JPH077170B2 - Flash photography system - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an improvement of a flash photography system that determines an optimum aperture based on a subject distance, a guide number of a dimming strobe (when fully emitting light), film sensitivity, and the like. Is.

(Background of the Invention) If the aperture is F and the subject distance is D, the guide number GNo of the strobe is GNo = F × D. Further, when the amount of light from the strobe is P, the brightness Eo on the subject surface is inversely proportional to the square of the distance D, and therefore is represented by an equation.

When the brightness of the subject surface is Eo, the brightness E of the film surface is inversely proportional to the square of the aperture F, Becomes The brightness E on the film surface must be reduced as the film sensitivity increases, so that the brightness E on the film surface must be inversely proportional to the film sensitivity S, where S is the film sensitivity. Therefore Becomes If we take the base 2 logarithm, everything can be expressed in APEX.

log ₂ S ＋ log ₂ P ∝log ₂ F ² ＋ log ₂ D ² ＝ log ₂ (GNo) ^{2 In} equation ² , log ₂ (k ₁ S) ＝ Sv, log ₂ (k ₂ P) ＝ Pv, log ₂ F ² ＝
If Av, log ₂ D ² = Dv, log ₂ (GN0) ² = Gv (k ₁ and k ₂ are constants), the formula becomes the following simple formula.

Sv ＋ Pv ＝ Av ＋ Dv ＝ Gv Since Sv, Av is officially defined, here Pv, Dv, Gv
Is defined.

Pv is the light intensity of the strobe, and its size is generally judged by the guide number at ISO100, so it is defined by the GNo at ISO100. Dv and Gv are the same as Av Defined in the series. If the definition is made as shown in FIG. 13 based on the above assumptions, the above formula is established.

When using a manual strobe (a strobe that cannot be used for light control) manually, determine the guide number in consideration of film sensitivity. Then, the camera is focused and the distance is obtained from the distance ring of the lens, and the aperture is calculated from the formula and set manually. The same thing can be done by replacing the same thing with APEX and using an expression. Since this manual strobe is complicated to operate, an auto strobe (light control type) that can be used easily by setting the aperture without performing such complicated operations is
It has become popular in recent years. In this equation, the aperture Av is set by the photographer, and the guide number Gv changes according to the distance Dv. That is, the maximum GNo (at full light emission)
The following GNo can be used for shooting. In the case of a dimming strobe, the formula can be rewritten as Av + Dv ≤ Sv + Pv (max) = Gv (max), and then Av ≤ Sv + Pv (max) -Dv. This is the basic APEX formula for dimming strobes.

However, there is a drawback that the exposure becomes insufficient when the Dv is a certain value or more, that is, a certain distance or more.

Therefore, the photographer tends to expand the photographing range by using the aperture on the open side as much as possible. However, when shooting with an aperture on the open side, shooting without adequate focusing may result in out-of-focus photographs, or due to the limited flash control performance of close-up shots, overexposure may occur. It becomes a photo.

As a solution to the above-mentioned point, the strobe pre-flashes by the first stroke of the release button, detects the reflected light from the main subject and measures the distance, and the camera measures the distance information from the strobe and the strobe guide. A strobe light control system that calculates the minimum aperture (aperture stop closest to the aperture) that can be used for strobe light control from the number (at full flash) and film sensitivity, and adjusts the aperture of the camera to this calculated aperture has already been used. ing. According to this, defocusing does not occur, proper exposure is achieved even in short-distance shooting, and it is possible to shoot as far as possible.

By the way, in the dimming strobe, considering the recycling time, it is possible to avoid using a too large dimming GNo.
This is advantageous in enabling continuous light emission. The above strobe light control system is insufficient in this respect.

(Object of the Invention) An object of the present invention is to solve the above-mentioned problems and to provide a flash photography system capable of improving the continuous light emission performance of a flash device.

(Characteristics of the Invention) In order to achieve the above object, the present invention calculates a limiting aperture value on the aperture side necessary for obtaining an appropriate exposure based on a subject distance, a maximum light emission guide number of a flash device, and film sensitivity. Then, the limit aperture value is set to the photographing aperture, the reflected light from the subject due to the light emission of the flash device is transmitted to the film surface through the photographing diaphragm, and the reflected light from the film surface is received by the light receiving circuit. In a flash photography system that stops the light emission of the flash device when the amount of light received by the light receiving circuit reaches a predetermined value, the limit is set when the limit aperture value represents an aperture value on the open side of a predetermined aperture value. The aperture value is set as a shooting aperture value, and when the limit aperture value represents an aperture value closer to the aperture than a predetermined aperture value, the aperture value obtained by shifting the aperture value by a predetermined value to the limit aperture value is set as the shooting aperture value. It is characterized in that a diaphragm setting means for setting is provided.

An example of aperture control according to the present invention is shown in FIG. Given value
I am in F5.6. If the minimum aperture calculated from distance etc. is less than or equal to the predetermined value F5.6, adjust the camera aperture to the minimum aperture, and in the case of F5.6 to F16, set the camera aperture to F5.
6 Keep it constant, in the case of F16 to F64, the aperture of the camera is set to 3 stages open from the minimum aperture, and in the case of F64 or more,
Set the aperture of the camera to F22 constant.

(Embodiment of the Invention) FIG. 2 shows a strobe circuit used for carrying out an example of the present invention.

A terminal X is a terminal connected to a known X contact on the camera side, a terminal S is a terminal for inputting a signal from the camera side for instructing that light emission is possible at a low level and stop emission at a high level, and terminal C is a fixed terminal. The terminal where the voltage Vc is input from the camera side,
The terminal A is a terminal for outputting the apex value of the aperture as a voltage to the camera side, and the terminal G is a grounded terminal, which is connected to the corresponding terminal of the camera.

