JP5371474B2 - Imaging apparatus, control method, and program - Google Patents

Description

The present invention relates to an imaging apparatus having an electronic viewfinder function, a control method thereof, and a program .

  Conventionally, an imaging apparatus having a moving image monitoring function is known. The moving image monitor function is a so-called live view function for displaying an image of a subject before photographing on a monitor (display unit) of the imaging apparatus. In this type of imaging apparatus, a video signal obtained by photoelectrically converting an optical image of a subject by an imaging device (such as a CMOS image sensor or a CCD image sensor) is subjected to predetermined processing by a data processing circuit or the like, and is then applied to a monitor. Display as an image (movie).

  The exposure of the image displayed on the monitor of the image pickup apparatus is switched between three control parameters (charge storage time for the image pickup element: Tv, aperture: Av, ISO sensitivity: Sv) so that the video signal becomes a predetermined value. It is controlled by. A combination of the three control parameters is determined based on a program diagram stored in the imaging apparatus. When the value of the luminance Ev of the subject is obtained, the value of the brightness Bv is determined from the values of the three control parameters. The following expression is a relational expression between Ev and Bv, Tv, Av, Sv.

Ev = Bv + Sv = Tv + Av
On the other hand, there has been proposed a technique related to a function of suppressing a change in aperture value by providing a hysteresis with respect to a change in luminance Ev of a subject in aperture driving in which an exposure amount is controlled by controlling an aperture Av with an imaging device. (For example, refer to Patent Document 1).

  Here, let us consider a case where the program diagram at the time of live view is determined as follows in an imaging apparatus having a live view function. That is, an increase in noise at a high ISO sensitivity, a sense of incongruity due to loss of continuity between frames at a short accumulation time (high speed Tv), a change in image exposure amount and depth due to a change in aperture Av, and a driving sound Assume that the determination is made as shown in FIG.

  In FIG. 6, the upper horizontal axis and the left vertical axis indicate the luminance Ev of the subject, the lower horizontal axis indicates the accumulation time Tv, and the right vertical axis indicates the aperture Av. The “arrow-shaped” arrow pointing downward to the right indicates a change that darkens, and the “arrow-shaped” arrow pointing upward to the left indicates a change that brightens. In the program diagram of FIG. 6, a solid line is selected when the luminance Ev of the subject changes from low luminance to high luminance, and a two-dot chain line is selected when the luminance Ev changes from high luminance to low luminance.

  That is, there is a hysteresis in the aperture Av with the luminance of Ev4 to Ev8 and Ev8 to Ev12 (a solid line selected when changing from low luminance to high luminance, and a two-dot chain line selected when changing from high luminance to low luminance). Different characteristics).

  For example, in FIG. 6, when the luminance Ev of the subject changes from low luminance to high luminance, the aperture value is changed when it exceeds Ev8, whereas when the luminance Ev changes from high luminance to low luminance, it falls below Ev8. Also, the aperture value is not changed, and the aperture value is changed by falling below Ev4. In this way, the aperture is frequently changed by changing the luminance that becomes the changing point for changing the aperture value when the luminance Ev of the subject changes from low luminance to high luminance and when the subject changes from high luminance to low luminance. It can suppress that a value changes.

  FIG. 7 is a flowchart showing control parameter calculation processing (schematic control for determining the value of each control parameter in the program diagram of FIG. 6) of the imaging apparatus according to the conventional example.

  In FIG. 7, when the control unit of the imaging apparatus starts the control parameter calculation process (step S701), the next value is acquired. That is, the aperture value PreAv calculated in the previous calculation process and the luminance Ev of the subject immediately before the current calculation process are acquired (steps S702 and S703). Next, the control unit checks whether or not the luminance Ev of the subject is within the interlocking range of the previous aperture value PreAv, and determines whether or not the aperture value needs to be changed from the aperture value PreAv (step S1). S704). Here, the interlocking range is a range indicated by a horizontal thick line (thick solid line, thick two-dot chain line) in the program diagram of FIG.

