JPH0514256B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an automatic exposure control device for a camera, and more specifically, during daytime synchronized photography using a strobe, when the shooting distance is within a predetermined distance, the exposure value is adjusted to be lower than the appropriate value. The present invention relates to a device that is made small to make the standing light (natural light) present in the photographic scene insufficient, and supplements it with strobe light to maintain the exposure value at an appropriate value when the distance is exceeded.

If the main subject is dark compared to the background, such as in backlighting, the main subject will be underexposed, but if you use a strobe in conjunction with daytime sync shooting,
Since the main subject is illuminated with strobe light, this main subject can also be properly exposed. Furthermore, when shooting indoors, or shooting in the morning or evening, where the intensity of ambient light present in the shooting scene (subject brightness) is relatively low, the color temperature changes, resulting in poor color reproducibility. Since strobe light has a color temperature close to that of sunlight, using a strobe to take pictures in the above cases can improve color reproducibility.
With 35mm roll film, there is a latitude of +4EV on the overexposed side, so EE is 100% (EV = LV)
Although it is possible to obtain good print photos even when shooting with a strobe under
Accurate exposure control is required. When using an instant camera that uses this instant film, the exposure value is set to 80% of the appropriate value during daytime synchronization shooting.
(0.8EV=LV), correct the exposure value so that the constant light that contributes to film exposure is 20% short, and supplement this shortfall of constant light with strobe light.
%, and an automatic exposure control device is known that exposes a film using a mixture of light of 20% and strobe light.

Strobes have a fixed maximum light output, so
Up to a certain distance, film exposure can be performed by accurately maintaining the ratio of 80% constant light and 20% strobe light, but beyond this distance, the ratio of strobe light contributing to film exposure gradually decreases, and At distances greater than that, the proportion of strobe light becomes zero. Therefore, the image appearing on the instant film will have a high density because it will be underexposed by the amount of the strobe light.

SUMMARY OF THE INVENTION The present invention is intended to solve the above-mentioned drawbacks, and it is an object of the present invention to provide an automatic exposure control device that can perform almost appropriate exposure without being affected by the photographing distance.

In the present invention, during daytime synchronized photography, when the distance is within a reference distance defined between the distance at which the proportion of strobe light contributing to film exposure starts to decrease and the distance at which the strobe light no longer contributes to film exposure, The exposure value is set to be smaller than the appropriate value, and when the reference distance is exceeded, the exposure value becomes the appropriate value.

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 shows an embodiment of an automatic exposure control device of the present invention. A light-receiving element 1 and a resistor 2 are connected in series, and a photocurrent flows through the light-receiving element 1 in accordance with the average value of the intensity of stationary light (subject brightness) present in a photographic scene. This photocurrent is input to the buffer circuit 3, where it is exchanged into a voltage value, and then
It is input to one side input terminal of the analog switch 4 and the comparator 5. Note that in this example, CdS is used as the light receiving element 1;
Because CdS has a slow response, it does not follow the reflected light of the instantaneous strobe light. Comparator 5
, the reference voltage divided by resistors 6 and 7 is input to the + side input terminal, and the steady light intensity at which the shutter speed reaches the limit of camera shake (in this example, it is BV3,
At proper exposure using ISO100 film, LV=
(EV=8), the output of the comparator 5 becomes "H". Therefore, the comparator 5 outputs a signal indicating that a camera shake limit will occur if the strobe is not used, and this signal is input to the AND circuit 8.

The constant voltage circuit 9 outputs a voltage of logic level "H", and a strobe switch 10 and a distance switch 11 are connected to this, respectively. The strobe switch 10 is turned on in conjunction with the main switch of the strobe or the pop-up of a movable strobe, and generates a strobe use signal indicating the usage status of the strobe. The distance switch 11 generates a distance signal by turning on and off depending on the shooting distance, and is set at a distance at which the proportion of strobe light contributing to film exposure begins to decrease (3 m in this embodiment).
and the distance at which the strobe light no longer contributes to film exposure (in this embodiment, 6 m) is turned on. This distance switch 11
is turned on and off in conjunction with the lens mirror copper 12, for example.

