Imaging apparatus, control method, and program

Abstract

To solve the problem in which, with the conventional highlight metering method, the metering is focused on highlight areas, making it impossible to make fine adjustments, and in some scenes, the brightness may be reduced too much, and if there are important areas other than the highlight areas, the important areas may be underexposed due to overcorrection.SOLUTION: The correction level for highlight metering can be selected to control high brightness.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to an imaging apparatus, a control method, and a program, and more particularly to exposure control. [Background technology]

[0002] When performing photometry control in a digital camera, a known method is to calculate the average brightness value of the captured image, determine the exposure correction step that will converge this average value to the appropriate brightness, and then feed it back to exposure control such as aperture, shutter, and ISO to keep the image at an appropriate level.

[0003] By using this method, it is possible to converge to the appropriate brightness level without any problems in scenes with little brightness difference within the screen. However, in scenes where high and low brightness areas coexist within the screen, if the above exposure calculation is performed, there is a high possibility that the exposure will shift in the direction that eliminates the gradation in either the bright or dark areas.

[0004] To avoid this, Patent Document 1 discloses a light metering method called highlight metering, which focuses on measuring the light in high-luminance areas of the screen, thereby controlling the gradation in the high-luminance areas to be brought out. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2006-106617 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, because conventional highlight metering focuses on high-luminance areas, it is not possible to make fine adjustments, and the brightness of important areas other than high-luminance areas may be reduced too much. For example, when a high-luminance subject enters the field of view, the exposure may be too low compared to other subject areas. In such scenes, it is desirable to keep the brightness of the object that the user wants to keep in gradation within an appropriate range. [Means for solving the problem]

[0007] In view of the above problems, an imaging device according to the present invention comprises an imaging means and a setting means for setting a photometry mode, a first luminance calculation means for calculating a first luminance evaluation value from the entire area of ​​an image acquired by the imaging means, a second luminance calculation means for calculating a second luminance evaluation value from an area of ​​the area having a luminance value equal to or greater than a predetermined threshold value, and a determination means for determining a target luminance value, wherein when a first mode is set by the setting means, the determination means determines the target luminance value using the first luminance evaluation value, and when a second mode different from the first mode is set, the determination means determines the target luminance value using the second luminance evaluation value. Effect of the Invention

[0008] As a result, even in scenes with large differences in brightness within the screen, the user can control the gradation of highlights (high brightness areas), making it possible to shoot with the exposure that the user expects. [Brief description of the drawings]

[0009] [Figure 1] Block diagram of the first embodiment of the present invention [Diagram 2] Highlight metering process flow [Diagram 3] A diagram showing the problem [Figure 4] A diagram showing multiple highlight threshold settings in the present case. [Diagram 5] Block diagram of a second embodiment of the present invention [Figure 6]Highlight metering process flow including low brightness threshold [Figure 7] Histogram diagram of the processing flow in Figure 2 [Figure 8] Histogram diagram in the processing flow of FIG. 6 DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, the embodiments will be described in detail with reference to the attached drawings. Note that the following embodiments do not limit the invention according to the claims. Although the embodiments describe a number of features, not all of these features are essential to the invention, and the features may be combined in any manner. Furthermore, in the attached drawings, the same reference numbers are used for the same or similar configurations, and duplicated descriptions are omitted.

[0011] [First embodiment] Hereinafter, the configuration and processing flow of an imaging device according to a first embodiment of the present invention will be described with reference to FIG. 1 and other figures. In this embodiment, a digital camera is exemplified as an imaging device, but the imaging device is not limited to this. For example, the present invention can be applied to any electronic device having an imaging function, such as a smartphone or tablet.

[0012] (Configuration of imaging device) FIG. 1 is a block diagram showing the functional configuration of a digital camera 100 (hereinafter referred to as "camera 100") according to an embodiment of the present invention.

[0013] The operation unit 101 is a user interface made up of switches, buttons, and the like that are operated by the user to input various instructions to the camera 100. The operation unit 101 includes a shutter switch, a touch sensor (which enables operation by touching the display device), and the like. When the operation unit 101 detects an operation input made to various user interfaces, it outputs a corresponding control signal to the control unit 102.

[0014] The control unit 102 includes a CPU, a non-volatile memory, and a RAM (not shown). The CPU reads out a program stored in the non-volatile memory, expands the program in the RAM, and executes the program to realize various functions. For example, the control unit 102 can control the operation of each unit shown in FIG. 1 in response to an instruction from the operation unit 101.

