the light emission amount QVf from the register 48 is D-A.
Input to converter DA ₀ .

FIG. 5 is a block diagram showing the operation of the arithmetic circuit AL when data on the amount of light emission QVf is input to the arithmetic circuit AL in the exposure time priority mode. In the subtraction circuit 30, the subject brightness from the register 24 is
(BVa−TVs) is calculated from the data corresponding to BVa and the data corresponding to the set exposure time TVs from the register 22. Next, in the subtraction circuit 54, the subtraction circuit 3
Data from 0 and set light emission amount from register 48
The following calculation is performed from the data corresponding to QVf: QVf-(BVa-TVs)=△ ₂ ...(9). In this equation (9), △ ₂ is the amount of light emission QVf
and the amount of incident light due to steady light during the exposure time BVa−
It corresponds to the difference between TVs and is generally called lighting contrast.

The data corresponding to the writing contrast △ ₂ from the subtraction circuit 54 is converted to log(1) by the ROM 56.
+2△ ₂ ) and sent to the display device DS, but here log ₂ (1+2△ ₂ ) = △ ₁ ...(10), so from this ROM 56 the stage difference △ ₁ This means that data corresponding to is output,
This data is sent to the display device DS. here(10)
To explain the reason why the formula holds, first, the above
Transforming equation (1) using equation (9), we get 2 ^BVa-TVs (1+2△ ₂ )=2 ^QVt ...(1-3), and taking the logarithm of both sides of equation (1-3), we get log ₂ (1+2△ ₂ )=QVt−(BVa−TVs) (11). By the way, the right side of equation (11) is the step difference △ from equation (4).
Since it is equal to ₁ , log ₂ (1+2△ ₂ )=△ ₁ …(10) holds true.

The adder circuit 32 receives data corresponding to the stage number difference △ ₁ from the ROM 56 and (BVa) from the subtracter circuit 30.
-TVs), the following calculation is performed: _Δ1 +(BVa-TVs)=QVt (4-1), and the total light amount QVt is calculated. Data corresponding to the total light amount QVt of this adder circuit 32 and film sensitivity SV from the register 26
The addition circuit 36 calculates QVt+SV=AVx (3-1) from the data corresponding to the aperture value AVx to calculate the data corresponding to the aperture value AVx, and sends this data to the display device DS and the aperture control device CA. Also, register 22
The data corresponding to the set exposure time TVs is sent to the shutter control device CS, and the data corresponding to the light emission amount QVf from the register 48 is sent to the D-A converter.
Sent to DA ₀ .

FIG. 6 is a block diagram showing the operation when the light emission amount QVf is input to the arithmetic circuit AL in the aperture priority mode. The adder circuit 58 calculates QVf+SV=AVf (2) based on data corresponding to the set light emission amount QVf from the register 48 and the film sensitivity SV from the register 26. From the data of the addition circuit 58 and the data corresponding to the set aperture value AVs from the register 38, the subtraction circuit 60 calculates data corresponding to AVs-AVf=Δ ₃ (12). △ ₃ in this formula (12) is
As is clear from equations (2) and (3), this corresponds to the difference between the apex value QVt of the total light amount and the apex value QVf of the light emission amount of the flashlight emitting device ST. This data △ ₃ is
The ROM 62 converts the data into data corresponding to -log ₂ (1-2Δ ₃ ).

On the other hand, in the adder circuit 64, the data corresponding to the subject brightness BVa from the register 24 and the register 2
From the data corresponding to the film sensitivity SV from 6, the following calculation is performed: BVa+SV=EVa (5), and data corresponding to the exposure value EVa is calculated.

