JP2003131298A - Stroboscopic device and film unit with lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a photographic image good in granularity in stroboscopic photography. SOLUTION: This stroboscopic device is set so that exposure by strobe light may be higher than the proper one by +0.5 EV at maximum and the exposure by the strobe light on a short distance side may be a little higher near the proper one by adjusting the respective resistance values of the variable resistor 58 of a level adjusting part 46 and a short distance correction resistance 54. A high-sensitivity film is loaded in the unit main body of the film unit with a lens. Since the stroboscopic device is set so that the exposure by the strobe light may be higher than the proper one, photography that the underexposure area of the high-sensitivity film whose granularity is deteriorated is used is reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a strobe device having a light control function and a film unit with a lens.

[0002]

2. Description of the Related Art A strobe device is used as an auxiliary light source when photographing in a dark place, and many compact cameras and the like currently on the market have a strobe device built therein. As one type of strobe device, an automatic light control type device generally called an auto strobe is known.

In the automatic light control type strobe device, at the same time as strobe light is applied to a subject, the strobe reflected light reflected by the main subject is received by a light receiving element, and a photoelectric current flowing by the receipt of the strobe reflected light is received. Then, the light quantity integration of the strobe reflected light is performed. Then, when the integrated amount of light reaches a predetermined light emission stop level, strobe light emission is stopped. The flash stop level is the aperture value at which the flash fires so that the proper exposure can be obtained with the flash light.
It is decided based on the film sensitivity of the photo film. As a result, the flash light amount is automatically adjusted, and the main subject can be exposed with an appropriate exposure amount.

On the other hand, the present applicant manufactures and sells a lens-fitted film unit in which an unexposed photographic film is incorporated in a unit body in which a photographic lens and a photographic mechanism such as a shutter mechanism are incorporated. In addition, a film unit with a lens that has a built-in strobe device is also widely known.
Recently, a lens-fitted film unit with a built-in automatic light control strobe device is also commercially available.

Further, with the improvement of the technology relating to photographic films, high-sensitivity films such as ISO800 and ISO1600 are being used on a daily basis. When a strobe device is used with such a high-sensitivity film, the shooting distance where the lighting effect of the strobe light can be obtained becomes long, and the background that would have been dark with the low-sensitivity film is reproduced with appropriate brightness. There are advantages such as being able to.

[0006]

By the way, in the automatic light control type strobe device as described above, since the strobe reflection light reflected from the main subject is received and the light amount is integrated, the reflection of the main subject is reflected. The relationship between the amount of strobe light emitted and the integrated amount of strobe reflected light changes depending on the ratio, the proportion of the main subject in the light receiving area received by the light receiving element in the shooting screen, and the like. For this reason, even if the main subject at the same shooting distance is stroboscopically shot, variations in the exposure amount due to the strobe light occur, and underexposure and overexposure are unavoidable.

On the other hand, in the high-sensitivity photographic film as described above, when the exposure amount is underexposed, the grain size is significantly deteriorated. For this reason, even when the automatic flash control device and high-sensitivity photo film are combined, the granularity of the subject will be worse even for subjects with an underexposure due to the strobe light due to differences in the reflectance of the main subject. Will end up.

The present invention has been made in view of the above circumstances, and an automatic light control type strobe device and lens capable of performing photography while suppressing deterioration of graininess even when a high-sensitivity film is used. It is intended to provide an attached film unit.

[0009]

In order to achieve the above object, in the strobe device according to the first aspect, the exposure amount by the strobe light is adjusted to be larger than the proper exposure amount in the range of +1.0 EV or less. The light emission stop level for stopping the flash light emission of the optical circuit is set.

In the film unit with a lens according to the present invention, the stroboscopic light emission of the built-in strobe device is stopped so that the stroboscopic light exposure amount becomes larger than the proper exposure amount in the range of +1.0 EV or less. The light emission stop level for setting the light emission is set.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the external appearance of a lens-fitted film unit incorporating a flash device embodying the present invention. The film unit with a lens is the unit body 2
And a label 3 that partially covers the unit main body 2. The unit main body 2 incorporates various photographing mechanisms such as a shutter device and a film feeding mechanism, and an automatic light control strobe device. There is.

