Imaging apparatus, method for controlling the same, and program

Abstract

To suppress the occurrence of exposure deviation in an image, while increasing the maximum strobe synchronization shutter speed.SOLUTION: An imaging apparatus 100 includes: a strobe device 400 which has a strobe light emitting part 401 for emitting strobe light; a shutter 102 which has a front curtain and a rear curtain for controlling exposure for an imaging element 103; and a system control part 120 which sets the emitted light quantity of the strobe light emitting part 401. The system control part 120 sets the upper limit value of the emitted light quantity of the strobe light emitting part 401 when performing strobe synchronization photographing at the maximum strobe synchronization shutter speed on the basis of the traveling time of the front curtain.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to an imaging apparatus and a control method and program therefor, and more particularly to control of the amount of light emitted and the shutter speed during flash photography. [Background technology]

[0002] There is a known technology for increasing the maximum strobe-synchronized shutter speed when using an imaging device for strobe photography. The maximum strobe-synchronized shutter speed refers to the fastest shutter speed at which photography can be performed with the front and rear curtains open while the strobe is firing, in a shutter system in which photography is performed by moving a front curtain that starts exposure and a rear curtain that ends exposure. For example, Patent Document 1 discloses an imaging device that increases the maximum strobe-synchronized shutter speed by shortening the time of the electronic shutter used as the front curtain compared to the time of the mechanical shutter used as the rear curtain. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-060640 Summary of the Invention [Problem to be solved by the invention]

[0004] In the technology described in Patent Document 1, the travel time of the front curtain is different from the travel time of the rear curtain, and therefore the exposure time changes between the top and bottom of the captured image due to the difference in travel time between the front curtain and the rear curtain, resulting in a problem of exposure deviation between the top and bottom of the captured image.

[0005] SUMMARY OF THE INVENTION An object of the present invention is to provide an imaging apparatus that can increase the maximum strobe synchronization shutter speed while suppressing exposure deviation within an image. [Means for solving the problem]

[0006] The imaging device according to the present invention comprises a strobe light emitting means, a shutter having a front curtain and a rear curtain that controls exposure to an imaging element, and a setting means that sets the amount of light emitted by the strobe light emitting means, wherein the setting means sets an upper limit of the amount of light emitted when strobe sync shooting is performed at the maximum strobe sync shutter speed based on the travel time of the front curtain. [Effects of the Invention]

[0007] According to the imaging device of the present invention, it is possible to increase the maximum flash synchronization shutter speed while suppressing exposure deviation between the top and bottom of a captured image. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a block diagram showing a schematic configuration of an imaging system according to an embodiment. [Figure 2] FIG. 10 is a diagram illustrating an increase in the maximum flash synchronization shutter speed. [Figure 3] 10 is a flowchart of a flash synchronization maximum shutter speed update process. [Figure 4] 10A and 10B are diagrams illustrating the influence of the front curtain running speed on exposure when the shutter speed and the light emission amount curve are the same. [Figure 5] 10 is a diagram showing an example of the relationship between the shutter method and the maximum strobe synchronization shutter speed, and an example of the corresponding upper limit value of the light emission amount for each size of the image sensor. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings. Here, an imaging system according to the present invention will be described, in which a lens barrel (interchangeable lens) and a strobe device (illumination device) are attached to an imaging device such as a digital camera.

[0010] In this description, the term "imaging device" refers to an imaging device body equipped with an imaging element. However, for convenience, devices in which the taking lens (lens unit) is integrated with the device body, such as compact digital cameras and digital video cameras, are also included in the term "imaging device."

[0011] 1 is a block diagram showing a schematic configuration of an image capturing system 1000 according to an embodiment. The image capturing system 1000 includes an image capturing device 100, a lens barrel 300 and a strobe device 400 attached to the image capturing device 100, and an external storage medium 200 in which the image capturing device 100 is housed.

[0012] Specifically, the imaging device 100 is a digital camera, and in this embodiment, it is assumed to be a mirrorless digital single-lens camera. The imaging device 100 has a lens mount 160, an imaging element 103, a shutter 102, a shutter control unit 115, an A / D conversion unit 106, an image processing unit 107, a memory control unit 110, a D / A conversion unit 109, an image display memory 112, and a temporary storage memory 113. The imaging device 100 also has a compression / decompression unit 111, a timing generation unit 108, an electronic viewfinder 105, a rear display unit 114, a system control unit 120, a main memory 121, a non-volatile memory 123, an operation unit 133, a mode dial 130, and a release button 131. The imaging device 100 has a playback button 132, a power switch 134, a power control unit 124, a first camera I / F 140, a second camera I / F 150, a third camera I / F 170, a first camera connector 141, a second camera connector 151, and a third camera connector 171.

[0013] The external storage medium 200 includes a media connector 203 , a media I / F 202 , and a storage unit 201 .

[0014] The lens barrel 300 includes a camera mount 320 , a lens connector 311 , a lens I / F 310 , an imaging lens group 301 , an aperture 302 , an aperture driver 303 , a lens driver 304 , and a lens controller 305 .

[0015] The flash device 400 includes a flash connector 411 , a flash I / F 410 , a flash control unit 402 , and a flash light emitting unit 401 .

[0016] In the imaging device 100, the imaging element 103 is, for example, a charge-accumulating photoelectric conversion device such as a CMOS. An optical image of a subject that is incident through the lens barrel 300 and focused on the imaging surface of the imaging element 103 is converted into an analog image signal by photoelectric conversion, and the generated analog image signal is output to the A / D conversion unit 106.

[0017] The shutter 102 includes front and rear curtains, which are mechanical components, and an actuator that drives the front and rear curtains, and drives the front and rear curtains to open or block the light path between the lens barrel 300 and the image sensor 103. Note that the shutter 102 is not limited to a mechanical configuration that drives the front and rear curtains, but can also be realized by an electronic shutter function that resets or reads image data captured by the image sensor 103 through electrical control. The shutter control unit 115 controls the driving of the shutter 102 (front and rear curtains) in accordance with commands from the system control unit 120.

