Imaging apparatus

Abstract

To suppress deterioration of image quality due to image processing performed to suppress deterioration of a luminance in a low luminance region, in exposure control for making the luminance in a high luminance region close to a target luminance.SOLUTION: An imaging apparatus comprises: first exposure control means which performs first exposure control for suppressing halation of a captured image; image processing means which on the basis of a control amount of the first exposure control, performs image processing for suppressing deterioration of a luminance in a low luminance region of the image; and second exposure control means which performs second exposure control for making a luminance in a high luminance region of a captured image close to a target luminance set by a user. When the second exposure control is performed, the first exposure control means does not perform the first exposure control.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to an imaging device. [Background technology]

[0002] Patent Document 1 discloses a technique for lowering the exposure to suppress whiteout in a captured image, and compensating for the decrease in brightness in low-brightness areas caused by the exposure reduction through gamma processing. Patent Document 2 discloses a technique for using highlight-weighted metering to measure the brightness of high-brightness areas of an image, and bringing the brightness of high-brightness areas closer to a target brightness set by a user. By combining these two techniques, it is possible to bring the brightness of high-brightness areas closer to the target brightness while suppressing the decrease in brightness in low-brightness areas. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2010-193098 A [Patent Document 2] JP 2015-166767 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, simply combining the two above-mentioned technologies may result in degradation of image quality. For example, the luminance of low-luminance areas and the luminance of high-luminance areas may become closer to each other due to gamma processing (image processing) that compensates (suppresses) the luminance decrease in low-luminance areas and exposure reduction (exposure control) that brings the luminance of high-luminance areas closer to the target luminance. As a result, an image with low contrast (a hazy image with poor visibility) may be obtained.

[0005] The present invention aims to provide a technology that can suppress degradation of image quality caused by performing image processing to suppress reduction in brightness in low-brightness areas when performing exposure control to bring the brightness of high-brightness areas closer to a target brightness. [Means for solving the problem]

[0006] A first aspect of the present invention is an imaging device comprising a first exposure control means for performing a first exposure control that suppresses whiteout in a captured image, an image processing means for performing image processing that suppresses a decrease in luminance in low-luminance areas of the image based on a control amount of the first exposure control, and a second exposure control means for performing a second exposure control that brings the luminance of high-luminance areas of the captured image closer to a target luminance set by a user, wherein when the second exposure control is performed, the first exposure control means does not perform the first exposure control.

[0007] A second aspect of the present invention is an imaging device comprising a first exposure control means for performing a first exposure control to suppress whiteout in a captured image, an image processing means for performing image processing to suppress a decrease in luminance in low-luminance areas of the image based on a control amount of the first exposure control, and a second exposure control means for performing a second exposure control to bring the luminance of high-luminance areas of the captured image closer to a target luminance set by a user, wherein when the second exposure control is performed, the second exposure control means performs the second exposure control after the first exposure control, and the first exposure control means determines the control amount of the first exposure control by reducing the control amount in the case where the second exposure control is not performed in accordance with the target luminance.

[0008] A third aspect of the present invention is a method for controlling the brightness of a high brightness area of ​​a captured image by a first setting means for setting whether or not to perform a first exposure control for suppressing whiteout of a captured image, and a method for controlling the brightness of a high brightness area of ​​a captured image by a user. The imaging device has a second setting means for setting whether or not to perform a second exposure control to bring the brightness closer to a set target brightness, and a recording means for recording a captured image on a recording medium, wherein a first luminance, which is the luminance of the low-luminance area of ​​a captured image recorded without performing the first exposure control and the second exposure control, is approximately equal to a second luminance, which is the luminance of the low-luminance area of ​​a captured image recorded after performing the first exposure control without performing the second exposure control, and a third luminance, which is the luminance of the low-luminance area of ​​a captured image recorded after performing the first exposure control and the second exposure control, is lower than the first luminance and the second luminance.

[0009] A fourth aspect of the present invention is a control method for an imaging device, comprising the steps of performing a first exposure control for suppressing whiteout in a captured image, and performing image processing for suppressing a decrease in luminance in low-luminance areas of the image based on a control amount of the first exposure control, and is capable of executing a second exposure control for bringing the luminance of high-luminance areas of the captured image closer to a target luminance set by a user, and characterized in that when the second exposure control is performed, the first exposure control is not performed.

