JP2008152097A - Continuous photography control method and imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a continuous photography control method for controlling quantity of flash light neither too much nor too little for respective frames in a continuous photographing period when performing continuous photography with flash light, and an imaging apparatus to which the method is applied. <P>SOLUTION: When continuously photographing a subject at predetermined time intervals, information on quantity of reflected light from the subject is acquired in each photography, and the quantity of flash light and an exposure value suitable for photographing the subject are adjusted based on the information on the acquired quantity of reflected light, and are applied to photographing processing for the next frame. The imaging apparatus is equipped with: a photographing means for continuously photographing the subject at the predetermined time intervals; a reflected light quantity measuring means for measuring the quantity of reflected light from the subject in the process of each photographing processing by the photographing means; and an adjusting means for adjusting the quantity of flash light and the exposure value suitable for photographing the subject based on the information on the quantity of reflected light acquired by measurement by the reflected light quantity measuring means, and serving them to the photographing processing for the next frame by the photographing means. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a continuous shooting control method for controlling continuous shooting with a flash and an imaging apparatus to which the continuous shooting control method is applied.

In continuous shooting with flash, the flash emission amount and exposure value are determined based on the brightness information of the subject obtained by preliminary flash emission at the start of shooting, and the flash emission amount and exposure value are determined for each frame during continuous shooting. This is applied to flash emission control and exposure control.
As an example of the technique related to the control of such continuous shooting, shooting in which the flash is emitted in the next frame from the light emission amount obtained by the dimming calculation performed before the start of shooting and the charge amount at the time of shooting of each frame. There is a technique for determining whether or not the light emission is possible and stopping the flash emission when the charge amount is insufficient for the flash emission (see Patent Document 1).
JP 2005-284166 A

  By the way, when shooting a moving subject, it is necessary to consider that the flash light amount and exposure time required for shooting the subject dynamically change during the continuous shooting according to the movement of the subject. For example, when continuously shooting a subject that is moving closer to the photographer, the flash light amount appropriate for shooting the subject captured in the several frames of the continuous shooting is the flash light amount obtained at the start of shooting. And the appropriate exposure value will change accordingly.

In this way, despite the possibility that the flash light amount and exposure value required during continuous shooting may change, the conventional continuous shooting control technology takes a picture in order to shorten the continuous shooting interval. The flash light quantity is calculated and the exposure value is determined by a one-time dimming operation based on information obtained at the time of preliminary light emission at the start.
When such a control method is applied, the amount of light obtained at the start of shooting is applied as it is even if the frame is overexposed from the middle of continuous shooting. Therefore, the capacitor for driving the flash is consumed more than necessary. In such a case, since the capacitor is excessively discharged in order to emit excessive light, the number of frames that can be continuously photographed with a flash is limited more than necessary.

  An object of the present invention is to provide a continuous shooting control method capable of controlling the amount of light of a flash without excess or deficiency for each frame in a continuous shooting period, and an imaging apparatus to which the same is applied.

The continuous shooting control method according to the present invention is configured as follows.
When the subject is continuously photographed at a predetermined time interval, information on the amount of reflected light from the subject is acquired in each photographing, and the flash light amount and exposure value suitable for photographing the subject based on the obtained information on the reflected amount of light Is applied to the shooting process of the next frame.
The first imaging device according to the present invention is configured as follows.

  The photographing means continuously photographs the subject at a predetermined time interval. The reflected light amount measuring means measures the reflected light amount from the subject in the course of each photographing process by the photographing means. The adjusting unit adjusts the flash light amount and the exposure value suitable for photographing the subject based on the information related to the reflected light amount acquired by the measurement by the reflected light amount measuring unit, and provides the next frame with the photographing process by the photographing unit.

The second imaging device according to the present invention is configured as follows.
In the imaging means provided in the first imaging device described above, the detection means detects a charging voltage of a capacitor that drives a light source that generates a flash light amount. The determination unit determines whether or not the charge accumulated in the capacitor is sufficient for generating the flash light amount based on the charging voltage and the charge amount necessary for generating the flash light amount adjusted by the adjustment unit.