1 is a xenon discharge tube for main light emission, 2 is a main capacitor charged by a DC-DC converter (not shown), 3 is a known trigger circuit, 4 is a commutation circuit connected in series to the xenon discharge tube 1 for main light emission , 5 and 6 are voltage dividing resistors, 7 is a comparator to which a constant voltage Vrefl generated in the strobe is applied to the inverting input terminal, and the comparator 7 charges the main capacitor 2 at a high level when the charging voltage reaches a predetermined value. Output a completion signal. 8 is a resistor, 9 is a light emitting diode which is a charging completion display means, 10 is an AND gate, 11 and 12 are inverters, 13 and 14
Are OR gates and AND gates that form a flip-flop, 15, 16 and 17 are diodes, resistors and capacitors that form a differentiation circuit that detects only the completion of the pulse input to the terminal S, 18 is a resistor, and 19 is a charge completion signal. It is turned on, and a current is drawn from the camera side through the resistor 20 and the terminal C, thereby transmitting to the camera side that the strobe is ready to emit light, 21 is a resistor, and 22 is a transistor for turning on the transistor 19 by turning on. Transistor for turning off and transmitting flash light emission start to the camera side, 23 is a constant voltage Vref2 (<Vc) is applied to the inverting input terminal, and whether the constant voltage Vc is input to the terminal C from the camera side or not Comparator, 24 is an AND gate, 25 is a one-shot circuit that outputs a pulse having a pulse width longer than the pre-flash, and 26 is a trigger Circuit, 27 xenon discharge tube for pre-emission, 28 pre-emission capacitor, 29 infrared filter, 30 inverter, 31, 32, 33 inverter
Rise of pulse output from 30 (one-shot circuit 25
(Falling edge of the output pulse of), a capacitor, a diode and a resistor that form a differentiating circuit that detects only the output pulse, 34 is a lens that defines the acceptance angle, and 35 is the infrared light of the xenon discharge tube 27 for pre-light emission reflected by the subject. Silicon photodiodes that receive light, 36 and 37 are resistors and operational amplifiers that convert the current of the silicon photodiode 35 into a voltage, 38 is a high-pass filter, and 39, 40, 41 and 42 are resistors that form an integrating circuit, integrating capacitors, and analog switches. And operational amplifier, 43 is an A / D converter, 44 is a latch circuit that performs a clear operation by the roll bell output of the AND gate 24, and performs a latch operation by the differential output from the resistor 33, 45 is a D / A converter, and FVc is a strobe It is a constant voltage made by.

The strobe operation will be described with reference to the timing chart of FIG.

When the power switch (not shown) of the strobe is turned on, the main capacitor 2 and the pre-emission capacitor 28 are charged. When the charging voltage of the main capacitor 2 reaches a voltage at which the xenon discharge tube 1 for main light emission can emit light, the comparator 7 outputs a high-level charge completion signal, which causes the light emitting diode 9 to emit light to indicate the completion of charging. At the same time, the transistor 19 is turned on. After that, when the first stroke of the release button of the camera is pressed, a constant voltage Vc is applied from the camera side to the terminal C, and a current is drawn through the terminal C, thereby transmitting to the camera side that light emission is possible.
Further, the output of the comparator 23 becomes high level, the output of the AND gate 24 also becomes high level, and the one-shot circuit 25 operates. As a result, the xenon discharge tube 27 for pre-light emission emits light and radiates infrared light to the subject. The reflected light enters the silicon photodiode 35 through the lens 34,
A voltage according to the brightness of the subject is obtained from the operational amplifier 37. The high-pass filter 38 removes natural light that hardly changes as compared with the pre-emission flash waveform, and passes only the pre-emission flash waveform. This voltage is naturally proportional to the inverse square of the distance. Since the analog switch 41 is off while the output of the one-shot circuit 25 is at the high level, the output voltage of the high-pass filter 38 is integrated by the current flowing through the resistor 39 and the integrating capacitor 40, and the operational amplifier 42.
Is output from. This integrated output is converted into a digital value by the A / D converter 43, and is stored by the latch circuit 44 when the output pulse of the one-shot circuit 25 falls. The stored digital value is (11 + Dv−Pv (max)) × V based on the constant voltage Vc of the terminal C by the D / A converter 45.
Converted to a manageable voltage of c / 16, analog distance information
It is transmitted to the camera side as VEF. Pv = 5 [GNo = 32 (IS
O100)] analog distance information VEF is shown in FIG.

The camera side processes this analog distance information VEF, obtains the Av value, and controls the aperture of the camera. Then, when the second stroke of the release button is pressed, the voltage of the terminal S first becomes low level, and then the voltage of the terminal X becomes low level. As a result, the output of the AND gate 10 becomes high level, the trigger circuit 3 operates, and the main light emission xenon discharge tube 1 emits light. At the same time, the output of AND gate 14 also goes high, turning on transistor 22
Turn off 19. Therefore, the drawing of the current to the terminal C is stopped. On the other hand, the camera begins to perform TTL and film surface reflection dimming operations. Then, when the voltage reaches the appropriate level, the voltage of the terminal S becomes high level, the differential pulse generated in the resistor 16 at its rise is input to the commutation circuit 4, and the emission of light from the xenon discharge tube 1 for main emission is stopped. Figure 3 shows
An example is shown in which the charging completed state is maintained even after the first strobe light emission ends, and the charging end state is not reached by the second strobe light emission. It goes without saying that the distance information (Pv (max) -Dv) transmitted from the terminal A to the camera side may be a digital value instead of an analog value.

FIG. 5 shows a circuit on the camera side for carrying out an example of the present invention.

