JP6222904B2 - Imaging apparatus and control method thereof - Google Patents

Description

  The present invention relates to an imaging apparatus, and more particularly to an exposure control technique for an imaging apparatus.

  Imaging devices such as digital cameras equipped with a display device such as a liquid crystal display (LCD) are widely used. In such an imaging apparatus, in general, when a release switch (shutter button) is half-pressed while an image is displayed live on a display device, shooting such as autofocus (hereinafter referred to as “AF”) processing is performed. A preparatory operation is performed. When the release switch is fully pressed, the image capturing operation from the main shooting to the image recording is performed.

  Here, as one AF processing method, a method is known in which a lens position at which a high frequency component of a luminance signal obtained from an imaging device using a CCD (charge coupled device) or the like is maximized is set as a focusing position. . As one of the methods, an evaluation value based on the high frequency component of the luminance signal obtained from the image sensor while moving the lens over the entire AF range is stored each time, and the maximum value among the stored values is stored. A scanning method is known in which the corresponding lens position is the in-focus position.

  Focusing on the aperture at the time of executing such AF processing (hereinafter referred to as “AF time”), the depth of field becomes shallower as the aperture value is moved closer to the open position, and thus the evaluation value varies depending on the lens position. Becomes larger. Therefore, by setting the aperture value closer to the open position, it becomes possible to obtain the maximum value of the evaluation value that is the in-focus position with high accuracy, and focusing accuracy by AF processing (hereinafter referred to as “AF accuracy”). It becomes possible to improve.

  On the other hand, in the automatic exposure control (hereinafter referred to as “AE”) processing for controlling the optimum aperture value and shutter speed at the time of AF and actual shooting, in order to reduce the release time lag by suppressing the aperture operation time, A method is known in which the aperture value is the same during AF and main shooting. For example, a method for maintaining the aperture value used for capturing an image displayed live immediately before an instruction is issued until the instruction is canceled after the instruction for recording or recording the captured image is issued is proposed. (See Patent Document 1).

JP 2006-60409 A

  However, with the conventional technique disclosed in Patent Document 1, the aperture value cannot be maintained during AF and during actual photographing, and it may be difficult to shorten the release time lag.

  For example, when the release switch is held in the half-pressed state, AE lock (an operation for fixing the aperture value, shutter speed, and sensitivity) is executed, and the exposure value is not changed while the half-pressed state is released. There is a case of using a program shift function for changing the shutter value. In this case, when changing the aperture value during actual shooting using the program shift function, the same aperture value as during live display is used in AF processing by pressing the release switch halfway again. A different aperture value is used.

  In some cases, the user uses an exposure correction function for changing the exposure amount with respect to the exposure condition determined by the AE process. In this case, in the AF method in which the lens position where the high frequency component of the luminance signal obtained from the image sensor is maximized is the in-focus position, an appropriate exposure is made so that the frequency component can be easily acquired during AF processing. Is desirable. On the other hand, during actual shooting, the user may intentionally cause overexposure or blackout due to exposure correction. In this case, a difference occurs in the exposure condition between the AF process and the actual photographing, and as a result, a difference in the aperture value may occur. In addition, when the aperture at the time of recording preparation is a small aperture, in addition to an increase in the release time lag, the AF accuracy decreases.

  An object of the present invention is to provide an exposure control technique capable of maintaining AF accuracy and reducing a release time lag in exposure control from AF processing to main photographing processing in an imaging apparatus. .

An imaging device according to the present invention includes an imaging device that converts reflected light from an object into an electrical signal and outputs the output, a diaphragm that controls the amount of light incident on the imaging device, and the imaging device that receives the reflected light and charges. A shutter for controlling the charge accumulation time for storing the image, a first operating means for receiving an instruction to execute a photographing standby operation including at least AE processing and AF processing from the user, the aperture value and the autofocus means for executing a second operation unit that accepts a program shift instruction to change the aperture value in performing the photographing without changing the exposure amount determined by the shutter value, the AF processing for the previous SL subject If, as the AE processing, and control means for setting, based the value of the shutter and the aperture value in response to said object brightness in a predetermined combination, prior Symbol aperture value Without changing the exposure amount determined by the value of the shutter, and a shifting means for changing the aperture value at the time of executing the present photographing, the control means, the photographing stand by the first operating means When an instruction to execute an operation is received, before the AF process is executed by the autofocus means, the first aperture value and the shutter value are set based on a predetermined combination according to subject brightness. After the AF processing is executed by the autofocus means, the aperture value and the shutter value are set to a second combination different from the first combination according to the subject brightness. When the shift means accepts a program shift instruction by the second operation means after the second combination is set, the aperture value in the second combination Without changing the exposure amount determined by the shutter value, the aperture value at the time of executing the main photographing is changed, and the control means receives the program shift instruction from the second operating means and then receives the program shift instruction. when receiving an instruction of execution of the photographing standby operation by one operation unit is not the value of the aperture of the first combination, and preferentially a modified grain Rinone by said shifting means, said autofocus The aperture value and the shutter value before the AF process is executed by the means are set .

