JPH0830837B2 - Camera exposure controller - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention uses the TTL automatic light control method according to the exposure value obtained from the photometric data of the central area of the shooting screen (hereinafter referred to as the field) to be shot. The present invention relates to an exposure control device for a camera capable of flash photography.

B. Conventional Technology As a method for measuring the brightness of a subject, a partial metering method in which only the central area of the field is illuminated as shown in FIG. 7 is used to measure the central area of the field as shown in FIG. A center-weighted photometry system for preferential photometry is known, as shown in FIG. 9, which is a multi-pattern photometry system in which the field is divided into, for example, five regions, and each region is individually metered. In addition, in the multi-pattern photometry method, it is possible to select a method that places emphasis on the photometry information in the central area.

On the other hand, the TTL automatic light control method is known as a flash photography method using a flash tube. This is the amount of light incident through the taking lens at the shutter speed set within the time slower than the limit tuning time of the flash device and the aperture value corresponding to this, that is, from the subject by the flash light. The amount of reflected light is measured, and when a predetermined level is reached, light emission is stopped and proper exposure is obtained.

C. Problems to be solved by the invention As shown in FIG. 10, when a person is placed in the center of the field and the background is bright and the luminance ratio of both is large, the person is photographed with proper exposure. So-called daytime sync photography is performed. However, as described above, with a camera that calculates the exposure value based on the photometric information of the central area of the scene, such as the partial metering method or the center-weighted method, the exposure value suitable for a person whose brightness is lower than the background is used. Therefore, there is a possibility that the background may be over at the time of daytime synchronization shooting.

When the brightness of the subject due to natural light is low, such as at night or indoors, the shutter speed is usually fixed at the limit tuning time (for example, 1/125, 1/250) of the flash device. Therefore, although the proper exposure can be obtained for the main subject by the TTL automatic light control, the background is not fully exposed because the shutter speed is fast, and the background is underexposed.

An object of the present invention is to provide an exposure control device for a camera, which can appropriately expose both of a main subject and a background when the exposure value is obtained from the photometric information of the central region of the field even when the luminance ratio between the main subject and the background is large. To do.

D. Means for Solving Problems According to the present invention, light emitted from a flash tube and then reflected by a subject is measured through a photographing lens, and when the amount of light reaches a predetermined level, the flash tube stops emitting light. It is applied to the exposure control device of a camera equipped with a TTL automatic light control circuit and capable of flash photography. The above-mentioned problem is that the photometric means for photometrically measuring the central area of the photographing screen to be photographed before the start of the exposure operation and the standard exposure value for calculating the standard exposure value for obtaining the proper exposure for the central area based on the photometric information from the photometric means. Value calculation means,
When the standard exposure value is at least within the range of 0Bv ~ 9Bv, the standard exposure value is corrected by a predetermined amount to obtain a corrected exposure value and a corrected exposure value calculation means for obtaining a corrected exposure value, and in order to obtain the corrected exposure value, Exposure control means for controlling the exposure at the shutter speed set during the flash photography limit synchronization time or at a time slower than that and exposure control by the exposure control means A shooting mode setting means for setting a mode is provided, and by setting the shooting mode during flash shooting, the aperture and shutter are controlled according to the corrected aperture value and shutter time, while TTL
This is solved by controlling the light emission amount of the flash tube by an automatic light control circuit.

E. Action When the above shooting mode is set during flash photography, the shutter speed and aperture value are controlled by the corrected exposure value obtained by largely correcting the standard exposure value to obtain the proper exposure for the central area. Even in the case of performing the daytime synchronized photographing by the photometric information regarding the background, the background is prevented from becoming over as in the conventional case. On the other hand, the same applies to nighttime flash photography.