[0010] A fifth aspect of the present invention is a control method for an imaging device, comprising the steps of performing a first exposure control to suppress whiteout in a captured image, and performing image processing to suppress a decrease in luminance in low-luminance areas of the image based on a control amount of the first exposure control, and capable of executing a second exposure control to bring the luminance of high-luminance areas of the captured image closer to a target luminance set by a user, wherein when the second exposure control is performed, the second exposure control is performed after the first exposure control, and the control amount of the first exposure control is determined by reducing the control amount in a case where the second exposure control is not performed in accordance with the target luminance.

[0011] A sixth aspect of the present invention is a program for causing a computer to function as each of the means of the imaging device described above.A seventh aspect of the present invention is a computer-readable storage medium storing a program for causing a computer to function as each of the means of the imaging device described above. Effect of the Invention

[0012] According to the present invention, when performing exposure control to bring the luminance of a high-luminance area closer to a target luminance, it is possible to suppress deterioration in image quality caused by performing image processing to suppress a decrease in luminance of a low-luminance area. [Brief description of the drawings]

[0013] [Figure 1] 1 is a block diagram showing a configuration of a digital camera according to an embodiment of the present invention. [Diagram 2] FIG. 4 is a diagram showing a selection screen according to the embodiment. [Diagram 3] FIG. 2 is a diagram showing a plurality of blocks of an image according to the present embodiment. [Figure 4] FIG. 2 is a diagram showing an image according to the embodiment; [Diagram 5] FIG. 4 is a schematic diagram showing a luminance histogram of an image according to the embodiment. [Figure 6] 4 is a flowchart showing a process according to the present embodiment. [Figure 7] 7 is a diagram showing a correspondence relationship between target luminance and correction coefficients according to the embodiment. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0015] <Digital camera configuration> 1 is a block diagram showing the configuration of a digital camera 100, which is an example of an image capturing apparatus according to this embodiment. The digital camera 100 includes, as an image capturing mechanism, a photographing lens 101, an aperture and shutter 102, an automatic exposure (AE) processing unit 103, a focus lens 104, an autofocus (AF) processing unit 105, and an autofocus (AF) processing unit 106. The camera includes a focus (AF) processing unit 105, an image sensor 106, and an A / D conversion unit 107.

[0016] The photographing lens 101 has a zoom mechanism. The aperture and shutter 102 controls the amount of incident light, which is reflected light from a subject, that enters the image sensor 106 and the charge accumulation time according to instructions from the AE processing unit 103. The AE processing unit 103 controls the operation of the aperture and shutter 102 to control exposure. The AE processing unit 103 also controls an A / D conversion unit 107. The focus lens 104 focuses on the light receiving surface of the image sensor 106 according to a control signal from the AF processing unit 105 to form an optical image. The AF processing unit 105 also calculates distance information from the digital camera 100 to the subject.

[0017] The imaging element 106 converts the optical image formed on the light receiving surface into an electrical signal using a photoelectric conversion element such as a CCD element or a CMOS element, and outputs the electrical signal to the A / D conversion unit 107. The A / D conversion unit 107 converts the received electrical signal (analog signal) into a digital signal (RAW signal). The A / D conversion unit 107 includes a CDS circuit that removes noise from the received electrical signal, and a nonlinear amplification circuit that nonlinearly amplifies the received electrical signal before converting it into a digital signal.

[0018] The digital camera 100 also includes an image processing unit 108 , an image recognition unit 109 , a format conversion unit 110 , and a DRAM (Dynamic RAM) 111 .

[0019] The image processing unit 108 performs a development process. In the development process, for example, a predetermined image process (for example, a resizing process such as pixel interpolation or image reduction, and a color conversion process) is performed on the digital signal input from the A / D conversion unit 107. The image processing unit 108 also adjusts the image quality by performing a white balance (WB) adjustment and a gradation correction that increases or decreases the luminance (luminance level) of the image on the digital signal input from the A / D conversion unit 107. For example, the image processing unit 108 increases or decreases the luminance with a uniform amplification factor over the entire image, or converts the luminance depending on the magnitude of the original luminance. The image processing unit 108 can also perform a gradation correction process corresponding to the scene based on the result of recognition by the image recognition unit 109.

[0020] Image data processed by the image processing unit 108 can be input to the image recognition unit 109. The image recognition unit 109 can recognize the brightness of the input image by performing photometry (photometric processing). For example, the image recognition unit 109 sets a plurality of regions in the image and performs photometry for each region. This allows the image recognition unit 109 to obtain the photometric results for each region and determine high-luminance regions. The photometric results (including the determination results for high-luminance regions) are output to the AE processing unit 103.