The unit main body 2 is loaded with a film cartridge made up of a cartridge for storing an unexposed photographic film and a photographed photographic film at the time of manufacture. In this lens-fitted film unit, a high-sensitivity film such as ISO800 is loaded as a photographic film.

On the front surface of the unit body 2, the taking lens 4, the object side window 5a of the finder 5, the strobe light emitting portion 7 of the strobe device, the strobe operating member 8, and the light receiving window 9 for dimming.
Is provided. In addition, on the upper surface of the unit body 2,
A release button 10, a counter window 11 for displaying the number of remaining shots, and a charging display window 12 for displaying the completion of charging are provided. Furthermore, a winding knob 13 that is rotated for each frame is exposed on the back surface, and an eyepiece side window (not shown) of the finder 5 is provided at a position facing the objective side window 5a. Label 3 is the unit body 2
It is attached to the central part of the, and the photographing lens 4, the finder 5, the counter window 11 and the like are exposed to the outside through the openings provided in the respective parts.

The strobe operating member 8 is interlocked with a strobe switch of a strobe device. When the strobe operating member 8 is slid upward and set to an on position, the strobe switch is turned on and charging is started. After the charging is completed, when the release button 10 is pressed while the strobe operation member 8 is in the on position to perform photographing, strobe light is emitted from the strobe light emitting section 7 toward the subject in synchronization with this photographing. When the strobe operation member 8 is slid downward from the on position and set to the off position shown in the drawing, strobe light emission is prohibited.

A phototransistor 16 (see FIG. 2) serving as a light-receiving element for light control is arranged behind the light-receiving window 9. When strobe light is emitted, this phototransistor 16
Receives the reflected light from the subject with and controls the amount of strobe light.

FIG. 2 shows a circuit configuration of a strobe device built in the lens-fitted film unit. The strobe device includes a battery 21 as a power source, a booster circuit 22, a trigger circuit 23, a main capacitor 24, a strobe discharge tube 25,
It is composed of a dimming circuit 26, an operating voltage generating circuit 27, and the like. As the battery 21, for example, an AA type dry battery having an electromotive force of 1.5 V is used.

FIG. 3 shows a circuit example of the booster circuit 22 and the trigger circuit 23. The booster circuit 22 includes the strobe switch 3
1, an oscillating transistor 32, an oscillating transformer 33, a rectifying diode 34 and the like. The oscillating transistor 32 and the oscillating transformer 33 constitute a known blocking oscillating circuit. The low voltage of the battery 21 is converted into a high voltage and outputted to the secondary side of the oscillating transformer 33, and the high voltage is used to output the main capacitor 24. To charge.

The strobe switch 31 is turned on and off in conjunction with the sliding movement of the strobe operating member 8, and turned on by setting the strobe operating member 8 to the on position. While the strobe switch 31 is on, the blocking oscillation circuit operates to increase or decrease the primary side current flowing through the primary coil 33a of the oscillation transformer 33. Due to this increase / decrease in the primary side current, an alternating high voltage is generated in the secondary coil 33b. The rectifying diode 34 rectifies and outputs the alternating current generated in the secondary coil 33b.

The main capacitor 24 is connected between the output terminals of the booster circuit 22, that is, between the emitter terminal of the oscillation transistor 32 and the anode of the rectifying diode 34, and the output current from the booster circuit 22 causes a high voltage. Be charged. At the time of this charging, the main capacitor 24 is negatively charged so that the potential of the positive terminal indicated by “+” in the figure is constant and the potential of the negative terminal on the anode side of the rectifying diode 34 becomes low.

The strobe discharge tube 25 is connected between the terminals of the main capacitor 24. This strobe discharge tube 2
5 is arranged in the stroboscopic light emitting section 7, and when a trigger voltage is applied through the trigger electrode 25a, the electric charge of the main capacitor 24 is discharged between the electrodes to emit stroboscopic light.

The trigger circuit 23 includes a trigger capacitor 3
5, a synchro switch 36, a trigger coil 37 and the like. Like the main capacitor 24, the trigger capacitor 35 is charged with the output current from the booster circuit 22. The synchro switch 36 is turned on / off in synchronization with opening / closing of a shutter blade (not shown). When the shutter blade is fully opened and the synchro switch 36 is turned on while the strobe switch 31 is on, the charged trigger capacitor 35 causes a discharge current to flow to the primary side of the trigger coil 37. When the discharge current flows to the primary side, the trigger coil 37 generates a trigger voltage of, for example, about 4 kV on the secondary side, and applies this to the strobe discharge tube 25 via the trigger electrode 25a. As a result, strobe emission is started at the moment when the shutter blades are fully opened.