[0018] The A / D conversion unit 106 converts the analog image signal output from the image sensor 103 into digital image data, and outputs the generated digital image data to the image processing unit 107 and the memory control unit 110. The image processing unit 107 performs various processes, such as white balance adjustment and gradation processing, on the digital image data sent from the A / D conversion unit 106. The image processing unit 107 can also perform processing to cut out a part of the image.

[0019] The memory control unit 110 controls writing and reading of various data acquired from the A / D conversion unit 106 , image processing unit 107 , and compression / decompression unit 111 to and from the image display memory 112 and temporary storage memory 113 .

[0020] The image display memory 112 temporarily stores digital image data for display of images to be displayed on the electronic viewfinder 105 and rear display unit 114. The digital image data for display written to the image display memory 112 is sent to the D / A conversion unit 109 via the memory control unit 110. The D / A conversion unit 109 performs D / A conversion on the digital image data for display, generates analog image data for display, and supplies it to the electronic viewfinder 105 and rear display unit 114.

[0021] The temporary storage memory 113 temporarily stores image data output from the image processing unit 107 and image data read from the external storage medium 200, and is also used as a work area for the system control unit 120. The compression / decompression unit 111 reads the image data stored in the temporary storage memory 113 and compresses or decompresses the image data using a predetermined image compression method and image decompression method in accordance with various uses.

[0022] The timing generating unit 108 generates operation signals (control signals such as clock signals) to be supplied to the image sensor 103, the A / D conversion unit 106, the D / A conversion unit 109, etc. The timing generating unit 108 also controls the accumulation of charges in the image sensor 103 by controlling the reset timing of the accumulated charges in the image sensor 103.

[0023] The electronic viewfinder 105 and rear display unit 114 are configured with a liquid crystal panel, an organic EL panel, or the like, and display a subject image and a menu screen for making various settings for the image capture device 100. The electronic viewfinder 105 is configured so that the user can check the displayed content by placing their eye on it, and the rear display unit 114 is attached to the rear of the image capture device 100 via a vari-angle mechanism or a tilt mechanism.

[0024] The system control unit 120 controls not only the image capture device 100 but also the overall operation of the image capture system 1000. A specific example will be described below, but the processing executed by the system control unit 120 is not limited to the following specific example.

[0025] The system control unit 120 performs photometry calculations using image data acquired by the image sensor 103, calculates the brightness value of the subject (obtains brightness information), and determines the exposure conditions for the image sensor 103. Parameters that determine the exposure conditions include aperture value, shutter speed, and shooting sensitivity (ISO sensitivity). In this way, appropriate exposure for the image sensor 103 is controlled. Furthermore, the system control unit 120 controls the position of the lens group in the lens barrel 300 (focus control) based on the focus detection result for the subject so as to focus on the subject. Note that focus control methods include a contrast method, a phase difference method, and an in-plane phase difference method for the image sensor.

[0026] The system control unit 120 issues instructions to the strobe control unit 402 to control the amount and timing of light emitted by the strobe light emitting unit 401 according to the photometric calculation results, exposure conditions, and the state of the strobe device 400. The system control unit 120 controls, in particular, the shutter 102 when capturing a still image, and in particular the image sensor 103 when capturing a live view image or capturing a video, thereby controlling the charge accumulation time in the image sensor 103.

[0027] When capturing still images and moving images, the system control unit 120 controls the display of a live view image for confirming the subject on the electronic viewfinder 105 and the rear display unit 114. The system control unit 120 also uses image data obtained by the image sensor 103 to detect the presence or absence of flicker in the shooting environment and its frequency.

[0028] The system control unit 120 controls the start and end of video recording in accordance with an input signal from the operation unit 133, and can also switch the imaging range of the image sensor 103 to capture images using pixel output from the entire imaging surface or a cropped portion of the imaging surface. For example, the user can switch between capturing a full-size image or capturing an image within the APS-C size range. When capturing an image by cropping a portion of the imaging surface, the image processing unit 107 may crop a portion of the output from pixels on the entire imaging surface, or may extract pixel signals from only a portion of the imaging surface.

[0029] Returning to the description of other components of the imaging apparatus 100, the main memory 121 is, for example, a ROM, and stores data related to the operation of the imaging apparatus 100, such as information related to appropriate exposure for brightness values ​​(table data and program diagrams), constants for operations executed by the imaging apparatus 100, various exposure conditions, and arithmetic expressions. The main memory 121 is also used to store settings related to the front curtain run time, the upper limit of the light emission amount of the strobe light emitting unit 401, and the maximum strobe synchronization shutter speed. The non-volatile memory 123 is, for example, an EEPROM or the like that can be electrically erased and stored, and stores various setting values ​​for the imaging system 1000.

[0030] The operation unit 133 is composed of buttons, switches, dials, a touch panel, a line-of-sight detection device, a voice recognition device, or a combination of these, which input various operational instructions to the system control unit 120. Note that the operation members included in the operation unit 133 are operation members other than the mode dial 130, the release button 131, the playback button 132, and the power switch 134, which are separately shown in FIG.

[0031] The mode dial 130 is a rotary operating member used to set an arbitrary shooting mode from among a plurality of shooting modes that can be set in the imaging device 100. The imaging device 100 can be set to a still image mode for capturing still images and a video mode for recording videos. Furthermore, in each of the still image and video shooting modes, various modes are available in which exposure parameters can be set automatically or manually, such as full auto, program, aperture priority, shutter speed priority, and manual, and it is also possible to set whether or not to use flash when capturing still images.