The third imaging device according to the present invention is configured as follows.
In the imaging unit provided in the second imaging apparatus described above, the mode holding unit receives in advance an instruction from the user to select either the mode that prioritizes flash light emission or the mode that prioritizes the imaging interval. Holds mode information indicating the mode. The shooting control means refers to the mode information held in the mode holding means according to the determination result that the charge accumulated in the capacitor by the determination means is insufficient, and the mode giving priority to the continuous shooting interval by the mode information. If you are instructed to stop the continuous shooting, and if you are instructed to prioritize the flash emission, wait until the capacitor is charged to a charging voltage sufficient to generate the amount of flash light. Do.

The 4th imaging device concerning the present invention is constituted as follows.
In the adjustment unit provided in the first imaging device described above, the measurement value holding unit and the reflected light amount measurement unit acquired in the course of the photographing process of at least two consecutive frames that precede the adjustment target frame Holds measurement results. The distance estimation unit is configured to detect the subject in the adjustment target frame based on a change in the distance from the subject between at least two consecutive frames estimated corresponding to a change in the measurement result corresponding to at least two consecutive frames. And estimate the distance. The calculation means calculates a flash light amount and an exposure value suitable for photographing the subject based on the distance estimated by the distance estimation means.

According to the continuous shooting control method according to the present invention and the imaging apparatus to which the continuous shooting control method is applied, even when shooting a moving subject continuously, a flash light amount that is not excessive or insufficient is determined according to a change in the distance to the subject, The subject can be photographed with appropriate brightness in each frame photographed continuously.
In addition, by performing such control, the capacitor that drives the flash light source is not wastedly discharged by generating a flash light amount that is overexposed, so that the capacity of the capacitor can be used effectively. Can do. In addition, when shooting a subject approaching the photographer, the number of frames that can be shot continuously is increased compared to when shooting continuously using the flash issue amount determined based on preliminary flash. It is also possible to make it.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
(First embodiment)
FIG. 1 shows a first embodiment of an imaging apparatus according to the present invention.
In the digital camera shown in FIG. 1, the light imaged on the image sensor 22 by the imaging optical system 21 at the time of capturing an image is converted into an electric signal corresponding to the intensity by the image sensor 22, and It is converted into digital data by an analog / digital (A / D) converter 23 and held in the memory 24.

  The memory 24 illustrated in FIG. 1 is connected to an image processing unit 25, a recording processing unit 26, and a photographing control unit 28 via a bus. The digital data stored in the memory 24 as described above is subjected to image processing including encoding processing by the image processing unit 25, and the compressed image data obtained as a result of this image processing is recorded via the bus. Is passed to the unit 26 and recorded in the storage medium 27. The operations of these units, an autofocus control unit (not shown), and a strobe drive circuit 30 that drives the light source of the strobe are controlled by the photographing control unit 28 in accordance with instructions input by the user via the operation panel 29.

In addition, the photometric data collection unit 31 illustrated in FIG. 1 has completed the processing by the image data stored in the memory 24 or the image processing unit 25 in response to a request from the light control calculation processing unit 32 or the adjustment processing unit 33. Information to be used for measuring the luminance of the subject is extracted from the image data, and the extracted imaging information (image information) is returned to the light control calculation processing unit 32 or the adjustment processing unit 33 as the request source.
Based on the instruction from the imaging control unit 28, the above-described dimming calculation processing unit 32 is based on the information received via the photometric data collecting unit 31 at the time of starting the continuous shooting, and performs shooting as described later. The basic flash light amount and exposure value are calculated, and these values are provided to the processing of the photographing control unit 28. In addition, the adjustment processing unit 33 uses the flash obtained by the dimming calculation processing unit 32 based on an instruction from the imaging control unit 28 and information received through the photometric data collection unit 31 during continuous shooting. The light amount and the exposure value are adjusted and used for the processing of the photographing control unit 28.