A light emitting diode 38 is connected between the terminals of the tertiary coil 33c of the oscillation transformer 33 in order to indicate that the main capacitor 24 has been charged. Due to the rise of the charging voltage of the main capacitor 24, the tertiary coil 33c
Due to the voltage increase between the terminals of the light emitting diode 38, the light emitting diode 38 lights up while the blocking oscillation circuit is operating when the main capacitor 24 is charged to the specified charging voltage. The light from the light emitting diode 38 is guided to the charging display window 12. The photographer can know the completion of charging by confirming the lighting of the light emitting diode 38 through the charging display window 12.

The operating voltage generating circuit 27 is composed of a power feeding capacitor 41, a resistor 42, and a Zener diode 43, and outputs an operating voltage necessary for the operation of the dimming circuit 26 during flash light emission. The power feeding capacitor 41, the resistor 42, and the Zener diode 43 are connected in series in this order,
It is connected in parallel with the main capacitor 24. That is, one end of the power feeding capacitor 41 is connected to the plus terminal of the main capacitor 24, the other end is connected to the anode of the Zener diode 43 via the resistor 42, and the cathode of the Zener diode 43 is the negative terminal of the main capacitor 24. It is connected to the.

When the main capacitor 24 is charged, the power feeding capacitor 41 is charged with the output current from the booster circuit 22 to the same charging voltage as the main capacitor 24 so that the potential on the resistor 42 side becomes low. The Zener diode 43 has a Zener voltage of, for example, about 6 V and is connected in parallel with the dimming circuit 26. When the trigger voltage is applied to the strobe discharge tube 25 and the electric charge of the main capacitor 24 starts discharging, the power feeding capacitor 4
The electric charge stored in 1 is discharged through the strobe discharge tube 25, the Zener diode 43, and the resistor 42. During this discharge, a potential difference corresponding to the Zener voltage is generated at the connection point Pa on the anode side and the connection point Pb on the cathode side of the Zener diode 43. This potential difference is output as an operating voltage for driving the dimming circuit 26.

The discharge current from the power feeding capacitor 41 is
In addition to flowing through the Zener diode 43, it is supplied as a current for operating the dimming circuit 26. The resistor 42 limits the magnitude of the discharge current of the power feeding capacitor 41 so that the dimming circuit 26 is continuously operated for the time required for performing the dimming operation.

As shown in FIG. 2, the dimming circuit 26 includes
The light receiving unit 45, the level adjusting unit 46, the switching unit 47, the turn-off capacitor 48, the resistor 49, the three-terminal type thyristor 50, and the like are included.

The light receiving section 45 includes the phototransistor 16 described above, an integration capacitor 53, a short distance correction resistor 54,
It is composed of an initialization resistor 55. Phototransistor 1
6, the collector terminal of which is connected to the cathode of the Zener diode 43 via the resistor 56. In addition, the emitter terminal of the phototransistor 16 and the Zener diode 4
A short-distance correction resistor 54 and an integration capacitor 53 are connected in series with the anode of No. 3, and an initialization resistor 55 is connected in parallel with them.

The light-receiving section 45 thus connected receives the stroboscopic light reflected from the subject by the phototransistor 16, and the photocurrent corresponding to the intensity of the received light is passed through the short-distance correction resistor 54 and the integration capacitor 53. And the charge of the integrating capacitor 53 is performed to integrate the light quantity of the strobe reflected light, and the sum of the voltage between the terminals of the short-distance correction resistor 54 and the charging voltage of the integrating capacitor 53, that is, the connection point Pa and the connection point Pc. The voltage between them is output as an integrated voltage Vi according to the integrated amount of light. This integrated voltage Vi tends to increase the potential on the side of the connection point Pc. A photodiode or the like may be used instead of the phototransistor 16.

As will be described later, there is a slight delay (hereinafter referred to as a switching delay) from when the integrated voltage Vi reaches a predetermined light emission stop voltage Vs to when the thyristor 50 is turned on and the strobe light emission is stopped. When the main subject is close to the subject, a slight switching delay causes a large increase in the exposure amount because the strobe reflection light is strong. A short-distance correction resistor 54 is provided to prevent such a problem.