[0032] The release button 131 is an operating member for instructing the start of preparatory operations for still image shooting or video shooting, or the start of actual shooting. The release button 131 generates an SW1 signal with a first stroke (halfway pressed), and the system control unit 120 starts the shooting preparatory operations when it detects the SW1 signal. In the shooting preparatory operations, focus control, exposure control, auto white balance (AWB) processing, etc. are performed as necessary. The release button 131 generates an SW2 signal with a second stroke (full press). When the system control unit 120 detects the SW2 signal, a series of processes (shooting processes) are executed, from exposure processing for the image sensor 103 to storage processing of image data in the external storage medium 200.

[0033] The playback button 132 is an operating member that instructs the start of playback processing in which image data is read from the temporary storage memory 113 or the external storage medium 200 and displayed on the rear display unit 114. The power switch 134 is an operating member that switches on / off the supply of power from a power source (not shown) such as a battery to each unit of the image capture device 100. Note that when the power switch 134 is turned on, power can be supplied not only to the image capture device 100 but also to the lens barrel 300, the external storage medium 200, and the flash device 400.

[0034] The operation unit 133 is used for displaying a menu on the rear display unit 114, for various settings related to the imaging conditions in the imaging system 1000, and for various settings related to the playback of captured still images and videos. Here, specific examples will be described, but the operations that can be performed by the operation unit 133 are not limited to the following specific examples.

[0035] For example, the user can configure various settings for flash photography, shutter speed, aperture, ISO settings, flicker detection, and imaging range settings. Specifically, the imaging range can be switched by setting the still image crop / aspect ratio. The imaging range can be a "full size" imaging range that captures images using the entire imaging surface of the image sensor 103, a crop from full size at a ratio such as [16:9], [4:3], or [1:1], or a "crop" imaging range that captures only the APS-C range. The imaging range may be configured to automatically switch based on information from the lens barrel 300.

[0036] In addition, the user can select and set the shutter method from among electronic shutter, electronic front curtain, and mechanical shutter. When the electronic shutter is set, the system control unit 120 controls the front and rear curtains by resetting and reading out the electric charge at each pixel of the image sensor 103. When the mechanical shutter is set, the system control unit 120 controls both the front and rear curtains by operating a light-oblique member. When the electronic front curtain is set, the system control unit 120 controls the front curtain by resetting the electric charge at each pixel of the image sensor 103, and controls the rear curtain by operating a light-oblique member.

[0037] The user can set so-called electronic zoom (including electronic teleconverter settings) to crop, enlarge, and record a partial area from the imaging surface of the image sensor 103. Specifically, the user can set electronic zoom on / off and the zoom magnification.

[0038] The user can turn electronic stabilization on or off and set the stabilization strength for electronic stabilization. Electronic stabilization changes the position at which an image captured by the image sensor 103 is cropped to compensate for the amount of shake (blur), and the greater the stabilization strength, the smaller the cropped image size.

[0039] In addition, the user can set HDR (High Dynamic Range) imaging, which allows for the acquisition of images with a wide dynamic range by amplifying pixel signals with different gains. In HDR imaging, the drive mode of the image sensor 103 is set to DGO (Dual Gain Output) mode or DS (Dual Slope) mode.

[0040] Returning to the description of other components of the imaging device 100, the power supply control unit 124 includes a battery detection circuit, a DC-DC converter, a switch circuit used to switch between power supply blocks, and the like, and controls the power supply from the power supply unit to each unit of the imaging device 100. Based on instructions from the system control unit 120 in response to operation of the power switch 134, the power supply control unit 124 detects whether a battery is installed, the type of battery, and the remaining battery power, and supplies the required voltage to each unit of the imaging system 1000 for the required period of time.

[0041] First camera I / F 140 is an interface for communicatively connecting system control unit 120 and external storage medium 200. Second camera I / F 150 is an interface for communicatively connecting system control unit 120 and lens control unit 305. Third camera I / F 170 is an interface for communicatively connecting system control unit 120 and strobe control unit 402. Lens mount 160 is a mount unit on the imaging device 100 side that engages with camera mount 320 of lens barrel 300 to mechanically connect lens barrel 300 and imaging device 100.

[0042] The first camera connector 141 is connected to the media connector 203 of the external storage medium 200. This electrically connects the image capture device 100 and the external storage medium 200, enabling the transmission of various control signals, image data, etc., and also enabling the supply of power from the image capture device 100 to the external storage medium 200. The second camera connector 151 is connected to the lens connector 311, which electrically connects the image capture device 100 and the lens barrel 300, enabling the transmission of various control signals, status signals, data signals, etc., and the supply of power from the image capture device 100 to the lens barrel 300. The third camera connector 171 is connected to the strobe connector 411, which electrically connects the image capture device 100 and the strobe device 400, enabling the transmission of various control signals, status signals, data signals, etc., and the supply of power from the image capture device 100 to the strobe device 400. The second camera connector 151 and the third camera connector 171 may be configured to perform optical communication, audio communication, etc. in addition to electrical communication.

[0043] The external storage medium 200 is a memory card, a hard disk, etc., and the storage unit 201 is composed of a semiconductor memory, a magnetic disk, etc. The media connector 203 is electrically connected to the first camera connector 141 of the imaging device 100. The media I / F 202 is an interface for connecting the external storage medium 200 and the system control unit 120 so that they can communicate with each other.

[0044] Lens barrel 300 is an optical device that is detachable from image capture device 100 and forms an optical image of a subject on image sensor 103. Camera mount 320 is a mount unit on lens barrel 300 that engages with lens mount 160 of image capture device 100 to mechanically connect lens barrel 300 and image capture device 100. Lens connector 311 is provided inside camera mount 320 and electrically connects lens barrel 300 and image capture device 100. Lens connector 311 may be configured to be capable of optical communication, audio communication, and the like in addition to electrical communication, in accordance with the configuration of second camera connector 151. Lens I / F 310 is an interface for communicatively connecting lens control unit 305 and system control unit 120.