Furthermore, the subtraction circuit 66 inputs the exposure value EVa from the addition circuit 64 and the set aperture value from the register 38.
Based on the data corresponding to AVs, the following calculation is performed: EVa−AVs=TVa (6), and data corresponding to the appropriate exposure time TVa when there is only steady light is calculated. Then, in the addition circuit 68, TVa+{ _{- log 2} (1-2△ ₃ )}=TVx...(13) is calculated to determine the appropriate exposure time for flash photography.
Data corresponding to TVx is calculated and sent to the display device DS and shutter control device CS. To explain why the above equation (13) holds true, first of all, if you multiply both sides of the above equation (1) by 2 ^SV ,
From equations (2), (3), and (5), 2 ^AVf + 2 ^EVa-TVx = 2 ^AVs (1-4) holds true. When this equation (1-4) is transformed using the above equation (12), 2 ^EVa-TVx = 2 ^AVs (1-2△ ₃ ) ...(1-5), and both sides of this equation (1-5) Taking the logarithm of TVx=EVa−AVs−log ₂ (1−2△ ₃ )
...(13-1) Then, from the above equation (6), TVx=TVa-log ₂ (1-2△ ₃ ) ...(13) holds true.

The subtraction circuit 70 calculates (EVa-TVx) from the data corresponding to the exposure value EVa due to constant light from the addition circuit 64 and the data corresponding to the exposure time TVx from the addition circuit 68. Then, the subtraction circuit 72
Data corresponding to the set aperture value AVs from 8,
From the data corresponding to EVa-TVx from the subtraction circuit 70, perform the calculation AVs-(EVa-TVx)=△ ₁ ...(4-2) to calculate the data corresponding to the difference in the number of stages △ ₁ , and this data is Sent to display device DS.
In addition, the above equation (4-2) holds true.
This is clear from equations (3), (4), and (5). Further, data corresponding to the set light emission amount from the register 48 is sent to the DA converter DA ₀ , and data corresponding to the set aperture value AVs from the register 38 is sent to the aperture control device CA. .

FIG. 7 is a block diagram showing the manual setting mode. In this case, the same block diagram as in the case of exposure time priority mode shown in FIG. 2 or FIG.
Aperture value based on set exposure time TVs
AVx is calculated by the addition circuit 36, and the subtraction circuit 4
0 is the difference between the aperture value AVx from this adder circuit 36 and the data corresponding to the set aperture value AVs from the register 38 _{△ 3} AVs - AVx = △ ₃ (14) Display the value on the display device DS. Data corresponding to the aperture value AVx in the register 38 is sent to the aperture control device CA, while control of the shutter control device CS is performed based on preset data.

In addition, when the data corresponding to the step number difference △ ₁ and the light emission amount QVf are not input to the corresponding circuits,
Exposure calculations are performed only for normal stationary light, but since they are well-known calculations, their explanation will be omitted.

Next, FIG. 8 shows an example of a specific circuit of the flashlight emitting device of FIG. 1. In Figure 8, the switch
SW ₈ is the main switch, and this switch SW ₈
Switch SW ₁₀ also opens and closes in conjunction with this. switch
When SW ₈ is closed, the booster circuit DD operates, and the main capacitor C ₄ is charged via the rectifier diode D ₄ . When the charging voltage of the main capacitor _C4 reaches a predetermined value, the neon tube NE becomes conductive and lights up, indicating that the xenon tube XE is now able to emit light.

In addition, the neon tube NE becomes conductive, causing resistance.
Current flows through R ₁₀ and R ₁₂ , and the potential at the connection point between resistors R ₁₀ and R ₁₂ becomes a potential that allows transistors BT ₀ and BT ₄ to conduct, causing transistors BT ₄ and BT ₆ to conduct, and resistors R ₆ and R The potential at the connection point ₈ becomes “High”. The "High" signal at this connection point is transmitted to the camera side via connection terminals J ₃₀ and J ₃₂ .

Note that the capacitor _C6 continues to operate as a transistor even after the xenon tube XE emits light and the charging voltage of the main capacitor _C4 drops, and the neon tube NE becomes non-conductive
BT ₀ and BT ₄ serve to keep conductive for a while. Furthermore, the circuit constants are determined so that the conduction time of the transistors BT ₀ and BT ₄ is longer than the time during which the flashlight emitting device emits all light.

Amount of light emitted from the DA converter DA ₀ on the camera side QVf
The analog signal corresponding to is input to the flash light emitting device ST via connection terminals J ₄₀ and J ₄₁ . That is, this analog signal is compared with the output voltage of the constant voltage source CE by the comparator OA ₀ , and the output voltage of the constant voltage source CE is
If the output voltage of
When the output voltage of the CE is smaller, the light emission amount is controlled based on a signal corresponding to the light emission amount QVf from the camera side.

