Patent Publication Number: US-2022239819-A1

Title: Device, control method, and storage medium

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a Continuation of International Patent Application No. PCT/JP2018/046254, filed Dec. 17, 2018, which claims the benefit of Japanese Patent Application No. 2017-241983, filed Dec. 18, 2017, both of which are hereby incorporated by reference herein in their entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The technique of this disclosure relates to a device, a control method, and a storage medium capable of acquiring a high dynamic range image. 
     Background Art 
     There is conventionally known a technique of generating a high dynamic range image (hereinafter referred to as “HDR image”) with a wide dynamic range in a digital camera, a digital video camera, and the like. PTL 1 discloses a method of acquiring an HDR image by one time image capturing by image capturing an object using an image capturing element capable of controlling different exposure conditions for each pixel. According to the method disclosed in PTL 1, an image multivalued by applying a low-pass filter to an image binarized using luminance is used as an exposure time map, thereby preventing the occurrence of a false contour at the boundary between pixels of different exposure times. 
     In the case of setting different exposure times for each pixel in image capturing, a long exposure time is set for a pixel corresponding to a dark object. Depending on exposure conditions, however, the long exposure time may cause a blur in the acquired HDR image. 
     The technique of this disclosure has been accomplished in view of the above problem and aims to generate a high quality HDR image in the case of setting different exposure conditions for each area in image capturing. 
     CITATION LIST 
     Patent Literature 
     PTL 1 Japanese Patent Laid-Open No. 2011-004088 
     SUMMARY OF THE INVENTION 
     A device according to the technique of this disclosure is a device configured to control an image capturing element capable of controlling an exposure condition for each of areas, the device comprising: an acquisition unit configured to acquire an exposure value map obtained by preliminary exposure using the image capturing element; and a setting unit configured to set the exposure condition including a shutter speed and an ISO sensitivity for each of the areas based on the exposure value map. 
     Further features of the technique of this disclosure will become apparent from the following description of an exemplary embodiment to be given with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram showing an example of the appearance of an image capturing device in a first embodiment; 
         FIG. 2  is a diagram showing an example of the hardware configuration of the image capturing device in the first embodiment; 
         FIG. 3  is a block diagram showing an example of the functional configuration of an image processing unit in the first embodiment; 
         FIG. 4  is a flowchart showing an example of a main procedure in the first embodiment; 
         FIG. 5  is a diagram showing an example of a UI of the image capturing device in the first embodiment; 
         FIG. 6A  is a schematic diagram showing an example of a scene to be captured in the first embodiment; 
         FIG. 6B  shows an example of an exposure value map generated in an LDR image capturing mode; 
         FIG. 6C  shows an example of an exposure value map generated in an HDR image capturing mode; 
         FIG. 7  is a flowchart showing an example of a correction procedure of an exposure condition in the first embodiment; 
         FIG. 8A  is a diagram showing a specific example of exposure conditions in a correction target area; 
         FIG. 8B  is a diagram showing a specific example of exposure conditions in the correction target area; 
         FIG. 8C  is a diagram showing a specific example of corrected exposure conditions in the correction target area; 
         FIG. 9  is a diagram showing an example of a UI for adjusting the amount of correction in the first embodiment; 
         FIG. 10  is a block diagram showing an example of the functional configuration of an image capturing device in a second embodiment; 
         FIG. 11  is a flowchart showing an example of a correction procedure of an exposure condition in the second embodiment; 
         FIG. 12A  is a diagram showing an example of an exposure value map before setting a correction target area; and 
         FIG. 12B  is a diagram showing an example of an exposure value map after setting a correction target area. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     First Embodiment 
     In the first embodiment, a description will be given of a method of generating an HDR image by controlling exposure conditions for each area. In particular, both of an exposure time (shutter speed) and an ISO sensitivity (analog gain) are controlled for each area, thereby performing image capturing depending on the brightness of each area. 