[0021] Furthermore, the image recognition unit 109 can recognize (identify) a scene by using a known technique. The image recognition unit 109 can detect the face, upper body or whole body of an animal such as a person, a dog, a cat, or a bird, or detect a vehicle such as a car or a motorcycle from an image, and recognize a scene based on the detected subject. For example, when the image recognition unit 109 detects a person's face, it can recognize that the scene is one in which a person is to be photographed. Furthermore, when the image recognition unit 109 detects a plurality of cars running side by side, it can recognize that the scene is a motorsports scene. Information on the scene recognized by the image recognition unit 109 is output to the AE processing unit 103.

[0022] The user can select a metering mode by operating the operation unit 116. The operation unit 116 notifies the metering mode selected by the user to the AE processing unit 103. The AE processing unit 103 performs automatic exposure (AE) processing based on the metering result acquired by the image recognition unit 109, information on the scene recognized by the image recognition unit 109, and the metering mode selected by the user. .

[0023] Furthermore, the image recognition unit 109 can recognize the focus state of the input image. The AF processing unit 105 performs autofocus (AF) processing based on the recognition result of the focus state. Furthermore, the image recognition unit 109 can generate a luminance histogram of the input image. The image processing unit 108 performs gradation correction processing corresponding to the scene based on the generated luminance histogram.

[0024] The format conversion unit 110 converts the format of the image data generated by the image processing unit 108 in order to store the image data in the DRAM 111. The DRAM 111 is an internal memory, and is used, for example, as a buffer for temporarily storing image data, or as a working memory in the compression / decompression processing of image data.

[0025] Digital camera 100 also includes an image recording unit 112, a system control unit 113, a VRAM (Video RAM) 114, a display unit 115, an operation unit 116, a main switch (main SW) 117, and a shooting switch (shooting SW) 118.

[0026] The image recording unit 112 has a recording medium (for example, a memory card) for storing captured images (still images or moving images) and an interface therefor.

[0027] The system control unit 113 has a CPU (processor), a ROM, and a RAM. The CPU controls the overall operation of the digital camera 100 by expanding a program stored in the ROM into a working area of ​​the RAM and executing it. For example, the system control unit 113 switches the mode of the image sensor 106 between a plurality of predetermined image capture drive modes. The VRAM 114 is a memory for displaying images.

[0028] The display unit 115 is, for example, an LCD (Liquid Crystal Display). The display unit 115 can display images, display for operational assistance, and display the status of the digital camera 100. When shooting, the display unit 115 displays a shooting screen and displays a distance measurement area on the shooting screen. The display unit 115 can also display a selection screen for the user to select (specify) a target luminance of a high luminance area. FIG. 2 shows an example of the selection screen. A method in which the user selects a target luminance using the selection screen will be described later.

[0029] The operation unit 116 is a member that allows the user to operate the digital camera 100. The user can perform various settings, such as exposure compensation, aperture setting, and image playback setting, by operating the operation unit 116. The operation unit 116 has a menu switch, a zoom lever that instructs the zoom operation of the photographing lens, and an operation mode changeover switch that switches the operation mode between the photographing mode and the playback mode.

[0030] As described above, the user can select a metering mode by operating the operation unit 116. The metering modes selectable by the user include, for example, an evaluative metering mode, a partial metering mode, and a highlight-weighted metering mode.

[0031] The evaluative metering mode measures the light for each of multiple areas set in the captured image, and determines the final exposure based on the subject's brightness distribution, color, distance, and composition information. The evaluative metering mode is suitable for general photography, including backlit photography. The partial metering mode measures the light for the center of the image. The partial metering mode is effective when there is strong light around the subject (for example, a backlit scene). The highlight-weighted metering mode measures the light for the high-brightness areas of the image. In general, the exposure is adjusted so that the high-brightness areas have the appropriate brightness based on the metering results in the highlight-weighted metering mode. When control is performed, a darker image is captured than when exposure control is performed based on the photometry results in the evaluative photometry mode.

[0032] Furthermore, the user can select a target luminance for a high-luminance area by operating the operation unit 116. The target luminance selected by the user is output to the AE processing unit 103 and used for exposure control. The target luminance is also output to the image processing unit 108 and used for image processing control.