First, let's explain the case where it is controlled by the light emission amount signal from the camera side. In this case, the comparator
Since the output of OA ₀ is “Low”, the P-channel MOSFETs, FT ₂ , FT ₄ and ET ₈ are each “ON”, and the N-channel MOSFETs, FT ₀ and FT ₆ are each “OFF”. . X contact on camera side
When SX is closed, transistors BT ₀ and BT ₂ are turned "ON", the gate potential of thyristor SC ₀ rises and this thyristor SC ₀ becomes conductive, and as a result, the xenon tube XE is turned on by the trigger circuit TR. and thyristor SC ₂ are triggered, and the xenon tube
XE conducts and emits light.

In addition, when the transistor BT ₀ becomes conductive, the transistors BT 8 , BT ₈ , which were conductive until then, simultaneously become conductive.
BT ₁₀ becomes non-conductive. Transistor BT ₈ is the discharge voltage transistor of the integrating capacitor C ₂ ,
And the transistor BT ₁₀ ensures that the output of the comparator OA ₄ is “Low” until the X contact SX is closed.
It is designed to make it look like it is.

When the xenon tube XE emits light, the output current of the phototransistor PT increases, and the voltage across the resistor R ₀ increases. Only this increased voltage (so-called alternating current component) is output from a high-pass filter consisting of a capacitor C ₀ and a resistor R ₂ . The voltage output from this high-pass filter is converted into a current by a voltage-current conversion circuit composed of an operational amplifier OA ₂ , a transistor BT ₁₄ , and a resistor R ₄ . The current of this voltage-current conversion circuit is
Through BT ₁₂ , FET, FT ₈ , diode D ₀ ,
D ₂ and flows into a known logarithmic compression integration circuit consisting of capacitor C ₂ . This logarithmic compression integrator circuit is
A voltage obtained by logarithmically compressing the integral value of the inflowing current is output across capacitor _C2 . this capacitor
C ₂ output voltage and camera side DA converter DA ₀
Comparator OA ₄ compares the analog signals corresponding to the light emission amount _QVf from Circuit 4 operates to make thyristor SC ₂ non-conductive,
As a result, the xenon tube XE stops emitting light. Therefore, the amount of light emitted by the xenon tube XE is determined by the D-A converter.
The light emission amount is controlled to correspond to the analog signal of the light emission amount QVf from DA ₀ .

The output voltage of the constant voltage source CE is the output voltage of the D-A converter DA ₀
When the signal from the comparator
OA ₀ output becomes “High” and N channel
MOSFET, FT ₀ , FT ₆ are “ON”, P channel
MOSFET, FT ₂ , FT ₄ and FT ₈ are turned “OFF”.
Therefore, the output current of the phototransistor PT flows directly into the logarithmic compression integration circuit composed of diodes _D0 , _D2 , and capacitor _C0 , while the output current to the (-) terminal of the comparator corresponds to the sensitivity of the film used, etc. The voltage from the variable voltage source VE that outputs the voltage is input, and the amount of light emitted is controlled by normal automatic dimming.

In the example shown above, the difference in the number of steps △ ₁ and the amount of light emitted
Although both QVf can be set, it is also possible to set only one. Further, the setting device may be provided not on the camera side but on the flashlight emitting device side. Furthermore, a photometry circuit for measuring the amount of light emitted by the flashlight emitting device and a comparator may be provided on the camera side, and the light emission stop signal may be output from the camera side.

Also, when using a lens shutter, the camera's shutter sends data from the arithmetic circuit directly to the shutter control device, while when using a focal plane shutter, the calculated exposure time is shorter than the tunable limit. Only when seconds
For example, a warning may be issued or the calculated exposure factor may be corrected so that the exposure time reaches the tuning limit.

Furthermore, it is very advantageous to use a microcomputer to carry out the invention.
According to the contents disclosed in the drawings shown in FIGS.
Programming a microcomputer is easy for those skilled in the art. Further, since the aperture and shutter control devices and display circuits may be well-known ones, the internal explanations are omitted.