In addition, an imaging device according to the present invention includes an imaging device that converts reflected light from an object into an electrical signal and outputs it, a diaphragm that controls the amount of light incident on the imaging device, and the imaging device that receives the reflected light. Te run a shutter controlling the charge storage time for accumulating charges, and the autofocus unit for performing an auto focus for the subject prior to performing the main imaging, and when the front running the Kio over autofocus, the present photographing in each case, and a control means for setting the value of the shutter and the aperture value in response to said object brightness, and exposure correction means for instructing correction of the exposure conditions at the time of the shooting, the said control means, When correction of the exposure condition is instructed by the exposure correction unit, the value of the aperture is set based on a predetermined combination when the autofocus is executed. The first combination is set according to the degree, and when performing the main photographing, the aperture value is set to a second combination different from the first combination according to the subject brightness, and the exposure correction is performed. When the correction of the exposure condition is not instructed by the means, the aperture value is set in accordance with the subject brightness in both the execution of the autofocus and the actual photographing. A combination is set, and the first combination gives priority to a value close to the open position as the aperture value over the second combination .

  According to the present invention, AF accuracy can be maintained in exposure control from AF processing to main photographing processing, and the release time lag can be shortened.

It is a block diagram which shows the structure of the digital camera which concerns on embodiment of this invention. 2 is a flowchart illustrating an operation according to the first embodiment from when power is turned on to a camera system until actual shooting is performed in the digital camera of FIG. 1. FIG. 2 is a diagram illustrating values for main photographing and AF processing of an aperture and a shutter speed when executing program shift in the digital camera of FIG. 1. 3 is a flowchart showing a method for setting a program diagram according to the presence or absence of program shift in the digital camera of FIG. 1. FIG. 2 is a diagram of various programs used in the digital camera of FIG. 1 during main photographing and AF processing. 6 is a flowchart illustrating an operation according to a second embodiment from when power is turned on to the system until actual shooting is performed in the digital camera of FIG. 1. 2 is a flowchart showing a method for setting a program diagram according to the presence or absence of exposure correction in the digital camera of FIG. 1.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Here, a so-called digital camera is taken up as the imaging apparatus according to the embodiment of the present invention, but the present invention is not limited to this.

<< First Embodiment >>
<Configuration of digital camera>
FIG. 1 is a block diagram showing a configuration of a digital camera according to an embodiment of the present invention. The digital camera includes a photographing lens 101, an aperture and shutter 102, an automatic exposure (AE) processing unit 103, a focus lens 104, an autofocus (AF) processing unit 105, an image sensor 106, and an A / D conversion unit. 107.

  The taking lens 101 has a zoom mechanism. In accordance with an instruction from the AE processing unit 103, the aperture and shutter 102 controls the amount of incident light and the charge accumulation time of incident light, which is reflected light of the subject, on the image sensor 106. The AE processing unit 103 controls the operation of the aperture and shutter 102 based on a program diagram showing the relationship between the aperture value, shutter speed, and sensitivity, and also controls the A / D conversion unit 107 described later. The focus lens 104 focuses on the light receiving surface of the image sensor 106 in accordance with a control signal from the AF processing unit 105 to form an optical image.

  The image sensor 106 converts an optical image formed on the light receiving surface into an electrical signal by a photoelectric conversion means such as a CCD element or a CMOS element, and outputs the electrical signal to the A / D converter 107. The A / D converter 107 converts the received electrical signal (analog signal) into a digital signal. The A / D converter 107 includes a CDS circuit that removes noise from the received electrical signal, and a nonlinear amplifier circuit that performs nonlinear amplification before converting the received electrical signal into a digital signal.

  The digital camera also includes an image processing unit 108, a format conversion unit 109, and a DRAM 110. The image processing unit 108 performs predetermined resizing processing such as pixel interpolation and image reduction and color conversion processing on the digital signal output from the A / D conversion unit 107, and outputs image data. The format conversion unit 109 performs format conversion of the image data generated by the image processing unit 108 in order to store the image data in the DRAM 110. The DRAM 110 is an example of a high-speed built-in memory, and is used as a high-speed buffer that manages temporary storage of image data, or as a working memory in image data compression / decompression processing.