Reference numeral 50 is a single-chip type microprocessor having a ROM and a RAM in the chip, and has 24 input / output ports, a reset terminal RS and an 8-bit parallel data bus terminal DB. Hexadecimal numbers are used in the calculation inside the microprocessor 50, and the hexadecimal numbers in FIG. 14 are associated with the various apex values of the camera. For example, the aperture F1.4 is Apex 1 and the hexadecimal number is 08H (H represents the hexadecimal number). The shutter speed 1/4000 second is an Apex 13, hexadecimal 68H.
Also, to make the explanation easier to understand, the maximum lens aperture value is F1.4, the minimum lens aperture value is F32, the maximum shutter speed is 1/4000 seconds, the synchronization time is 1/250 seconds to 1/60 seconds, The maximum time is set to 1 second, but needless to say, it is not limited to this value.

Reference numeral 51 is a power-up clear circuit that outputs a power-up clear signal for a certain period of time when power is supplied from a power supply circuit (not shown), and 52 is an analog voltage from 0 to Vc, which is a 256-stage digital signal shown in FIG. An A / D converter that converts the value into a value, 53 is a digital value from the microprocessor 50
D / A converter for converting to analog voltage shown in Fig. 16, 54 and 55 are analog switches, 56 is a silicon photodiode that measures the brightness of the subject, 57 is a logarithmic compression diode, 58 is an operational amplifier, and 59 to 62 are A resistor, 63 is an operational amplifier, 64 is a silicon photodiode for measuring the reflected light of a strobe film, 65 is a logarithmic compression diode, 66 is an operational amplifier, 67 is an expansion transistor, 68 is an inverter, 69
Is an analog switch, 70 is a strobe dimming integration capacitor, 71 is an operational amplifier, and 72 is a constant voltage source that outputs the reference voltage of the dimming comparator. For explanation, this reference voltage is Vc
Set to + 1.0V.

73 is a dimming comparator, 74 is an inverter, 75 is an OR gate, 76 is a film sensitivity ISO input circuit, 77 is a shutter speed setting value in the shutter priority mode, and an aperture setting value is in the aperture priority mode. A set value input circuit, 78 is a first tension magnet that releases the first tension of the camera and starts a mechanical release sequence, 79 is an aperture control magnet that controls the automatic aperture of the camera, and 80 is a shutter front curtain. A front curtain magnet for traveling, 81 is a rear curtain magnet for traveling the shutter rear curtain, and 82 to 85 are transistors.

86 is the first that turns on with the first stroke of the release button
Use the stroke switch to start metering the camera. 87
Is a second stroke switch that is turned on by the second stroke of the release button, and starts shutter release of the camera. 88 is an aperture switch linked to the automatic aperture that turns on and off once each time the aperture is reduced by 1/8. 89 is a mirror-up switch that is turned on when the mirror is raised, 90 is a rear-curtain switch that is turned on when the shutter trailing curtain is completed, 91 is a first mode setting that sets the shutter priority mode when it is off and the aperture priority mode when it is on The switch 92 is off, and the second mode setting switch 93 to set the program mode with priority over the mode set by the first mode setting switch 91.
99 is a pull-up resistor, 100 to 102 is a resistor, 103 is an operational amplifier, 104 is an analog switch, 105 is a comparator, 106
Is a shutter-second display circuit, which latches the data on the data bus at the rising edge of port P04 and performs a display corresponding to the data. When the signal level of the port P16 is high level, the display blinks and a warning is displayed. Reference numeral 107 denotes a diaphragm display circuit, which latches the data on the data bus at the rising edge of the port P05 and performs a display corresponding to the data. Also,
When the signal level of port P17 is high level, the display blinks and a warning is displayed. 108 is an X contact. Vc, Vc
c, 2 × Vc is a constant voltage supplied from a power supply circuit (not shown).

Since the shutter time display circuit 106 and the aperture display circuit 107 have the same circuit configuration, an example of the shutter time display circuit 106 is shown in FIG.

200 is a latch circuit, which is a port P05 of the microprocessor 50.
Latch the data on the data bus at the rising edge of. The output terminals T _{0 to} T ₃ are the first digit of the hexadecimal number, and T _{4 to} T ₇ are the second digit of the hexadecimal number.
Represent each digit. 201 to 204 are inverters, 205
Is a NAND gate, port P16 of microprocessor 50
When is low level, it outputs high level, and when it is high level, it inverts the clock pulse and outputs it. 206 is a clock pulse generation circuit for blinking display, 207, 208, 209, 210
Is an AND gate for displaying 1/4000 seconds when the output of the latch circuit 200 is 68H to 6FH, a NAND gate, a resistor and a light emitting diode.When the output port P16 becomes high level, the light emitting diode 210 blinks, Display a warning. 2
11 to 214 are 1/2000 when the output of the latch circuit 200 is 60H to 67H
A set of similar elements for displaying seconds, 215-218 are latch circuits
A similar set of elements that display 1/1000 seconds when the output of 200 is 58H to 5FH, 219 to 223, the output of latch circuit 200 is 08H to 0F
It is a similar set of elements that display 1 second when H.

The operation of the microprocessor 50 will be described with reference to the flowcharts of FIGS.

In the description of the flowchart, the ports P00 to P07 will be collectively referred to as PORT0. Also, set ports P10 to P17 to P
Call it ORT1. When operating each port one by one, for example, when setting the port P01 to the high level, it is expressed as P01 ← 1. When setting it to the low level, similarly set P01 ← 0. POR
When operating 8 ports such as T0 collectively, for example, PO
If you want to set P17, P16, P15, ... P10 of RT1 to 10100101, use PO
Notated as RT1 ← A5H.

When inputting data from the A / D converter 52 etc., first enter P
Select photometry as 00 ← 1, wait until the A / D conversion operation of photometry information is completed, read 8-bit data from the data bus terminal DB, and then set P00 ← 0 to cancel the A / D conversion selection. The operation to do is necessary, but omit it and write as follows.

ACC ← (AEAD) ACC means accumulator. Similarly, when analog distance information is A / D converted with P01 ACC ← (EFAD) When ISO information is input with P02 ACC ← (ISO) When setting value is input with P03 Notated as ACC ← (ATP).