F. Embodiment An embodiment of the present invention will be described with reference to FIGS.

(I) Configuration of Embodiment FIG. 1 shows an overall configuration of an example of an exposure control device. In this exposure control device, a control circuit 1 including a CPU and the like.
Various devices are controlled by. The film sensitivity reading circuit 2 reads the film sensitivity and outputs the film sensitivity information. The photometric circuit 3 is a photometric light receiving element 4 via a taking lens.
It receives the subject light incident on and outputs photometric information corresponding thereto. The light receiving element 4 is, for example, 5 as shown in FIG.
The photometric circuit 3 is divided and outputs the luminance data of each region of the light receiving element divided into five. The lens information output circuit 5 outputs the open F value (Fo), the focal length (f), the exit pupil (Po) or the reciprocal (1 / Po) of the shooting lens to be mounted.

The photometric method selection switch 6 selects either multi-pattern photometry or center-weighted photometry. When multi-pattern photometry is selected, the standard exposure value calculation is performed from the photometric data of each of the five divided areas as is well known. The circuit 7 calculates the standard exposure value Bva according to the luminance distribution in the object field, and when the center-weighted photometry is selected, the standard exposure value Bva for obtaining the proper exposure for the central area is calculated. Also in this embodiment, center-weighted photometry is forcibly selected when lens information is not input.

The exposure mode selection switch 8 uses the standard exposure value Bva described above as the exposure value when setting the shutter speed or aperture value.
Select a standard mode using, or a correction mode that uses the corrected exposure value Bvc, which is the standard exposure value Bva corrected by a predetermined amount, and the corrected exposure value Bvc is
It is corrected by the corrected exposure value calculation circuit 9 according to the graph of FIG. 2, for example. The shutter control device 10 and the aperture control device 11 are
Standard exposure value Bva obtained according to the selected mode
Alternatively, the shutter and the diaphragm are controlled based on the corrected exposure value Bvc.

On the other hand, reference numeral 12 denotes a light emitting circuit, which causes the light emitting tube F to start emitting light when the X contact (not shown) is closed in response to the release signal.
Further, 13 is a TTL automatic light control circuit, which emits a light emission stop signal when the amount of reflected light from the subject incident on the light receiving element 14 through the photographing lens reaches a preset level.
To stop the light emission. Here, the light amount level of the TTL automatic light control circuit 13 of this embodiment is set as shown in FIG. 3 according to the standard exposure value Bva. The light amount level may be set in accordance with the corrected exposure value Bvc as in FIG.

SW1 is a half-push switch that is turned on by half-pressing release lead, and SW2 is a full-press switch that is turned on by full-pressing release lead.

(II) Operation of Embodiment The operation of the exposure control device configured as described above will be described based on the flowchart of FIG.

When this processing procedure is started by turning on the half-push switch SW1, first, in step S1, the photometric processing is performed and the photometric data of each area is input. In step S2, it is determined whether or not center-weighted photometry is performed. When the multi-pattern photometry is selected by the photometry method selection switch 6 and the lens information signal is output from the lens information output circuit 5, it is determined to be the multi-pattern photometry mode, and when the center-weighted photometry is selected by the switch 6, Alternatively, when the lens information signal is not output, the center weighted metering mode is determined.

When step S2 is affirmed and the process proceeds to step S3, the standard exposure value calculation circuit 7 calculates the standard exposure value Bva using the photometric data of the central region or the photometric data with emphasis on the central region. Next, in step S4, it is determined whether or not flash photography is performed. When the calculated standard exposure value Bva is equal to or less than the predetermined value, or when the backlight scene is determined from the difference between the maximum brightness and the minimum brightness of the plurality of areas, the determination is affirmative and the process proceeds to step S5.

In step S5, it is determined whether the exposure control mode is the correction mode. The correction mode is selected when the correction mode is selected by the selection switch 8 and during daytime synchronized photography. If step S5 is positive, step S6
Then, using the standard exposure value Bva calculated by the standard exposure value calculation circuit 7, the correction exposure value calculation circuit 8 calculates the correction exposure value Bvc according to the graph of FIG. Further, in step S7, the light amount level of the TTL automatic light control circuit 13 is set based on the standard exposure value Bva according to the graph of FIG. 3, and in step S8 it is determined whether or not the full-press switch SW2 is on. If denied, half-press switch SW1 in step S10
Is turned on, and if denied, it proceeds to return,
When affirmative, it returns to step S8.