The short-distance correction resistor 54 has an integrated voltage Vi corresponding to an inter-terminal voltage generated by a photocurrent flowing therethrough.
Increase. The stronger the reflected strobe light is, the larger the photocurrent is. Therefore, the inter-terminal voltage of the short-distance correction resistor 54 becomes higher as the strobe reflected light is stronger. Therefore, by the short-distance correction resistor 54, the integrated voltage Vi is made higher than the charging voltage of the integrating capacitor 53 as the reflected light from the strobe is stronger, and the time to reach the light emission stop voltage Vs is shortened. This shortens the time for the integrated voltage Vi to reach the light emission stop voltage Vs so as to cancel the delay until the strobe light emission is stopped, and improves the dimming accuracy when the main subject is close.

When the main subject is far, the strobe reflection light from the main subject is weak and the photocurrent flowing through the short-distance correction resistor 54 is small. Therefore, the short distance correction resistor 54
Has almost no effect of increasing the integrated voltage Vi.

The initialization resistor 55 discharges the electric charge remaining in the integration capacitor 53 after one flash emission is completed and initializes it. As a result, the light amount integration at the time of the next strobe emission is correctly performed.

The level adjusting section 46 comprises a fixed resistor 57, a variable resistor 58, and an adjusting transistor 59. One end of the fixed resistor 57 is connected to the connection point Pb, the other end is connected to one end of the variable resistor 58, and the other end is connected to the connection point Pa via the variable resistor 58. The resistance value of the variable resistor 58 is adjustable.
The adjusting transistor 59 is of NPN type, its base terminal is connected to the connection point Pc, and its emitter terminal is the connection point Pd of the fixed resistor 57 and the variable resistor 58.
It is connected to the. The adjusting transistor 59 is turned on when a predetermined on-voltage V1 is applied as an input voltage between the base and the emitter to make the collector-emitter conductive.

Fixed resistor 5 connected in series as described above
7. The variable resistor 58 divides the operating voltage kept constant by the Zener diode 43 to generate an offset voltage V2 between both terminals of the variable resistor 58 to raise the emitter potential of the adjusting transistor 59. As a result, when the integrated voltage Vi reaches the light emission stop voltage Vs (= V1 + V2) which is the sum of the ON voltage V1 and the offset voltage V2, the adjustment transistor 59 is turned on, and the adjustment of the variable resistor 58 is performed. The emission stop voltage Vs corresponding to the emission stop level can be adjusted by increasing or decreasing the offset voltage V2.

When the resistance value of the variable resistor 58 is increased (the offset voltage V2 is increased) to increase the light emission stop voltage Vs, the light emission stop level is increased and the exposure amount by the strobe light is adjusted to be higher. On the contrary, the resistance value of the variable resistor 58 is made small (the offset voltage V2 is made small).
Then, when the light emission stop voltage Vs is reduced, the light emission stop level is lowered and the exposure amount by the strobe light is adjusted to be low.

The fixed resistor 57 and the variable resistor 58, which are connected in series between the connection points Pa and Pb, are initialized by discharging the turn-on capacitor 48 and a function-decreasing capacitor 65, which will be described later, after completion of strobe light emission. It also has a function.

The switching unit 47 is composed of an NPN type transistor 47a and a PNP type transistor 47b. The collector terminal of the transistor 47a is connected to the base terminal of the transistor 47b and the collector terminal of the adjusting transistor 59, and is also connected to the connection point Pb via the resistor 61. The base terminal of the transistor 47a is connected to the collector terminal of the transistor 47b, and the emitter terminal is connected to the connection point Pa via the resistor 62. The emitter terminal of the transistor 47b is connected to the connection point Pb.

When the adjusting transistor 59 is turned on,
The base terminal of the transistor 47b is connected to the connection point Pa via the adjusting transistor 59 and the variable resistor 58, and the base potential decreases to turn on. Transistor 4
When 7b is turned on, the transistor 47a is turned on by the base current flowing between the emitter and collector of the transistor 47b. And the transistor 47
When a is turned on, this transistor 47a, resistor 62
Since the base current flows through the transistor 47b through the transistor 47b, even if the adjusting transistor 59 is turned off, the base current continuously flows through the transistor 47b and is kept on. As a result, both of the transistors 47a and 47b, that is, the switching transistor 47b is switched. The unit 47 continues to turn on. Switching unit 47 allows current to flow from the emitter terminal of transistor 47b toward the emitter terminal of transistor 47a when it is on.