Further, the mode setting holding unit 34 shown in FIG. 1 holds setting information indicating a mode (described later) related to continuous shooting set by the user via the operation panel 29.
For example, when continuous shooting is instructed by the user, when the flash light level seems to be insufficient, the shooting interval is extended (flash priority mode) and the shooting end mode (interval priority mode). ) Is selected, and setting information indicating the selected mode is held in the mode setting holding unit 34.

Prior to shooting, when the release button is half-pressed, the autofocus control unit drives the shooting optical system 21 to perform focusing processing for the subject. Information indicating the distance to the subject obtained in is passed to the dimming calculation processing unit 32 via the imaging control unit 28 as necessary.
Hereinafter, the continuous shooting operation by the imaging apparatus according to the present invention will be described in detail.

FIG. 2 is a flowchart showing the continuous shooting operation.
As described above, when continuous shooting is instructed by the user and when start of shooting is instructed by fully pressing the release button, the continuous shooting operation shown in FIG. 2 is started, and preliminary light emission is performed first. (Step S1). At this time, power for preliminary light emission corresponding to an instruction from the imaging control unit 28 is released from the main capacitor in the strobe driving circuit 30 and applied to a discharge tube (not shown), and a photometric data collection unit 31. Thus, photometric data corresponding to the image data obtained by the image sensor 22 during preliminary light emission is collected.

  The photometric data collected corresponding to the preliminary light emission in this way is passed to the dimming calculation processing unit 32 together with information indicating the distance to the subject obtained in the above-described autofocus control unit, and based on these information Then, the light control calculation processing unit 32 obtains the luminance of the subject, and further calculates an appropriate flash emission amount and exposure value based on the luminance of the subject and the distance from the subject described above (step). S2).

In this way, after the flash emission amount is obtained, the imaging control unit 28 acquires the charging voltage of the main capacitor in the strobe driving circuit 30 via the strobe driving circuit 30 (step S3), and this charging voltage. And whether or not flash emission is possible is determined based on the emission power required to generate the flash emission amount (step S4).
If sufficient charge is accumulated in the main capacitor described above (Yes determination in step S4), the shooting control unit 28 determines that shooting with a flash is possible and causes the flash drive circuit 30 to perform the above flash emission. Instructing the discharge of the electric power corresponding to the amount and controlling the electronic shutter of the image sensor 22 according to the above-described exposure value, the photographing is executed (step S5).

At this time, in response to a request from the adjustment processing unit 33, the photometric data collecting unit 31 collects photometric data from the imaging data or image data obtained by the imaging element 22 (step S6).
In this way, photometric data is collected from the imaging data or image data obtained at the time of actual photographing, and based on this photometric data, the adjustment processing unit 33 performs a process of adjusting the flash light amount and the exposure value (step). S7).

  At this time, for example, the adjustment processing unit 22 compares the collected measured light data with ideal photometric data that should be obtained when photographing with appropriate light control, and brings the measured light data closer to the ideal photometric data. Necessary correction values are obtained for the flash emission amount and the exposure value, and these values can be adjusted by adding these correction values to the flash emission amount and the exposure value obtained in step S2.

By performing such correction processing and adjusting the flash light amount and exposure value during continuous shooting, for example, when the subject is moving closer to the photographer, the subject is appropriately shot. Therefore, the change in the flash light amount and the exposure value required for this can be reflected in the flash light amount and the exposure value applied to the next shooting.
After adjusting the flash light amount and the exposure value based on the photometric data obtained in the actual photographing in this way, the process returns to step S3, whereby the main capacitor charging voltage obtained in step S3 and the adjusted flash are adjusted. Based on the emission power necessary for generating the light amount, it can be determined whether or not the flash light amount required for photographing the next frame can be generated (step S4).