  The digital camera includes an image recording unit 111, a system control unit 112, a VRAM 113, a display unit 114, an operation unit 115, a main switch (main SW) 116, a first switch (SW1) 117, and a second switch. (SW2) 118.

  The image recording unit 111 includes a recording medium such as a memory card that records captured images (still images and moving images) and an interface thereof. The system control unit 112 includes a CPU, a ROM, and a RAM. The CPU expands and executes a program stored in the ROM in a work area of the RAM, thereby performing overall operation control of the digital camera. The VRAM 113 is an image display memory. The display unit 114 is, for example, an LCD or the like, and displays an imaging screen and an AF area at the time of shooting, in addition to displaying an image, displaying for operation assistance, and displaying a camera state.

  The user operates the digital camera from the outside by operating the operation unit 115. The operation unit 115 includes, for example, a menu switch for performing various settings such as exposure correction, aperture value setting, and image reproduction setting, a zoom lever for instructing a zoom operation of the photographing lens, and an operation mode switching switch between the photographing mode and the reproduction mode. Etc. The main switch 116 is a switch for turning on the power of the digital camera system. The first switch 117 is a switch for performing a shooting standby operation such as AE processing or AF processing, and the second switch 118 is a switch for instructing the system control unit 112 to perform shooting after operating the first switch 117. It is.

<Operation of Digital Camera in First Embodiment>
FIG. 2 is a flowchart illustrating an operation in the digital camera from when the camera system is turned on until the actual shooting is performed. Each process shown in the flowchart of FIG. 2 controls the operation of each part of the digital camera by the CPU of the system control unit 112 developing and executing a predetermined program stored in the ROM in the work area of the RAM. Is realized. As a result, the predetermined processing is performed by, for example, the AE processing unit 103 or the AF processing unit 105 that has received a command from the system control unit 112.

  Here, a case will be described in which a program shift function is used in which the AE lock is performed while the first switch 117 is held, and the aperture value and the shutter speed are changed without changing the exposure amount while the first switch 117 is released. In the present embodiment, the AE lock operation is an operation for fixing the aperture value, shutter speed, and sensitivity while the first switch 117 is held.

  First, in step S201, the system control unit 112 determines whether or not an AE lock operation is performed when the first switch 117 is not operated. If the AE lock operation is performed (YES in S201), the system control unit 112 advances the process to step S202. If the AE lock operation is not performed (NO in S201), the system control unit 112 advances the process to step S203.

  In step S202, the system control unit 112 receives a program shift instruction. FIG. 3A shows controllable values of the aperture and shutter speed for main photographing when the program shift is executed. When AE lock is executed in a scene where the aperture and shutter speed at the time of actual shooting are [F4.0, 1/60 seconds], the program shifts [F2.0, 1/250 seconds] to [F8.0,1. / 15 seconds] can be controlled. By limiting to such a combination, it is possible to change the aperture and the shutter speed without changing the exposure amount. Here, it is assumed that the aperture and shutter speed can be changed in increments of one step.

  Upon receiving the program shift instruction, system control unit 112 advances the process to step S203. In step S203, the system control unit 112 determines whether or not the first switch 117 is turned on. If the first switch 117 has not been turned on (NO in S203), the system control unit 112 returns the process to step S201, and if the first switch 117 has been turned on (YES in S203), the process proceeds to step S204. Proceed to

  In steps S204 to S206, the AE processing unit 103 and the AF processing unit 105 that have received a command from the system control unit 112 perform a shooting standby operation such as AE processing or AF processing. Here, when the program shift instruction is accepted in step S202, the AE processing unit 103 performs AE processing so that the instructed aperture and shutter speed are obtained. As a specific procedure, first, in step S204, the AE processing unit 103 sets an exposure condition for executing the AF process (first exposure control). Details of setting exposure conditions (AE processing before AF processing) when executing this AF processing will be described later with reference to FIGS.

  After step S204, in step S205, the AF processing unit 105 performs AF processing. Here, as the AF processing method, a method is adopted in which the lens position where the high frequency component of the luminance signal obtained from the image sensor 106 is maximized is the in-focus position. More specifically, the focus lens 104 is moved over the entire AF range, and an evaluation value based on the high frequency component of the luminance signal obtained from the image sensor is stored each time, and the maximum value of the stored value is stored. AF processing is performed by a scanning method in which the corresponding lens position is the focusing position.