     Configuration of Image Capturing Device 
       FIG. 1  is a schematic diagram showing an example of the appearance of an image capturing device in the present embodiment. An image capturing device  100  comprises an optical unit  101 , an image capturing button  102 , a display unit  103 , and an operation button  104 . The optical unit  101  includes a zoom lens, a focus lens, a blur correction lens, a diaphragm, and a shutter to concentrate light information on an object. The image capturing button  102  is a button for accepting an image capturing instruction from a user. The display unit  103  includes a liquid crystal display or the like to display image data processed by the image capturing device  100  and various types of data. The operation button  104  functions as an operation unit for accepting various instructions from a user. For example, a user can input an exposure condition to the image capturing device  100  via the operation button  104 . 
     Hardware Configuration of Image Capturing Device 
       FIG. 2  is a block diagram showing an example of the hardware configuration of the image capturing device  100  in the present embodiment. An image capturing element unit  201  is a group of image capturing elements that convert light concentrated by the optical unit  101  into a current value. The image capturing device  100  can acquire color information by using the image capturing element unit  201  in combination with a color filter and the like. In the present embodiment, an HDR sensor capable of setting exposure conditions for each pixel or each area is applied to the image capturing element unit  201 . In the present embodiment, “exposure condition” is a general term of parameters concerning the brightness of an image. The image capturing element unit  201  acquires an HDR image by adaptively controlling exposure conditions (such as an exposure time and analog gain) for each pixel or each area. In the case of controlling exposure in units of areas, exposure conditions are generally controlled for each 2×2 or 3×2 pixel area, but the embodiment is not limited to this. 
     A CPU  202  has control over each constitutional element of the image capturing device  100  and sequentially reads commands stored in a storage area such as a read only memory (ROM)  203  into a random access memory (RAM)  204 . The CPU  202  interprets the read command and executes processing according to the result of interpretation. An image capturing system control unit  205  performs control according to an instruction from the CPU  202  such that, for example, the optical unit  101  focuses, opens the shutter, or adjusts the aperture. A device control unit  206  performs control according to a user instruction accepted via the image capturing button  102  such that, for example, the image capturing device  100  starts or finishes image capturing operation. The device control unit  206  also performs control according to a user instruction accepted via the operation button  104  such that, for example, the display unit  103  displays a predetermined operation screen. A graphic generation unit  207  functions as a display control unit of the image capturing device  100  and generates an image signal indicating a character, figure, image or the like to be displayed on the display unit  103 . An A/D conversion unit  208  converts the amount of light of an object detected by the image capturing element unit  201  into a digital signal. An image processing unit  209  processes the digital signal converted by the A/D conversion unit  208 , thereby processing image data corresponding to the digital signal. An encoder unit  210  converts the image data processed by the image processing unit  209  into a file format such as jpeg. An input/output interface (“interface” will be hereinafter referred to as “I/F”)  211  is an I/F used to transmit/receive image data to/from an external device such as a PC or various storage media (such as a hard disk, memory card, CF card, and SD card). The constitutional elements of the image capturing device  100  described above are connected via a system bus  212  so as to communicate with each other. 
     Functional Configuration of Image Capturing Device 
       FIG. 3  is a block diagram showing the functional configuration of the image processing unit  209  in the present embodiment. The function of each block shown in  FIG. 3  is implemented by the CPU  202  reading a program code stored in the ROM  203  into the RAM  204  and executing the code. Alternatively, some or all of the functions of the blocks in  FIG. 3  may be implemented by hardware such as an ASIC or electronic circuit. The same applies to the block diagram subsequent to  FIG. 3 . 
     In the image capturing device  100  of the present embodiment, the image processing unit  209  comprises an exposure value map generation unit  301 , an exposure condition acquisition unit  302 , a reference determination unit  303 , an area selection unit  304 , and an exposure condition correction unit  305 . The exposure value map generation unit  301  generates, according to image data sent from the A/D conversion unit  208  in preliminary exposure, an exposure value map in which an exposure value is stored for each pixel. An exposure value is a parameter for controlling brightness recorded using an ISO sensitivity and an exposure time. The exposure condition acquisition unit  302  reads exposure conditions corresponding to the exposure value and acquires exposure conditions for each area. The reference determination unit  303  determines reference exposure conditions based on a plurality of exposure conditions. The area selection unit  304  selects a correction target area for which exposure conditions are to be corrected from among areas partitioned in preliminary exposure. The exposure condition correction unit  305  corrects the exposure conditions for the correction target area based on the reference exposure conditions. 