  As described above, by controlling the flash light amount for continuous shooting for each frame to be shot, for example, when shooting continuously a subject moving closer to the photographer, the distance to the subject Since the flash light amount is controlled to gradually decrease in accordance with the shortening, it is possible to reliably prevent the subject from being overexposed from a frame in the middle of continuous shooting.

In such a case, the charge accumulated in the main capacitor at the start of continuous shooting is released in an amount corresponding to the amount of flash light required in each frame, so the same over the continuous shooting period. It is also possible to increase the number of frames that can be continuously shot as compared with the case of releasing a large amount of electric charge.
In this way, the continuous shooting is continued while adjusting the flash light amount, and when it becomes impossible to release the charge necessary for generating the adjusted flash light amount from the main capacitor (determination in step S4), the shooting is performed. The control unit 28 refers to the mode setting holding unit 34 shown in FIG. 1 and determines whether or not the light emission priority mode is set (step S8).

  When information indicating the light emission priority mode is held in the mode setting holding unit 342 described above (Yes determination in step S8), the imaging control unit 28 determines whether or not the release button is fully pressed. It is determined whether or not the user is instructed to continue continuous shooting (step S9). If the determination in step S9 is affirmative, the flash adjusted by charging the main capacitor in the strobe drive circuit 30 (step S10). Steps S3, S4, and S8 to S10 are repeated until a light emission amount can be generated. In this case, shooting is performed by applying the adjusted flash light amount after the main capacitor of the strobe is charged.

By performing such control, even after the main capacitor charge is released, if the user has previously set the emission priority mode, the shooting interval is extended and the main capacitor is charged while flashing. Continuous shooting with light emission can be continued.
On the other hand, when information indicating the interval priority mode is held in the mode setting holding unit 34 (No determination in step S8) and when it is detected in step S9 that the release button is fully pressed ( In negative determination in step S9), the imaging control unit 28 ends the continuous imaging process.
(Second Embodiment)
FIG. 3 shows another embodiment of the adjustment processing unit according to the present invention.

In the adjustment processing unit 33 shown in FIG. 3, the dimming calculation processing unit 35 uses a guide number GNo indicating an appropriate flash light amount based on photometric data received at the time of actual photographing via the photometric data collecting unit 31 and an appropriate An F value and a sensitivity Sv indicating a proper exposure value are obtained, and these values are passed to the correction processing unit 38 and the subject distance estimation unit 36 as a dimming processing result of the immediately preceding frame.
The subject distance estimation unit 36 shown in FIG. 3 estimates the change in the subject distance based on the change in the calculation result received from the dimming calculation processing unit 35, and estimates the distance to the subject in the next frame of the continuous shooting. . This estimation result is provided to the processing of the correction processing unit 38 and is also passed to the estimation information holding unit 37. The estimation information holding unit 37 stores at least the subject distance and the dimming value (guide) corresponding to the immediately preceding frame. (Number, F value and sensitivity) and the newly estimated subject distance and dimming value are sequentially estimated together with the shooting time of these frames as estimated information corresponding to two consecutive frames prior to the frame for which the correction value is to be calculated. Retained.

The correction processing unit 38 corrects the guide number indicated by the calculation result obtained by the dimming calculation processing unit 35 based on the information on the subject distance held in the estimation information holding unit 37, and is obtained. The correction result is subjected to a shooting control process by the shooting control unit 28.
Hereinafter, the dimming value adjustment processing by the adjustment processing unit will be described in detail.
FIG. 4 is a flowchart showing the dimming value adjustment operation according to the present invention.

The processing of step S11 to step S15 shown in FIG. 4 is positioned at step S7 of the flowchart shown in FIG.
First, based on the photometric data received from the photometric data collection unit 31, the dimming calculation processing unit 35 shown in FIG. 3 performs processing equivalent to the dimming calculation processing unit 32 shown in FIG. A guide number indicating the main light emission amount to be applied when the subject brightness Ev ₁ and subject distance D ₁ when data is obtained is equivalent to the subject brightness Ev _n and subject distance D _n in the next frame to be photographed. GNo ₁ , an F value F ₁ indicating an appropriate exposure value, and a sensitivity Sv ₁ are obtained (step S11).

