JP7467086B2 - Imaging device, control method thereof, and program - Google Patents

Description

The present invention relates to an imaging device and a control method and program thereof, and in particular to an imaging device having an exposure control function and a control method and program thereof.

In recent years, many types of video cameras have an automatic exposure control function that automatically changes the brightness of a subject depending on the subject being shot. Specifically, when the automatic exposure control function determines that the brightness of a subject is not properly exposed based on the brightness information of the subject being shot, it changes the exposure parameters (aperture value, ND, shutter speed, ISO sensitivity, etc.) so that the brightness of the subject becomes properly exposed. Since each of these exposure parameters has a different controllable resolution, the level to which the brightness of the subject can be brought closer to proper by each exposure parameter depends on the resolution. For this reason, a technique is known in which the coarsest resolution for each exposure parameter is stored in advance, and when the proper exposure falls within the range of the resolution, subsequent control is stopped. For example, if the coarsest aperture resolution among the resolutions for changing exposure is 1/8 stop, the range for determining proper exposure is set to 1/8 stop, and if the current exposure is within ±1/16 stop from the proper exposure, the control of the aperture is stopped.

On the other hand, when automatic exposure control changes exposure parameters to track the brightness of the subject being shot, the brightness of the entire screen changes as the brightness of the subject changes, creating an unnatural feeling. In particular, in cinema and news shooting, manual exposure control is often used to avoid the unnatural feeling that can occur with automatic exposure control. However, if the current exposure deviates to a certain extent from the correct exposure, phenomena such as blown-out highlights and crushed shadows will occur in parts of the image, so in such cases it is desirable to change from manual exposure control to automatic exposure control. Such phenomena occur, for example, when the environment changes or an unexpected subject appears during shooting with a fixed camera or long takes.

The frequency of automatic exposure control can be reduced by widening the range that is determined to be the correct exposure as described above. For example, the range of ISO sensitivity that can be changed during HDR is reduced compared to SDR, so the frequency of changes to exposure parameters other than ISO sensitivity, such as aperture and shutter, during automatic exposure control increases. To solve this problem, Patent Document 1 widens the range that is determined to be the correct exposure set for aperture and shutter during HDR compared to SDR, reducing the frequency of automatic exposure control.

JP 2015-19281 A

However, Patent Document 1 does not mention the target brightness. If the range set for the aperture and shutter to determine proper exposure is widened, when the brightness of the subject exceeds the range determined to be proper exposure, it becomes necessary to greatly change the aperture value and shutter speed to achieve proper exposure. This results in a large change in exposure, and a deterioration in image quality.

The object of the present invention is to provide an imaging device, a control method and a program that can reduce both the frequency of exposure control in automatic exposure control and the amount of exposure change when performing exposure control, and prevent deterioration of image quality due to automatic exposure control.

The imaging device according to claim 1 of the present invention comprises an imaging means, a detection means for detecting the brightness of a subject imaged by the imaging means, a first calculation means for calculating the difference in brightness of the detected subject from a preset appropriate brightness, a second calculation means for calculating a target value which is the target brightness of exposure control, an exposure change means for changing an exposure parameter according to the target value, and a setting means for setting a first range based on the appropriate brightness as a range within which the exposure parameter is not changed by the exposure change means according to changes in the brightness of the subject, the exposure change means does not change the exposure parameter when the difference is within the first range, and the second calculation means calculates a value located at the end of the first range that is closest to the brightness of the detected subject as the target value when the difference is beyond the first range.

According to the present invention, it is possible to reduce both the frequency of exposure control in automatic exposure control and the amount of exposure change when performing exposure control, thereby preventing deterioration of image quality due to automatic exposure control.

1 is an external view of a camera as an imaging apparatus according to a first embodiment. FIG. 2 is a block diagram showing the internal configuration of the camera shown in FIG. 1 . 4 is a flowchart of an exposure control process according to the first embodiment. 4 is a flowchart of a calculation process of a target BV in step S304 of FIG. 3. 10 is a flowchart of an exposure control process according to a second embodiment. 6 is a flowchart of a process for determining an allowable range and a target range for AE in step S501 of FIG. 5;

The following describes in detail the embodiments of the present invention with reference to the attached drawings. Note that the following embodiments do not limit the scope of the present invention, and not all of the combinations of features described in the present embodiments are necessarily essential to the solution of the present invention.