     Main Procedure 
       FIG. 4  is a flowchart showing a main procedure of the image capturing device  100  in the present embodiment. The processing in the flowchart shown in  FIG. 4  is performed by the CPU  202  reading a program code stored in the ROM  203  into the RAM  204  and executing the code. In the description below, sign “S” indicates a step in the flowchart. The same applies to the flowcharts subsequent to  FIG. 4 . 
     In S 401 , the device control unit  206  sets exposure conditions such as a lens aperture value, a shutter speed, and an ISO sensitivity according to a user instruction accepted via the operation button  104 . In the present embodiment, the shutter speed and the ISO sensitivity, which are also camera parameters, correspond to the exposure time and the analog gain, respectively. Exposure conditions other than these camera parameters may be set according to an image capturing mode.  FIG. 5  is a diagram showing an example of a user interface (“user interface” will be hereinafter referred to as “UI”) of the image capturing device  100  in the present embodiment.  FIG. 5  shows an UI for setting an HDR image capturing mode, the UI being displayed on the display unit  103 . A user can select a desired image capturing mode by inputting an instruction via the operation button  104 . The image capturing mode set in S 401  is not limited to the HDR image capturing mode and may be an image capturing mode other than the HDR image capturing mode such as an image capturing mode according to the type of object such as a person or scenery or an image capturing mode according to a weather such as sunny or cloudy. 
     In S 402 , the device control unit  206  determines whether the image capturing button  102  has been pushed. In a case where the image capturing button  102  has been pushed (S 402 : YES), the processing proceeds to S 403 . In a case where the image capturing button  102  has not been pushed (S 402 : NO), S 402  is repeated. 
     In preliminary exposure in S 403 , exposure conditions for each area in the image capturing element unit  201  are set. More specifically, the exposure value map generation unit  301  generates an exposure value map in which an exposure value is stored for each pixel according to image data sent from the A/D conversion unit  208  in the preliminary exposure. The image processing unit  209  (exposure condition acquisition unit  302 ) of the present embodiment can read exposure conditions ( FIG. 8A  to  FIG. 8C ) corresponding to an exposure value and acquire exposure conditions for each area. A description will be given of settings of exposure conditions for each area of the image capturing element unit  201  with reference to  FIG. 6A  to  FIG. 6C . 
       FIG. 6A  is a schematic diagram showing an example of a scene to be captured in the present embodiment. In the scene to be captured in  FIG. 6A , a person in a room is captured by the image capturing device  100 . The room where the person is present has a window and light enters from outside through the window. 
       FIG. 6B  shows an example of an exposure value map generated in the case of capturing the scene in a low dynamic range (LDR) image capturing mode in the present embodiment. The LDR image capturing mode is a mode for acquiring a captured image with a dynamic range narrower than that in the HDR image capturing mode and is applied, for example, in a case where “tone oriented” is selected in the UI shown in  FIG. 5 . In the LDR image capturing mode, settings are made such that exposure is appropriate for the person. At this time, since an exposure value shown in the exposure value map in  FIG. 6B  is set for the entire scene to be captured shown in  FIG. 6A , overexposure occurs in the window area brighter than the inside of the room where the person is present. 
       FIG. 6C  shows an example of the exposure value map generated in the case of capturing the scene in the HDR image capturing mode in the present embodiment. The HDR image capturing mode is a mode for acquiring a captured image with a dynamic range wider than that in the LDR image capturing mode and is applied, for example, in a case where “D range oriented” is selected in the UI shown in  FIG. 5 . At this time, the exposure value shown in the exposure value map in  FIG. 6B  is set for the indoor area including the person and an exposure value lower than that for the indoor area is set for the window area, whereby overexposure in the window area can be suppressed. 
     Areas for which exposure values are to be set are not limited to those. For example, an exposure value may be set for each pixel as shown in  FIG. 6C . Alternatively, an exposure value may be set for a relatively large area such as the area corresponding to the window. 