When step S8 is affirmed, the process proceeds to step S9, in which the aperture value is set at the shutter speed based on the corrected exposure value Bvc, and the shutter control device 10 and the aperture control device 11 drive and control the shutter and aperture. Further, in response to the X contact being turned on, a light emission start signal is supplied to the light emitting circuit 12, and the light emitting tube F starts emitting light. After light emission, the reflected light from the subject enters the TTL automatic light receiving element 14 through the taking lens, and the TTL automatic light control circuit 13 integrates the signal from the light receiving element 14, and when the set light amount level is reached, the light emitting circuit 12 A light emission stop signal is sent to stop the light emission of the arc tube F.

Furthermore, if it is determined in step S5 that the correction mode is not set, the shutter speed is set to, for example, 1/2 in step S11.
Fix the limit tuning time of 50 seconds and proceed to step S8. Therefore, in this case, in step S9, the aperture is controlled to an aperture value that gives the standard exposure value Bva at the shutter speed of 1/250, and shooting is performed.

On the other hand, if step S2 is denied, that is, if multi-pattern photometry is selected as described above, step S12
Standard exposure value based on photometric data of multiple areas at
When Bva is calculated and the process proceeds to step S13, and flash photography is determined, the steps from step S8 are executed to perform flash photography as described above in step S9.

If it is determined in step S4 or S13 that the flash photography is not performed, it is determined in step S14 whether or not the full-press switch SW2 is turned on, and if affirmative, the standard exposure value B is set in step S16.
Normal photography is performed by exposure control using va. If step S14 is denied, the half-press switch is pressed in step S15.
It is determined whether SW1 is on, and if negative, the procedure proceeds to return, and if affirmative, the procedure proceeds to step S14.

According to the above procedure, the center-weighted metering method is selected by the metering method selection switch 6 or when the lens information output circuit 5 does not output the lens information because the lens information storage unit such as the lens ROM is not provided in the mounted lens. It At this time, if the correction mode is selected as the exposure control mode, the standard exposure value Bva calculated by the photometric data of the central region or the photometric data with emphasis on the central region is largely corrected by a predetermined amount as shown in FIG. To obtain the corrected exposure value Bvc,
This corrected exposure value Bvc controls the shutter speed and / or the aperture value.

That is, when the limit tuning time of the flash device is set to 1/250 second, for example, when 1/60 second, which is slower than the limit time in the shutter priority mode, is manually input, the shutter speed 1 /
The aperture value at which the corrected exposure value Bvc is obtained is set by 60. Therefore, for example, in a backlit scene as shown in Fig. 10, if the exposure is controlled with the standard exposure value Bva calculated to obtain the proper exposure of the person by the center-weighted metering method and the daytime synchronized shooting is performed, the background will be over. As in the present invention, the exposure is controlled by the corrected exposure value Bvc, which is the standard exposure value Bva that has been corrected to a large degree, so that the background becomes underexposed and the exposure is more appropriate than before.

Also, when the correction mode is selected during night shooting,
The shutter speed is not fixed to 1/250 of the limit tuning time of the flash device, but in the program mode, the shutter priority mode, and the aperture priority mode, the shutter within the time later than the limit tuning time is based on the corrected exposure value Bvc. 1/250 which is the limit tuning time when flash photography is possible at the time and / or aperture value.
There is no risk of the background being underexposed as when fixing to. Furthermore, in the flash photography at night,
Even if there is a bright subject such as a neon light or street light in the background of the person arranged in the center as well as the scene in the figure, the standard exposure value Bva that gives the proper exposure in the center area was corrected to a large value as described above. Since the exposure is controlled by the corrected exposure value Bvc, the exposure is slightly shifted to the under side (for example, the shutter speed becomes faster), and the background is prevented from being overexposed.

Further, according to the present invention, as a result of being calculated by the standard exposure value calculating circuit 7, when Bva is between 9Bv and 0Bv, that is, when it is determined that the brightness of the subject to be exposed is 9Bv to 0Bv, Since the exposure is controlled by the exposure value corrected as described above, it is possible to obtain a proper exposure in a considerably wide range from night view to general daytime shooting.