  After step S205, in step S206, the AE processing unit 105 sets exposure conditions for main photographing (second exposure control). The details of setting the exposure conditions for the main photographing (AE processing for the main photographing) will be described later with reference to FIG.

  Upon completion of step S206, when the main shooting AE process by pressing the first switch 117 is completed and the shooting standby operation is completed, the system control unit 112 releases the ON state of the first switch 117 in step S207. It is determined whether or not. When the ON state of the first switch 117 is released (YES in S207), the system control unit 112 returns the process to step S201, and when the ON state of the first switch 117 is not released (NO in S207), The process proceeds to step S208.

  In step S208, the system control unit 112 determines whether the second switch 118 has been turned ON. If the second switch 118 has not been turned on (NO in S208), the system control unit 112 advances the process to step S209. If the second switch 118 has been turned on (YES in S208), the process proceeds to step S210. Proceed to

  When the second switch 118 is not turned ON, the ON state of the first switch 117 is maintained. Therefore, the system control unit 112 continues to accept the release of the first switch 117 or the ON operation of the second switch 118. However, while the first switch 117 is held in the ON state, an AE lock instruction is issued in step S209. Accept. When receiving the AE lock instruction, the system control unit 112 causes the AE processing unit 103 and the AF processing unit 105 to hold the values of the aperture, shutter speed, and sensitivity for main photographing determined in step S206.

  When the second switch 118 is turned on, in step S210, the system control unit 112 issues a shooting instruction to the AE processing unit 103 and the AF processing unit 105, and the AE processing unit 103 and the AF processing unit 105 perform the main shooting process. Do. In the main photographing process, the AF process result and the exposure condition (AE process result) in steps S205 to S206 are used.

<Selecting program diagram during program shift>
With reference to the flowchart of FIG. 4, AE control according to the presence or absence of program shift will be described. FIG. 4 is a flowchart showing a program diagram setting method according to the presence or absence of program shift.

  First, in step S401, the system control unit 112 determines whether there is a program shift instruction from the user before photographing. If there is a program shift instruction (YES in S401), the system control unit 112 advances the process to step S402. If there is no program shift instruction (NO in S401), the system control unit 112 advances the process to step S403.

  In the AE process before the AF process in step S402, the AE processing unit 103 sets the exposure condition based on the aperture priority AF diagram during actual photographing. FIG. 3B shows controllable values of the aperture and shutter speed for AF processing during program shift execution. For example, in a scene where the aperture and shutter speed at the time of actual shooting are [F4.0, 1/60 seconds], when the program shift is performed by performing AE lock, the same aperture value at the time of actual shooting is changed. The aperture value can be used during AF. For this purpose, [F2.0, 1/250 seconds] to [F5.6, so that the proper exposure can be maintained without changing the exposure amount by changing the shutter speed by the variation of the aperture value. The program shift is controlled in the range of 1/30 second].

  Here, unlike the case of FIG. 3A, the reason for not using [F8.0, 1/15 seconds] is to prevent a reduction in AF accuracy by providing a restriction on the shutter speed during AF. Yes. That is, when the shutter speed is slow (exposure time is long), it is difficult to acquire frequency components during AF due to camera shake or subject blur, so that only an appropriate shutter speed can be used. Here, as an example, the frame rate of the image sensor 106 when performing AF processing is 30 fps, and a shutter speed that is the same as or faster than the inverse of the frame rate (short exposure time), that is, 1/30 second or less is appropriate. To do.

  In step S403, since there is no program shift instruction, the AE processing unit 103 sets the program diagram used in the AE processing during AF as the aperture priority AF diagram during main photographing. As a result, the aperture value is the same during AF and during actual shooting, so the release time lag can be shortened.

<Program diagram>
The characteristics of the program diagram at the time of AF and the actual photographing used in the digital camera according to the present embodiment will be described with reference to FIG. The program diagram is stored in the ROM or RAM provided in the system control unit 112. Further, here, in the digital camera according to the present embodiment, the aperture value is Av2 to 6 (F2.0 to F8.0), the shutter speed is Tv0 to 11 (1 second to 1/2000 second), and the gain increase amount is set. It is assumed that Gain 0 to 4 (ISO 100 to ISO 1600) can be set. The AE processing unit 103 that receives a command from the system control unit 112 controls the gain increase amount.