     Returning to the flowchart of  FIG. 4 , in S 404 , the exposure conditions set in the preliminary exposure in S 403  are corrected so as to reduce differences in exposure conditions between the areas. 
     Correction Procedure of Exposure Conditions 
       FIG. 7  is a flowchart showing an example of a correction procedure of exposure conditions in S 404  in the present embodiment. The exposure condition correction processing will be described in detail with reference to the flowchart of  FIG. 7 . 
     In S 701 , the exposure condition acquisition unit  302  acquires exposure conditions for each area from the exposure conditions set in S 401  and the exposure value map generated in S 403 . 
     In S 702 , the reference determination unit  303  determines exposure conditions to be a reference (hereinafter referred to as “reference exposure conditions”) based on the exposure conditions acquired in S 701 . In the present embodiment, the reference exposure conditions determined in S 702  are a shutter speed and an ISO sensitivity. As the reference exposure conditions, for example, exposure conditions corresponding to an area of a main object in a captured image obtained by capturing the scene to be captured of  FIG. 6A  may be selected. 
     The method of determining the reference exposure conditions is not limited to the method of selecting exposure conditions corresponding to an area of a main object, provided that the reference exposure conditions can be suitably selected according to a scene to be captured. For example, in the case of using a focused area as a reference, exposure conditions corresponding to the focused area can be automatically determined as the reference exposure conditions. In the case of accepting selection of a desired area via the operation button  104 , exposure conditions corresponding to the desired area can be determined as the reference exposure conditions. Alternatively, the reference determination unit  303  can determine exposure conditions corresponding to an arbitrary area as the reference exposure conditions based on the exposure conditions acquired in S 701 . 
     In S 703 , the area selection unit  304  selects a correction target area for which exposure conditions are to be corrected from among areas partitioned in the preliminary exposure in S 403 . The area selection unit  304  can select the correction target area in an arbitrary order each time the loop processing from S 703  to S 705  is executed. For example, the area selection unit  304  may select the correction target area while scanning an area of interest in the order from upper left to lower right of the captured image. At this time, in a case where a difference between the reference exposure condition and exposure condition for the correction target area is small, the advantageous result obtained by correcting the exposure condition also becomes small. Thus, an area of interest may be selected as the correction target area in a case where the difference between the reference exposure condition and the exposure condition for the area of interest is larger than a predetermined threshold. 
     In S 704 , the exposure condition correction unit  305  corrects the exposure conditions for the correction target area selected in S 703  based on the reference exposure conditions determined in S 702 . The exposure condition correction processing will be described in detail with reference to  FIG. 8A  to  FIG. 8C . 
       FIG. 8A  and  FIG. 8B  are tables showing specific examples of exposure conditions set in S 401  for a correction target area. On the other hand,  FIG. 8C  is a table showing a specific example of exposure conditions corrected in S 704  for a correction target area. The exposure condition acquisition unit  302  can acquire exposure conditions corresponding to an exposure value of each area (pixel) stored in the exposure value map by referring to the tables of  FIG. 8A  and  FIG. 8B . For example, a description will be given of a case where the shutter speed “ 1/100 sec” and the ISO sensitivity “400” associated with the exposure value “0” are set as reference exposure conditions. 
       FIG. 8A  shows an example of adjusting exposure conditions by changing only the shutter speed. Since the exposure value of the person area is “0” in the scene to be captured of  FIG. 6A , exposure conditions set for the person area are the shutter speed “ 1/100 sec” and the ISO sensitivity “400.” In contrast, since the exposure value of the window area is “−2,” exposure conditions set for the window area are the shutter speed “ 1/400 sec” and the ISO sensitivity “400.” At this time, the shutter speed differs four times between the person area and the window area. Accordingly, in a case where the scene to be captured of  FIG. 6A  includes a moving object, the amount of movement also differs four times between the areas. As a result, in a case where the exposure values are adjusted based on only the shutter speed, a blur occurs in some local areas. In addition, the aspect of output such as a blur or multiple overlapping image may largely differ between local areas in an HDR image. 