[0015] The imaging unit 103 is an imaging element such as a CCD or CMOS sensor. The imaging unit 103 photoelectrically converts an optical image formed on an imaging surface via an imaging optical system including a lens 108a and the like, and a mechanical mechanism 109a including a shutter and the like, and outputs an electric charge according to the amount of light as an analog image signal. Here, for convenience, the imaging optical system in FIG. 1 is illustrated as only the lens 108a, but the imaging optical system may be composed of a plurality of lenses. In addition, in this embodiment, a case is described in which the imaging optical system, the mechanical mechanism, and the like are integrally provided with the camera body including the imaging unit 103. However, a configuration in which an interchangeable lens having the imaging optical system, the mechanical mechanism, and the like is detachable from the camera body may also be used.

[0016] The A / D conversion unit 104 applies sampling, gain adjustment, A / D conversion, etc. to the analog image signal output from the imaging unit 103, and outputs it as a digital image signal.

[0017] The image processing unit 105 performs various image processing on the digital image signal (hereinafter simply referred to as image) output from the A / D conversion unit 104, and outputs the processed image. For example, the image processing unit 105 performs YUV conversion on the image received from the A / D conversion unit 104 and outputs it. The image to which the image processing has been applied by the image processing unit 105 is stored in the memory unit 117, which will be described later.

[0018] The first luminance calculation unit 106 uses the image signal stored in the memory unit 117 to calculate an overall luminance evaluation value from the entire image.

[0019] The second luminance calculation unit 115 calculates a high luminance evaluation value from a high luminance area equal to or higher than a set threshold value, using the image signal stored in the memory unit 117. Here, the threshold value may be set by the user via the operation unit 101 or the like, or may be automatically set inside the camera 100.

[0020] The exposure compensation calculation unit 116 calculates an appropriate exposure compensation value using the overall luminance evaluation value and the high luminance evaluation value obtained by the first luminance calculation unit and the second luminance calculation unit.

[0021] Display unit 107 is a display device included in camera 100 and is configured with a liquid crystal screen or the like. Display unit 107 is capable of displaying an image (digital image signal) output from A / D conversion unit 104. Display unit 107 also functions as an electronic viewfinder by displaying a direct input of an analog image signal output by imaging unit 103 through the display.

[0022] An external monitor, a personal computer, etc. can be connected to the external connection unit 114. For example, if an external monitor is connected to the external connection unit 114, the screen displayed on the display unit 107 can be displayed on the external monitor.

[0023] Based on the image stored in the memory unit 117, the AF processing unit 108 adjusts the imaging optical system including the lens 108a so as to focus on an appropriate subject in the shooting settings.

[0024] The AE processing unit 109 calculates the difference between the image stored in the memory unit 117 and the appropriate brightness, and controls the driving of the mechanical mechanism 111 based on the exposure setting.

[0025] When the control unit 102 determines to emit light, the EF processing unit 110 causes the strobe unit 111 to emit light in an amount that will provide the appropriate brightness for the subject.

[0026] The encoder unit 112 converts the format of the output image into a format such as JPEG, and outputs the image to the image recorder 113 .

[0027] The image recording unit 113 performs a process of recording the format-converted image output from the encoder unit 112 in a memory (not shown) within the imaging device, a memory card inserted into the camera 100, a removable recording medium, etc. (not shown).

[0028] The memory unit 117 temporarily stores image data being processed by the control unit 102, the image processing unit 105, the encoder unit 112, etc. The image processing unit 105, the first luminance calculation unit 106, the second luminance calculation unit 115, and the exposure correction calculation unit 116 may be realized by a processor executing software, or may be realized by dedicated hardware. The image processing unit 105, the first luminance calculation unit 106, the second luminance calculation unit 115, and the exposure correction calculation unit 116 are shown as being separate from the control unit 102, but are not limited to this. At least some of the functions of the image processing unit 105, the first luminance calculation unit 106, the second luminance calculation unit 115, and the exposure correction calculation unit 116 may be included in the control unit 102. In that case, the functions included in the control unit 102 are realized, for example, by the CPU executing a program stored in a non-volatile memory.

[0029] (Overview of shooting operation) First, an outline of normal operations when photographing is performed using the camera 100 of this embodiment having such a configuration will be described.

[0030] First, when the operation unit 101 detects that the power button of the camera 100 has been turned on by the photographer, the control unit 102 detects the operation content by a corresponding control signal and controls so as to supply power to each unit constituting the camera 100. When power is supplied to each unit constituting the camera 100, the shutter is opened by the mechanical mechanism 109a, and the imaging unit 103 starts an imaging operation and outputs sequential log signals. The output analog image signal is subjected to predetermined processing in the A / D conversion unit 104 and the image processing unit 105, and then stored in the memory unit 117.

[0031] Next, the first luminance calculation unit 106 calculates an overall luminance evaluation value from the luminance of the entire screen of the image data stored in the memory unit 117. In this embodiment, an explanation will be given of an example in which the overall luminance evaluation value is calculated for Fig. 3(a). As shown in Fig. 3(b), the first luminance calculation unit divides the entire screen of the image corresponding to Fig. 3(a) into lattice-shaped block integrals, and obtains an average luminance by multiplying the luminance value obtained in each block by a weight for each region.