  FIG. 5 is a program diagram for the main photographing and AF processing used in the digital camera according to the present embodiment. More specifically, FIG. 5 (a) is an example of a diagram for actual photographing, and FIG. 5 (b) is an example of an open aperture priority AF diagram that preferentially uses an open aperture during AF. c) is an example of an aperture priority AF diagram at the time of main shooting that preferentially uses the same aperture as at the time of main shooting during AF. FIG. 5D is a diagram showing only the aperture values in FIGS. 5A to 5C, and FIG. 5E is the actual photographing when the shutter speed and the gain increase amount at the time of AF are limited. FIG. 5F is an example of an aperture priority AF diagram, and FIG. 5F is a diagram showing only the aperture values of FIGS. 5A, 5B, and 5E.

In each figure of FIG. 5, the solid line indicates the Av (Aperture Value) value, the broken line indicates the Tv (Time Value, shutter speed) value, and the dotted line indicates the Gain value. Further, the horizontal axis represents the subject brightness, and the brightness increases as going to the right side of the horizontal axis. The vertical axis represents the Av value, Tv value, and Gain value, and the values increase as they go upward on the vertical axis. Incidentally, the system control unit 112 calculates the output signal from the image sensor 106, and the aperture value and the shutter speed of the diaphragm and the shutter 102, the subject brightness from gay N'a-up amount.

  In general, the Av value and the Tv value are decreased and the Gain value is increased as the subject brightness decreases. In other words, an appropriate aperture can be taken for a dark scene by using an open aperture, a low shutter speed, and a large gain increase amount. On the other hand, the Av value and the Tv value are increased and the Gain value is decreased as the luminance increases. That is, the aperture is made small, the shutter speed is increased, and the gain increase amount is decreased.

  In the present embodiment, the shutter speed in the AF diagram is limited to 1/30 seconds or less. This is because if the shutter speed is increased, it is difficult to obtain a frequency component due to camera shake or subject blur. In order to avoid this problem, only an appropriate shutter speed can be used. In the present embodiment, the upper limit and the lower limit of the aperture value and gain increase amount are the same for AF and actual shooting. However, as with the shutter speed, appropriate processing is performed for each of AF and actual shooting. The upper and lower limits may be different from each other so that

  In the main imaging diagram of FIG. 5A, an area [A1] represents a behavior at low luminance. In the area [A1], the Tv value is changed according to the luminance, and as the shutter speed becomes slower (exposure time becomes longer), camera shake and subject shake tend to occur. The Tv value is shortened as the luminance increases. In the region [B1] where the Tv value is equal to or greater than the threshold value, the Gain value is changed. As the gain increase amount increases, noise is generated in the photographed image, resulting in poor appearance. Therefore, in the case of a Tv value that can suppress camera shake and subject blur, the shutter speed is increased as the brightness increases. Make the gain increase smaller than the high speed. As a result, it is possible to take a good-looking image.

  In the region [C1] brighter than the luminance at which the Gain value is minimized, the Av value is changed. Depending on the type of lens, it is possible to capture a high-resolution image by reducing the aperture to some extent rather than opening the aperture. Therefore, if the brightness is such that camera shake, subject blur, and noise can be suppressed, the aperture value is set so that a high-resolution image can be captured. In the area [D1] brighter than the aperture value at which a high resolution image can be taken, the Tv value is changed. Generally, when the aperture is too small, the resolution is lowered by the diffraction phenomenon. For this reason, the aperture is not reduced immediately even at high luminance, but is changed to the upper limit at which the Tv value can be set. Then, the Av value is changed in the region [E1] where the Tv value is brighter than the upper limit that can be set. When a plurality of shooting modes can be set in the digital camera, the actual shooting diagram may be changed for each shooting mode.

  In the open aperture priority AF diagram of FIG. 5B, the area [A2] represents the behavior at low luminance. In the region [A2], the Gain value is changed according to the luminance here. In a region [B2] brighter than the luminance at which the Gain amount is the minimum value, the Tv value is changed. In the region [C2] brighter than the luminance at which the Tv value becomes the maximum value, the Av value is set to a small aperture, and then the Tv value is changed again.

  This is due to the following reason. That is, it is known that, in AF processing that determines the in-focus position using the contrast data of the image data, generally a scene with a small Av value and Gain value has higher performance. This is because the depth of field becomes shallower as the Av value is decreased (the aperture is moved closer to the open position), and the difference between the focused portion and the unfocused portion becomes easier to understand. That is, since the peak value of the contrast data becomes easier to understand as the aperture is moved closer to the full aperture, accurate focusing becomes easier. On the other hand, increasing the Gain value means amplifying the signal output from the image sensor 106 to a greater extent, but at this time, noise is also amplified. Then, the influence of the noise on the contrast data becomes large, and the peak value of the contrast data may be erroneously determined, leading to a decrease in AF performance. For the above reasons, at the time of actual photographing, an AF aperture is emphasized, and a program diagram with priority on the wide aperture and low sensitivity is used.