First Embodiment
1 is an external view of a digital video camera (hereinafter, simply referred to as a camera) 100 as an imaging device according to this embodiment. In this embodiment, the camera 100 is more specifically a digital video camera, but is not limited to this as long as it is an imaging device that can perform the automatic exposure control described below. For example, the imaging device of the present invention may be a digital camera that performs the following automatic exposure control during live view display.

In FIG. 1, the camera 100 includes a display unit 28, a recording switch 61, an operation unit 70, a connector 112, and a recording medium slot 201. In addition, although not shown in FIG. 1 because they are located on the opposite side, the camera 100 also includes a mode changeover switch 60 for switching between various modes, and a power switch 81 for receiving an instruction from the user to switch the power on and off. Details of the mode changeover switch 60 and the power switch 81 will be described later using FIG. 2.

The display unit 28 displays images and various information.

The recording switch 61 is an operating member that accepts shooting instructions from the user.

The operation unit 70 is an operation member that accepts various operations from the user, such as various buttons and a four-way cross key for up, down, left, and right.

The connector 112 is a connector between the camera 100 and a connection cable for an external power source (not shown).

The recording medium slot 201 is a slot for storing the recording medium 200 (not shown in FIG. 1; described later in FIG. 2). The recording medium 200 stored in the recording medium slot 201 is capable of communicating with the camera 100.

Figure 2 is a block diagram showing the internal configuration of the camera 100.

2, the camera 100 includes a D/A converter 13, a recording medium I/F 18, an imaging unit 22, an A/D converter 23, an image processing unit 24, a display unit 28, a power supply unit 30, a memory 32, a gyro 40, a system control unit 50, a system memory 52, and a system timer 53. The camera 100 also includes a non-volatile memory 56, a mode change switch 60, a recording switch 61, an operation unit 70, a power supply control unit 80, a power switch 81, an aperture 101, a barrier 102, an imaging lens 103, an ND filter 104, a connector 112, and a recording medium 200.

The imaging lens 103 is a group of lenses including a zoom lens, a focus lens, and a shift lens, and forms a subject image (optical image) in the imaging unit 22.

The aperture 101 is used to adjust the amount of light guided to the imaging unit 22 via the imaging lens 103.

The ND filter 104 is an ND used to reduce the amount of light guided to the imaging unit 22 via the imaging lens 103.

The imaging unit 22 has an imaging element that is composed of a photoelectric conversion element such as a CCD or CMOS that photoelectrically converts the optical image formed on the imaging surface into an electrical signal (analog signal). The imaging unit 22 also has a function to control charge accumulation by an electronic shutter, a function to control analog gain, and a function to control readout speed. In other words, the imaging unit 22 can adjust exposure by the shutter speed of the electronic shutter.

The A/D converter 23 is used to convert the analog signal output from the imaging unit 22 into a digital signal and output it as image data. The image data output from the A/D converter 23 is written to the memory 32 via the image processing unit 24 and the memory control unit 15, or via the memory control unit 15.

The barrier 102 covers the imaging system of the camera 100, which includes the imaging lens 103, the aperture 101, the ND filter 104, and the imaging unit 22, thereby preventing the imaging system of the camera 100 from becoming dirty or being damaged.

The image processing unit 24 performs processes such as predetermined pixel interpolation and resizing such as reduction, color conversion, gamma correction, and ISO sensitivity setting by adding digital gain on the image data output from the A/D converter 23 or the memory control unit 15. It also performs predetermined calculations such as obtaining the average brightness value using the image data output from the A/D converter 23, and transmits the calculation results to the system control unit 50.

The gyro 40 detects the movement and attitude changes of the camera 100 caused by camera shake, the user's camerawork, etc.

The system control unit 50 performs AE (automatic exposure) processing, AWB (auto white balance) processing, TTL (through-the-lens) AF (auto focus) processing, etc. based on the calculation results sent by the image processing unit 24. The system control unit 50 also operates the shift lens of the imaging lens 103 in response to the movement and attitude change of the camera 100 detected by the gyro 40, or performs image blur correction by shifting the image in the image data output from the A/D converter 23 in the image processing unit 24.

The memory 32 stores image data that has been photoelectrically converted by the imaging unit 22 and converted into a digital signal by the A/D converter 23, and image data to be displayed on the display unit 28. The memory 32 has a storage capacity sufficient to store a predetermined period of moving images and audio. The memory 32 also serves as a memory (video memory) that stores image data to be displayed on the display unit 28.