  If the subject brightness Ev is outside the interlocking range, the control parameter calculation is performed so that the subject brightness Ev is within the interlocking range, and the values of the control parameters (Tv, Av, Sv) are calculated (step S705). When the luminance Ev of the subject is within the interlocking range, the control parameter calculation is performed based on the previous aperture value PreAv, and the values of the other control parameters (Tv, Sv) are calculated (step S706).

Japanese Patent Laid-Open No. 10-20358

  In the conventional imaging apparatus described above, the brightness with hysteresis in the aperture control is used to alleviate the phenomenon that other than the main subject is blurred compared to the main subject at the start of the live view and to clearly understand the focusing accuracy. In the range, the aperture on the open side is selected. That is, when the live view is started in the conventional imaging apparatus, the aperture value Av that is set to the most open aperture value (the smallest aperture value that can be set) is set.

  However, conventionally, since the aperture on the open side is selected as described above, when the live view is started, for example, the aperture is F1.8 at the luminance of Ev7 to Ev8 shown in FIG. In this case, when the luminance of the subject changes by about one step toward the high luminance side, the aperture value immediately changes. As a result, a change in depth, a change in sound, a change in luminance of an image, and the like occur with a change in aperture value, and there is a problem that the operator feels uncomfortable.

  The present invention has been made in view of the above problems, and an object thereof is to make it difficult for an operator to feel a sense of discomfort by suppressing a change in aperture value.

  In order to achieve the above object, an imaging apparatus according to the present invention includes an imaging device that converts an optical image of a subject into an electrical signal, and display means that can sequentially display an image obtained using the imaging device. And an imaging device that controls the diaphragm to adjust the amount of light incident on the imaging device, the calculating unit calculating the luminance of the subject, and the luminance calculated by the calculating unit is within a predetermined range Control means for changing the aperture value of the aperture in a case where the control means changes the predetermined range before and after the sequential display of the images by the display means and during the sequential display, If the luminance of the subject is within the predetermined range before the start of sequential display, the aperture value is changed before the start of sequential display of the images.

  According to the present invention, it is possible to make it difficult for an operator to feel a sense of discomfort such as a change in depth, a change in sound, and a change in screen brightness due to a change in aperture value.

It is a block diagram which shows the structure of the imaging device which concerns on embodiment of this invention. It is a flowchart which shows the control parameter calculation process which concerns on embodiment of this invention. It is a normal program diagram used with the imaging device concerning an embodiment of the invention. It is the program diagram for the time of the live view start used with the imaging device which concerns on embodiment of this invention. It is a program diagram used when the accumulation time Tv used in the imaging apparatus according to the embodiment of the present invention can be selected up to the high speed side. It is a program diagram used with the imaging device which concerns on a prior art example. It is a flowchart which shows the control parameter calculation process in the imaging device which concerns on the past.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a block diagram showing a configuration of an imaging apparatus according to an embodiment of the present invention.

  In FIG. 1, an imaging apparatus 100 is configured as a digital camera, and a recording medium 200 and a lens unit 300 are detachably mounted. The imaging apparatus 100 includes a shutter 12, an imaging element 14, an image processing circuit 20, an image display unit 29, a distance measurement control unit 42, a photometry control unit 44, a system control unit 50, and the like. The recording medium 200 includes a recording unit 202 and the like. The lens unit 300 includes a photographing lens 310, a diaphragm 312, a lens system control unit 350, and the like. The description of the configuration of FIG. 1 that is not directly related to the gist of the present invention is simplified or omitted.

  The shutter 12 controls the exposure amount to the image sensor 14. The image sensor 14 converts an optical image of a subject into an electrical signal. The mirrors 130 and 132 guide the light beam incident on the photographing lens 310 of the lens unit 300 to the optical viewfinder 104 by a single lens reflex system. The mirror 130 may have either a quick return mirror or a half mirror. At the time of photographing, the light beam incident on the photographing lens 310 is imaged on the image sensor 14 as an optical image through the aperture 312, the lens mount 306, the lens mount 106 of the imaging device 100, the mirror 130, and the shutter 12. When the mirror 130 is a quick return mirror, the mirror 130 moves to the retracted position at the time of photographing, so that the light beam incident on the photographing lens 310 forms an image on the image sensor 14 without passing through the mirror 130.