[0045] The lens control unit 305 performs overall control of each unit of the lens barrel 300 in accordance with commands from the system control unit 120. The lens control unit 305 holds information such as operating constants, variables, operating programs, identification information (manufacturing ID) of the lens barrel 300, management information, maximum aperture value, minimum aperture value, and focal length.

[0046] The imaging lens group 301 is composed of multiple lenses such as a focus lens, a zoom lens, and an image stabilization lens, and focuses incident light onto the imaging surface of the image sensor 103. The lens driver 304 adjusts the optical axis positions of the focus lens and zoom lens in accordance with instructions from the lens controller 305, and also drives the image stabilization lens within a plane perpendicular to the optical axis. The diaphragm 302 adjusts the amount of light flux from the subject that passes through the imaging lens group 301 and enters the image sensor 103. The diaphragm 302 and the shutter 102 can be controlled in conjunction with each other. The diaphragm driver 303 adjusts the opening amount of the diaphragm 302 in accordance with instructions from the lens controller 305.

[0047] The strobe device 400 is detachable from the imaging device 100 and emits a flash (strobe light) to a subject depending on the shooting environment. The strobe connector 411 is electrically connected to the third camera connector 171. The strobe connector 411 may be configured to be capable of optical communication, audio communication, and the like in addition to electrical communication, depending on the configuration of the third camera connector 171. The strobe I / F 410 is an interface for communicatively connecting the strobe control unit 402 and the system control unit 120. The strobe light emitting unit 401 is, for example, a xenon tube. The strobe control unit 402 controls light emission by the strobe light emitting unit 401 in accordance with commands from the system control unit 120. The strobe control unit 402 stores information such as operating constants and variables, operating programs, identification information (manufacturing ID), management information, guide number, and color temperature. Various settings of the strobe device 400 can be made by operating an operation unit (not shown) provided in the strobe device 400 and / or by communication from the imaging device 100.

[0048] Note that processing blocks such as the system control unit 120, image processing unit 107, strobe control unit 402, and lens control unit 305 can be realized by hardware such as an ASIC or programmable logic array (PLA). However, this is not limiting, and each processing block may be realized by a programmable processor such as a CPU or MPU executing software (a combination of software and hardware). In other words, the same hardware may be configured to function as multiple functional blocks.

[0049] Next, we will explain the process of updating the maximum flash synchronization shutter speed executed by the image capture device 100. In this embodiment, since control that does not synchronize flash emission and shutter operation during flash photography is not covered, in the following explanation, the maximum flash synchronization shutter speed will be abbreviated as "maximum synchronization speed."

[0050] By operating the operation unit 133, the user can set whether or not to use the flash when taking still images, the shutter speed (shutter time) when taking flash-synchronized images, and the like, and can also set the maximum synchronization speed to be increased.

[0051] In this embodiment, when the increase in maximum synchronization speed is enabled, the maximum synchronization speed is increased by 1 / 3 stop (0.33 EV) compared to when the increase in maximum synchronization speed is disabled. At this time, an upper limit is set for the amount of light emitted by the strobe light emitter 401, and the maximum synchronization speed is increased by limiting the amount of light emitted. Note that 1 / 3 stop is just an example, and a different number of stops may be used.

[0052] The system control unit 120 stores an upper limit value for the amount of light emitted by the flash light emitting unit 401 in the main memory 121, clips the amount of light emitted by the flash light emitting unit 401 at the stored upper limit value during flash synchronous shooting, and transmits the clipped amount of light emitted to the flash device 400 (flash control unit 402). The flash control unit 402 limits the amount of light emitted by the flash light emitting unit 401 by making the flash light emitting unit 401 emit light at the received amount of light emitted.

[0053] FIG. 2 is a diagram illustrating an increase in the maximum synchronization speed. FIG. 2(a) is a diagram illustrating the relationship between the maximum synchronization speed of the shutter and the amount of light emitted when the maximum synchronization speed is not increased, and FIG. 2(b) is a diagram illustrating the relationship between the maximum synchronization speed of the shutter and the amount of light emitted when the maximum synchronization speed is increased. In FIGS. 2(a) and 2(b), 'S1' and 'S2' schematically represent the travel of the front curtain of the shutter 102, and the travel of the rear curtain of the shutter 102, respectively. In FIGS. 2(a) and 2(b), the gradient of the front curtain travel S1 (front curtain travel speed) and the gradient of the rear curtain travel S2 (rear curtain travel speed) are the same.

[0054] If the shutter 102 is a mechanical shutter, exposure is initiated by the travel S1 of the front curtain of the shutter, and light is blocked by the travel S2 of the rear curtain of the shutter for the image sensor 103. If the shutter 102 is an electronic shutter, the accumulated charge in the horizontal direction of the image sensor 103 is reset by the control of the front curtain, and the accumulated charge of the pixels in each row of the image sensor 103 is read out sequentially by the control of the rear curtain.

[0055] The period 'A' in Figures 2(a) and (b) represents the travel time of the front curtain of the shutter 102. The light emission amount curves in Figures 2(a) and (b) represent the change in light emission amount over time when the strobe is emitting light. Here, the maximum light emission amount is represented as '1', and the light amount at which the light emission amount is half of its peak is represented as '1 / 2'. The time until the light emission amount drops to half of its peak is defined as the "strobe emission period." Therefore, the strobe emission period is represented by 'B' in both Figures 2(a) and (b), and if both the front and rear curtains are open during the strobe emission period, it can be said that strobe synchronization has been achieved.

[0056] In both Figures 2(a) and 2(b), the rear curtain starts traveling immediately after the end of strobe light emission period B, achieving strobe synchronization. The charge accumulation time in the image sensor 103 is represented by 'A+B', and accumulation time A+B is the maximum synchronization speed. In contrast to the example in Figure 2(a), where the maximum synchronization speed is not increased, in the example in Figure 2(b), the maximum synchronization speed is increased by reducing the amount of light emitted and shortening strobe light emission period B.