The D/A converter 13 converts the image data to be displayed on the display unit 28 stored in the memory 32 into an analog signal and supplies it to the display unit 28. In this way, the image data to be displayed on the display unit 28 written in the memory 32 is displayed by the display unit 28 via the D/A converter 13.

The display unit 28 is a display device composed of an LCD or the like, and displays on its screen according to the analog signal from the D/A converter 13. The analog image data from the imaging unit 22 may be digitized by the A/D converter 23 and stored in the memory 32, and then re-analogized by the D/A converter 13 and sequentially transferred to and displayed on the display unit 28. This realizes an electronic viewfinder and allows for through-image display.

The non-volatile memory 56 is an electrically erasable and recordable memory, and may be, for example, an EEPROM. The non-volatile memory 56 stores constants, programs, etc. for the operation of the system control unit 50. The programs referred to here are programs for executing various flowcharts described below. The system control unit 50 controls the entire camera 100 using the operating constants recorded in the non-volatile memory 56. Furthermore, by executing the programs recorded in the non-volatile memory 56, the system control unit 50 executes each process of this embodiment described below. Furthermore, the non-volatile memory 56 stores the exposure controllable range, allowable range, target range, etc. described below.

The system memory 52 is composed of RAM. In the system memory 52, constants, variables, programs, etc. for the operation of the system control unit 50 that are read from the non-volatile memory 56 are expanded. The system control unit 50 also controls the display of image data on the screen of the display unit 28 by controlling the memory 32, the D/A converter 13, the display unit 28, etc.

The system timer 53 is a timing unit that measures the time used for various controls and the time of the built-in clock.

The mode changeover switch 60, the recording switch 61, and the operation unit 70 are operation members for receiving various operational instructions from the user to the system control unit 50, and the received operational instructions are output sequentially to the system control unit 50.

The mode changeover switch 60 accepts an operation instruction from the user to switch the operation mode of the system control unit 50 to one of the video recording mode, still image recording mode, playback mode, etc. The video recording mode and still image recording mode also include modes such as auto shooting mode, auto scene determination mode, manual mode, various scene modes that are shooting settings for each shooting scene, program AE mode, and custom mode. After switching to the video recording mode by operating the mode changeover switch 60, the user can directly switch to one of these modes included in the video recording mode by further operating the mode changeover switch 60. Furthermore, after switching to the video recording mode by operating the mode changeover switch 60, the user can also switch to one of these modes included in the video recording mode by using other operating members such as the operating unit 70.

The recording switch 61 accepts a shooting instruction from the user. Specifically, when the recording switch 61 is turned OFF by the user, the camera 100 is switched to a shooting standby state, and when the recording switch 61 is turned ON by the user, the camera 100 is switched to a shooting state. When the recording switch 61 is turned ON, the system control unit 50 switches the camera 100 to a shooting state and starts a series of operations from reading a signal from the imaging unit 22 to writing video data to the recording medium 200.

The operation unit 70 is composed of operation members such as various buttons and a cross key. The various buttons and cross key are assigned appropriate functions by the user selecting various functional icons displayed on the display unit 28, and operate as various functional buttons. Examples of the functional buttons include an end button, a back button, an image forward button, a jump button, a filter button, an attribute change button, a menu button, and a SET button. For example, when the user presses a button that operates as a menu button on the operation unit 70, a menu screen on which various settings can be made is displayed on the display unit 28. The user can intuitively make various settings using the menu screen displayed on the display unit 28 and the button that operates as the cross key or SET button on the operation unit 70.

The power supply control unit 80 is composed of a battery detection circuit, a DC-DC converter, a switch circuit that switches between blocks to which electricity is applied, and the like, and detects whether a battery is installed, the type of battery, and the remaining battery power. The power supply control unit 80 also controls the DC-DC converter based on the detection results and instructions from the system control unit 50, and supplies the required voltage to each unit including the recording medium 200 for the required period of time. The power supply control unit 80 also accepts instructions from the user to switch the power on and off via the power switch 81, controls the DC-DC converter in response to the instructions, and supplies the required voltage to the system control unit 50.