Even when outputting data to the shutter time display circuit 106 etc., set P04 ← 1 to the accumulator A on the data bus terminal DB.
It is necessary to output 8-bit data from CC and then latch it as P04 ← 0, which is expressed as (TvDISP) ← ACC. Similarly, the output to the aperture display circuit 107 is expressed as (AvDISP) ← ACC, and the output to the D / A converter 53 is expressed as (DAP) ← ACC.

When power is supplied from a power supply circuit (not shown), the power-up clear circuit 51 outputs a low level for a certain period of time to reset the microprocessor 50. The reset microprocessor 50 executes the program sequentially from A in the flowchart of FIG.

# 1 PORT0 ← 00H, PORT1 ← 00H Set all outputs of ports P00 to P07 and P10 to P17 to low level. As a result, the A / D converter 52 and film sensitivity I
The SO input circuit 76, the set value input circuit 77, the shutter speed display circuit 106, the aperture display display circuit 107 and the D / A converter 53 are deselected, the magnets 78 to 81 are all turned off, and the strobe dimming integration capacitor 70 is selected. Is discharged, the voltage of the terminal S is set to a high level, and the blinking of the shutter speed display circuit 106 and the aperture display display circuit 107 is switched to lighting.

# 2 (TvDISP) ← 00H, (AvDISP) ← 00H 00 in shutter speed display circuit 106 and aperture display display circuit 107
Outputs H and turns off the display.

# 3 P20 Sense port P20. If the first stroke switch 86 is off, the loop of # 1, # 2 and # 3 is repeated to
Wait for stroke switch 86 to turn on.

"Strobe Program Mode" Now, assume that the charging of the camera is completed, the rear curtain switch 90 is turned off, and the main capacitor 2 (Fig. 2) of the strobe is completed. Further, it is assumed that the second mode setting switch 92 is off and the program mode is set. When the photographer captures the subject with the viewfinder and presses the first stroke of the release button, the first stroke switch 86 is turned on and the camera starts photometry. In FIG. 7, the branch instruction of # 3 branches to # 4.

# 4 ACC ← (AEAD) Measures the brightness Bv of external light with a silicon photodiode 56.

Current Is flowing through the silicon photodiode 56 when Bv = 0
If pd is io, then Ispd = 2 ^Bv x io when the brightness is Bv.

If the output voltage of the operational amplifier 58 is V ₅₈ , Express.

However, k: Boltzmann's constant q: Electron charge T: Absolute temperature Is: Reverse saturation current In addition, the output V ₆₃ of the operational amplifier ₆₃ is the resistance values of the resistors 59, 62, 60, ₆₁ R ₁ , R ₂ , If R ₃ and R ₄ Express.

Resistance so that _{R 1, R 2, R 3} , by selecting the R _4, V ₆₃
= Vc (1-Bv / 32).

# 5 Bv ← −ACC The brightness Bv of the external light is inverted by the operational amplifier 63, and is returned to the original value by taking a negative hexadecimal number. For example,
When Bv = 1, the A / D conversion value is F8H, and if you take a negative hexadecimal number, it will be 08H, that is, the apex value of Bv = 1. When Bv = 8, the A / D converted value is C0H and the negative number is 40H. This value is stored in register Bv.

# 6 Sv ← (ISO) Input the apex code of ISO from the film speed ISO input circuit 76 and store it in the register Sv.

# 7 Ev ← Bv + Sv Ev value is calculated from the external light brightness Bv and the film sensitivity Sv and stored in the register Ev.

# 8 P07 ← 1 Set port P07 to high level and turn on analog switch 104. Then, the output of the operational amplifier 103 is fed back through the resistor 100, so that the voltage at the terminal C rises to Vc. Now, when the strobe is charged, a constant current is absorbed from the terminal C, so the output voltage of the operational amplifier 103 is V
higher than c. Therefore, the voltage at the non-inverting input terminal of the comparator 105 also exceeds Vc, and the output of the comparator 105 is inverted to the high level.

At this time, when the voltage at the terminal C rises, the strobe emits infrared pre-light as described above to measure the subject distance, convert it into an analog voltage, and output it as analog distance information VEF from the terminal A.

# 9 P27 The output of the comparator 105 is determined. Assuming that the strobe is in the charging completed state, the output of the comparator 105 is at a high level as described in # 8.
Branch to # 10 in the figure.

# 10 ACC ← (EFAD) Converts analog distance information VEF from the flash into a digital value and stores it in the accumulator.

# 11 AvEF ← Sv + 58H-ACC / 2 Calculate the minimum aperture (apex value) from the digital distance information and store it in register AvEF. 58H is a constant. A
CC is halved to convert the one-step Vc / 16 on the strobe side to the one-step Vc / 32 on the camera side.

For example, for a subject at a distance of ISO100, GNo = 32,8m,
Since the diaphragm is 32 ÷ 8 = F4, the voltage of terminal A is 3Vc / 4, the A / D conversion value is C0H from Fig. 4, and AvEF = 28H + 58H-C0H / 2 = 20H, that is, the diaphragm code of F4. Become.

# 12 P26 The state of the second mode setting switch 92 is determined. Now that the program mode is selected, it is off and the process branches to # 13.

# 13 to # 19 use the Ev value calculated in # 7 to determine the shutter speed and aperture on the strobe program line SP shown in FIG.

# 13 Ev: 98H Compare the Ev value with Apex 19 (98H in hexadecimal), and if larger, proceed to # 14.

# 14 Tv ← 1/250, Av ← F32, P17 ← 1 When shutter speed is 1/250 sync seconds, the aperture is set to F32 which is the minimum aperture of the camera, but still the external light is over, so aperture display circuit 107 Blinking for warning.