  The A / D converter 16 A / D converts the analog signal output from the image sensor 14 into a digital signal. The timing generation circuit 18 is controlled by the memory control circuit 22 and the system control unit 50, and supplies a clock signal and a control signal to the image sensor 14, the A / D converter 16, and the system control 50.

  The image processing circuit 20 performs predetermined pixel interpolation processing and color conversion processing on the data output from the A / D converter 16 or the memory control circuit 22. In addition, the image processing circuit 20 obtains a correlation shift amount and direction between frames using two consecutive images, and performs predetermined arithmetic processing using the captured image data as necessary. Further, the image processing circuit 20 calculates the luminance of the subject based on data obtained by A / D converting the electrical signal output from the image sensor 14 by the A / D converter 16.

  In addition, the image processing circuit 20 uses a TTL (through-the-lens) AF (where the system control unit 50 controls the shutter control unit 40 and the distance measurement control unit 42 based on the obtained calculation result. Autofocus) processing and AE (automatic exposure) processing are performed. Further, the image processing circuit 20 performs predetermined arithmetic processing using the captured image data, and also performs TTL AWB (auto white balance) processing based on the obtained arithmetic result.

  In the present embodiment, since the distance measurement control unit 42 and the photometry control unit 44 are exclusively provided, when the optical viewfinder 104 is used, the AF processing is performed using the distance measurement control unit 42 and the photometry control unit 44. , AE processing and EF (flash dimming) processing are performed. When an electronic viewfinder (hereinafter referred to as EVF) is used, the system control unit 50 automatically switches to perform AF processing, AE processing, and EF processing using the image processing circuit 20.

  The memory control circuit 22 controls the A / D converter 16, the timing generation circuit 18, the image processing circuit 20, the image display memory 24, the D / A converter 26, the memory 30, and the compression / decompression circuit 32. The control signal of the timing generation circuit 18 is also input to the system control unit 50. Thereby, the system control unit 50 can know the timing of the imaging control. Data output from the A / D converter 16 is written into the image display memory 24 or the memory 30 via the image processing circuit 20 and the memory control circuit 22 or directly via the memory control circuit 22.

  The image display unit 29 is composed of, for example, a TFT LCD, and displays an image of a subject (still image, moving image) photographed by the imaging device 100. The imaging apparatus 100 can function as an EVF by sequentially displaying an image before photographing of a subject on an external monitor (not shown) via the image display unit 29 or the image output unit. In the present embodiment, it is assumed that the imaging apparatus 100 executes a live view function that uses the image display unit 29 or an external monitor as an EVF by operating the operation unit 70.

  The memory 30 stores captured still images and moving images, and has a sufficient storage capacity to store a predetermined number of still images and a predetermined time of moving images. The memory 30 can also be used as a work area for the system control unit 50. The compression / decompression circuit 32 is a circuit that compresses / decompresses image data by adaptive discrete cosine transform (ADCT) or the like, reads the image data stored in the memory 30, performs compression processing or decompression processing, and finishes the processing. The image data is written into the memory 30.

  The shutter control unit 40 controls the shutter 12 in cooperation with the aperture control unit 340 that controls the aperture 312 of the lens unit 300 based on the photometry information from the photometry control unit 44. The distance measurement control unit 42 performs AF processing. A light beam incident on the photographing lens 310 is incident on the distance measurement control unit 42 through a diaphragm 312, lens mounts 306 and 106, a mirror 130, and a distance measuring sub mirror (not shown) by a single lens reflex method, thereby forming an optical image. The in-focus state of the imaged image is measured.

  The photometry control unit 44 performs AE processing. A light beam incident on the photographic lens 310 is incident on the photometry control unit 44 through a diaphragm 312, lens mounts 306 and 106, mirrors 130 and 132, and a photometric lens (not shown) by a single-lens reflex method, thereby forming an optical image. Measure the exposure of the image.

  When the EVF is used, the system control unit 50 performs the following control based on the calculation result obtained by calculating the image data captured by the image sensor 14 by the image processing circuit 20. Exposure control and AF control are performed using a video TTL system that controls the shutter control unit 40, the aperture control unit 340, and the distance measurement control unit 342.