The power supply unit 30 is composed of a primary battery such as an alkaline battery or a lithium battery, a secondary battery such as a NiCd battery, a NiMH battery, or a Li-ion battery, an AC adapter, etc. When the power supply unit 30 receives power from an external power source via the connector 112, it charges the secondary battery and supplies power to the power supply control unit 80 via the AC adapter.

The recording medium I/F 18 is an interface with the recording medium 200.

The recording medium 200 is an external memory such as a memory card made of semiconductor memory or a hard disk made of a magnetic disk. The recording medium 200 communicates with the camera 100 via the recording medium I/F, and records the subject image captured by the camera 100 as image data.

Figure 3 is a flowchart of the exposure control process in this embodiment. This process is executed by the system control unit 50 by expanding a program recorded in the non-volatile memory 56 into the system memory 52.

In FIG. 3, first, the brightness of the subject is detected (step S301). Specifically, in this embodiment, the system control unit 5 (detection unit) calculates the average brightness value of the image data output from the imaging unit 22 via the A/D converter 23 in the image processing unit 24, and detects the calculated average brightness value as the brightness of the subject. Note that the unit of brightness is expressed in BV based on the so-called APEX (Additive System of Photographic Exposure) system, but it may also be expressed in units of brightness information (Y value).

Next, the difference between the current brightness of the subject determined in step S301 and the brightness at which the subject will be appropriate is calculated (step S302). For example, if the average brightness of an image taken with the current exposure is Yt, and the target brightness value, which is the average brightness of an image taken with an exposure at which the subject will be appropriately luminanced according to a predetermined standard, is Ys, the exposure difference ΔY of the average brightness with respect to the target brightness value is given by
ΔY=log ₂ (Yt/Ys) (Equation 1)
For example, ΔY is 1 when Yt is twice as large as Ys, and 2 when Yt is four times as large as Ys. Note that this embodiment is configured to obtain ΔY, which is a relative value, based on the brightness at which the subject is appropriate, and in this case, an allowable range and a target range, which will be described later, are determined based on the brightness at which the subject is appropriate.

Next, it is determined whether ΔY calculated in step S302 is within an allowable range based on the brightness at which the subject is appropriate (step S303). The allowable range of ΔY is determined in advance, and it is determined whether ΔY is within the allowable range. The allowable range here refers to the allowable range of deviation of the BV of the current brightness (current BV) from the BV at which the subject is appropriate, and is set in advance and stored in non-volatile memory 56. For example, if the current BV is 4BV and the allowable range is ±2BV, then if the BV at which the subject is appropriate is 2BV to 6BV or less, then ΔY is within the allowable range.

When the resolution of the aperture 101 (exposure change section), which is the coarsest among the resolutions for changing exposure, is 1/8 stop, the exposure controllable range is set to ±1/16 according to this resolution. Conventional automatic exposure control is performed based on this exposure controllable range. In contrast, the allowable range in this embodiment is set to a range at least wider than this exposure controllable range, and in this embodiment, it is set without taking into account the resolution for changing exposure.

If the result of the determination in step S303 is that ΔY is within the allowable range, this process ends without changing the exposure. On the other hand, if ΔY is not within the allowable range, the process proceeds to step S304, where a calculation process is performed for the brightness of the subject that is the target of the exposure (hereinafter, the target BV). The details of the calculation process of the target BV will be described later with reference to FIG. 4.

When the target BV is calculated in step S304, exposure parameters that will result in the target BV are determined (step S305). The manner in which the exposure parameters change (hereinafter referred to as the program diagram) is determined in advance according to the program AE mode. For example, when the subject changes from a bright subject to a dark subject during video shooting, the aperture value first changes from the minimum aperture value to F4.0, and then the shutter speed changes from 1/250 to 1/60. After that, the aperture value changes from F4.0 to the maximum aperture value, and then the ISO sensitivity is increased from the minimum sensitivity to the maximum sensitivity. Here, the minimum aperture value, maximum aperture value, minimum sensitivity, and maximum sensitivity change according to the state of the camera 100 and settings related to exposure. The state of the camera 100 refers to the zoom position, focus position, insertion status of the ND filter 104, etc. Also, the settings related to exposure refer to settings such as whether to control each exposure parameter automatically or manually, the extension function of the ISO sensitivity, and gamma correction settings. A program diagram is determined according to the state of the camera 100 at the time of calculating the target BV in step S304 and the settings related to exposure, and exposure parameters for achieving the target BV are determined based on the program diagram.