       FIG. 8B  shows an example of adjusting exposure conditions by changing only the ISO sensitivity. Since the exposure value of the person area is “0” in the scene to be captured of  FIG. 6A , exposure conditions set for the person area are the shutter speed “ 1/100 sec” and the ISO sensitivity “400.” In contrast, since the exposure value of the window area is “−2,” exposure conditions set for the window area are the shutter speed “ 1/100 sec” and the ISO sensitivity “100.” At this time, the ISO sensitivity differs four times between the person area and the window area. Accordingly, in a case where the scene to be captured of  FIG. 6A  includes a moving object, the amount of noise also differs four times between the areas. As a result, in a case where the exposure values are adjusted based on only the ISO sensitivity, the amount of noise increases in some local areas. In addition, the aspect of output of noise may largely differ between local areas in an HDR image. In other words, a difference in level of noise may be observed between local areas. 
       FIG. 8C  shows an example of exposure conditions corrected by the exposure condition correction unit  305 . Since the exposure value of the person area is “0” in the scene to be captured of  FIG. 6A , exposure conditions set for the person area are the shutter speed “ 1/100 sec” and the ISO sensitivity “400.” In contrast, since the exposure value of the window area is “−2,” exposure conditions set for the window area are the shutter speed “ 1/200 sec” and the ISO sensitivity “200.” At this time, a difference between the reference shutter speed “ 1/100” and the corrected shutter speed “ 1/200” to be set for the person area is reduced to two times. Similarly, a difference between the reference ISO sensitivity “400” and the corrected ISO sensitivity “200” to be set for the window area is also reduced to two times. In this manner, the exposure condition correction unit  305  controls not either but both of the shutter speed and the ISO sensitivity, thereby reducing the adverse effect of controlling only either one of these conditions. Further, correcting the shutter speed and the ISO sensitivity at the same or substantially the same rate enables a reduction in a difference in aspect of appearance of a blur or noise between local areas. In addition, since correction is made not only to exposure conditions corresponding to the boundary between the correction target area and the adjacent area but to exposure conditions corresponding to the entire correction target area, a false contour can also be reduced in an HDR image. As a result, according to the control method of the image capturing device in the present embodiment, a high quality HDR image can be generated in the case of setting different exposure conditions for each area in image capturing. 
     The correction described above may be made according to a desired method as long as differences between the reference exposure conditions and exposure conditions for each area can be reduced. For example, on the assumption that the exposure value in the reference exposure conditions is E, the shutter speed is T, the ISO sensitivity is G, the exposure value of the correction target area is E′, the corrected shutter speed is T′, and the corrected ISO sensitivity is G′, T′ and G′ can be calculated by the following formulae, respectively: 
     
       
         
           
             
               
                 
                   
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     In the above formulae, α is a coefficient that is a real number satisfying 0.0≤α≤1.0.  FIG. 8A  corresponds to the case of =1.0,  FIG. 8B  corresponds to the case of α=0.0, and  FIG. 8C  corresponds to the case of α=0.5. The above formulae are not necessarily used and an arbitrarily adjusted coefficient α may be used instead. 
       FIG. 9  is a diagram showing an example of a UI for adjusting the amount of correction in the present embodiment. As shown in the example of the UI in  FIG. 9 , a user can adjust the coefficient α by moving a knob  901  of a slider bar included in the UI right or left. For example, in a case where the knob is moved right (direction of “sensitivity oriented”) to reduce a, a difference between the reference shutter speed and the shutter speed in the correction target area is reduced, whereby the occurrence of a blur or multiple overlapping image caused by a moving object can be more reduced. In contrast, in a case where the knob is moved left (direction of “Tv oriented”) to increase a, a difference between the reference ISO sensitivity and the ISO sensitivity in the correction target area is reduced, whereby the occurrence of a difference in level of noise can be more reduced. In this manner, the exposure condition correction unit  305  can correct the shutter speed and the ISO sensitivity at weighted rates, thereby reducing a difference in aspect of appearance of a blur or noise between local areas. 