  The aperture priority AF diagram for main shooting in FIG. 5C and the aperture priority AF diagram in FIG. 5B share the technical idea of the program diagram, but the aperture priority AF line for main shooting. The figure differs from the open aperture priority AF diagram in that the aperture value is changed in the region [C3]. This is because the aperture is switched with the same luminance as that of the main photographing diagram of FIG. Therefore, as is apparent from a comparison between FIG. 5A and FIG. 5C, the aperture value in the main imaging diagram and the aperture priority AF diagram during main imaging are the same for any subject brightness. I understand.

  Note that it is possible to make the aperture value the same during AF and during actual photographing by adjusting the shutter speed and gain increase amount in the program diagram during AF. However, as shown in the example of FIG. 3B, the upper limit / lower limit of the shutter speed and the upper limit / lower limit of the gain increase amount may be different between AF and actual photographing. In this case, the program diagram is such that the same aperture value can be used in the widest subject luminance range within the limit range of the shutter speed and gain increase amount during AF. For example, if the shutter speed increases, it becomes difficult to acquire frequency components during AF due to camera shake or subject blur, so the shutter speed is limited to the same or shorter reciprocal of the frame rate of the image sensor 106 when performing AF processing. Things. Further, since there is a possibility that the AF accuracy may be reduced by increasing the gain, the gain may be limited so that the gain is increased only to a predetermined value.

  In the aperture priority AF diagram for actual photographing shown in FIG. 5E, the shutter speed during AF is Tv 8 to 11 (1/250 sec to 1/2000 sec), and the gain increase amount is Gain 0 to 1 (ISO 100 to ISO 200). Restricted to When such a restriction is provided, as shown in FIG. 5F, there are subject luminance regions having different aperture values in the main imaging diagram and the main imaging aperture priority AF diagram. . In this case, as shown in FIGS. 5 (e) and 5 (f), a program diagram that allows the same aperture value to be used in the widest subject luminance range within the range in which the shutter speed and the gain increase amount can be controlled. To.

  In addition, when the same aperture value as that used in the actual photographing is used during AF, depending on the aperture value, there is a possibility that the subject depth becomes deep and the AF accuracy decreases. In order to deal with this problem, an AF diagram is set so that the aperture value is the same between the actual aperture and the AF at an aperture value within a predetermined range from the open aperture that can guarantee high accuracy. May be. In a digital camera in which a plurality of shooting modes can be set, the aperture priority AF diagram for main shooting may be changed and used in each shooting mode.

  According to the above method, according to the first embodiment, AF accuracy can be maintained and the release time lag can be shortened even when performing program shift in exposure control from AF to actual shooting. .

<< Second Embodiment >>
In the second embodiment, the operation of the digital camera when the user performs an exposure correction operation when shooting using the digital camera shown in FIG. 1 will be described.

<Operation of Digital Camera in Second Embodiment>
FIG. 6 is a flowchart showing an operation of the digital camera from when the camera system is turned on until the actual shooting is performed. Each process shown in the flowchart of FIG. 6 is performed by the CPU of the system control unit 112 controlling the operation of each unit of the digital camera by developing and executing a program stored in the ROM in the work area of the RAM. Realized. As a result, the predetermined processing is performed by, for example, the AE processing unit 103 or the AF processing unit 105 that has received a command from the system control unit 112.

  First, in step S <b> 601, the system control unit 112 receives a setting of an exposure correction amount in the main shooting from the user from when the digital camera is turned on until the first switch 117 is operated. In a digital camera, for example, when the proper exposure is set to ± 0, exposure correction can be set with an upper limit of ± 2 steps in 1/3 steps.

  Subsequently, in step S602, the system control unit 112 determines whether or not the first switch 117 is turned on by the user. If the first switch 117 is turned on (YES in S602), the system control unit 112 advances the process to step S603. If the first switch 117 is not turned on (NO in S602), the process goes to step S601. Return and accept an exposure compensation instruction.

  In steps S603 to S605, the AE processing unit 103 and the AF processing unit 105 that have received a command from the system control unit 112 perform a shooting standby operation such as AE processing or AF processing. As a specific procedure, the AE processing unit 103 sets exposure conditions during AF in step S603. Details of the setting of exposure conditions during AF (AE processing before AF processing) will be described later with reference to FIG.