  In this case, the AF control may be performed by using both the measurement result by the distance measurement control unit 42 and the calculation result obtained by calculating the image data captured by the image sensor 14 by the image processing circuit 20. The exposure control may be performed using both the measurement result by the photometry control unit 44 and the calculation result obtained by calculating the image data captured by the image sensor 14 by the image processing circuit 20.

  The system control unit 50 controls the entire imaging apparatus 100, and executes the processing shown in the flowchart of FIG. 2 based on a program (an algorithm for calculating control parameter values for image control). The system control unit 50 stores a plurality of program diagrams (algorithms for calculating control parameter values for image control) for controlling the brightness of a pre-photographing image of a subject displayed by EVF. In the present embodiment, the plurality of program diagrams include a normal program diagram shown in FIG. 3, a program diagram used at the start of live view shown in FIG. 4, and a short accumulation time (high-speed Tv) shown in FIG. There is a program diagram that is used when up to Details will be described later.

  Further, the system control unit 50 converts the luminance of the subject calculated by the image processing circuit 20 into a value of a control parameter for image control. In addition, the system control unit 50 performs control so that the luminance that becomes a change point for changing the aperture 312 of the lens unit 300 differs between the start of live view and during live view in the control parameter calculation processing of image control. Further, the system control unit 50 performs control to switch the accumulation time Tv that can be set by the program diagram based on the result of detecting the movement of the subject by the image processing circuit 20 during the live view.

  The display unit 54 performs display output / voice output of the operation state, messages, and the like as characters and images in accordance with the execution of the program by the system control unit 50. The display unit 54 is composed of, for example, a combination of an LCD, an LED, a sound generating element, and the like. The display unit 54 has a part of its function installed in the optical viewfinder 104.

  The shutter switches SW1 and 62 are turned on during the operation of a shutter button (not shown), and instruct to start operations such as AF processing, AE processing, AWB processing, and EF processing.

  The shutter switches SW2 and 64 are turned on when the operation of the shutter button is completed, and instruct the operation start of a series of processing (exposure processing, development processing, recording processing). In the exposure process, the signal read from the image sensor 14 is written as image data in the memory 30 via the A / D converter 16 and the memory control circuit 22. The development process is performed using an operation in the image processing circuit 20 or the memory control circuit 22. In the recording process, image data is read from the memory 30, compressed by the compression / decompression circuit 32, and written to the recording medium 200.

  The operation unit 70 includes a menu button, a set button, a cross button used for menu selection, a quick review ON / OFF switch, a compression mode switch, a playback switch, an AF mode setting switch, and the like. The operation unit 70 includes a live view switch that instructs the start of the live view function. When the optical viewfinder is used, the EVF can be used by operating the live view switch, and the live view function is executed.

  Note that, instead of providing a dedicated switch for instructing the start of the live view function, the start of the live view function may be instructed by another configuration. For example, a configuration may be provided in which a shooting mode selection switch for selecting an arbitrary shooting mode from a plurality of shooting modes is provided, and the start of the live view function is instructed when the live view mode or the moving image shooting mode is selected.

  The interface unit 90 manages an interface between the imaging device 100 and the recording medium 200. The connector 92 is connected to the connector 206 of the recording medium 200 and electrically connects the imaging device 100 to the recording medium 200.

  The optical viewfinder 104 guides the light beam incident on the photographing lens 310 through the diaphragm 312, the lens mounts 306 and 106, and the mirrors 130 and 132 by the single-lens reflex method, and forms and displays it as an optical image. Thereby, it is possible to perform photographing using only the optical viewfinder 104 without using the image display unit 29 as an EVF. Also, some functions of the display unit 54 (for example, focus display, camera shake warning display, flash charge display, shutter speed display, aperture value display, exposure correction display, etc.) are installed in the optical viewfinder 104. .

  The interface unit 120 connects the imaging device 100 to the lens unit 300 in the lens mount 106. The connector 122 is connected to the connector 322 of the lens unit 300, and electrically connects the imaging device 100 to the lens unit 300. Whether or not the lens unit 300 is attached to the lens mount 106 and / or the connector 122 of the imaging apparatus 100 is detected by a connection detection unit (not shown).