The turn-on capacitor 48 has one end connected to one end of the resistor 49 and the other end connected to the connection point Pa. The other end of the resistor 49 is connected to the connection point Pb. When the stroboscopic light emission is started, the turn-on capacitor 48 is charged by the discharge current of the power feeding capacitor 41 flowing through the resistor 49.

When the switching unit 47 is turned on, the turn-on capacitor 48 is discharged via the resistor 49, the switching unit 47 and the resistor 62. When the discharge current flows through the resistor 49 during this discharge, a terminal voltage Vr corresponding to the discharge current and the resistance value of the resistor 49 is generated between the terminals of the resistor 49.

Thyristor 50 as a contactless switch
Has a gate and a cathode connected to both ends of the resistor 49, and an anode connected to the plus terminal of the main capacitor 24 via the choke coil 64. The thyristor 50 is turned on by applying the inter-terminal voltage Vr of the resistor 49 when the turn-on capacitor 48 is discharged between the gate and the cathode as a gate voltage. Thyristor 5
When 0 is turned on, that is, when its anode / cathode is conductive, the main capacitor 24 is connected to the strobe discharge tube 2
The thyristor 50 having an impedance lower than 5 is discharged through the anode and cathode of the thyristor 50, and the stroboscopic light emission is stopped.

Since the main capacitor 24 is charged with a high voltage, the discharge current flowing from the main capacitor 24 to the thyristor 50 suddenly increases and becomes excessive at the moment when the thyristor 50 is turned on, and the thyristor 50 is discharged. It may be deteriorated or destroyed. In order to prevent such a problem, the choke coil 64 is provided between the main capacitor 24 and the thyristor 50 as described above.
Connect the main capacitor 24 to the thyristor 50.
It is prevented that the discharge current flowing through the capacitor suddenly increases and becomes excessive.

Further, in the light control circuit 26, in order to prevent the strobe device from fully emitting light without turning on the thyristor 50 when the main subject is at a close distance, the light receiving portion immediately after the start of strobe light emission. A function lowering capacitor 65 for lowering the function of 45 is connected in parallel with the light receiving circuit 45. Immediately after the start of strobe light emission, the function lowering capacitor 65 is charged by the current flowing through the resistor 56, so that the charging voltage, that is, the voltage applied to the light receiving unit 45 gradually increases. In this way, the light receiving unit 45 is operated from the start of strobe light emission until a predetermined time elapses.
The voltage applied to the turn-on capacitor 4 is reduced to reduce the photocurrent flowing through the phototransistor 16.
The integrated voltage Vi reaches the light emission stop voltage Vs after 8 is charged to a level necessary to surely turn on the thyristor 50.

The dimming circuit 26 configured as described above is
Even if the amount of exposure due to the strobe light varies due to differences in the reflectance of the main subject, the apparent size of the main subject, etc., in order to prevent underexposure in most cases, the amount of exposure by the strobe light is used. Is +1.
The emission stop level is set to be higher than the proper value in the range of 0 EV or less.

In consideration of the depiction performance of the background and the like, it is preferable that the exposure amount by the stroboscopic light is +
It is preferable to set the light emission stop level so as to increase in the range of 0.5 EV or less. Also, in the case of shooting at a short distance, when a person occupies most of the shooting screen, it depends on the color of the face, but the image quality may deteriorate even if the shot image is reproduced with a little underexposure. I don't feel that much. For this reason, it is also preferable to set the light emission stop level so that the exposure amount by the strobe light is appropriate or slightly higher than the appropriate value on the near side of the shooting distance.

In this example, the variable resistor 58 of the adjusting section 46 is used.
The light emission stop level is set so that the exposure amount by the strobe light is +0.5 EV higher than the appropriate amount by adjusting the resistance value of the light emission stop voltage Vs. Further, by adjusting the resistance value of the short-distance correction resistor 54, the exposure amount by the strobe light on the short-distance side is set to be slightly higher than appropriate. In addition,
When the distance is short, that is, when the photocurrent is large, the integrated voltage Vi becomes faster than the switching delay and the light emission stop voltage Vs becomes faster.
By adjusting the resistance value of the short-distance correction resistor 54 so as to reach, the dimming level can be set so that the exposure amount by the strobe light on the short-distance side is slightly higher than appropriate.