  When the pre-AF process AE process is completed, the AF processing unit 105 performs the AF process in step S604. The AF process here is performed using the same method as that described for the AF process in step S205 shown in FIG. 2, and the description thereof is omitted here. However, in the AF process in step S604, it is desirable to set the appropriate exposure so that the frequency component can be easily acquired. Therefore, even if an exposure correction instruction is given in step S601, exposure correction is not applied. .

  When the AF process is completed, the AF processing unit 105 sets the exposure conditions for the main shooting in step S605. Since the method for setting the exposure condition during the main photographing (that is, the AE process during the main photographing) is the same as that described with reference to FIG. 5, the description is omitted here.

  In step S606 after the completion of step S605, the system control unit 112 determines whether or not the ON state of the first switch 117 is released. When the ON state of the first switch 117 is released (YES in S606), the system control unit 112 returns the process to Step S601, and when the ON state of the first switch 117 is not released (NO in S606), The process proceeds to step S607.

  In step S607, the system control unit 112 determines whether or not the second switch 118 has been turned ON. If the second switch 118 has not been turned on (NO in S607), the system control unit 112 returns the process to step S606. That is, when the ON state of the first switch 117 is not released and the ON operation of the second switch 118 is not performed, the ON state of the first switch 117 is maintained. 2 An ON operation of the switch 118 is accepted.

  When the second switch 118 is turned on (YES in S607), the system control unit 112 advances the process to step S608. In step S608, the system control unit 112 issues a shooting instruction to the AE processing unit 103 and the AF processing unit 105, and the AE processing unit 103 and the AF processing unit 105 perform a main shooting process. In the main photographing process, the AF process result and the exposure condition (AE process result) in steps S604 to S605 are used.

<Selecting program diagram for exposure compensation>
With reference to the flowchart of FIG. 7, AE control according to the presence or absence of exposure correction will be described. FIG. 7 is a flowchart showing a method for setting a program diagram according to the presence or absence of exposure correction.

  First, in step S701, the system control unit 112 determines whether or not there has been an exposure correction instruction from the user before shooting. If there is an exposure correction instruction (YES in S701), the system control unit 112 advances the process to step S702. If there is no exposure correction instruction (NO in S701), the system control unit 112 advances the process to step S703.

  In step S702, the AE processing unit 103 sets the program diagram used in the AE processing during AF as the open aperture priority AF diagram. This is due to the following reason. That is, in general, the depth of field becomes shallower as the aperture is moved closer to the open position, and the difference between the in-focus portion and the in-focus portion becomes easier to understand. As a result, AF accuracy is improved. . Therefore, if there is a possibility that the release time lag at the time of shooting cannot be shortened due to a difference between the aperture value at the time of AF and the actual shooting due to the exposure compensation instruction, focus on the AF accuracy and give priority to the open aperture. Use the AF diagram.

  Here, when there is an exposure correction instruction, the open aperture priority AF diagram is set. On the other hand, if the aperture value at the time of main shooting by applying exposure compensation can be grasped at the stage of AE processing before AF processing, it is opened only when the aperture value at the time of AF and main shooting changes due to exposure correction. An aperture priority AF diagram may be used. Thereby, even when there is an exposure correction instruction, it is possible to increase the frequency of shooting with a reduced release time lag.

  In addition, only when the exposure conditions during main shooting are corrected to the high luminance side by exposure correction, the aperture priority AF diagram is used, and when it is corrected to the low luminance side, aperture priority AF during main shooting is used. A diagram may be used. When the exposure condition is corrected to the high brightness side, the aperture value is more easily set to the open side.Therefore, in the images and movies shot by actual shooting, the part that is not in focus is not in focus. The difference appears to be large. At this time, if the area desired by the user using the digital camera is not in focus, the user will feel uncomfortable. In such a case, in order to place importance on the AF accuracy, an AF diagram that prioritizes the open aperture is used to facilitate focusing on the area desired by the user.

  On the other hand, in step S703, the AE processing unit 103 sets the program diagram used in the AE processing during AF as the aperture priority AF diagram during main photographing. As a result, the release time lag can be shortened because the aperture value at the time of AF is the same as that at the time of actual photographing.

  With the above method, according to the second embodiment, AF accuracy can be maintained and the release time lag can be shortened even when exposure correction is performed in exposure control from AF to actual shooting. .

<Other embodiments>
Although the present invention has been described in detail based on preferred embodiments thereof, the present invention is not limited to these specific embodiments, and various forms within the scope of the present invention are also included in the present invention. included. Furthermore, each embodiment mentioned above shows only one embodiment of this invention, and it is also possible to combine each embodiment suitably.