[0033] The main switch 117 is a switch for turning on the power to the digital camera 100. The shooting switch 118 is a switch that can be operated in two stages depending on how deeply it is pressed. When the shooting switch 118 is pressed halfway (SW1 operation, shooting preparation instruction), the system control unit 113 performs shooting preparation operations including AE processing and AF processing. When the shooting switch 118 is pressed all the way (SW2 operation, shooting instruction), the system control unit 113 performs shooting processing.

[0034] A series of processes performed by the digital camera 100 will be described. When the power of the digital camera 100 is turned on by pressing the main switch 117, the digital camera 100 enters the shooting standby state (a state in which imaging processing is performed by the imaging device 106 at a predetermined period (for example, a 33 ms period), and the captured images are sequentially displayed on the display unit 115). When the shooting switch 118 is pressed (SW2 operation), the main imaging process by the imaging device 106 is executed, and the image (image data) obtained by the main imaging process is recorded in the image recording unit 112 through image processing by the image processing unit 108. Thereafter, the digital camera 100 returns to the shooting standby state again. When the main switch 117 is pressed again, the power of the digital camera 100 is turned off.

[0035] <D+ correction> The digital camera 100 is capable of performing exposure control to suppress (reduce) overexposure of the captured image, and image processing (tone correction) to suppress a decrease in the luminance of the low-luminance region of the image based on the control amount. Hereinafter, the combination of this exposure control and image processing will be referred to as D+ correction. For D+ correction, known techniques, for example, the technique disclosed in Patent Document 1 (Japanese Patent Application Laid-Open No. 2010-193098), can be used. By performing D+ correction, in a scene where a low-luminance subject and a high-luminance subject are mixed, it is possible to suppress overexposure (saturation) of the high-luminance subject while maintaining the brightness of the low-luminance subject. The low-luminance region is not particularly limited, but is, for example, a region composed of one or more pixels whose luminance is equal to or lower than a threshold value. The threshold value is, for example, the luminance at the center of the range of possible luminance (dynamic range), or a luminance lower than that.

[0036] Normally, before shooting, shooting conditions such as the aperture value, shutter speed, and gain are set (determined) so that shooting is performed with appropriate exposure according to the luminance information of the subject and the presence or absence of a person's face. However, the dynamic range of the image to be captured is not wide. For example, in a backlit scene where the subject is photographed with the sun behind, no matter what shooting conditions are set, the luminance of the bright background is saturated and overexposure occurs.

[0037] In the D+ correction, the system control unit 113 uses the AE processing unit 103 to set (change) the exposure value to an underexposed value so as to prevent whiteout. Furthermore, the system control unit 113 uses the image processing unit 108 to perform image processing to increase the brightness of low brightness areas of the captured image. This image processing is, for example, gamma processing using a gamma curve. In general, image processing is performed so that the decrease in brightness of low brightness areas due to lowering the exposure is compensated for, and the brightness of the low brightness areas becomes the same as that at the time of proper exposure. This makes it possible to suppress (reduce) whiteout in the background while maintaining the brightness of the low brightness subject.

[0038] The system control unit 113 determines, for example, the amount of change in exposure in the D+ correction (the amount of control of exposure control, the amount of D+ correction) according to the brightness of the scene. An example will be described below.

[0039] First, the system control unit 113 sets a plurality of regions (a plurality of blocks) for an image (through image) obtained by periodic imaging processing in a shooting standby state, and obtains a representative luminance for each block. Here, it is assumed that the through image is obtained in a state where exposure control (normal exposure control) is performed to bring the average luminance of the entire image closer to a predetermined luminance. FIG. 3 shows an example of a plurality of blocks. In FIG. 3, a plurality of blocks are set in a part of the image, but the entire image area may be divided into a plurality of blocks. The representative luminance of a block is, for example, the average luminance, maximum luminance, minimum luminance, intermediate luminance, or most frequent luminance of the block. In this embodiment, it is assumed that the representative luminance is the average luminance.

[0040] Next, the system control unit 113 counts the number of blocks (saturated blocks) whose average brightness has reached the saturation value (upper limit) of 255. The system control unit 113 reduces the exposure according to the number of saturated blocks. For example, the system control unit 113 reduces the exposure by a larger amount as the number of saturated blocks increases. At this time, the system control unit 113 changes the setting of the gamma curve according to the amount of exposure reduction so as not to change the brightness of low brightness areas of the through-the-lens image.