  The recording medium 200 is composed of, for example, a memory card or a hard disk. The recording medium 200 includes a recording unit 202 composed of a semiconductor memory or a magnetic disk, an interface unit 204 that manages an interface with the imaging device 100, and a connector 206 that connects to the imaging device 100.

  The lens unit 300 is an interchangeable lens type, and includes a photographing lens 310, an aperture 312, a lens mount 306, an interface unit 320, a connector 322, an aperture control unit 340, a distance measurement control unit 342, a lens system control unit 350, and the like. . The diaphragm 312 adjusts the amount of light with respect to the imaging element 14 of the imaging apparatus 100. The lens mount 306 mechanically couples the lens unit 300 to the imaging device 100 and includes various functions for electrically connecting the lens unit 300 to the imaging device 100.

  The interface unit 320 connects the lens unit 300 to the imaging device 100 in the lens mount 306. The connector 322 electrically connects the lens unit 300 to the imaging device 100.

  The aperture control unit 340 controls the aperture 312 in cooperation with the shutter control unit 40 based on the photometric information from the photometry control unit 44 or the calculation result obtained by calculating the image data captured by the image sensor 14 by the image processing circuit 20. To do. The distance measurement control unit 342 controls focusing of the photographing lens 310. The image stabilization control unit 344 controls the image stabilization unit 314.

  The lens system control unit 350 controls the entire lens unit 300. The lens system control unit 350 includes a memory for storing operation constants, variables, programs, identification information such as numbers unique to the lens unit, management information, function information such as an open aperture value, a minimum aperture value, and a focal length. And a function of a nonvolatile memory for holding past setting values and the like.

  Next, the operation of the imaging apparatus of the present embodiment having the above configuration will be described with reference to FIGS.

  In the imaging apparatus according to the present embodiment, when the live view function using the image display unit 29 as an EVF is started, the luminance Ev of the subject is calculated in order to perform image exposure control. Furthermore, based on the calculated luminance Ev of the subject, the control parameters for image control are accumulation time: Tv (charge accumulation time for the image sensor 14), aperture value: Av, and ISO sensitivity: Sv (output from the image sensor 14). It is necessary to determine the gain of the electrical signal to be generated. The luminance Ev of the subject when using the EVF is a value obtained by calculating the image data captured by the image sensor 14 by the image processing circuit 20.

  FIG. 2 is a flowchart illustrating control parameter calculation processing in the imaging apparatus 100. In this embodiment, it is assumed that the control parameter calculation process is performed when the live view function is started and every time a predetermined period elapses during the live view.

  In FIG. 2, the system control unit 50 of the imaging apparatus starts the control parameter calculation process (step S201), and acquires the next value. That is, the aperture value PreAv calculated in the previous calculation process and the luminance Ev of the subject immediately before the current calculation process are acquired (steps S202 and S203). If the current calculation process is performed at the start of the live view, the aperture value PreAv = 0 is set assuming that no calculation process has been performed before the current calculation process.

  Next, the system control unit 50 determines whether or not the current calculation process is a calculation process performed at the start of the live view (step S204). If the calculation process is not performed at the start of the live view, it is checked whether or not the luminance Ev of the subject is within the interlocking range of the aperture value PreAv, and it is determined whether or not the aperture value needs to be changed from the aperture value PreAv. (Step S205).

  When the subject brightness Ev is out of the interlocking range, the system control unit 50 performs control parameter calculation so that the subject brightness Ev is within the interlocking range, and calculates the values of the control parameters (Tv, Av, Sv). (Step S206). On the other hand, when the luminance Ev of the subject is within the interlocking range, the system control unit 50 performs a control parameter calculation based on the aperture value PreAv and calculates values of other control parameters (Tv, Sv) (step S207).

  Further, when the current calculation process is a calculation process at the start of live view, the system control unit 50 compares the luminance at which the aperture value changes with the luminance Ev of the subject, and the subject luminance Ev changes at the aperture value change point. It is determined whether or not it is within a predetermined range with reference to luminance (step S208). Here, the luminance that becomes the changing point of the aperture value is the luminance at the turning point of the solid line shown in FIG.