     Returning to the flowchart of  FIG. 7 , in S 705 , the exposure condition correction unit  305  determines whether the processing has been completed for all the areas. In a case where the processing has been completed for all the areas (S 705 : YES), the processing returns to the flowchart of  FIG. 4 . In a case where the processing has not been completed for all the areas (S 705 : NO), the processing returns to S 703  to perform the loop processing from S 703  to S 705 . 
     Returning to the flowchart of  FIG. 4 , in S 405 , the image capturing system control unit  205  causes the image capturing system to perform image capturing operation based on the exposure conditions corrected in S 404 . In image capturing in S 405 , the image capturing system control unit  205  drives the optical unit  101  to acquire the amounts of light of objects, and the acquired amounts of light are detected by the image capturing element unit  201 . The A/D conversion unit  208  converts the amounts of light detected by the image capturing element unit  201  into an electric signal to acquire RAW image data. As publicly known in the technical field of image processing, RAW image data is image data in which any one of R, G, and B color components is stored in each pixel in a predetermined arrangement such as the Bayer arrangement. 
     In S 406 , the image processing unit  209  performs development processing for the RAW image data. By applying development processing to the RAW image data, RGB image data (3-channel image data having all of the R, G, and B color components in each pixel) is generated. Although the development processing is generally accompanied with sub-processing such as white balance processing, demosaicing processing, and gamma processing, the description thereof will be omitted since they are not the main focus of the present embodiment. 
     In S 407 , the image processing unit  209  outputs the RGB image data generated in S 406 . The output RGB image data is sent to the encoder unit  210  and converted into a file format such as jpeg. Next, the RGB image data is output to an external device or storage medium via the input/output I/F  211 . Upon the completion of S 407 , the flowchart is finished. 
     As described above, according to the control method of the image capturing device of the present embodiment, in the case of setting different exposure conditions for each area in image capturing, the shutter speed and the ISO sensitivity are controlled, thereby reducing the adverse effect of controlling only either one of these conditions. Therefore, according to the control method of the image capturing device of the present embodiment, a difference in aspect of appearance of a blur or noise between local areas and a false contour can be reduced and a high quality HDR image can be generated. 
     Second Embodiment 
     In the correction processing of exposure conditions in the first embodiment (S 404 ), exposure conditions for the correction target area are corrected based on the reference exposure conditions. However, in a case where a difference between the reference exposure condition and the exposure condition for the correction target area are small, the advantageous result obtained by correcting the exposure condition also becomes small. Therefore, in the present embodiment, a difference in exposure condition between adjacent areas is considered. In case where there the difference is large, exposure conditions for an area of interest are corrected. The description of the same features as those of the first embodiment will be simplified or omitted and features unique to the present embodiment will be mainly described. 
     Functional Configuration of Image Capturing Device 
       FIG. 10  is a block diagram showing the functional configuration of the image capturing device  100  in the present embodiment. 
     The image processing unit  209  of the present embodiment comprises an exposure value determination unit  1001  instead of the reference determination unit  303  in the first embodiment. The exposure value determination unit  1001  determines whether an area of interest out of areas partitioned in preliminary exposure is a correction target area to be a target of correction. 
     Correction Procedure of Exposure Conditions 
       FIG. 11  is a flowchart showing the correction procedure of exposure conditions in S 404  in the present embodiment. The exposure condition correction processing will be described in detail with reference to the flowchart of  FIG. 11 . 
     First, in the loop processing from S 1101  to S 1104 , a correction target area for which exposure conditions are to be corrected is determined. 
     In S 1101 , the exposure value determination unit  1001  selects an area of interest from among areas of the image capturing element unit  201  partitioned in the preliminary exposure. The area of interest can be selected in an arbitrary order each time the loop processing from S 1101  to S 1104  is executed. For example, the area may be selected in the order from upper left to lower right in the captured image. 
     In S 1102 , the exposure value determination unit  1001  compares an exposure value of the area of interest selected in S 1101  and an exposure value of an adjacent area adjacent to the area of interest. In a case where a difference in exposure value is equal to or larger than a predetermined threshold (S 1102 : YES), the processing proceeds to S 1103 . In a case where the difference in exposure value is smaller than the predetermined threshold (S 1102 : NO), the processing skips S 1103  and proceeds to S 1104 . 