  The present invention can also be realized by executing the following processing. That is, software (program) that realizes the functions of the above-described embodiments is supplied to a system or apparatus via a network or various storage media, and a computer (or CPU, MPU, etc.) of the system or apparatus reads the program code. It is a process to be executed. In this case, the program and the storage medium storing the program constitute the present invention.

DESCRIPTION OF SYMBOLS 101 Shooting lens 102 Aperture and shutter 103 AE processing unit 104 Focus lens 105 AF processing unit 106 Image sensor 112 System control unit 114 Display unit 117 First switch (SW1)
118 Second switch (SW2)

Claims (5)

An image sensor that converts reflected light from an object into an electrical signal and outputs the electrical signal;
A diaphragm for controlling the amount of light incident on the image sensor;
A shutter that controls a charge accumulation time in which the image sensor receives the reflected light and accumulates charges;
First operating means for receiving an instruction to perform a shooting standby operation including at least AE processing and AF processing from a user;
Second operating means for receiving a program shift instruction from a user for changing the aperture value when executing actual photographing without changing the exposure amount determined by the aperture value and the shutter value;
And autofocus means for executing the AF processing with respect to pre-Symbol subject,
As the AE processing, and control means for setting, based the value of the shutter and the aperture value in response to said object brightness in a predetermined combination,
Without changing the exposure amount determined by the value before Symbol aperture value and the shutter, and a shifting means for changing the aperture value at the time of executing the present photographing,
The control means, when receiving an instruction to execute the photographing standby operation by the first operation means, before the AF processing is executed by the autofocus means, the value of the aperture according to subject brightness And the shutter value are set to a first combination based on a predetermined combination, and after the AF processing is executed by the autofocus means, the aperture value and the shutter value are set according to the subject brightness. Set a second combination different from the first combination;
When the shift means receives a program shift instruction from the second operation means after the second combination is set, the shift means sets the exposure amount determined by the aperture value and the shutter value in the second combination. Without changing, change the aperture value when performing the actual shooting,
When the control means receives the program shift instruction from the second operation means and then receives an instruction to execute the shooting standby operation from the first operation means, the aperture value of the first combination rather, preferentially a modified grain Rinone by said shifting means, said automatic focusing means by an imaging apparatus characterized by setting the value of aperture value and shutter before the AF process is executed . In the case where the AF process is performed after the aperture value is changed by the shift unit, the control unit changes the shutter speed by the shutter by an amount corresponding to the changed aperture value. the imaging apparatus according to claim 1. The first combination is an imaging apparatus according to claim 1 or 2, characterized in that the shutter speed of the shutter is to limit within a predetermined range. The first combination is characterized in that the shutter speed by the shutter is limited to a value that is the same as or less than the reciprocal of the frame rate of the image sensor when the AF process is executed. The imaging device according to claim 3 . An image sensor that converts reflected light from an object into an electrical signal and outputs it, a diaphragm that controls the amount of light incident on the image sensor, and a charge accumulation time that the image sensor receives the reflected light and accumulates charges a shutter that a control method of an image pickup apparatus having,
A first operation step for receiving an instruction to execute a photographing standby operation including at least an AE process and an AF process from a user;
A second operation step of receiving a program shift instruction from a user to change the aperture value when executing actual photographing without changing the exposure amount determined by the aperture value and the shutter value;
An autofocus step for performing the AF process on the subject;
As the AE processing, and a control step of setting based on the value of the shutter and the aperture value in response to said object brightness in a predetermined combination,
Without changing the exposure amount determined by the value of the value before Symbol aperture shutter, and a shift step of changing the aperture value at the time of executing the present photographing,
In the control step, when an instruction to execute the photographing standby operation is received in the first operation step, the aperture value is set according to subject brightness before the AF processing is executed in the autofocus step. And the shutter value are set to a first combination based on a predetermined combination, and after the AF process is executed by the autofocus step, the aperture value and the shutter value are set according to the subject brightness. Set a second combination different from the first combination;
In the shift step, when a program shift instruction is received in the second operation step after the second combination is set, the exposure amount determined by the aperture value and the shutter value in the second combination is set. Without changing, change the aperture value when performing the actual shooting,
In the control step, when an instruction to execute the photographing standby operation is received in the first operation step after receiving the program shift instruction in the second operation step , the aperture value of the first combination rather, in favor of grain Rinone changed by the shift step, the control method characterized by setting the value of the previous aperture value and a shutter that said AF process by auto focus steps are performed .

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