  When the luminance Ev of the subject is within the predetermined range, the system control unit 50 performs control parameter calculation so that the aperture value Av becomes the aperture value on the smallest aperture side that can be set on the program diagram, The value of the control parameter (Tv, Av, Sv) is calculated (step S209). Note that the smallest aperture value that can be set on the program diagram corresponds to the largest value that can be set on the program diagram.

  When the luminance Ev of the subject is out of the predetermined range, the system control unit 50 performs control parameter calculation so that the aperture value on the most open side that can be set on the program diagram is calculated, and the control parameters (Tv, Av, The value of Sv) is calculated (step S210). The aperture value on the most open side that can be set on the program diagram corresponds to the smallest value that can be set on the program diagram.

  Next, a specific example of the control of the imaging apparatus 100 will be described with reference to the program diagrams of FIGS.

  FIG. 3 is a normal program diagram used in the imaging apparatus 100. FIG. 4 is a program diagram used when the live view is started in the imaging apparatus 100. FIG. 5 is a program diagram used when the imaging apparatus 100 can select the accumulation time Tv up to the high speed side.

  In FIG. 3, the upper horizontal axis and the left vertical axis indicate the luminance Ev of the subject, the lower horizontal axis indicates the charge accumulation time Tv with respect to the image sensor 14, and the right vertical axis indicates the aperture value Av. In the imaging apparatus using the program diagram of FIG. 3, the ISO sensitivity: Sv is fixed at 100, the accumulation time Tv is switched between 1/8 and 1/8000, and the aperture value Av is switched between F1.8 and F29. Appropriate exposure control can be performed within the range of the luminance Ev0-18 of the subject. The present embodiment is characterized in that when the luminance Ev of the subject is in the range indicated by the oblique lines in FIG. 3, the aperture value is changed to an aperture value that does not easily change even if the luminance Ev of the subject changes.

  The brightness (predetermined brightness) as a change point of the aperture value for comparison with the brightness Ev of the subject is indicated by the bold solid line turning point (the change point of the corner corresponding to the upper left arrow) in FIG. It corresponds to the turning point (the change point of the corner corresponding to the arrow pointing downward to the right). That is, the luminance that becomes a change point for increasing the aperture value corresponds to a turning point of a thick solid line, and the luminance that serves as a changing point for decreasing the aperture value corresponds to a turning point of a two-dot chain line. In step S208 of FIG. 2 described above, the turning point of a solid line with a thick luminance that becomes a changing point for increasing the aperture value is set as the luminance that becomes the changing point of the aperture value.

  As shown in FIG. 3, as a program diagram, with priority given to Av so as to maintain the aperture value as constant as possible, the luminance Ev0 to 8 is an interlocking range at F1.8, the luminance Ev4 to 12 at F7.1, In F29, the luminances Ev8 to 18 are in the interlocking range. The aperture value Av changes from F1.8 to F7.1 when the subject brightness exceeds Ev8 when the aperture value Av is controlled at F1.8 (the folding point of the lower solid line in FIG. 3). ).

  Further, after the aperture value Av becomes F7.1, the aperture value Av becomes F1.8 when the brightness of the subject is lower than Ev4 (the folding point of the two-dot chain line on the lower side of FIG. 3). is there. That is, in the program diagram of FIG. 3, the control when the aperture is reduced is indicated by a solid line, and the control when the aperture is opened is indicated by a two-dot chain line. The same applies when the aperture value Av changes from F7.1 to F29 and when the aperture value Av changes from F29 to F7.1.

  From the flowchart in FIG. 2 and the program diagram in FIG. 3, if the image capturing apparatus is in live view, the aperture value Av changes from F1.8 to F7.1 as described above. It is a case where it exceeds.

  Conventionally, at the start of live view, the aperture value on the open side was selected to alleviate the phenomenon of blurring other than the main subject compared to the main subject, and to clearly see the focusing accuracy. . However, when the luminance of the subject at the start of live view is in the range of Ev7 to Ev8, for example, the aperture changes when the luminance of the subject becomes 1 Ev. Disturbed exposure of the displayed image may occur.