Next, the exposure is changed based on the exposure parameters determined in step S305 (step S306). Specifically, the system control unit 50 transmits control commands to the aperture 101, the imaging unit 22, and the image processing unit 24 so that the aperture value, shutter speed, and ISO sensitivity are included in the exposure parameters determined in step S305. This changes the aperture value of the aperture 101, the shutter speed of the electronic shutter in the imaging unit 22, and the ISO sensitivity set by the image processing unit 24, resulting in the desired exposure.

Figure 4 is a flowchart of the target BV calculation process in step S304 of Figure 3.

In this embodiment, the target range of ΔY is set in advance and stored in the non-volatile memory 56. For example, if the control resolution of the aperture 101 is the coarsest of the exposure parameters, which is 1/8 step, there is a possibility that the exposure cannot be changed within the range of ±1/16 (=0.0625) steps (exposure controllable range). Therefore, the target range is set inside the allowable range by 1/16 steps, which is half the control resolution at both ends. In other words, the target range is set to ±1.9375 (=2-0.0625). The target range is set based on the allowable range and the control resolution so long as it is within a range in which the exposure change can be reliably performed, and the target range does not need to be narrower than the allowable range as in this embodiment. For example, the change in brightness of the image due to the exposure change in step S306 in FIG. 3 will be larger than in this embodiment, but the target range may be set outside the allowable range by 1/16 steps, which is half the control resolution at both ends.

In FIG. 4, first it is determined whether ΔY is a value of 0 or less (ΔY≦0) (step S401). If the result of the determination is that ΔY is 0 or less (ΔY≦0) (YES in step S401), the target BV is set to the value obtained by adding ΔY to the current BV and then adding the upper limit of the target range for ΔY (=1.9375) (step S402).

The current BV is calculated based on exposure parameters such as aperture value (AV), shutter speed (hereafter referred to as accumulation time) (TV), and ISO sensitivity (SV). For example, the current BV can be calculated using the following formula:

BV = AV + TV - SV (Equation 2)

For the ND filter 104, the BV is calculated by adding the number of steps that will be darkened by inserting it to Equation 2. For example, if an ND filter with a transmittance of 1/4 is inserted, an additional 2 is added to Equation 2, and if it is 1/8, an additional 3 is added to Equation 2. The current BV can be calculated by substituting values into Equation 2 based on the exposure parameters of the camera 100. Also, since the brightness of the subject when photographed with an exposure that is the current BV for the appropriate brightness is ΔY, the value obtained by adding ΔY to the current BV becomes the BV of the subject brightness.

In other words, in step S402, the target BV is set near the end closest to the BV of the current brightness of the target range based on the brightness at which the subject is appropriate.

On the other hand, if the result of the determination in step S401 is that ΔY is greater than 0 (ΔY>0), the target BV is set to the current BV plus ΔY plus the lower limit of the target range (=-1.9375) (step S403).

That is, in step S403, the target BV is set to match the darker end of the target range (first range). Note that in this embodiment, one end of the target range is set to the target BV, but the allowable range may be set to a range that takes into account the control resolution, and one end of that range may be set as the target BV.

In step S401, a case is shown in which it is determined whether or not to calculate the target BV using the target range, but it is also possible to determine whether or not to calculate the target BV using the tolerance range. This is effective in cases where there is little need to consider the target range, such as when the target range and the tolerance range are the same.

As described above, according to the exposure control process of this embodiment, if ΔY, which indicates the difference between the current brightness and the brightness of the subject, is within the allowable range, no exposure change is performed. This makes it possible to reduce the frequency of exposure control compared to conventional methods, and to reduce deterioration of image quality due to automatic exposure control.

In addition, if ΔY exceeds the allowable range, the target BV is set near the end closest to the BV of the current brightness within the range in which the exposure based on the appropriate brightness of the subject is not changed. Therefore, compared to conventional automatic exposure control in which the target BV is set to the BV of the subject's brightness, the amount of exposure change when performing exposure control can be reduced, and deterioration of image quality due to automatic exposure control can be prevented.