# 15 Ev: 70H Ev value is compared with Apex 14 (hexadecimal 70H), and if larger, branch to # 16.

# 16 Tv ← 1/250, Av ← Ev−Tv The aperture is calculated by calculating the shutter speed at 1/250 sync seconds. In this case, the aperture will be in the range of F5.6 to F32.

# 17 Ev: 60H Compare the Ev value with Apex 12 (60H in hexadecimal), and if larger, branch to # 18.

# 18 Av ← F5.6, Tv ← Ev−Tv Set the aperture to F5.6 and calculate the shutter speed by calculation. In this case, the shutter speed is within the range of 1/60 to 1/250.

# 19 Tv ← 1/60, Av ← Ev−Tv Set the shutter speed to 1/60 second and calculate the aperture.
In this case, the aperture will be in the range of F1.4 to F5.6.

By the calculation of # 13 to # 19, the combination of shutter speed and aperture that is appropriate for external light was obtained. Also, at this time, the shutter speed is 1/250 to 1/60, so that the slit exposure is not performed by selecting the synchronization time.

# 20 Bv: 30H If Bv value is Apex 6 (cloudy) or above, go to # 21, 6
If it is below, branch to # 24.

# 21 AvEF: F1.4 If the brightness Bv of the external light is 6 or more, it is determined that the daytime synchro shooting with priority on the external light, and the appropriate shutter speed for the external light obtained in # 13 to # 19. Control is performed using time and aperture. Therefore, at this time, the strobe emits light as auxiliary light for external light.

However, the minimum aperture AvEF calculated from the distance information from the flash is F1.4 or less, that is, the subject distance when ISO 100 is
If the length is 32 m or more, there is no flash firing effect, so use # 2.
Branch to 2.

# 22 AvEF + 28H: Av Minimum aperture AvEF for which an appropriate aperture Av for external light is calculated
If the flash is on the narrower side by 5 steps or more, that is, even if the flash fires at full intensity, it is under 5 steps or more, there is no effect of the flash, so the process branches to # 23.

# 23 P16 ← 1, P17 ← 1 Shutter speed display circuit 106
And the aperture display circuit 107 blink at the same time.

If Bv ≦ 6 in # 20, the process branches to # 24. In # 24 to # 31, the minimum aperture AvEF calculated from the distance information from the strobe
Determine the aperture of the camera based on.

# 24 AvEF: F64 If AvEF is greater than F64, branch to # 25.

# 25 AvEF ← F22 Limit the narrowing down side of AvEF with F22.

# 26 AvEF: F16 If AvEF is greater than F16, branch to # 27.

# 27 AvEF ← AvEF-18H If F6 ≦ AvEF <F64, reduce AvEF by 3 steps (18H). When the distance is shorter than 2m (ISO100, GNo = 30), the strobe is controlled by the aperture that is open three steps from the aperture that fully fires the flash, and the light emission is made with a guide number that is three steps smaller to shorten the recycling time and continuous emission. To enable. Further, since the aperture is shifted in three steps, it is possible to stop the light emission at the attenuated portion of the flash waveform even during short-distance photography, and it is possible to achieve proper exposure.

# 28 AvEF: F5.6 If AvEF is greater than F5.6, branch to # 29.

# 29 AvEF ← F5.6 If F5.6 ≦ AvEF <F16, keep the aperture constant at F5.6.

If AvEF is F5.6 or less, use the minimum aperture calculated from the distance information from the flash. This is because when the subject is farther than 5.6 m, by selecting a diaphragm that emits full light, a sufficient amount of light can reach even a far subject. In addition, out-of-focus can be prevented as much as possible rather than fixing to the open aperture F1.4.

# 30 Av: AvEF Aperture AvEF based on distance information from the strobe obtained in # 24 to # 29 and aperture Av based on external light obtained in # 13 to # 19
Compare with.

# 31 Av ← AvEF Aperture When the AvEF is closer to the aperture than the aperture Av, that is, when the strobe light becomes the main light, Substituting AvEF for Av determines the aperture AvEF based on the distance from the flash as the aperture of the camera. To do. As described above, the aperture determined by # 24 to # 31 is as shown in FIG. # 24 to # 31 relate to the features of the present invention.

When the aperture AvEF is on the open side of the aperture Av, that is, when the external light becomes the main light, the aperture Av based on the external light is determined as the aperture of the camera.

# 32 Av: F1.4 Compare the aperture Av with F1.4.

# 33 Av ← F1.4, P16 & P17 ← 1 When the aperture Av is closer to the aperture than the aperture F1.4, the aperture of the camera is set to F1.4 and the shutter speed display circuit 106 and aperture display circuit 107 blink. Let This warns that proper exposure cannot be performed either by external light or by strobe light.

FIG. 11 shows the diaphragms determined in # 13 to # 33. Fig. 11 (A) shows ISO6, Fig. 11 (B) shows ISO100, and Fig. 11 (C) shows
The case of ISO1600 is shown respectively. The area below the dotted line in FIG. 11 is the warning area.

From # 33, through C, proceed to # 34 in FIG.

# 34 (TvDISP) ← Tv, (AvDISP) ← Av Displays shutter speed and aperture.

# 35 P21 Sense the second stroke switch 87. If the second stroke switch 87 is not turned on, return to # 3, #
The loop of 3 to # 34 is repeated, and photometry and calculation display are repeated. When the release button is pushed to the second stroke, the second stroke switch 87 is turned on and the process branches to # 36.

# 36 P24 Sense the trailing curtain switch 90. If the charging is not completed, the process branches to # 3. If the charging is completed, the process proceeds via E to the release control shown in FIG.

# 37 P10 ← 1 Output high level to port P10. As a result, the transistor 82 is turned on to excite the first tension magnet 78. The first tightening of the camera is released, and the mechanical release sequence (not shown) is started.

# 38 P11 ← 1 By outputting a high level to the port P11, the transistor 83 is turned on and the diaphragm control magnet 79 is excited to start diaphragm control.