[0041] Then, the system control unit 113 counts the number of saturated blocks in the captured through-the-lens image again.

[0042] The system control unit 113 repeats counting the saturated blocks and reducing the exposure until the number of saturated blocks becomes 0. Then, when the number of saturated blocks becomes 0, the system control unit 113 determines the total amount of exposure reduction as the D+ correction amount for the current scene (a provisional D+ correction amount described later).

[0043] <Highlight-weighted exposure control> The digital camera 100 can also execute highlight-weighted exposure control. Highlight-weighted exposure control is exposure control that brings the luminance of a high-luminance area of ​​a captured image closer to a target luminance set by the user, and is performed in a highlight-weighted metering mode. For highlight-weighted exposure control, a known technique, such as the technique disclosed in Patent Document 2 (JP Patent Publication 2015-166767), can be used. An example will be described below.

[0044] For example, the system control unit 113 displays the selection screen (user interface) of Fig. 2 on the display unit 115, and allows the user to select the target luminance of the high luminance area from among options TH1, TH2, and TH3. By selecting (specifying) the target luminance, the user can adjust the luminance of the high luminance area of ​​the captured image to the luminance as intended by the user. Note that the number of options may be more or less than three.

[0045] When the photographing switch 118 is pressed (SW2 operation), the system control unit 113 sets a plurality of blocks for the through image obtained at that time, and obtains a representative luminance for each block. As described above, in this embodiment, the representative luminance is the average luminance.

[0046] Next, system control unit 113 selects the block with the highest average luminance from the multiple blocks as a high luminance area (highlight portion).

[0047] Then, the system control unit 113 converts the target luminance and the luminance of the high-luminance region into the signal values before gamma processing by performing inverse gamma processing (inverse conversion of gamma processing), and calculates the exposure difference between the two obtained signal values. As the exposure difference, for example, the difference in APEX value (Additi ve system of Photographic EXposure) is calculated. Assuming that the linear signal value before gamma processing of the target luminance is the signal value Ya, and the linear signal value before gamma processing of the luminance of the high-luminance region is the signal value Yb, the exposure difference between the signal value Ya and the signal value Yb can be calculated by Log(Ya / Yb).

[0048] Here, assume that 200 is selected as the JPEG luminance (tone value of the JPEG image), which is the target luminance. Also assume that the luminance of the high-luminance region is 240. If the signal value Ya corresponding to the target luminance 200 is 5000, and the signal value Yb for the luminance 240 of the high-luminance region is 10000, then Log(Ya / Yb) = -1. Therefore, the system control unit 113 can make the luminance of the high-luminance region approach the target luminance by increasing the exposure value of the aperture and shutter 102 by one step from the current value. In this way, the system control unit 113 can control the exposure so that the luminance of the high-luminance region substantially matches the target luminance specified by the user according to the exposure difference (exposure difference between the target luminance and the luminance of the highlight part) between the signal value Ya and the signal value Yb.

[0049] <Problems caused by the combination of D+ correction and highlight priority exposure control> By combining D+ correction and highlight priority exposure control, it is possible to keep the luminance of the low-luminance region at the luminance during normal exposure control while bringing the luminance of the high-luminance region closer to the target luminance specified by the user. However, simply combining D+ correction and highlight priority exposure control may cause a deterioration in image quality. An example will be described below with reference to FIGS. 4(A), 4(B), 5(A) to 5(C).

[0050] Fig. 4(A) shows an example of an image captured when normal exposure control is being performed. The image in Fig. 4(A) is an image of a scene in which the sky and backlit trees are included in the angle of view. Fig. 5(A) shows a luminance histogram (luminance distribution) of the image in Fig. 4(A). In Fig. 5(A), the luminance of the sky area (area with relatively high luminance) has reached a saturation value of 255 by performing normal exposure control based on the average luminance of the entire image.

[0051] By performing D+ correction, as shown in FIG. 5B, it is possible to reduce blown-out highlights in the sky area while maintaining the brightness of the tree area (low brightness area).

[0052] When highlight-weighted exposure control is performed in the state of FIG. 5(B), the luminance (maximum luminance) of the high luminance area can be reduced to the target luminance of 200 designated by the user, as shown in FIG. 5(C).