[0057] 3 is a flowchart of the maximum tuning speed update process. Each process (step) indicated by an S number in this flowchart is realized by the system control unit 120 executing a predetermined program to comprehensively control the operation of each unit in the imaging system 1000.

[0058] In S301, the system control unit 120 acquires setting values ​​necessary for updating the maximum synchronization speed. The settings acquired in S301 include settings for increasing the maximum synchronization speed, shutter method, still image crop / aspect, electronic zoom, electronic image stabilization, and settings related to HDR shooting.

[0059] In S302, the system control unit 120 determines whether at least one of the settings acquired in S301 has been changed. For example, the setting values ​​used in the previous determination process in S302 are stored in the main memory 121, and by comparing them with the most recent setting acquired in S301, it is possible to determine whether each setting has been changed.

[0060] If the system control unit 120 determines that none of the settings acquired in S301 have been changed (No in S302), it ends this process. On the other hand, if the system control unit 120 determines that at least one of the settings acquired in S301 has been changed (Yes in S302), it executes the process of S303.

[0061] In S303, the system control unit 120 calculates the front curtain run time. The front curtain run time is the period indicated by 'A' in Fig. 2, and takes a value according to the setting acquired in S301. In other words, the front curtain run time changes depending on the change in the setting acquired in S301.

[0062] For example, in the case of an electronic shutter system, the leading curtain travel time is the time required to reset the charge of the image sensor 103, and in the case of a mechanical shutter system, the leading curtain travel time is the time required to complete the operation of the light-oblique member of the shutter 102. In the case of an electronic shutter system, the reset speed of the image sensor 103 is directly linked to the leading curtain travel time, so it becomes necessary to consider the drive mode of the image sensor 103.

[0063] Furthermore, the on / off setting for HDR shooting has a significant impact on the drive mode used when reading out accumulated charge from the pixels of the image sensor 103. In HDR shooting, the dynamic range is expanded by using signals read out from the image sensor 103 at different sensitivities using a dual slope drive mode or the like. When operating the image sensor 103 in such a special drive mode, the reset speed of the image sensor 103 may change, so the first curtain run time must be calculated taking the HDR shooting setting into consideration.

[0064] Furthermore, with regard to still image crop / aspect ratio, for example, the first curtain run time is shorter in the case of "full size," which captures the entire image pickup surface of the image sensor 103, than in the case of "crop," which captures only the APS-C range. Furthermore, the first curtain run time is shorter in the latter case because the exposure range is narrower in the mechanical shutter system, and the range over which the image signal is reset is narrower in the electronic shutter system. Thus, the first curtain run time must be calculated taking into account the shooting range according to the still image crop / aspect ratio setting.

[0065] With electronic zoom, the shorter the front curtain run time is, the narrower the range from which signals are extracted from the imaging surface of the image sensor 103. In other words, the greater the zoom magnification of electronic zoom, the shorter the front curtain run time is, so the front curtain run time must be calculated taking into account the electronic zoom settings.

[0066] With electronic image stabilization, a portion of the image captured by the image sensor 103 is cut out, so the first curtain travel time changes depending on the cut-out range. The greater the image stabilization strength, the narrower the cut-out range and the shorter the first curtain travel time. Therefore, it is necessary to calculate the first curtain travel time taking into account the settings of electronic image stabilization.

[0067] In this way, in S303, the first curtain run time is calculated taking into account the effects of changes in the shooting range depending on the shutter method, HDR shooting on / off, still image crop / aspect setting, electronic zoom, and electronic image stabilization settings.

[0068] In S304, the system control unit 120 determines whether or not increasing the maximum tuning speed is enabled based on the setting acquired in S301. If the system control unit 120 determines that increasing the maximum tuning speed is disabled (NO in S304), it executes the process of S305.

[0069] In S305, the system control unit 120 sets the upper limit of the light emission amount to the full light emission value, and stores this in the main memory 121. Note that allowing full light emission effectively means that the light emission amount is not limited.

[0070] In S306, the system control unit 120 calculates the normal synchronization maximum speed, which is the shutter speed when the maximum synchronization speed is not increased. The normal synchronization maximum speed is calculated by adding the front curtain run time calculated in S303 and the strobe light emission period at full light emission set in S305. The system control unit 120 stores the calculated normal synchronization maximum speed in the main memory 121 and ends this processing. In this way, when increasing the maximum synchronization speed is disabled, the light emission amount upper limit value and the maximum synchronization speed stored in the main memory 121 are updated by the processing of S305 and S306, and the processing to update the maximum synchronization speed ends.

[0071] If it is determined in the determination process of S304 that increasing the maximum tuning speed is effective (YES in S304), the system control unit 120 executes the process of S307.

[0072] In S307, the system control unit 120 calculates the maximum speed-up tuning speed. The maximum speed-up tuning speed is calculated by adding 1 / 3 stop (0.33 EV) to the maximum normal tuning speed, which is the maximum tuning speed when no speed-up is performed. The system control unit 120 stores the calculated maximum speed-up tuning speed in the main memory 121. Note that, as in S306, the maximum normal tuning speed is calculated by adding the front curtain travel time calculated in S303 and the light emission period at full light emission.

[0073] In S308, the system control unit 120 calculates the maximum light emission amount that will allow the light emission duration to fall within the time obtained by subtracting the front curtain travel time from the maximum high-speed synchronization speed calculated in S307, and stores this in the main memory 121 as the upper limit of the light emission amount, thereby terminating this processing.

[0074] In this way, when increasing the maximum tuning speed is enabled, the upper limit light emission amount and the maximum tuning speed stored in the main memory 121 are updated in steps S307 and S308, and the process of updating the maximum tuning speed is then completed. As explained above, the upper limit light emission amount and the maximum tuning speed stored in the main memory 121 are updated by the values ​​calculated in steps S305 and S306 or the values ​​calculated in steps S307 and S308 each time this flow is executed.