# 39 WAIT 10ms Wait for 10ms, which is a sufficient time for the first tension to be released.

# 40 P10 ← 0 Stop excitation of the first tension magnet 78.

# 41 ACC ← Av-F1.4 Find the aperture level difference between the determined camera aperture Av and the maximum aperture F1.4, and store it in the accumulator.

Steps # 42 to # 44 are a narrowing-down control routine. The mechanical release sequence started at # 37 drives the diaphragm mechanism, and the diaphragm is started from the open position. Accordingly, each time the aperture is narrowed down by 1/8, the aperture switch 88 turns on and off once to generate one pulse.

# 42 ACC: 0 If the number of stages to be narrowed down is 0, branch to # 45.

# 43 P22 1 pulse Wait for 1 pulse to be generated by turning on / off the aperture switch 88.

# 44 ACC ← ACC-1 Subtract 1 from the accumulator value.

By the loop of # 42 to # 44, when the number of pulses corresponding to the number of narrowing steps obtained in # 41 is counted, the process proceeds to # 45.

# 45 P11 ← 0 Stop the excitation of the aperture control magnet 78 to stop the aperture mechanism. In this way, the aperture of the camera can be matched with the aperture Av.

# 46 P27 Determine if the flash is fully charged. If charging is not completed, proceed to # 55. Now that charging is complete, proceed to # 47.

# 47 Bv: 28H When the Bv value is larger than Apex 5, proceed to # 49, and when it is smaller, proceed to # 48.

# 48 (DAP) ← Outputs film sensitivity to Sv D / A converter 53. The D / A converter 53 has a transistor 67 for extending the voltage shown in FIG.
Output to the emitter of. For example, when ISO100, Vc− (4kT /
q) Output the voltage of ln2.

# 54 P14 ← 1, P15 ← 1 Output high level from ports P14, P15. As a result, the short circuit of the strobe dimming integration capacitor 70 is released, and integration is started. At first, the electric charge of the integrating capacitor 70 for strobe dimming is 0, so the output of the operational amplifier 71 is
Vc, and hence the output of the dimming comparator 73 is at a low level. Since the two inputs of the OR gate 74 both become low level, the voltage of the terminal S also becomes low level,
Enables flash firing.

# 55 P12 ← 1 The front curtain magnet 83 is excited, and the shutter front curtain starts running.

# 56 WAIT Wait for a fixed time.

# 57 P12 ← 0 Stop the excitation of the front curtain magnet 83. When traveling of the shutter front curtain is completed, the X contact 108 is turned on, and the strobe light is emitted.

The strobe light reflects off the subject and is exposed on the film through the taking lens. Let Lf be the amount of light applied to the film. Further, a part of the light applied to the film is reflected by the film surface and is incident on the silicon photodiode 64. This amount of light is Lspd. Lspd is assumed to be 2 ^-4 times the intensity of the film surface. The photocurrent of the silicon photodiode 64
If Ispd, the output voltage V ₆₆ of the operational amplifier ₆₆ is as follows.

The base-emitter voltage Vbe of the transistor is expressed by the following formula when ISO100.

Therefore, the collector current Ice of the extension transistor 67
Is Ice = Is · e ^{(q / kT) vbe} = 2 ⁴ · Ispd. That is amplified 2 ^four times. Similarly, ISO6
2 ⁰ times, is two ^eight times when the ISO1600 when. Collector current I
When ce is accumulated in the strobe dimming integration capacitor 70, the output voltage V ₇₁ of the operational amplifier 71 becomes Then, the output voltage V ₇₁ rises from Vc according to the light emission of the strobe and becomes equal to the voltage of the constant voltage source 72, the output of the dimming comparator 73 is inverted from the low level to the high level, and the voltage of the terminal S becomes the high level. To launch. Thereby, as described above, the commutation circuit 4 (FIG. 2) stops the strobe emission. If the amount of film exposure by the strobe at this time is P, Becomes Assuming that the conversion efficiency δ of the silicon photodiode 64 is 4nA per 1lux, Becomes If C = 400 pF and ΔV = 1.0 V are set, then P = 0.1 lux · sec. In other words, it is possible to stop the stroboscopic light emission at the proper film exposure amount of ISO100.

In addition, since the current amplification factor of the expansion transistor 67 changes by changing ISO, it is possible to perform appropriate strobe exposure corresponding to ISO.

# 58 TIMER ← Tv Substitute shutter time for timer.

# 59 TIMER Complete Wait while the timer measures the shutter speed.

# 60 P13 ← 1 The rear curtain magnet 81 is excited to start the traveling of the shutter rear curtain.

# 61 WAIT Wait for a fixed time.

# 62 P13 ← 0 Stop the excitation of the rear curtain magnet 81.

# 63 P14 ← 0, P15 ← 0 Discharges the electric charge accumulated in the strobe dimming integration capacitor 70. In addition, the voltage of the terminal S is held at a high level to prohibit the flash light emission. After that, through D, 7th
Return to # 3 in the figure.

As described above, when the brightness Bv of external light is less than or equal to the apex 5, the film can be properly exposed by the strobe.

When the brightness Bv of external light is # 5 or more in Apex at # 47, it is determined to be daytime sync photography, and the process branches to # 49. The daytime synchronized shooting is performed to properly expose both the main subject and the background by using the strobe as auxiliary light when the difference in brightness between them is large.

However, if the background is properly exposed and the main subject is properly exposed by a strobe, an unnatural photograph such as a composite photograph will result. Therefore, the background is properly exposed and the strobe is dimmed under 1-2 steps to create a natural daytime synchronized photography.