Next, the subject distance estimation unit 36 reads the subject distance and shooting time held corresponding to the two frames preceding the estimation target frame from the estimation information holding unit 37, and a new image is taken based on these information. The distance D _n to the subject in the frame is estimated (step S12).
The distance D _{n to the} subject in the newly shot frame is newly taken as the subject distance D1 and shooting time T1 in the frame immediately before this frame, and the subject distance D2 and shooting time T2 in the immediately preceding frame. This is expressed as in equation (1) using the estimated shooting time T _n of the frame.

ここで、被写体との距離Ｄと適正なガイドナンバーＧＮｏとの間には、撮影に適用されるＦ値Ｆ、感度Ｓｖと基準値との差ΔＳｖ、被写体輝度Ｅｖと適正値との差ΔＥｖとを用いて、式(２)で示されるような関係がある。なお、感度Ｓｖと基準値との差ΔＳｖは、基準値５から撮影時に使用したＳｖ値を差し引いた値として与えられる。また、被写体輝度Ｅｖと適正値との差ΔＥｖは、ΔＥｖ＝ｌｏｇ_２(被写体輝度／適正値)として与えられる。

Here, between the distance D to the subject and the appropriate guide number GNo, the F value F applied to photographing, the difference ΔSv between the sensitivity Sv and the reference value, and the difference ΔEv between the subject brightness Ev and the appropriate value There is a relationship as shown in equation (2). The difference ΔSv between the sensitivity Sv and the reference value is given as a value obtained by subtracting the Sv value used at the time of shooting from the reference value 5. The difference ΔEv between the subject brightness Ev and the appropriate value is given as ΔEv = log ₂ (subject brightness / appropriate value).

D = GNo / (F * 2 ^{(ΔSv / 2)} * 2 ^{(ΔEv / 2)} ) (2)
By organizing by using the equation (2) and the above-mentioned formula (1), the guide number GNo _n to be applied in a frame to be newly captured calculated in step S11 guide number GNo ₁ and proper exposure value Expression (3) expressed using an F value F ₁ indicating the following is obtained.
_{GNo n = GNo 1 + (D} n -D 1) * F 1 ··· (3)
Accordingly, the correction processing unit 38 shown in FIG. 3 first calculates the subject distance estimated value Dn obtained in step S12 and the subject distance D1 and F value F1 corresponding to the immediately preceding frame held in the estimated information holding unit 37. are substituted into equation (4) shown below obtain a correction value DerutaGNo (step S13), and by correcting the addition the obtained correction value DerutaGNo the guide number GNo ₁ obtained in step S11 (step S14) The light control value reflecting the estimation result of the distance to the subject in the newly shot frame can be obtained.

ΔGNo = (D _n −D ₁ ) * F ₁ (4)
In this way, after completing the dimming value correction process, the estimation information including the subject distance D _n estimated corresponding to the estimation target frame and the estimation including the subject distance D ₁ corresponding to the immediately preceding frame are performed. The information is held in the estimated information holding unit 37 as estimated information corresponding to the immediately preceding frame and estimated information corresponding to the previous frame (step S15), and used for adjustment processing of the dimming value relating to the new frame. The

As the subject distance estimation process, for example, an appropriate weight can be set to the subject distance held corresponding to three or more frames to estimate the subject distance more precisely.
Further, when the subject distance is estimated for the first frame and the second frame of continuous shooting, the focus information obtained by the autofocus processing unit can be used.

  On the other hand, the subject distance obtained from the photometric data as described above can be passed to the AF mechanism 39 via the photographing control unit 28 as shown in FIG. 3 and used for autofocus control.