A signal obtained by inverting the strobe use signal, the distance signal, and the output signal of the comparator 5 with an inverter 13 is input to an AND circuit 14,
From the logical product, it is determined whether daytime synchro photography is being performed and the photographing distance is within the reference distance. If this condition is met, proper exposure can be achieved with a mixture of ambient light and strobe light, so the output signal of the AND circuit 14 becomes "H" and the transistor 15 is turned on.
If the above conditions are not met, the shooting distance exceeds the effective distance for strobe photography.
The output signal of the AND circuit 14 becomes "L", and the transistor 15 is turned off.

The variable resistor 16 is adjusted according to the film sensitivity, and a resistor 1 is connected in series with the variable resistor 16.
7 and 18 are connected. The transistor 15 is connected in parallel to this resistor 17, and the connection point 19 is turned on and off by the transistor 15.
voltage changes. The voltage at this connection point 19 is applied to the shutter control circuit 20 as a film sensitivity value (SV).
When the transistor 15 is turned on, the exposure value (EV) becomes smaller than the light value (LV), resulting in underexposure.

The shutter control circuit 20 is widely known in the camera field, and the switch 21 is turned off at the same time as the shutter is opened, and the capacitor 22 is supplied with a current determined according to the brightness of the subject and the film sensitivity.
is charged. When this capacitor 22 reaches a predetermined voltage, the current of the magnet 23 is cut off.
The shutters are closed. This shutter uses shutter blades that also serve as an aperture, and controls exposure using a program method in which the aperture aperture and shutter speed are combined in a predetermined relationship.

The series circuit of resistors 24 and 25 is used at LV8, where the shutter speed reaches the limit of camera shake when using a strobe.
This is to release the EE and fix the shutter speed (in this example, 1/3 second) at which the camera shake limit speed is higher than the maximum aperture and the aperture is open in the following cases.
The voltage at that connection point is input to the analog switch 26. This analog switch 26 is
It turns on when the output signal of the AND circuit 8 is "H".
On the other hand, since the output signal of the AND circuit 8 is inverted by the inverter 27 and then inputted to the analog switch 4, the output signal of the AND circuit 8 is "L".
Turns on when These analog switches 4,
The voltage selectively extracted at step 26 is input to the shutter control circuit 20 as a brightness value (BV).

Next, the operation of this automatic exposure control device will be explained. When photographing without using a strobe, the strobe switch 10 is turned off, so the output signal of the AND circuit 8 is "L". Therefore, since the analog switch 4 is on and the analog switch 26 is off, a voltage corresponding to the steady light intensity measured by the light receiving element 1 is inputted to the shutter control circuit 20 as a brightness value (BV). On the other hand, since the output signal of the AND circuit 14 is "L", the transistor 15 is off, and the voltage at the connection point 19 is inputted to the shutter control circuit 20 as a sensitivity value (SV).

When the release button (not shown) is pressed, the shutter starts to open, and the switch 21 is turned off in conjunction with this, and the capacitor 22 is supplied with current according to the brightness value (BV) and film sensitivity value (SV).
is charged. When the capacitor 22 reaches a predetermined voltage, the magnet 23 is de-energized and the shutter blade begins to close.

When shooting without using a strobe, the shutter operates so that the light value (LV) and exposure value (EV) are equal. Therefore, since it is 100% EE, the film exposure amount is an appropriate value within the EE interlocking range.

When shooting with a strobe, the exposure changes depending on whether the steady light intensity is at least BV3, which is the limit speed for camera shake, and whether the shooting distance is at least the reference distance.