# 49 Bv: 48H Compare the brightness of external light Bv with Apex 9.

# 50 (DAP) ← Sv + 0CH When Bv is 9 or more, 1.5 steps (0CH) under strobe light control is performed.

# 51 ACC ← Bv-28H # 52 ACC ← (3 × ACC) / 8 # 53 (DAP) ← Sv + ACC In # 51 to # 53, Bv is between apex 5 and 9 depending on the brightness. Turn the light under a little. For example, if Bv = 6, 3/8 round under, Bv = 7
In case of, make 3/4 steps under. The dimming level of the calculation result of # 48 to # 53 is as shown in FIG.

As described above, in the strobe program mode, the optimum shutter speed, aperture and dimming level can be determined from the external light brightness and the main subject distance.

[Strobe Aperture Priority Mode, Strobe Shutter Priority Mode] Next, in the flash mode, the aperture priority mode in which the photographer sets the aperture and the shutter priority mode in which the shutter speed is set will be described.

Since # 1 to # 11 are the same as the strobe program mode,
The description will be omitted, and the description will start from # 12 in FIG.

# 12 P26 If port P26 is at low level, aperture priority is given to shutter, so proceed to # 64.

# 64 P25 Determines the on / off state of the first mode setting switch 91.
If it is off, the shutter priority mode is in effect, so branch to # 71. If it is on, the aperture is in priority mode.
Branch to 65.

# 65 Av ← (ATP) Supports the aperture set by the photographer from the setting value input circuit 77.
A hexadecimal number is entered.

# 66 Tv ← Ev−Av Calculate Tv at shutter speed.

# 67 Tv: 1/250 Compare the calculated shutter time with 1/250 second.

# 68 Tv ← 1/250, P16 ← 1 If the calculated shutter time is faster than 1/250 seconds of the synchronization time, the shutter time is set to 1/250 seconds and the shutter time display circuit 106 is used for warning. Blinking.

# 69 Tv: 1 second Compare the calculated shutter time with 1 second.

# 70 Tv ← 1 second, P16 ← 1 If the calculated shutter speed is slower than 1 second which is the longest time,
The shutter time is set to 1 second, and the shutter time display circuit 106 blinks for warning. In this way, the shutter time appropriate for the external light is calculated for the set diaphragm.

# 71 Tv ← (ATP) A hexadecimal number corresponding to the shutter speed set by the photographer is input from the set value input circuit 77.

# 72 Tv: 1/250 Compare the set shutter speed with 1/250 second.

# 73 Tv ← 1/250 When shutter speed faster than 1/250 second of sync time is set, slit exposure becomes slit exposure.
In seconds.

# 74 Av ← Ev−Tv Calculate the appropriate aperture Av for the external light.

# 75 AvE: F32 Compare the calculated aperture with F32.

# 76 Av ← F32, P17 ← 1 If the calculated aperture is on the aperture side of F32, turn the aperture to F
Then, the aperture display circuit 107 is made to blink for warning.

# 77 Av: F1.4 Compare the calculated aperture with F1.4.

# 78 Av ← F1.4, P17 ← 1 If the calculated aperture is on the open side of F1.4, open the aperture by F1.4.
Then, the aperture display circuit 107 is caused to blink for warning.

# 79 AvEF: F1.0 If the distance information from the strobe is farther than F1.0 in terms of the aperture, the strobe cannot give a sufficient amount of light for proper exposure, so branch to # 80.

# 80 P16 ← 1, P17 ← 1 Both the shutter time display circuit 106 and the aperture display circuit 107 blink to warn that the light from the strobe will not reach before shooting.

# 81 Bv: 30H If Bv> 6, branch to # 83; if Bv ≦ 6, branch to # 82.

# 82 AvEF + 18H: Av If the minimum aperture AvEF calculated in # 11 is larger than the actual aperture Av of the camera to be controlled (on the aperture side), the strobe guide number gives a sufficient amount of light to the main subject for adjustment. Show that you can shine. On the other hand, if the minimum aperture AvEF is smaller than the aperture Av of the camera (on the open side), the appropriate amount of light cannot be given even if the flash fires fully,
I have to warn you.

However, in # 82, a warning is issued only when the minimum aperture AvEF is smaller than the aperture Av of the camera by 3 steps or more. This is Bv ≦ 6
This is because, in consideration of an error in distance measurement, a warning is not issued to an exposure value that is acceptable as a photograph to some extent even if it is a little under.

# 83 AvEF + 28H: Av Bv> 6, daytime synchro shooting is performed and the underexposure is slightly exposed as explained in # 49 to # 53. Therefore, when the minimum aperture AvEF is 5 or more steps smaller than the camera's aperture Av. Warn only.

The subsequent operation is the same as in the strobe program mode.

"AE mode" If the strobe is not connected, or if the strobe main capacitor 2 (Fig. 2) is not completely filled,
The camera controls the AE mode.

# 1 to # 9 are similar to the strobe mode. Although the analog switch 104 is turned on in # 8, since the terminal C is in the open state, the output of the operational amplifier 103 becomes Vc and the output of the comparator 105 becomes low level. Therefore, in # 9, the process branches to # 84.

# 84 P26 The state of the second mode setting switch 92 is determined, and if it is the program mode, the process branches to # 98.

# 85 P25 Determines the state of the first mode setting switch 91. If it is the shutter priority mode, it branches to # 92, and if it is the aperture priority mode, it branches to # 86.

# 86 to # 91 are aperture-priority calculations, and similar to # 65 to # 70, the shutter speed suitable for outside light is calculated for the set aperture Av.

# 92 to # 97 are shutter-priority calculations, and, similarly to # 71 to # 78, a diaphragm suitable for outside light is calculated with respect to the set shutter speed Tv.