[0053] However, in Fig. 5(C), the luminance of the tree area and the luminance of the sky area are close to each other. Therefore, as shown in Fig. 4(B), a low-contrast image (a hazy image with poor visibility) is obtained. The larger the D+ correction amount is, or the lower the target luminance is, the closer the luminance of the low-luminance area and the luminance of the high-luminance area become, and the decrease in contrast becomes more noticeable.

[0054] <How to solve problems caused by combinations> Fig. 6 is a flow chart showing an example of processing performed by digital camera 100. The processing in Fig. 6 includes D+ correction and highlight-weighted exposure control, and the above-mentioned problems caused by the combination of D+ correction and highlight-weighted exposure control can be solved by the processing in Fig. 6. The details will be described later. For example, when digital camera 100 is turned on and goes into a shooting standby state, the processing in Fig. 6 is started.

[0055] In step S601, system control unit 113 prompts the user to specify a target luminance for a high luminance area using the method described above, and acquires the target luminance specified by the user.

[0056] In step S602, the system control unit 113 calculates the D+ correction amount from the through-the-lens image by the method described above, and determines the calculated D+ correction amount as a provisional D+ correction amount.

[0057] In step S603, the system control unit 113 reduces the provisional D+ correction amount according to the target luminance obtained in step S601, thereby determining the final D+ correction amount. For example, the system control unit 113 reduces the provisional D+ correction amount by a correction coefficient previously associated with the target luminance obtained in step S601. A value larger than 0 and smaller than 1 is used as the correction coefficient. As described above, the larger the D+ correction amount is or the lower the target luminance is, the more significant the reduction in contrast becomes. Therefore, the lower the target luminance is, the smaller the correction coefficient is used. The correction coefficient to be used is determined, for example, by using a table or function indicating the correspondence between the target luminance and the correction coefficient. The ROM of the system control unit 113 may previously store a table as shown in FIG. 7 (three correction coefficients corresponding to three options of the target luminance (three luminances that can be set as the target luminance)). As described above, the number of options may be more or less than three.

[0058] The method of reducing the provisional D+ correction amount is not limited to the above method. For example, the system control unit 113 may reduce the provisional D+ correction amount using a function that uses the target luminance as an input value and the final D+ correction amount as an output value. The system control unit 113 may not perform D+ correction when the target luminance is lower than a predetermined threshold. The system control unit 113 may not perform D+ correction when performing highlight-focused exposure control, regardless of whether the target luminance is lower than a predetermined threshold.

[0059] Furthermore, if highlight-weighted exposure control is not performed, the process of reducing the provisional D+ correction amount is not performed. Therefore, the provisional D+ correction amount can be regarded as the final D+ correction amount when highlight-weighted exposure control is not performed.

[0060] Furthermore, in step S603, the system control unit 113 controls the exposure and sets the gamma curve according to the final D+ correction amount. The system control unit 113 applies the set gamma curve to the through image (the through image obtained in a state where the exposure is controlled according to the final D+ correction amount).

[0061] In step S604, the system control unit 113 determines whether or not a shooting instruction has been received (full press operation of the shooting switch 118, SW2 operation). If the system control unit 113 determines that a shooting instruction has not been received, the process returns to step S601, and if the system control unit 113 determines that a shooting instruction has been received, the process proceeds to step S605.

[0062] In step S605, the system control unit 113 performs highlight-weighted exposure control by the above-mentioned method. Here, highlight-weighted exposure control is performed on the through image reflecting the D+ correction. For this reason, a gamma curve whose setting is changed according to the final D+ correction amount is used for the inverse gamma process. Since the D+ correction amount is reduced in step S603, the luminance of the high-luminance area of ​​the through image becomes higher and the exposure reduction amount by the highlight-weighted exposure control becomes larger than when the D+ correction amount is not reduced.

[0063] In step S606, the system control unit 113 acquires an image by performing the main imaging process at the exposure determined in step S605 (in a state in which D+ correction and highlight-weighted exposure control have been performed).

[0064] In step S607, the system control unit 113 applies the gamma curve set in step S603 (the gamma curve according to the final D+ correction amount) to the image acquired in step S606.

[0065] As described above, according to this embodiment, the final D+ correction amount is determined by reducing the provisional D+ correction amount according to the target luminance (or, when highlight-weighted exposure control is performed, the D+ correction is omitted). This makes it possible to suppress degradation of image quality caused by gamma processing included in the D+ correction when performing highlight-weighted exposure control. For example, in the case of the scenes in Fig. 4(A) and Fig. 5(A), the luminance of the tree region (low luminance region) is reduced by reducing the D+ correction amount, and the luminance histogram in Fig. 5(D) is obtained. In the luminance histogram in Fig. 5(D), it can be seen that the luminance of the tree region and the luminance of the sky region are far apart, and a high-contrast image is obtained.