When the steady light intensity is BV3 or higher, it is daytime synchronized shooting using a strobe, and in this case,
Since the output signal of the AND circuit 8 is "L", the analog switch 4 is on. When the shooting distance is within the reference distance, the distance switch 11 is turned on, so the output signal of the AND circuit 14 becomes "H" and the transistor 15 is turned on. Therefore, the voltage at the connection point 19 becomes high, and even if an ISO 100 film is used, for example, it becomes the same as when an ISO 125 film is used. Therefore, LV=
It becomes 0.8EV, and the film exposure amount by constant light is 80% of the appropriate value. This 20% deficit is supplemented with strobe light as described later, and exposure is performed with a mix of 80% constant light and 20% strobe light. Incidentally, in the case of instant film, there is a latitude of ±1/3 to 1/2 EV, so in order to stay within this range, for example, the strobe light may be set to 30%, so that the exposure is slightly overexposed.

During daytime synchronized photography when the photographing distance exceeds the reference distance, the distance switch 11 is turned off, and therefore the transistor 15 is also turned off. As a result, the shutter operates so that LV=EV, resulting in 100% EE, and the amount of film exposure due to constant light becomes an appropriate value.

If the steady light intensity is lower than BV3, which is the camera shake limit speed, normal strobe photography is performed. At this time, the output signal of the AND circuit 8 is "H"
Therefore, the analog switch 26 is turned on and the analog switch 4 is turned off. Since a constant voltage divided by resistors 24 and 25 is input to the shutter control circuit 20 as a brightness value (BV), the shutter speed is fixed at 1/32 second.

In the embodiment described above, the inverter 13 is provided to adjust the film sensitivity only during daytime synchronized photography, but the inverter 13 may be omitted. In this case, the film sensitivity will be adjusted depending on the shooting distance even during nighttime strobe photography. However, in most flash photography at night, the constant light no longer contributes to film exposure, so the shutter speed simply changes from 1/30 second to 1/38 second, and has no effect on film exposure.

FIG. 2 shows a shutter program diagram. As is well known, the shutter blades of this shutter also serve as an aperture. At exposure values below EV10, the aperture is wide open (F2.8) and only the shutter speed changes. Above EV10, both aperture and shutter speed change. Furthermore, when using a strobe and the steady light intensity is lower than BV3, the limiter works and fixes it to EV8, the shutter speed becomes 1/32 second and the aperture becomes 2.8.

FIG. 3 shows an embodiment of an auto strobe that is used with the automatic exposure control device of the present invention and controls the amount of light emitted so as to compensate for the lack of constant light during daytime synchronized photography. The strobe reflected light detection section 30 operates in synchronization with the light emission of the flash discharge tube 29, measures the strobe reflected light reflected from the subject, and outputs a signal V _F having the waveform shown in FIG.
This signal V _F is integrated by an integrating section 31 to become a signal V _FC .

The stationary light detection unit 32 measures the intensity of stationary light existing in the scene to be photographed, that is, the subject brightness, and its output signal is input to the stationary light intensity setting unit 33 and the aperture aperture correction unit 34. be done. The steady light intensity setting section 33 outputs a signal V A determined depending on the steady light intensity, and the aperture aperture correction section 3 outputs a signal V _A determined depending on the steady light intensity.
4 outputs a signal _VTH determined according to the aperture diameter shown in FIG.

The adding section 35 receives the signal output from the integrating section 31.
V _FC and the signal V _A output from the steady light intensity setting section 38 are added, and the resulting signal V _FA is output.

The comparator 36 receives the signal output from the adder 35.
V _FA and the signal output from the aperture correction section 34
When the signal V _FA becomes larger than the signal V _TH , a light emission stop signal is outputted and sent to _the well-known light emission control circuit 37. This light emission control circuit 37
The main capacitor is charged when the main switch 38 is on, and when the synchro switch 39 is on, the electrical energy stored in the main capacitor is applied to the flash discharge tube 29 to cause it to emit light, and the light emission stop signal is issued. When input, the flash discharge tube 29 stops emitting light.