Here, for example, FIG. 5 and FIG. 6 show the deviation amount from the proper exposure value of the background with respect to the standard value which gives the proper exposure to the central region. The conventional method shown in FIG. As shown in FIG. 6, it can be seen that the amount of deviation in the correction method is smaller than that in the case where no correction is performed.

Further, as shown in FIG. 3, the larger the standard exposure value Bva is, the closer the light emission stop light amount level of the TTL automatic light control circuit 13 is to the level 0. This is for the following reason.

That is, if the shutter speed becomes faster within the synchronization time, the amount of exposure light due to natural light decreases. Therefore, in order to cover that amount, the light amount level is set higher as the standard exposure value Bva increases.

In the above description, the exposure calculation is performed by the photometric information of the central area only under predetermined conditions in the multi-pattern side optical circuit.
(Fig.) And center-weighted metering system (Fig. 8).

G. Effect of the Invention According to the present invention, when an exposure control mode called, for example, a correction mode is selected during flash photography, the standard exposure value calculated using the photometric information of the central area is increased by a predetermined amount. Since the exposure is controlled using this corrected exposure value, a simple exposure value calculation can be performed on a subject with a large brightness difference, such as a backlit scene, without performing complicated calculations such as multi-pattern metering. On the other hand, the deviation from proper exposure can be made smaller than before.

Further, even during nighttime flash photography, exposure control can be performed within a time slower than the limit tuning time of the flash device, and the background can be appropriately exposed as compared with the case where the limit tuning time is fixed.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram showing an embodiment of an exposure control device, FIG. 2 is a graph showing the relationship between standard exposure value Bva and corrected exposure value Bvc, and FIG. 3 is standard exposure value Bva and TTL automatic light control. 4 is a graph showing the relationship with the light emission stop light amount level in FIG. 4, FIG. 4 is a flowchart showing the processing procedure of exposure control, and FIG. 5 is a diagram showing the amount of deviation from the proper exposure value of the background with respect to the conventional standard exposure value Bva, FIG. 6 is a similar diagram in this embodiment. Each of FIGS. 7 to 9 is a diagram showing an example of division of the photometric region of the object field in each photometric method, FIG. 9B is an output waveform diagram of luminance data, and FIG. 10 is a typical backlight scene. FIG. 1: Control circuit, 3: Photometric circuit 5: Lens information output circuit 6: Photometric method selection switch 7: Standard exposure value calculation circuit 8: Exposure mode selection switch 9: Corrected exposure value calculation circuit 12: Light emission circuit 13: TTL automatic adjustment Optical circuit

Claims (3)

[Claims] 1. A TTL automatic light control circuit for measuring the light reflected by a subject after being emitted from a flash tube through a photographing lens and stopping the emission of the flash tube when the amount of light reaches a predetermined level. In an exposure control device for a camera capable of flash photography, a photometric unit that measures the central area of the photographic screen to be photographed before the start of the exposure operation, and a standard exposure that obtains a proper exposure for the central area based on the photometric information from the photometric unit. A standard exposure value calculation means for calculating a value, and when the standard exposure value is at least within the range of 0Bv to 9Bv, a corrected exposure value calculation for correcting the standard exposure value by a predetermined amount to obtain a corrected exposure value. In order to obtain this corrected exposure value, the exposure is controlled by the shutter speed and the aperture value corresponding to the shutter speed set during the flash synchronization limit synchronization time or within the slower time. The exposure control means and the shooting mode setting means for setting a mode for performing the exposure control by the exposure control means. By setting the shooting mode during flash photography, the corrected aperture value and shutter speed are set. An exposure control device for a camera, wherein the TTL automatic light control circuit controls the light emission amount of the flash tube while at the same time controlling an aperture and a shutter. 2. The photometric means divides and photometers a plurality of areas of a photographing screen, and calculates the standard exposure value based on photometric information of a central area under predetermined conditions. The exposure control device for the camera according to. 3. The camera according to claim 1, wherein the predetermined light amount level of the TTL automatic light control circuit is changed according to the standard exposure value or the corrected exposure value. Exposure control device.