An example of the relationship between the shooting distance of the strobe device set as described above and the exposure amount by the strobe light is shown by a solid line in FIG. In FIG. 4, as the exposure amount by the strobe light,
The difference between the proper exposure amount and the actual exposure amount is represented by an EV value and drawn. The exposure amount difference is calculated by irradiating a 50 mm × 50 cm gray standard reflecting plate, to which a flash meter is attached, with strobe light, and reading the measured value of the flash meter for each photographing distance. In addition, the alternate long and short dash line in FIG. 4 shows an example of the relationship between the shooting distance and the exposure amount difference of the conventional auto strobe device, and the alternate long and two short dashes line shows the case where the flash control function of the stroboscopic device is disabled and full flash is performed. The relationship between the shooting distance and the exposure amount difference is shown.

Next, the operation of the above configuration will be described.
When performing nighttime photography or indoor photography, the photographer slides the strobe operation member 8 to the ON position. This allows
The stroboscope 31 is turned on, the booster circuit 22 starts operating, and the main capacitor 24 and the trigger capacitor 3
5. The power feeding capacitor 41 is charged. When the main capacitor 24 reaches the specified charging voltage, the light emitting diode 38 lights up. When the photographer confirms that the light emitting diode 38 is turned on through the charge display window 12, the photographer looks through the finder 5 to determine the composition, and then presses the release button 10 to perform photographing.

The shutter blade is opened and closed by pressing the release button 10, and the synchro switch 36 is turned on at the moment when the shutter blade is fully opened. Since the flash switch 31 is turned on, when the synchro switch 36 is turned on, the trigger capacitor 35 is discharged and a trigger voltage is generated on the secondary side of the trigger coil 37. The trigger voltage generated in the trigger coil 37 is the strobe discharge tube 25.
The electric charges stored in the main capacitor 24 are discharged through the strobe discharge tube 25. As a result, strobe light is emitted from the strobe discharge tube 25, and the strobe light is emitted from the strobe light emitting section 7 toward the subject.

Simultaneously with the discharge of the main capacitor 24, the power feeding capacitor 41 starts discharging through the strobe discharge tube 25, and a part of this discharge current is generated by the resistor 49, the turn-on capacitor 48, the resistor 42, and the power feeding capacitor 41. And the turn-on capacitor 48 is charged. Further, since a part of the discharge current from the power feeding capacitor 41 flows as a Zener current of the Zener diode 43, both ends of this Zener diode 43 are kept at a constant Zener voltage. This Zener voltage is supplied to the dimming circuit 26 as an operating voltage.

When the subject is irradiated with the strobe light, the strobe light is reflected by the subject, and a part of the strobe reflected light enters the phototransistor 16 through the light receiving window 9,
A photocurrent having a magnitude corresponding to the intensity of the strobe reflected light flows through the phototransistor 16 to charge the integrating capacitor 53. Immediately after the start of strobe light emission, the function of the light receiving unit 45 is deteriorated by the function lowering capacitor 65, so that the magnitude of the photocurrent is smaller than the intensity of the strobe reflected light received during that period.

In this way, the phototransistor 16
The integrating capacitor 53 integrates the light amount of the strobe reflected light received in step S1, and the integrated voltage Vi rises. Integrated voltage Vi
Reaches the light emission stop voltage Vs, the adjustment transistor 5
9 is turned on, and in response thereto, the switching unit 47 is turned on.

When the switching unit 47 is turned on, the turn-on capacitor 48 is discharged through the resistor 49, the switching unit 47 and the resistor 62, and the inter-terminal voltage Vr generated across the resistor 49 at this time turns on the thyristor 50. As a result, the electric charge stored in the main capacitor 24 is discharged through the thyristor 50 instead of the strobe discharge tube 25, and the light emission in the strobe discharge tube 25 is stopped. Then, when the charging voltage of the main capacitor 24 becomes a predetermined value or less, the thyristor 50 is turned off.