[0075] In this embodiment, the maximum synchronization speed is increased by setting an upper limit on the amount of light emitted and limiting the amount of light emitted by the strobe, thereby making it possible to suppress exposure deviations at the top and bottom of the captured image due to differences in the travel times of the front and rear curtains.

[0076] Furthermore, if the light emission amount is set to the same under conditions where the same maximum synchronization speed is used but the front curtain run time is different, the light emission period and the run of the rear curtain may overlap, resulting in uneven brightness at the top and bottom of the captured image. In response to this problem, this embodiment sets an upper limit on the light emission amount according to the front curtain run time, thereby avoiding this problem.

[0077] This effect will be explained with reference to Figures 4 and 5. Figure 4 is a diagram illustrating the influence of the front curtain running speed on exposure when the shutter speed (shutter time T) and the light emission amount curve are the same. Figure 4(b) shows the working example, and Figures 4(a) and (c) show comparative examples 1 and 2, respectively.

[0078] The embodiment in FIG. 4(b) shows how the maximum synchronization speed is increased in accordance with the speed of the front curtain travel S1a. The speed of the rear curtain travel S2a is the same as the speed of the front curtain travel S1a. In this embodiment, light is emitted at the end of the front curtain travel, and the rear curtain begins traveling when the amount of light emitted has fallen to half of its peak, making it possible to obtain an image with consistent exposure throughout the entire image. The maximum synchronization speed (shutter time T) and light emission curve L in the embodiment in FIG. 4(b) correspond to, for example, the combination of full size, electronic front curtain, and speed increase on in FIG. 5, which will be described later.

[0079] FIG. 4(a) shows Comparative Example 1 in which the same shutter speed T and light emission curve L as in FIG. 4(b) are applied to the front curtain travel S1b, which is faster than the front curtain travel S1a. The speed of the rear curtain travel S2b is the same as the speed of the front curtain travel S1b. In Comparative Example 1, the rear curtain starts traveling after time C has elapsed from the point when the amount of light emission has decreased to half (the end of light emission period B). This indicates that the shutter speed can be further increased (the shutter speed can be shortened) by the time C, and / or the upper limit of the amount of light emission can be increased without changing the shutter speed.

[0080] FIG. 4(c) shows Comparative Example 2, in which the same shutter speed T and light emission curve L as in FIG. 4(b) are applied to a front curtain travel S1c that is slower than the front curtain travel S1. The speed of the rear curtain travel S2c is the same as the speed of the front curtain travel S1c. In Comparative Example 2, the front curtain travel time is longer than in the example, and therefore the tunable light emission period is shorter. However, light is emitted according to the same light emission amount curve L as in the example, and the rear curtain begins traveling before the light emission amount drops to half of its peak. As a result, not all of the strobe light enters the exposure period for the upper part of the screen, and the latter half of the light emission is vignetted, resulting in an image in which the upper part of the screen is darker than the lower part of the screen.

[0081] In this way, in this embodiment, the maximum synchronization speed is determined in accordance with the front curtain travel time, and the upper limit value of the light emission amount is calculated in accordance with the determined maximum synchronization speed, so that the maximum synchronization speed and the upper limit value of the light emission amount can be set appropriately to obtain an image with no uneven exposure.

[0082] Fig. 5(a) is a diagram showing an example of the relationship between the shutter type and the maximum synchronization speed for each size of image sensor, and Fig. 5(b) is a diagram showing an example of the upper limit of the light emission amount set corresponding to Fig. 5(a).

[0083] The image sensor is assumed to be full-size, and examples are given of full-size photography and photography cropped to APS-C size. The shutter methods discussed include electronic shutter, electronic front curtain, and mechanical shutter. It is assumed here that the front curtain travel speed of the electronic shutter is faster than that of the mechanical shutter. In this case, using an electronic shutter allows for a faster maximum synchronization speed (shorter shutter time) than using a mechanical shutter. The front curtain travel speed of the electronic front curtain is basically matched to the curtain speed of the mechanical shutter, but there is room to shorten the front curtain travel time compared to the mechanical shutter by optimizing the front curtain travel curve. Therefore, it is assumed here that the front curtain travel speed of the electronic front curtain is faster than that of the mechanical shutter. Therefore, when using an electronic front curtain, although the maximum synchronization speed is slower than that of an electronic shutter, it is possible to achieve a faster maximum synchronization speed than a mechanical shutter.

[0084] In the case of full-frame cameras, the normal maximum sync speeds (with acceleration off) are 1 / 320, 1 / 250, and 1 / 200 for the electronic shutter, electronic first curtain, and mechanical shutter, respectively. When shooting cropped to APS-C size, the first curtain travel time is shorter than when shooting in full frame. Therefore, the normal maximum sync speeds are 1 / 400, 1 / 320, and 1 / 250 for the electronic shutter, electronic first curtain, and mechanical shutter, respectively.

[0085] The maximum high-speed synchronization speed (maximum synchronization speed when the maximum synchronization speed is increased (high-speed: ON)) is set to a shutter speed that is 1 / 3 stop faster than when the maximum synchronization speed is not increased. Therefore, the maximum high-speed synchronization speeds for full-size cameras are 1 / 400, 1 / 320, and 1 / 250 for the electronic shutter, electronic front curtain, and mechanical shutter, respectively. Also, the maximum high-speed synchronization speeds for APS-C size cameras are 1 / 500, 1 / 400, and 1 / 320 for the electronic shutter, electronic front curtain, and mechanical shutter, respectively.

[0086] Regarding the upper limit of the light emission amount, regardless of the shutter method and whether shooting in full size or APS-C size, if the maximum synchronization speed is not increased, there will be no limit on the light emission amount; in other words, light emission will be permitted up to full size.