  Therefore, in the present embodiment, if the luminance of the subject at the start of live view is within a predetermined range based on the luminance that becomes the changing point for increasing the aperture value, the aperture value is more suitable for the change in the luminance of the subject. Control so that it does not change easily. Specifically, if the luminance of the subject at the start of live view is within the range of Ev7 to Ev8, or within the range of Ev11 to Ev12, the aperture value on the small aperture side is selected. Otherwise, the aperture value on the open side is selected. Control to select. Then, control values of other control parameters are calculated based on the selected aperture value and the luminance of the subject.

  On the other hand, in the case of TV priority in which the accumulation time Tv is controlled to be long so that the continuity between frames of the display image is not impaired, the arithmetic processing may be performed as follows. Unlike the case of Av priority, if the brightness of the subject at the start of the live view is within a predetermined range based on the brightness that becomes the changing point for reducing the aperture value, the aperture value on the open side must be selected. For example, control may be performed so that the aperture value on the small aperture side is selected.

  That is, when the aperture value is increased when the luminance of the subject exceeds the luminance at the change point, the luminance at the change point at the start of the live view is set to be lower than the luminance at the change point in the live view. On the other hand, when the aperture value is decreased when the luminance of the subject falls below the change point luminance, the luminance that is the change point at the start of the live view is set to be higher than the luminance of the change point during the live view. Further, in the present embodiment, for convenience of explanation, the number of stages for switching the selection of the aperture value at the start of the live view is one, but the present invention is not limited to this. The predetermined range based on the luminance serving as the change point may be changed without departing from the gist of the present invention.

  In the present embodiment, the aperture value is switched based on the result of comparing the difference between the luminance at the start of the live view and the luminance that is the change point of the aperture value in the program diagram using one program diagram. However, the present invention is not limited to this. The system control unit 50 of the imaging apparatus may be equipped with a program diagram for starting live view as shown in FIG. For example, when it is determined in step S204 in FIG. 2 that the calculation process is performed at the start of the live view, the program diagram is switched to the program diagram shown in FIG. 4 and the value of each control parameter is calculated. do it.

  Note that whether or not the continuity between frames of the pre-photographing image displayed during live view is lost is closely related to the charge accumulation time in the image sensor 14 during live view and the movement of the subject on the imaging screen. Come. For example, for a slow-moving subject or a non-moving subject, it is unlikely that the continuity between frames will be lost even if the accumulation time is shortened.

  Therefore, if the movement of the subject is not more than a predetermined amount, a program diagram that can use the accumulation time Tv shown in FIG. 5 up to the high speed side may be used. In the program diagram of FIG. 5, the accumulation time Tv can be used up to a higher speed side, and the aperture value can be controlled to be kept constant accordingly.

  Note that the image processing circuit 20 may determine whether or not the movement of the subject is equal to or less than a predetermined amount. As a method of detecting the movement (movement amount) of the subject or the moving speed of the subject, any of the following methods is used. It may be used. That is, a method for detecting the movement or speed of the subject based on the correlation between successive frames, and the movement of the subject based on the change in the contrast component of the image captured by the image sensor 14 (the amount of change in the evaluation value of the imaging surface AF). Alternatively, any method for detecting the speed may be used.

  However, even when using any of the methods described above to determine whether or not the movement of the subject is equal to or less than a predetermined amount, the determination cannot be made because no image has been acquired at the start of live view. Therefore, if it is determined in step S204 in FIG. 2 that the current calculation process is not the calculation process performed at the start of the live view, it is determined whether or not the movement of the subject is equal to or less than a predetermined amount before performing step S205. Good.

  As described above in detail, in this embodiment, when the aperture value at the start of live view is determined based on the program diagram, control is performed so as to suppress the change in aperture value even if there is a change in the luminance of the subject. doing. As a result, it is possible to reduce the frequency with which changes in depth, changes in sound, changes in screen brightness, and the like occur due to a change in aperture, so that it is possible to make it difficult for the operator to feel discomfort.

[Other Embodiments]
The object of the present invention is achieved by executing the following processing. That is, a storage medium that records a program code of software that realizes the functions of the above-described embodiments is supplied to a system or apparatus, and a computer (or CPU, MPU, etc.) of the system or apparatus is stored in the storage medium. This is the process of reading the code.

  In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiments, and the program code and the storage medium storing the program code constitute the present invention.