Furthermore, the step number difference setting device _SE2 shown in FIG. 1 can be modified as follows. Based on the output of one spot metering circuit, the brightness of the main subject BVa ₁
and the brightness BVa ₂ of the sub-subject, calculate BVa ₂ - BVa ₁ = △ ₄ ... (15) from these two data, and use this △ ₄ as the step difference △ ₁ to calculate the light emission amount.
By determining the QVf, even when the main subject is darker than the sub-subject, such as in backlit photography, the main and sub-subjects can be photographed with proper exposure and the same brightness.

In addition, in order to make it possible to photograph the main subject brighter than the sub-subject even if the main subject is darker, a device is provided to set the number of steps k indicating how many steps brighter the image should be taken, and the above formula (15) is used. The light emission amount QVf may be determined by adding the determined data △ ₄ and the set data k and using this value as the step number difference △ ₁ △ ₄ + k = △ ₁ (16).

Furthermore, by finding and displaying the difference between the manually set step difference △ ₁ and the data △ ₄ determined by equation (15) above, △ ₅ = △ ₁ − △ ₄ (17), the set step difference can be calculated. The difference in brightness between the main subject and the sub-subject of the photo taken based on △ ₁ can be seen in advance.

Note that as the photometric circuit for determining _Δ4 in the above equation (15), two spot photometric circuits may be used, or an average photometric circuit and a spot photometric circuit may be used.

This means that it is sufficient to find the light emission amount QVf such that the following relationship holds: 2 ^QVf + 2 ^BVa1-TV / 2 ^BVa2-TV = 2 ^k (18). Here, it is assumed that the secondary subject is not irradiated with light from the flashlight emitting device, so if we transform the above equation (18), we get 2 ^QVf + 2 ^BVa1-TV = 2 ^BVa2+K-TV = 2△ _4+k ... (18-1) From this equation, it can be seen that equation (16) holds true, and QVf=BVa ₁ −TV+log ₂ (2△ _4+k −1) can also be found. Note that the case where k=0 in this equation is the case of the modified example described above.

Also, when setting the step difference △ ₁ , the brightness of the main subject is QVt = BVa ₁ - TV + _{△ 1} , and the brightness of the secondary subject is BVa ₂ - TV, so QVt - (BVa ₂ - TV) = (BVa ₁ −BVa ₂ )＋△ ₁ =△ ₁ −△ ₄
...(17-1), and △ ₅ can be found.

In addition, in the so-called program mode where the combination of aperture value AVa and exposure time TVa is determined from the subject brightness BVa and film sensitivity SV, for example, the calculated aperture value AVa or exposure time TVa is set as the aperture priority mode or The same calculation as in the exposure time priority mode or the exposure time priority mode may be performed.

Effects As described in detail in the above embodiment, the exposure control device for flash photography according to the present invention allows the photographer to predict in advance how much brighter the subject will be when the flash is emitted compared to when the subject is exposed only to steady light. In addition, the photographer can select how much brightness he or she wants and emit the flash in an amount corresponding to the selected value. Further, the photographer can set the desired contrast between the main subject and the sub-subject, and emit a flash light to achieve this contrast.

Therefore, by using the device of the present invention, it is possible to automatically perform flash photography that takes into account the brightness of steady light, which was impossible with conventional devices. This has the advantage of further improving the performance.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of an exposure control device for flash photography according to the present invention, FIGS. 2 to 7 are block diagrams showing embodiments of the arithmetic circuit shown in FIG. 1, and FIG. 3 is a block diagram for explaining the operation of the arithmetic circuit when the exposure time priority mode is input and a step difference is input, and FIG. 3 is a block diagram for explaining the operation of the arithmetic circuit when the step difference is input in the aperture priority mode. Figure 4 is a block diagram to explain the operation of the arithmetic circuit when the difference in the number of stages and the amount of light emitted is input, and Figure 5 is the calculation when the amount of light is input in exposure time priority mode. A block diagram for explaining the operation of the circuit. Figure 6 is a block diagram for explaining the operation of the calculation circuit 3 when the light emission amount is input in aperture priority mode. Figure 7 is a block diagram for explaining the operation of the arithmetic circuit 3 in the manual setting mode. FIG. 8 is a block diagram for setting the operation of the arithmetic circuit, and is a circuit diagram showing a specific example of the flash light emitting device of FIG. 1. SE ₀ ; Light emission amount setting device, SE ₂ ; Step number setting device,
SE ₄ ; Aperture setting device, SE ₆ ; Exposure time setting device,
SE ₈ : Film sensitivity setting device, LM ₀ : Light metering circuit for steady light metering, AL: Arithmetic circuit, ST: Flash light emitting device.