[0066] Here, the system control unit 113 can set whether or not to perform D+ correction and whether or not to perform highlight-weighted exposure control. For example, the system control unit 113 performs these settings in response to an instruction from a user. In this case, according to the present embodiment, the following relationship is established. In the following relationship, the first luminance is the luminance of a low-luminance area of ​​a captured image recorded without performing D+ correction and highlight-weighted exposure control (with normal exposure control). The second luminance is the luminance of a low-luminance area of ​​a captured image recorded without performing highlight-weighted exposure control and with D+ correction. The third luminance is the luminance of a low-luminance area of ​​a captured image recorded with D+ correction and highlight-weighted exposure control. The first luminance and the second luminance are approximately equal. The third luminance is lower than the first luminance and the second luminance.

[0067] The above-described embodiment (including the modified examples) is merely an example, and the present invention also includes configurations obtained by appropriately modifying or changing the configurations of the above-described embodiment within the scope of the gist of the present invention. The present invention also includes configurations obtained by appropriately combining the configurations of the above-described embodiment.

[0068] <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 storage 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) that implements one or more of the functions.

[0069] The disclosure of the present embodiment includes the following configuration, method, program, and medium. (Configuration 1) a first exposure control means for performing a first exposure control to suppress whiteout of a captured image; an image processing unit that performs image processing to suppress a decrease in luminance in a low-luminance area of ​​the image based on a control amount of the first exposure control; a second exposure control means for performing a second exposure control for bringing the luminance of a high luminance area of ​​a captured image closer to a target luminance set by a user; having When the second exposure control is performed, the first exposure control means does not perform the first exposure control. 1. An imaging device comprising: (Configuration 2) a first exposure control means for performing a first exposure control to suppress whiteout of a captured image; an image processing unit that performs image processing to suppress a decrease in luminance in a low-luminance area of ​​the image based on a control amount of the first exposure control; a second exposure control means for performing a second exposure control for bringing the luminance of a high luminance area of ​​a captured image closer to a target luminance set by a user; having When the second exposure control is performed, the second exposure control means performs the second exposure control after the first exposure control, The first exposure control means determines a control amount of the first exposure control by reducing a control amount in a case where the second exposure control is not performed in accordance with the target luminance. 1. An imaging device comprising: (Configuration 3) When the second exposure control is performed, the image processing means performs the image processing on an image captured under the second exposure control. 3. The imaging device according to configuration 2. (Configuration 4) The first exposure control means reduces the control amount when the second exposure control is not performed by a coefficient previously associated with the target brightness. 4. The imaging device according to configuration 2 or 3. (Configuration 5) a storage means for storing in advance a plurality of coefficients respectively corresponding to a plurality of luminances that can be set as the target luminance; Further having 5. The imaging device according to configuration 4. (Configuration 6) When the target luminance is lower than a threshold value, the first exposure control means does not perform the first exposure control. 6. The imaging device according to any one of configurations 2 to 5, wherein: (Configuration 7) a first setting means for setting whether or not to perform a first exposure control for suppressing whiteout of a captured image; a second setting means for setting whether or not to perform a second exposure control for bringing the luminance of a high luminance area of ​​a captured image closer to a target luminance set by a user; A recording means for recording the photographed image on a recording medium; having a first luminance, which is the luminance of a low-luminance region of a captured image recorded without performing the first exposure control and the second exposure control, is substantially equal to a second luminance, which is the luminance of a low-luminance region of a captured image recorded while performing the first exposure control without performing the second exposure control; A third luminance, which is a luminance of a low luminance area of ​​a photographed image recorded by performing the first exposure control and the second exposure control, is lower than the first luminance and the second luminance. 1. An imaging device comprising: (Method 1) performing a first exposure control for suppressing whiteout in a captured image; performing image processing to suppress a decrease in luminance in a low-luminance area of ​​the image based on a control amount of the first exposure control; having A second exposure control is capable of bringing the luminance of a high-luminance area of ​​a captured image closer to a target luminance set by a user; When the second exposure control is performed, the first exposure control is not performed. 23. A method for controlling an imaging apparatus comprising the steps of: (Method 2) performing a first exposure control for suppressing whiteout in a captured image; performing image processing to suppress a decrease in luminance in a low-luminance area of ​​the image based on a control amount of the first exposure control; having A second exposure control is capable of bringing the luminance of a high-luminance area of ​​a captured image closer to a target luminance set by a user; When the second exposure control is performed, the second exposure control is performed after the first exposure control, The control amount of the first exposure control is determined by reducing the control amount in a case where the second exposure control is not performed in accordance with the target brightness. 23. A method for controlling an imaging apparatus comprising the steps of: (program) A program for causing a computer to function as each of the means of the imaging device according to any one of configurations 1 to 7. (medium) A computer-readable storage medium storing a program for causing a computer to function as each of the means of the imaging device according to any one of configurations 1 to 7. [Explanation of symbols]