# 98 to # 107 are operations in the AE program mode.

# 98 Av ← Ev / 2−0CH Calculate aperture Av from Ev value.

# 99 Av: F32 Compare the calculated aperture with F32.

# 100 Av ← F32 If the calculated aperture is on the aperture side of F32, set the aperture to F
Set to 32.

# 101 Av: F1.4 Compare the calculated aperture with F1.4.

# 102 Av ← F1.4 If the aperture is on the open side of the calculated aperture F1.4, set the aperture to F1.4.

# 103 Tv ← Ev-Av Calculates the proper shutter speed Tv based on the calculated aperture value.

# 104 Tv: 1/4000 Compare the calculated shutter time with 1/4000 second.

# 105 Tv ← 1/4000, P16 ← 1, P17 ← 1 If the calculated shutter speed is faster than 1/4000 seconds, the shutter time is set to 1/4000 seconds and the shutter time display circuit 106 is used for warning. Also, the aperture display circuit 107 is caused to blink.

# 106 Tv: 1 second Compare the calculated shutter time with 1 second.

# 107 Tv ← 1 second, P16 ← 1, P17 ← 1 If the calculated shutter time is later than 1 second, the shutter time is set to 1 second and the shutter time display circuit 10 is used for warning.
6 and the aperture display circuit 107 are caused to blink. In this way, the program in the AE mode, shutter priority and shutter priority shutter speed and aperture are calculated. These values are as shown in the program line AE in FIG.

After that, like the strobe mode, the first stroke switch
While 86 is on, metering # 3 to # 9, # 84 to # 107
And the display routines of # 34 to # 36 are sequentially repeated.

Further, if the second stroke switch 87 is turned on,
Proceeding to the release control routine shown in the figure, the automatic diaphragm and shutter are controlled.

(Modification) In the illustrated embodiment, the distance information is obtained from the strobe,
It may be obtained from the distance detecting device of the camera or may be obtained from the distance ring.

(Effects of the Invention) As described above, according to the present invention, when the limit aperture value represents the aperture value on the open side of the predetermined aperture value, that is, when the subject is located far away, the limit is set. Since the aperture value is set as the shooting aperture so that proper exposure can be obtained even for a subject as far as possible, it is possible to expand the interlocking distance range in which proper exposure can be obtained, while the limit aperture value is set to a predetermined value. When expressing the aperture value on the aperture side of the aperture value of, that is, when the subject is located at a short distance, set the aperture value that has been moved to the open side with respect to the limit aperture value as the shooting aperture, When TTL dimming is performed, proper exposure can be obtained with a smaller amount of light emission than full light emission, so the consumption of flash energy of the flash device is reduced and the flash energy of the flash device until the next shooting is reduced. Short charging time, that is, recycling time Combing enables continuous light emission in a short time.

[Brief description of drawings]

FIG. 1 is a characteristic diagram showing an example of aperture control according to the present invention, FIG. 2 is a circuit diagram showing an example of a strobe used when implementing the present invention, and FIG. 3 is an operation of each part of the circuit shown in FIG. 4 is a timing chart showing an example of distance information of a strobe, FIG. 5 is a circuit diagram showing an example of a camera embodying the present invention, and FIG. 5 is a circuit showing an example of a shutter time display circuit. FIGS. 7, 7, 8 and 9 are flowcharts showing an embodiment of the present invention, FIG. 10 is a program diagram of strobe mode and AE mode, and FIG. 11 is a diagram showing strobe of strobe program mode. , FIG. 12 is a diagram showing strobe light control level characteristics, FIG. 13 is a diagram showing apex values of distance, light amount and guide number, and FIG. 14 is an apex value.
Figure showing correspondence of hexadecimal numbers, Figure 15 is a figure showing A / D converted values,
FIG. 16 is a diagram showing D / A conversion values. 1 ... Xenon discharge tube for main light emission, 4 ... Commutation circuit, 27 ...
Xenon discharge tube for pre-emission, 35 ... Silicon phototransistor, 40 ... Integrating capacitor, 45 ... D / A converter, VEF ... Analog distance information, 50 ... Microprocessor, 64 ... Silicon photodiode, 67 ... Extension transistor, 70 Strobe dimming integration capacitor, 76
...... Film sensitivity ISO input circuit, 77 …… Set value input circuit, 78 …… First tension magnet, 79 …… Aperture control magnet, 80 …… First curtain magnet, 81 …… Second curtain magnet,
86 …… First stroke switch, 87 …… Second stroke switch, 88 …… Aperture switch, 106 …… Shutter time display circuit, 107 …… Aperture display circuit 108 …… X contact, AvEF…
… Aperture based on distance information, Av …… Aperture.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Hiroyuki Kataoka, Inventor Hiroyuki Kataoka, 770 Shimonoge, Takatsu-ku, Kawasaki, Kanagawa Canon Inc., Tamagawa Plant (72) Toshiyuki Kumakura, 770, Shimonoge, Takatsu-ku, Kawasaki, Kanagawa Tamagawa Plant (56) Reference JP-A-58-117532 (JP, A)

Claims (2)

[Claims] 1. A limit aperture value on the aperture side necessary for obtaining proper exposure is calculated based on the subject distance, the maximum light emission guide number of the flash device, and the film sensitivity, and the limit aperture value is set as the shooting aperture. At the same time, the reflected light from the subject due to the light emission of the flash device is transmitted to the film surface through the photographing diaphragm, the reflected light from the film surface is received by the light receiving circuit, and the amount of light received by the light receiving circuit reaches a predetermined value. In the flash photography system that stops the emission of the flash device when the above, the limit aperture value is set as a photography aperture when the limit aperture value represents an aperture value on the open side of a predetermined aperture value, and the limit aperture value is set. When a value represents an aperture value closer to the aperture than a predetermined aperture value, an aperture setting means for setting an aperture value obtained by shifting a predetermined value to the open side with respect to the limit aperture value as a shooting aperture is provided. Flash photography system. 2. A flash device which pre-emits light, reflected light from a subject due to the pre-light is received by a light receiving section, and a limit aperture value is calculated according to the output of the light receiving section. The flash photography system according to the item.