FIG. 4 is a waveform diagram of the signal shown in FIG. 3. The steady light intensity setting unit 33 outputs a constant signal regardless of the steady light intensity at a steady light intensity of BV3 (LV8 at ISO 100) or higher at which the shutter speed reaches the limit of camera shake. When the shutter speed is fixed at the camera shake limit speed, at a constant light intensity below, for example, BV1 (LV6 at ISO100 in this example) at which the proportion of constant light contributing to film exposure becomes substantially zero, A constant signal is output regardless of the steady light intensity. Steady light intensity is BV1 (LV6)~
Between BV3 (LV8), it outputs a signal that changes in proportion to the constant light that contributes to film exposure. Note that this proportional change includes not only a linear change as in this embodiment, but also a curved or stepwise change.

The aperture aperture correction unit 34 changes the amount of light emitted by the flash discharge tube 29 according to the aperture aperture during strobe photography, and in the case of the shutter program diagram shown in FIG. If the film is LV10), it becomes a constant value when
Outputs a signal V _TH that gradually increases when BV5 is exceeded.

A signal V _A determined depending on this steady light intensity
When the sum of the signal V FC and the signal V _FC corresponding to the amount of reflected light from the strobe reaches a signal V _TH determined depending on the intensity of the steady light, the flash discharge tube 29 stops emitting light.

FIG. 5 shows signal waveforms when strobe photography is performed under arbitrary steady light intensity. The signal V _FA of the adder 35 changes with time, while the signal V _TH of the aperture aperture corrector 34 remains constant regardless of the passage of time. When this signal V _FA exceeds the signal V _TH , the flash discharge tube 29 stops emitting light.

FIG. 6 shows the amount of light on the image plane of the film when photographing is performed within the effective strobe distance (3 m in this example) at which the auto strobe operates normally.
For daytime synchronized shooting at LV8 or higher, constant light is approximately 80% of the appropriate exposure, and strobe light is approximately 20% of the appropriate exposure.
Film exposure is performed using light mixed with only 1.
Note that if you do not use a strobe, the ambient light will
Automatic exposure is performed to achieve 100% proper exposure. Also, the ratio of strobe light and constant light is
It can be arbitrarily determined in consideration of the auto strobe guide number, etc.

Between LV6 and LV8, the shutter is fixed at 1/32 seconds, so the steady light component decreases and the strobe light component increases to complement this. This results in
Excessive overexposure can be prevented.

At LV6 or lower, the camera will use the original strobe light, and the strobe light will provide 100% proper exposure.

FIG. 7 shows the relationship between photographing distance and film exposure amount during daytime synchronized photography.
The auto strobe shown in Figure 3 operates normally when the strobe is within 3 meters, which is the effective strobe distance.
The film is exposed to a mix of 80% constant light and 20% strobe light. However, if the photographing distance exceeds 3 m, the subject cannot be sufficiently illuminated, so the proportion of strobe light contributing to film exposure decreases with distance. When the photographing distance reaches 6 m, the strobe light hardly contributes to film exposure, resulting in underexposure. Therefore, this 6 m is set as the reference distance mentioned above, and when the distance is greater than or equal to this reference distance, the distance switch 11 shown in FIG. 1 is turned off. Therefore, when the shooting distance is 6m or more, LV=EV, and constant light
100% film exposure is done. Note that in this case, the strobe simply emits light.

FIG. 8 shows an example in which the reference distance is set to 4.5 m. In this example, the shooting distance is 4.5
Since LV=EV when the distance reaches m, it is possible to prevent underexposure between 4.5 m and 6 m.

FIG. 9 shows an example in which the reference distance is set to 3 m.

FIG. 10 shows an example of distance signal generating means. A rack gear 44 is provided integrally with the distance adjustment knob 43, and a pinion 45 is rotated by the rack gear 44. This pinion 4
The rotation of 5 is transmitted to a lens barrel 47 having a gear 46, and the photographing lens 48 is extended in the optical axis direction. This is well known as a focus adjustment mechanism, so
Disclosure of its specific structure will be omitted.

A projection 49 is formed on a portion of the rack gear 44, and the distance switch 50 (indicated by reference numeral 11 in FIG. 1) is turned on by the projection 49. Since this rack gear 44 is moved by the distance adjustment knob 43, the distance adjustment knob 43
is aligned within the reference distance mentioned above,
Distance switch 50 is turned on.