The method of calculating the brightness of the subject is not limited to the method in this embodiment. For example, it may be center-weighted, which averages the brightness of the center by weighting it, or the average brightness of the face. Similarly, ΔY, which is the difference between the brightness of the subject and the appropriate brightness, may be calculated as the difference in average brightness (= Yt - Ys) instead of using the formula (1). It may also be possible to calculate the difference between the BV of the brightness of the subject and the BV of the camera 100. In other words, the exposure control process in FIG. 3 only needs to be able to change the exposure when the brightness of the subject exceeds the allowable range, with the target being near the end of the allowable brightness range on the exceeded side.

Second Embodiment
In the first embodiment, when ΔY, which is the difference between the brightness of the subject and the appropriate brightness, exceeds the allowable range, the target BV is set to the end of the target range that is closest to the BV of the brightness of the subject, and exposure control is performed, thereby reducing the frequency of exposure control and the amount of change in exposure. In the exposure control process according to this embodiment, if the user presses a predetermined button (hereinafter referred to as the PushAE button) on the operation unit 70, exposure control is performed in the Push Auto Exposure (hereinafter referred to as the PushAE) mode. On the other hand, if the user does not press the PushAE button, exposure control is performed in the Auto Exposure (hereinafter referred to as the AE) mode, which performs exposure control similar to that of the first embodiment.

The external appearance and internal configuration of the imaging device according to this embodiment are the same as those of the camera 100 according to the first embodiment shown in Figures 1 and 2. Therefore, in the following description of this embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and duplicated descriptions will be omitted.

Figure 5 is a flowchart of the exposure control process in this embodiment. This process is executed by the system control unit 50 by expanding a program recorded in the non-volatile memory 56 into the system memory 52.

Note that this process differs from the exposure control process according to the first embodiment shown in FIG. 3 in that step S501 has been added.

In FIG. 5, first, the brightness of the subject is determined in the same manner as in the exposure control process according to the first embodiment (step S301), and the difference ΔY between the brightness of the subject and the appropriate brightness is calculated (step S302). Next, the process of determining the allowable range and target range for AE is executed (step S501).

Figure 6 is a flowchart of the process for determining the acceptable range and target range for AE in step S501 of Figure 5.

In FIG. 6, first, it is determined whether the PushAE button is being pressed (step S601). If the result of this determination is that the PushAE button is being pressed, the camera 100 transitions to the PushAE mode and sets the allowable range and target range for PushAE (step S602). On the other hand, if the result of the determination in step S601 is that the PushAE button is not being pressed, the camera 100 transitions to the AE mode and sets the allowable range and target range for AE (step S603).

Specifically, if the mode is switched to AE mode in step S602, the allowable range is set to ±2 and the target range is set to ±1.9375, as in the first embodiment. On the other hand, if the mode is switched to PushAE mode in step S603, the allowable range is set to ±0.0625 and the target range is set to 0. Note that these allowable ranges and target ranges are set in advance for each exposure control mode and are stored in non-volatile memory 56. In other words, the settings in step S603 are performed by reading the allowable ranges and target ranges corresponding to the current exposure control mode from non-volatile memory 56.

However, this is not limited to this embodiment as long as the allowable range in the AE mode is wider than the allowable range in the PushAE mode and the target range in the AE mode is set wider than the target range in the PushAE mode.

Returning to FIG. 5, it is then determined whether ΔY is within the tolerance range set in step S501 (step S303). If it is within the tolerance range, the process ends, whereas if it is outside the tolerance range, the process of calculating the target BV is executed (step S304).

In this embodiment, the tolerance range is set to ±2 and the target range is set to ±1.9375 in AE mode, so the target BV is calculated in the same way as in the first embodiment.

On the other hand, in PushAE mode, the target range is set to 0. Therefore, when ΔY exceeds the allowable range, the target BV becomes the BV of the brightness of the subject (the value obtained by adding ΔY to the current BV) regardless of whether ΔY≦0 (YES in step S401) or ΔY>0 (NO in step S401). When the target range is set to 0 in this way, the judgment in step S401 is not performed, and the target BV may be the value obtained by adding ΔY to the current BV.

Based on the target BV calculated by the above method, exposure parameters are determined (step S305) and exposure is changed (step S306) in the same manner as in the first embodiment. At this time, in the case of PushAE mode, the target BV becomes the BV of the brightness of the subject in step S304, so the exposure is changed to make the brightness of the subject appropriate. However, if ΔY is within the allowable range (-1/16≦Y≦1/16), no exposure change is made. On the other hand, in the case of AE mode, as in the first embodiment, if ΔY exceeds the allowable range, the exposure is changed so that the target BV is near the end of the target range (or allowable range) that is closest to the BV of the current brightness.