[0087] On the other hand, when increasing the maximum synchronization speed, the upper limit of the flash intensity is limited to a flash intensity that is reduced by the number of stops shown in FIG. 5(b) from the full flash value. For example, when increasing the maximum synchronization speed using an electronic shutter in full-frame photography, the upper limit of the flash intensity is set to a flash intensity that is one step below full flash. More specifically, as shown in FIG. 5(a), the maximum synchronization speed when using an electronic shutter in full-frame photography is set to 1 / 400. The time during which both the front and rear curtains are open is calculated by subtracting the front curtain run time from the accumulation time when the maximum synchronization speed is set to 1 / 400. Therefore, the upper limit of the flash intensity is set to one stop below full flash so that the flash intensity is contained within this time. Note that the setting of the upper limit of the flash intensity under other shooting conditions is similar to the example of full-frame photography and an electronic shutter described above, and therefore will not be described here. The values ​​shown in FIG. 5 and their magnitude relationships are merely examples and will vary depending on the performance of the imaging system. The values ​​shown in FIG. 5 do not limit the present invention.

[0088] As described above, the imaging device 100 can select one shutter method from among the electronic shutter, electronic front curtain, and mechanical shutter. Here, let's assume that the maximum synchronization speed in full frame for all shutter methods is 1 / 250 when speed-up is off and 1 / 320 when speed-up is on, without taking the front curtain travel speed into consideration. In this case, if the maximum synchronization speed is increased, for example, the state shown in FIG. 4(a) will occur when the electronic shutter is set, the state shown in FIG. 4(b) will occur when the electronic front curtain is set, and the state shown in FIG. 4(c) will occur when the mechanical shutter is set. In other words, there will be cases where not all shutter methods will be in the state shown in FIG. 4(b). Therefore, in this embodiment, the maximum synchronization speed is set for each shutter method based on the front curtain travel speed, and the light emission amount is limited based on the set maximum synchronization shutter speed, thereby avoiding the states shown in FIG. 4(a) or 4(c).

[0089] While the present invention has been described in detail above based on preferred embodiments thereof, the present invention is not limited to these specific embodiments, and various forms within the scope of the gist of the present invention are also included in the present invention. Furthermore, each of the above-described embodiments merely represents one embodiment of the present invention, and each embodiment can be combined as appropriate.

[0090] For example, in the above embodiment, the shutter method is described as being selected from among an electronic shutter, an electronic front curtain, and a mechanical shutter. However, the present invention is not limited to these, and a global shutter may also be used. However, with a global shutter, the front curtain run time does not depend on the shooting range, so there is no need to consider the settings of the still image crop / aspect, electronic zoom, and electronic image stabilization, which affect the shooting range. Furthermore, if the front curtain run time can be changed in a specific shooting mode, that setting may be acquired in S301, and the processing from S303 onward may be performed using the set front curtain run time.

[0091] In the above embodiment, the system control unit 120 calculates the front curtain run time and the upper limit of the light emission amount based on various conditions (shutter type and various settings acquired in S301 that affect the front curtain run speed). Here, if there are only a few combinations of various conditions, a lookup table defining the maximum synchronization speed and the upper limit of the light emission amount may be stored in the nonvolatile memory 123 or the main memory 121. For example, assume that the imaging system has exclusive functions for electronic zoom, electronic image stabilization, and HDR shooting in flash photography, and that the maximum synchronization speed and the upper limit of the light emission amount are constant regardless of the still image crop / aspect ratio. In this case, the lookup table defines the maximum synchronization speed and the upper limit of the light emission amount in the same way as in FIG. 5. In this case, the calculation process for the front curtain run time in step S303 can be omitted, and steps S305 to S308 can be performed by simply consulting the lookup table.

[0092] For example, in the above embodiment, a configuration was described in which the lens barrel 300 and the strobe device 400 were detachably attached to the image capture device 100, but the lens barrel 300 and the strobe device 400 may be integrally configured with the image capture device 100. In this case, the system control unit 120 also functions as the lens control unit 305 and the strobe control unit 402. Also, while a configuration in which the strobe device 400 is physically attached to the image capture device 100 via a connector has been described, the strobe device 400 and the image capture device 100 may be connected to each other via wireless communication so as to be controllable. Furthermore, while the image capture device 100 constituting the imaging system according to the present invention has been described as being a mirrorless digital camera, the image capture device 100 is not limited to this and may be a portable device such as a digital video camera or a smartphone.