As described above, the continuous shooting control method according to the present invention and the imaging apparatus to which the continuous shooting control method is applied can always shoot a subject with appropriate brightness when performing continuous shooting with a flash. It is useful in various imaging apparatuses having a continuous shooting function with a flash.
In addition, the continuous shooting control method according to the present invention and the image pickup apparatus to which the continuous shooting control method is applied have the charge accumulated in the main capacitor that drives the strobe light source by controlling the amount of flash light without excess or deficiency in each frame. It is also very useful in that it can be used effectively.

  Furthermore, according to the setting by the user, the control that performs continuous shooting with flash while charging the main capacitor has been realized, thereby increasing the number of options for continuous shooting and realizing shooting that reflects the user's preferences can do.

1 is a diagram illustrating a first embodiment of an imaging apparatus according to the present invention. It is a flowchart showing continuous imaging operation. It is a figure which shows another embodiment of the adjustment process part concerning this invention. It is a flowchart showing the light control value adjustment operation | movement concerning this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 21 ... Optical system, 22 ... Imaging device, 23 ... A / D converter, 24 ... Memory, 25 ... Image processing part, 26 ... Recording processing part, 27 ... Storage medium, 28 ... Shooting control part, 29 ... Operation panel, DESCRIPTION OF SYMBOLS 30 ... Strobe drive circuit, 31 ... Photometry data collection part, 32, 35 ... Dimming calculation processing part, 33 ... Adjustment processing part, 34 ... Mode setting holding | maintenance part, 36 ... Subject distance estimation part, 37 ... Estimation information holding part, 38: Correction processing unit, 39: AF mechanism.

Claims (5)

When shooting continuously at a predetermined time interval of the subject, obtain information on the amount of reflected light from the subject in each shooting,
Based on the acquired information on the reflected light amount, the flash light amount and the exposure value suitable for photographing the subject are adjusted and applied to the photographing process of the next frame.
A continuous shooting control method characterized by the above. Photographing means for continuously photographing a subject at predetermined time intervals;
A reflected light amount measuring means for measuring the reflected light amount from the subject in the course of each photographing process by the photographing means;
Adjusting means for adjusting a flash light amount and an exposure value suitable for photographing the subject based on information on the reflected light amount acquired by measurement by the reflected light amount measuring unit, and providing for a photographing process of the next frame by the photographing unit; An image pickup apparatus comprising: The imaging device according to claim 2,
The imaging means includes
Detecting means for detecting a charging voltage of a capacitor that drives a light source that generates the flash light amount;
Determination means for determining whether the electric charge accumulated in the capacitor is sufficient for generating the flash light amount based on the charging voltage and the charge amount necessary for generating the flash light amount adjusted by the adjusting means. An imaging apparatus comprising: The imaging device according to claim 3.
The imaging means includes
A mode holding means for receiving an instruction from the user in advance to select either the mode giving priority to flash emission or the mode giving priority to the shooting interval, and holding mode information indicating any one of the modes;
The mode information stored in the mode holding unit is referred to according to the determination result that the charge stored in the capacitor is insufficient by the determination unit, and the mode giving priority to the continuous shooting interval is determined based on the mode information. Control to end continuous shooting when instructed, and continue shooting after waiting for the capacitor to be charged to a charging voltage sufficient to generate the amount of flash light when instructed to prioritize flash emission An imaging apparatus comprising: an imaging control means for performing the above. The imaging device according to claim 2,
The adjusting means includes
A measurement value holding unit that holds a measurement result by the reflected light amount measurement unit, which is a frame preceding the adjustment target frame and acquired in the process of photographing at least two consecutive frames;
The subject in the adjustment target frame based on a change in distance to the subject between the at least two consecutive frames estimated corresponding to a change in measurement result corresponding to the at least two consecutive frames. Distance estimation means for estimating the distance to
An image pickup apparatus comprising: a calculation unit that calculates a flash light amount and an exposure value suitable for photographing the subject based on the distance estimated by the distance estimation unit.

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