  Moreover, the following can be used as a storage medium for supplying the program code. For example, floppy (registered trademark) disk, hard disk, magneto-optical disk, CD-ROM, CD-R, CD-RW, DVD-ROM, DVD-RAM, DVD-RW, DVD + RW, magnetic tape, nonvolatile memory card, ROM or the like. Alternatively, the program code may be downloaded via a network.

  Further, the present invention includes a case where the function of the above-described embodiment is realized by executing the program code read by the computer. In addition, an OS (operating system) running on the computer performs part or all of the actual processing based on an instruction of the program code, and the functions of the above-described embodiments are realized by the processing. Is also included.

  Furthermore, the present invention includes a case where the functions of the above-described embodiment are realized by the following processing. That is, the program code read from the storage medium is written in a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer. Thereafter, based on the instruction of the program code, the CPU or the like provided in the function expansion board or function expansion unit performs part or all of the actual processing.

14 Imaging device 20 Image processing circuit 29 Image display unit 50 System control unit 100 Imaging device 300 Lens unit 312 Aperture

Claims (10)

An image sensor that converts an optical image of a subject into an electrical signal;
An image pickup apparatus that adjusts an amount of light incident on the image pickup device by controlling a diaphragm, and a display unit capable of sequentially displaying images obtained using the image pickup device.
Calculating means for calculating the luminance of the subject;
Control means for changing the aperture value of the aperture when the brightness calculated by the calculating device is within a predetermined range;
The control unit changes the predetermined range before and after the sequential display of the image by the display unit, and the luminance of the subject is within the predetermined range before the sequential display of the image is started. The imaging apparatus is characterized in that the aperture value is changed before the start of sequential display of the images.   The imaging apparatus according to claim 1, wherein the control unit uses the aperture value changed before the sequential display of the images by the display unit is started at the start of sequential display of the images. The control means, when the brightness calculated by the calculation means is in a first range for changing the aperture value of the aperture to be larger than the predetermined range , The imaging apparatus according to claim 1, wherein the first range before the start of sequential display includes a range having a lower luminance than the first range during sequential display of the images. . Sequentially displaying the first range minimum luminance of the first luminance before the start of the image by the display means,
The lowest luminance in the first range during the sequential display of the image by the display means is a second luminance,
When the brightness of the subject is within the first range, the brightness is reduced to reduce the aperture value, and the third brightness is outside the first range.
The imaging apparatus according to claim 3, wherein a difference between the first luminance and the second luminance is smaller than a difference between the first luminance and the third luminance. The control means, when the luminance calculated by the calculation means is in a first range for changing the aperture value of the aperture to be smaller in the predetermined range , 3. The imaging apparatus according to claim 1, wherein the first range before the start of sequential display includes a range having higher luminance than the first range during sequential display of the image. . Maximum brightness the first luminance sequential display the first range before the start of the image by the display means,
The highest luminance in the first range during the sequential display of the image by the display means is the second luminance,
When the luminance of the subject is in the first range, the luminance is increased to reduce the aperture value, and the third luminance is outside the first range,
The imaging apparatus according to claim 5, wherein a difference between the first luminance and the second luminance is smaller than a difference between the first luminance and the third luminance. A motion detection means for detecting the motion of the subject on the imaging screen;
The imaging apparatus according to claim 1, wherein the control unit changes the predetermined range in accordance with a movement of the subject detected by the movement detection unit.   The imaging apparatus according to claim 1, wherein the control unit changes the predetermined range by changing a program diagram. An image sensor that converts an optical image of a subject into an electrical signal; and display means that can sequentially display an image obtained by using the image sensor, and controls the aperture to enter the image sensor A control method for an imaging apparatus that adjusts the amount of light,
A calculation step of calculating the luminance of the subject;
A control step of changing the aperture value of the aperture when the luminance calculated by the calculation step is within a predetermined range,
The control step changes the predetermined range before and after the sequential display of the images by the display unit, and the luminance of the subject is within the predetermined range before the sequential display of the images is started. A method for controlling an imaging apparatus, wherein the aperture value is changed before the start of sequential display of the images.   A program having computer-readable program code for causing a computer to execute the control method for an imaging apparatus according to claim 9.

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