[0070] 100: Digital camera 113: System control unit

Claims

1. a first exposure control unit that performs a first exposure control to suppress whiteout in a captured image; an image processing unit that performs image processing to suppress a decrease in brightness in low-brightness areas of the image based on a control amount of the first exposure control; a second exposure control means for performing a second exposure control to bring the luminance of a high-luminance area of ​​the captured image closer to a target luminance set by a user; and When the second exposure control is performed, the first exposure control means does not perform the first exposure control. An imaging device characterized by:

2. a first exposure control unit that performs a first exposure control to suppress whiteout in a captured image; an image processing unit that performs image processing to suppress a decrease in brightness in low-brightness areas of the image based on a control amount of the first exposure control; a second exposure control means for performing a second exposure control to bring the luminance of a high-luminance area of ​​the captured image closer to a target luminance set by a user; and When the second exposure control is performed, the first exposure control means determines the control amount of the first exposure control by reducing the control amount of the first exposure control when the second exposure control is not performed in accordance with the target brightness. An imaging device characterized by:

3. When the second exposure control is performed, the image processing means performs the image processing on an image captured under the second exposure control.

3. The imaging device according to claim 2.

4. The image processing is gamma processing using a gamma curve.

4. The imaging device according to claim 3.

5. The first exposure control means controls the second exposure by a coefficient that is previously associated with the target brightness. The control amount is reduced when no output control is performed.

3. The imaging device according to claim 2.

6. a storage means for storing in advance a plurality of coefficients respectively corresponding to a plurality of luminances that can be set as the target luminance; Further having 6. The imaging device according to claim 5.

7. The first exposure control means does not perform the first exposure control when the target brightness is lower than a threshold value.

3. The imaging device according to claim 2.

8. a first setting means for setting whether or not to perform a first exposure control for suppressing whiteout in a captured image; a second setting means for setting whether or not to perform a second exposure control for bringing the luminance of a high-luminance area of ​​a captured image closer to a target luminance set by a user; a recording means for recording the captured image on a recording medium; and a first luminance, which is the luminance of a low-luminance region of a photographed image recorded without performing the first exposure control and the second exposure control, is approximately equal to a second luminance, which is the luminance of a low-luminance region of a photographed image recorded by performing the first exposure control but not the second exposure control; A third luminance, which is the luminance of a low-luminance region of a photographed image recorded by performing the first exposure control and the second exposure control, is lower than the first luminance and the second luminance. An imaging device characterized by:

9. performing a first exposure control to suppress whiteout in a captured image; performing image processing to suppress a decrease in brightness in low-brightness areas of the image based on a control amount of the first exposure control; and a second exposure control is possible that brings the luminance of a high-luminance area of ​​a captured image closer to a target luminance set by a user; When the second exposure control is performed, the first exposure control is not performed.

10. A method for controlling an imaging device, comprising:

10. performing a first exposure control to suppress whiteout in a captured image; performing image processing to suppress a decrease in brightness in low-brightness areas of the image based on a control amount of the first exposure control; and a second exposure control is possible that brings the luminance of a high-luminance area of ​​a captured image closer to a target luminance set by a user; When the second exposure control is performed, the control amount of the first exposure control is determined by reducing the control amount of the first exposure control when the second exposure control is not performed in accordance with the target brightness.

10. A method for controlling an imaging device, comprising:

11. A program for causing a computer to function as each of the means of the imaging device according to any one of claims 1 to 8.

12. 9. A computer-readable storage medium storing a program for causing a computer to function as each of the means of the imaging device according to claim 1.

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