As described above, according to the exposure control process of this embodiment, in AE mode, the exposure is controlled in the same way as in the first embodiment, while in PushAE mode, the exposure is controlled so that the brightness is appropriate. This allows the user to adjust the brightness of the subject in the video to the appropriate brightness simply by pressing the PushAE button when the BV of the subject's brightness remains near the edge of the target range or allowable range for a certain period of time.

Note that it is sufficient that a different tolerance range and target range are set for each of the multiple exposure control modes, and the exposure control modes according to this embodiment may include modes other than the AE mode and the PushAE mode. For example, if it is determined in step S601 that the mode is the aperture priority mode or the shutter speed priority mode, a tolerance range and target range different from those for the AE mode and the PushAE mode may be set.

<Other embodiments>
The present invention can also be realized by a process in which a program for implementing one or more of the functions of the above-described embodiments is supplied to a system or device via a network or a recording medium, and one or more processors in a computer of the system or device read and execute the program. The present invention can also be realized by a circuit (e.g., ASIC) for implementing one or more of the functions.

22 imaging unit 23 A/D converter 24 image processing unit 50 system control unit 56 non-volatile memory 70 operation unit 100 camera 101 aperture 103 imaging lens 104 ND filter

Claims (8)

An imaging means;
a detection means for detecting the brightness of a subject imaged by the imaging means;
a first calculation means for calculating a difference in brightness of the detected object with respect to a preset appropriate brightness;
A second calculation means for calculating a target value which is a brightness that is a target of exposure control;
an exposure change means for changing an exposure parameter in accordance with the target value;
a setting means for setting a first range based on the appropriate brightness as a range within which the exposure parameter is not changed by the exposure changing means in response to a change in brightness of an object,
the exposure change means does not change the exposure parameter when the difference is within the first range,
an imaging device characterized in that, when the difference exceeds the first range, the second calculation means calculates as the target value a value that is closest to the brightness of the detected subject among values located at the end of the first range. the first calculation means calculates a difference in brightness of the detected object with respect to the predetermined appropriate brightness as a relative value;
The imaging device described in claim 1, characterized in that, when the value indicated by the difference is 0 or less, the second calculation means calculates a value obtained by adding the difference to the brightness of the subject and further adding an upper limit value of the first range to the value obtained by adding the difference to the brightness of the subject and further adding a lower limit value of the first range to the value obtained by adding the difference to the brightness of the subject and further adding a lower limit value of the first range to the value obtained by adding the difference to the brightness of the subject and further adding a lower limit value of the first range to the value obtained by adding the difference to the brightness of the subject and further adding The setting means can set a second range that is wider than the first range based on the appropriate brightness,
3. The imaging apparatus according to claim 1, wherein the exposure changer changes the exposure parameter when the brightness of the subject changes beyond the second range. Further comprising a plurality of exposure control modes;
4. The imaging apparatus according to claim 1, wherein the setting unit sets different allowable ranges and target ranges based on the appropriate brightness for each of the plurality of exposure control modes. The imaging device according to claim 4, characterized in that the multiple exposure control modes include at least an AE mode that automatically changes the exposure, and a PushAE mode that automatically changes the exposure while the user is pressing a button. The imaging device according to claim 5, characterized in that the allowable range in the AE mode is wider than the allowable range in the PushAE mode, and the target range in the AE mode is wider than the target range in the PushAE mode. A method for controlling an imaging device including an imaging means, comprising:
a detection step of detecting the brightness of a subject imaged by the imaging means;
a first calculation step of calculating a difference in brightness of the subject detected in the detection step with respect to a preset appropriate brightness;
a second calculation step of calculating a target value that is a target of exposure control;
an exposure changing step of changing an exposure parameter in accordance with the target value;
a setting step of setting a first range based on the appropriate brightness as a range within which the exposure parameter is not changed in the exposure changing step in response to a change in brightness of a subject,
In the exposure changing step, if the difference is within the first range, the exposure parameter is not changed,
a second calculation step of calculating a brightness of the detected subject from among values at the ends of the first range as the target value if the difference exceeds the first range; A program that executes the control method for an imaging device according to claim 7.

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