[0093] The disclosure of this embodiment includes the following configuration, method, and program. (Configuration 1) An imaging device comprising: a strobe light emitting means; a shutter having a front curtain and a rear curtain that controls exposure to an imaging element; and a setting means for setting the amount of light emitted by the strobe light emitting means, wherein the setting means sets an upper limit of the amount of light emitted when performing strobe sync photography at the maximum strobe sync shutter speed based on the travel time of the front curtain. (Configuration 2) The imaging device according to configuration 1, wherein the setting means sets the upper limit of the amount of light emitted in accordance with a shutter method used when driving the front curtain and the rear curtain. (Configuration 3) The imaging device according to configuration 2, wherein the shutter method is one of an electronic shutter, an electronic front curtain, and a mechanical shutter. (Configuration 4) An imaging device described in any one of configurations 1 to 3, characterized in that the imaging element can be controlled in multiple driving modes, and the setting means sets an upper limit value of the light emission amount depending on the driving mode. (Configuration 5) The imaging device according to configuration 4, characterized in that the setting means changes the upper limit value of the light emission amount depending on whether the drive mode is a mode in which the pixel signal output from the imaging element is amplified with a different gain. (Configuration 6) The imaging device according to any one of configurations 1 to 5, wherein the setting means sets the upper limit value of the light emission amount according to a cut-out setting for cutting out a part of the captured image from the imaging element. (Configuration 7) The imaging device described in Configuration 1, wherein the setting means sets the upper limit of the light emission amount based only on the shutter method when the shutter method for driving the front curtain and the rear curtain is a global shutter, and sets the upper limit of the light emission amount based on the shutter method and a crop setting that crops out a portion of the captured image from the imaging element when the shutter method is an electronic shutter, an electronic front curtain, or a mechanical shutter. (Configuration 8) The imaging device according to configuration 6 or 7, wherein the crop setting is full-size photography when the imaging element is full-size, or APS-C size photography. (Configuration 9) The imaging device according to configuration 6 or 7, wherein the crop setting is electronic zoom on / off and a zoom magnification when the electronic zoom is on. (Configuration 10) The imaging device according to configuration 6 or 7, wherein the crop settings are electronic image stabilization on / off and image stabilization strength when electronic image stabilization is on. (Method 1) A control method for an imaging device, comprising the steps of: acquiring a setting value that affects the maximum strobe synchronization shutter speed when performing strobe photography; calculating the travel time of the front curtain that controls exposure to the imaging element based on the setting value; and setting an upper limit value for the amount of strobe light emitted based on the travel time of the front curtain. (Method 2) The control method for an imaging device described in Method 1, characterized in that the step of setting an upper limit on the amount of flash light emitted by the strobe comprises the steps of: determining whether a setting to increase the maximum strobe synchronization shutter speed is enabled or disabled; and if the increase in speed is disabled, setting the upper limit on the amount of flash light emitted by the strobe device to full flash and setting the maximum strobe synchronization shutter speed to the sum of the first curtain travel time and the strobe light emission period at full flash; and if the increase in speed is enabled, setting the maximum strobe synchronization shutter speed to the sum of the first curtain travel time and the strobe light emission period at full flash plus an additional 1 / 3 stop, and setting the upper limit on the amount of flash light emitted by the strobe device to the maximum amount of flash light that fits within the time obtained by subtracting the first curtain travel time from the set maximum strobe synchronization shutter speed. (Program 1) A program that causes a computer to execute each step of the method for controlling an imaging device according to Method 1 or 2.

[0094] The present invention can also be realized by supplying a program that realizes one or more functions of the above-described embodiments to a system or device via a network or a storage medium, and having one or more processors in the computer of the system or device read and execute the program. It can also be realized by a circuit (e.g., ASIC) that realizes one or more functions. [Explanation of symbols]

[0095] 100 Imaging device 102 Shutter 103 Image sensor 120 System control unit 400 Strobe Device 401 Strobe light emitting unit 402 Strobe control unit 1000 Imaging System

Claims

1. strobe light emitting means; a shutter having a front curtain and a rear curtain for controlling exposure to the image sensor; a setting means for setting the light emission amount of the strobe light emitting means, The imaging device is characterized in that the setting means sets the upper limit of the amount of light emitted when performing flash synchronization photography at a flash synchronization maximum shutter speed based on a running time of the front curtain.

2. 2. The image pickup apparatus according to claim 1, wherein the setting means sets the upper limit of the amount of light emission in accordance with a shutter method used when driving the front curtain and the rear curtain.

3. 3. The imaging apparatus according to claim 2, wherein the shutter system is one of an electronic shutter, an electronic front curtain, and a mechanical shutter.

4. the imaging element can be controlled in a plurality of drive modes; 2. The imaging device according to claim 1, wherein the setting means sets the upper limit of the amount of light emitted depending on the drive mode.

5. 5. The imaging device according to claim 4, wherein the setting unit changes the upper limit of the light emission amount depending on whether the drive mode is a mode in which pixel signals output from the imaging element are amplified with different gains.

6. 6. The imaging device according to claim 1, wherein the setting unit sets the upper limit of the light emission amount in accordance with a cutout setting for cutting out a part of the captured image from the imaging element.

7. 2. The imaging device according to claim 1, wherein the setting unit sets the upper limit of the light emission amount based only on the shutter type when the shutter type used to drive the front curtain and the rear curtain is a global shutter, and sets the upper limit of the light emission amount in accordance with the shutter type and a crop setting that crops out a portion of the captured image from the image sensor when the shutter type is an electronic shutter, an electronic front curtain, or a mechanical shutter.

8. 7. The image pickup apparatus according to claim 6, wherein the crop setting is full-size photography when the image pickup element is full-size, or APS-C size photography.

9. 7. The imaging device according to claim 6, wherein the cutout settings are on / off of electronic zoom and a zoom magnification when the electronic zoom is on.

10. 7. The imaging apparatus according to claim 6, wherein the cutout settings are on / off of electronic image stabilization and image stabilization strength when the electronic image stabilization is on.

11. A control method for an imaging device, comprising: obtaining a setting value that affects the maximum flash sync shutter speed when performing flash photography; calculating a travel time of a front curtain that controls exposure to an image sensor based on the set value; and setting an upper limit of the amount of flash light emitted by the strobe based on the travel time of the front curtain.

12. The step of setting an upper limit value for the amount of strobe light emission includes: a step of determining whether the setting for increasing the maximum strobe synchronization shutter speed is valid or invalid; 12. The control method for an imaging device according to claim 11, further comprising the steps of: when the speed increase is disabled, setting an upper limit of the amount of light emitted by the strobe device to full light and setting the strobe synchronization maximum shutter speed to a time obtained by adding a strobe light emission period at full light emission to the front curtain travel time; and when the speed increase is enabled, setting the strobe synchronization maximum shutter speed to a time obtained by adding a strobe light emission period at full light emission to the front curtain travel time plus an additional 1 / 3 stop; and setting the upper limit of the amount of light emitted by the strobe device to a maximum amount of light emitted that fits within a time obtained by subtracting the front curtain travel time from the set strobe synchronization maximum shutter speed.

13. 13. A program that causes a computer to execute each step of the method for controlling an imaging apparatus according to claim 11 or 12.

Images