Claims (1)

[Scope of Claims] 1. Output means for outputting a signal corresponding to the amount of contribution to photography by light emission from a flashlight emitting device; Setting means for setting exposure time; Photometering means for metering ambient light; and the above-mentioned output means. , a calculation means for calculating the step difference in the apex system between the amount of contribution of steady light to photography and the amount of contribution to photography of steady light plus flash light based on the signals from the setting means and the photometry means; A display means for displaying a display based on a signal corresponding to the difference in the number of steps, and a control means for controlling the amount of light emitted by the flashlight emitting device based on the signal from the output means and the signal corresponding to the amount of light reflected from the subject of the flash. An exposure control device for flash photography characterized by: 2. Output means for outputting a signal corresponding to the amount of contribution to photography by light emission from a flashlight emitting device; Setting means for setting film sensitivity and aperture value; Photometering means for metering ambient light; and the above-mentioned output means and setting means. and a calculation means for calculating the exposure time for a proper exposure based on the signal from the photometry means, and the step difference in the apex system between the amount of contribution of constant light to photography and the amount of contribution to photography of constant light plus flash light. and a display means for displaying a display based on a signal corresponding to the difference in the number of steps from the calculation means, and controlling the amount of light emitted by the flash light emitting device based on the signal from the output means and the signal corresponding to the amount of light reflected from the subject of the flash. An exposure control device for flash photography, further comprising a control means for controlling a shutter according to the calculated exposure time. 3. Output means for outputting the step difference in the apex system between the amount of contribution of constant light to photography and the amount of contribution to photography of constant light plus flash, setting means for setting exposure time, and photometry for metering of constant light. means, calculation means for calculating the amount of contribution to photography by the light emission of the flashlight emitting device based on the signals from the output means, the setting means and the photometry means; and the signal corresponding to the amount of flashlight contribution from the calculation means and the amount of the flashlight. 1. An exposure control device for flash photography, comprising: control means for controlling the amount of light emitted by a flash light emitting device based on a signal corresponding to the amount of light reflected from a subject. 4 Output means for outputting the step difference in the apex system between the amount of contribution of constant light to photography and the amount of contribution to photography of constant light plus flash; setting means for setting film sensitivity and aperture value; a photometric means for measuring light; a setting means for setting the output means and the exposure time; an exposure time that provides an appropriate exposure based on signals from the output means, the setting means, and the photometry means; and photography using light emission from a flashlight emitting device. a calculation means for calculating the amount of contribution to the flash; and a calculation means for controlling the amount of light emitted by the flash light emitting device based on a signal corresponding to the amount of contribution from the flash light from the calculation means and a signal corresponding to the amount of reflected light from the subject of the flash, and controlling the amount of light emitted by the flash light emitting device based on the signal corresponding to the amount of light contribution from the flash light emitting device, 1. An exposure control device for flash photography, comprising: control means for controlling a shutter based on a signal corresponding to the above. 5. A first photometric means that measures the constant light from the secondary subject and outputs the first photometric signal; a second photometric device that measures the constant light from the main subject and outputs the second photometric signal; and during flash photography. a contrast setting means for setting the contrast between the main subject and the sub-subject and outputting a corresponding contrast signal; A flash light comprising: a calculation means for determining the amount of contribution; and a control means for controlling the amount of light emitted by the flash light emitting device based on a signal from the calculation means and a signal corresponding to the amount of light reflected from the subject of the flash light. Exposure control device for photography. 6. A patent claim characterized in that the first photometry means is an average photometry means that measures the average brightness of the field, and the second photometry means is a spot photometer that measures a relatively narrow part of the field. The exposure control device for flash photography according to item 5.