By stopping the stroboscopic light emission as described above, the exposure amount of the main subject by the stroboscopic light is controlled, and the photographic film is exposed. Even if the exposure amount of the strobe light becomes smaller than the proper amount due to the influence of the reflectance and size of the main subject, the light emission stop level is set to be +0.5 EV more than the proper exposure amount at the maximum. Most of the actual exposure amount by the strobe light does not cause underexposure because it is set to. Therefore, even when a high-sensitivity film is used, the deterioration of the image quality, particularly graininess is small, and a high-quality photographed image can be obtained.

Further, as shown in FIG. 4, the conventional automatic light control type strobe device causes a large overexposure on the short distance side (about 1 m or less), and the difference in the exposure amount from the background where the strobe light is not effective. growing. That is, in the conventional automatic light control type strobe device, if the correction is performed during the print processing so that the density of the main subject becomes appropriate, only a print photograph with a completely dark background can be obtained. However, in the strobe device configured as described above, overexposure does not occur even at a short distance due to the function of the short-distance correction resistor. Further, since the light emission stop level is higher than that of the proper exposure amount, underexposure is less likely to occur even on the long distance side.

The circuit of the strobe device described in the above embodiments is an example, and various types of booster circuits, trigger circuits, dimming circuits, etc. can be adopted. Also, various methods can be adopted for adjusting the dimming level, for example, by mounting a filter having an appropriate concentration on the front surface of the phototransistor that receives the reflected strobe light, or by integrating the condenser of the light receiving unit. The dimming level may be adjusted by adjusting circuit constants such as.

In the above embodiment, an example of the lens-fitted photo film unit has been described, but the present invention can also be applied to a lens-fitted photo film unit having a diaphragm switching mechanism, a compact camera and the like. Further, it can also be used for a strobe device mounted on a camera or the like.

[0058]

As described above, according to the present invention,
The light emission stop level for stopping the strobe light emission was set so that the light exposure amount by the strobe light would be higher than the appropriate light exposure amount in the range of +1.0 EV or less, so the reflectance of the main subject and the light receiving element in the shooting screen Even if the relationship between the amount of flash light emitted and the integrated amount of reflected strobe light changes due to the proportion of the main subject in the light receiving range received by It is hard to become. Therefore, even when a high-sensitivity photographic film is used, it is possible to obtain a high-quality photographed image with less deterioration of graininess.

[Brief description of drawings]

FIG. 1 is a perspective view showing an appearance of a lens-fitted film unit embodying the present invention.

FIG. 2 is a circuit diagram showing a dimming circuit of a strobe device.

FIG. 3 is a circuit diagram showing an example of a booster circuit and a trigger circuit.

FIG. 4 is a graph showing the relationship between the shooting distance and the difference in exposure amount between proper exposure with strobe light.

[Explanation of symbols]

7 Strobe emission part 9 Light receiving window 16 phototransistor 24 Main capacitor 25 Strobe discharge tube 26 Dimming circuit 45 Light receiving part 53 integrating capacitor 54 Short-distance correction resistor 46 Level adjuster

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G03B 17/04 G03B 17/04 G03C 3/00 575 G03C 3/00 575A 575B H05B 41/32 H05B 41/32 FF term (reference) 2H002 CD05 CD07 CD09 FB14 GA26 HA28 JA05 2H053 AD08 AD12 AD14 BA54 2H101 AA01 3K098 AA03 AA04 AA05 AA06 AA10 AA17 AA19 AA30 BB10 BB13 BB14

Claims (2)

[Claims] 1. An automatic dimming system having a dimming circuit for receiving strobe reflected light from a subject, integrating the amount of light, and stopping strobe light emission when the integrated amount of light reaches a predetermined light emission stop level. In the strobe device, the dimming circuit has an exposure amount of + 1.0E by the strobe light.
A strobe device, wherein the light emission stop level is set so as to be larger than an appropriate exposure amount in a range of V or less. 2. An automatic dimming type having a dimming circuit for receiving strobe reflected light from a subject, integrating the quantity of light, and stopping strobe light emission when the quantity of integrated light quantity reaches a predetermined light emission stop level. In a film unit with a lens having a built-in strobe device, the dimming circuit has an exposure amount of + 1.0E by strobe light.
A lens-fitted film unit, wherein the light emission stop level is set so as to be larger than an appropriate exposure amount in a range of V or less.