FIG. 11 shows an embodiment in which a distance signal is obtained from a distance measurement module. Various methods have been implemented for the distance measuring module 51, and the present invention can utilize any of these methods. In addition to the AF signal indicating focus detection, a distance signal indicating whether the distance is within the reference distance may be extracted from the ranging module 51.

In the above embodiment, the exposure value is corrected by changing the film sensitivity, but it is of course possible to change the brightness value measured by the light receiving element or the light value obtained by calculating the film sensitivity value and the brightness value. It is.

The present invention having the above configuration changes the exposure value depending on the photographing distance during daytime synchronized photography, so when the photographing distance is longer than that at which the strobe does not work, the conventional device would be underexposed, but the present invention Now you can get the exposure right. Therefore, the effect of the present invention is significant in cameras using Latude's narrow instant film, and beautiful instant photos can be taken.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of the present invention. FIG. 2 is a shutter program diagram of the automatic exposure control device shown in FIG. 1. FIG. 3 is a block diagram showing one embodiment of an autostrobe used with the automatic exposure control device of the present invention. FIG. 4 is a waveform diagram of the circuit shown in FIG. 3, with the steady light intensity plotted on the horizontal axis. FIG. 5 is a waveform diagram with time plotted on the horizontal axis under arbitrary steady light intensity. 6th
The figure is a graph showing the ratio of steady light and strobe light that contribute to film exposure when photographing within the effective strobe distance. 7 through 9 show the relationship between the photographing distance and the film exposure amount during daytime synchronized photography, and show graphs when the reference distance is changed. FIGS. 10 and 11 are explanatory views showing embodiments of the distance signal generating means, respectively. 1... Light receiving element, 10... Strobe switch,
11... Distance switch, 4, 26... Analog switch, 16... Film sensitivity setting resistor, 43
... Distance adjustment knob, 47 ... Lens barrel, 48
...Photographing lens, 50...Distance switch.

Claims (1)

[Claims] 1. A shutter blade that also serves as an aperture is provided, and the aperture aperture and shutter speed are program-controlled according to the intensity of the ambient light and the film sensitivity value. When the brightness is below the brightness level, this is an automatic exposure control device that regulates the shutter speed to the first shutter speed, which is at least the shutter speed that does not cause camera shake and has an open aperture. means for detecting the strobe reflected light coming through a fixed aperture; means for integrating the output of the strobe reflected light detecting means and outputting an integral signal; means for detecting stationary light through a fixed aperture; means for outputting a first signal determined according to the output of the detection means; means for adding the integral signal and the first signal to output an added signal; , means for outputting a second signal based on the output of the steady light detection means, means for comparing the addition signal and the second signal and outputting a light emission stop signal, and the shutter blade also serving as an diaphragm detects the steady light. A strobe for use with an auto strobe device comprising a light emission control circuit that causes a flash discharge tube to start emitting light when the aperture aperture determined according to the intensity of the flash is reached, and stops emitting light when the light emission stop signal is input. means for generating a strobe signal indicating whether the strobe is in use; means for generating a distance signal indicating whether the photographing distance is within a predetermined distance; and means for generating a distance signal indicating whether the shooting distance is within a predetermined distance; means for detecting and generating a high intensity signal;
and When inputting each of the above signals and determining that the shooting conditions are such that the shooting distance is within a predetermined distance for high-intensity strobe photography, the amount of constant light contributing to film exposure will be less than the appropriate value. 1. An automatic exposure control device comprising an exposure correction means for adjusting the exposure to a substantially appropriate value under other shooting conditions. 2. Claim 1, wherein the exposure correction means comprises an AND circuit for calculating the logical product of each of the signals, and means for adjusting the film sensitivity value according to the output signal of the AND circuit. Automatic exposure control device as described in section. 3. The film sensitivity value adjusting means includes a plurality of resistors connected in series, and a switching element connected in parallel to at least one of these resistors and turned on and off by the output of the AND circuit. The second claim characterized in that
Automatic exposure control device as described in section.