     In S 1103 , the exposure value determination unit  1001  determines the area of interest as a correction target area. 
     The method of determining the correction target area in the present embodiment will be described with reference to  FIG. 12A  and  FIG. 12B . 
       FIG. 12A  shows an example of an exposure value map input to the exposure value determination unit  1001 .  FIG. 12B  shows an example of an exposure value map output from the exposure value determination unit  1001 . That is, in the exposure value map shown in  FIG. 12B , shaded areas are determined as the correction target areas. In the example of  FIG. 12B , areas adjacent to the area of interest in eight directions (upper left, above, upper right, left, right, lower left, below, and lower right) are searched for. In a case where a difference in exposure value between the area of interest and an adjacent area is equal to or larger than 2, the area is determined as a correction target area. In this manner, based on the exposure value map generated by the preliminary exposure, an area largely different in exposure value from an adjacent area is determined as a correction target area. The method of determining the correction target area is not limited to above. Further, the difference in exposure value to be a determination condition may be other than “2.” 
     Next, in the loop processing from S 1105  to S 1107 , exposure conditions for the correction target area are corrected. 
     Returning to the flowchart of  FIG. 11 , in S 1105 , a correction target area for which exposure conditions are to be corrected is selected from among areas partitioned in the preliminary exposure in S 403 . The correction target area may be selected in an arbitrary order each time the loop processing from S 1105  to S 1107  is executed. For example, the area may be selected in the order from upper left to lower right in the captured image. 
     In S 1106 , the exposure condition correction unit  305  corrects exposure conditions for the correction target area selected in S 1105 . Since the method of correcting the exposure conditions is the same as that in the first embodiment, the description thereof is omitted. 
     In S 1107 , the exposure condition correction unit  305  determines whether the processing has been completed for all the areas. In a case where the processing has been completed for all the areas (S 1107 : YES), the processing returns to the flowchart of  FIG. 4 . In a case where the processing has not been completed for all the areas (S 1107 : NO), the processing returns to S 1105  and executes the loop processing from S 1105  to S 1107 . 
     As described above, according to the control method of the image capturing device of the present embodiment, in the case of setting different exposure conditions for each area in image capturing, if a difference in exposure condition between adjacent areas is large, correction is made so as to reduce the difference in exposure condition between the adjacent areas. Therefore, according to the control method of the image capturing device of the present embodiment, a high quality HDR image can be generated while reducing processing load caused by correction of exposure conditions, in addition to the advantageous result of the first embodiment. 
     OTHER EMBODIMENTS 
     Embodiment(s) of the technique of this disclosure can also be realized by a computer of a system or apparatus that reads out and executes computer executable instructions (e.g., one or more programs) recorded on a storage medium (which may also be referred to more fully as a ‘non-transitory computer-readable storage medium’) to perform the functions of one or more of the above-described embodiment(s) and/or that includes one or more circuits (e.g., application specific integrated circuit (ASIC)) for performing the functions of one or more of the above-described embodiment(s), and by a method performed by the computer of the system or apparatus by, for example, reading out and executing the computer executable instructions from the storage medium to perform the functions of one or more of the above-described embodiment(s) and/or controlling the one or more circuits to perform the functions of one or more of the above-described embodiment(s). The computer may comprise one or more processors (e.g., central processing unit (CPU), micro processing unit (MPU)) and may include a network of separate computers or separate processors to read out and execute the computer executable instructions. The computer executable instructions may be provided to the computer, for example, from a network or the storage medium. The storage medium may include, for example, one or more of a hard disk, a random-access memory (RAM), a read only memory (ROM), a storage of distributed computing systems, an optical disk (such as a compact disc (CD), digital versatile disc (DVD), or Blu-ray Disc (BD)™), a flash memory device, a memory card, and the like. 
     While the technique of this disclosure has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions. 
     According to the device of the technique of this disclosure, a high quality HDR image can be generated in the case of setting different exposure conditions for each area in image capturing.