[0032] Next, the second luminance calculation unit 115 calculates a high luminance evaluation value. Here, a histogram of accumulated block integrals in the image is obtained, and a luminance value that is a predetermined ratio is calculated by calculating (accumulating) from the high luminance side, and an evaluation value is calculated from the difference with the set threshold. The threshold here is a setting value that can be selected by the user, and the explanation will be given assuming that the threshold setting on the luminance histogram shown in FIG. 4 is used. The graph in FIG. 4 is a histogram in which the horizontal axis indicates the luminance gradation and the vertical axis indicates the accumulated value. In this case, three patterns of threshold setting are assumed. TH1 (threshold 1) indicates a luminance value Y100 in an 8-bit image showing the vicinity of the target luminance, TH3 (threshold 3) is a luminance value Y230 assuming that the luminance gradation in the screen can be used to the maximum, and TH2 (threshold 2) is a luminance value Y180 assuming an intermediate luminance between TH1 and TH3. Note that the patterns of thresholds that can be set by the user are not limited to this example.

[0033] Then, the exposure compensation value calculation unit 116 calculates the exposure step number. The operation of the exposure compensation value calculation unit 116 differs depending on the photometry method (mode) that has been set in advance. In this embodiment, the method of averaging the photometry of the angle of view is defined as evaluative photometry, and the method of superimposing a correction that takes highlights into consideration is defined as highlight photometry. When evaluative photometry is selected, the difference between the overall average luminance obtained by the first luminance calculation unit and the exposure appropriate target luminance is calculated, and the exposure step number for correcting this is calculated. When highlight metering is selected, the ratio of high luminance calculated by the second luminance calculation unit is used to calculate a correction value for converging this to a desired ratio, and the correction step number for highlight metering is obtained by adding this to the exposure step number. The details of this will be described below. In this embodiment, the case where the ratio of high luminance parts is calculated at the granularity of block integration is assumed, but the calculation of the ratio on a pixel-by-pixel basis is also assumed in this embodiment.

[0034] The obtained image is fed back to the AE processing section via the control section 102 using information on the subject area and the range-finding point area, and convergence control to the appropriate exposure is performed.

[0035] When the control unit 102 receives a notification of a first shutter switch signal SW1 from the shutter switch, it performs AF and AE processing using image information at that time, and obtains optimal focus and exposure setting conditions for shooting. Here, SW1 is a signal that is generated when the shutter switch is halfway pressed (instruction to prepare for shooting) during operation. Then, a signal called a second shutter switch signal SW2 is generated when the shutter switch is fully pressed (instruction to shoot) after operation of the shutter switch is completed.

[0036] When the control unit 102 receives the SW2 signal and transitions to actual shooting, a single-point shooting process is performed in which the charge generated by the light that entered the sensor unit via the lens and exposure mechanism is read out and output as an analog image signal to the A / D conversion unit. In addition, the current brightness value is detected from the image output from the image processing unit, and if it is determined to be darker than a predetermined threshold, the EF processing unit 110 determines whether to emit light, and the flash unit can perform the actual light emission process. It is possible to set in advance via the operation unit 101, etc. whether to execute the actual light emission process.

[0037] The A / D conversion unit performs sampling, gain adjustment, A / D conversion, etc. on the analog image signal output from the sensor unit and outputs it as a digital image signal. The image processing unit performs various image processing on the digital image signal and outputs the processed digital image signal.

[0038] The digital signal output from the image processing unit 105 is converted into a format such as JPEG by the encoder unit 112, and output to the image recording unit 113. The image recording unit 113 performs processing to record the format-converted image data in a predetermined memory. In addition, by connecting to an external monitor, the image on the display unit can also be played back on the external monitor.

[0039] (Control flow for highlight metering) Next, the flow of processing related to highlight metering will be described with reference to Fig. 2. This flow is executed by the control unit 102 reading out a program stored in the non-volatile memory, expanding it in the RAM, and executing it to control each part of the camera 100.

[0040] In step S201, first, the user turns on the power of the camera 100. In S201, in response to the power being turned on for the camera 100, the control unit 102 controls each unit of the camera 100 to start preparatory shooting. The control unit 102 maintains a predetermined frame rate, and the camera 100 captures images successively, and displays the captured images on the display unit 107.

[0041] In step S202, the first luminance calculation unit 106 sequentially obtains images (live images) obtained by imaging in step S201.

[0042] Next, in step S203, the first luminance calculation unit 106 divides the image acquired in step S202 into lattice blocks, acquires an integral value of the luminance of each block, and proceeds to step S204. Note that the method of acquiring the integral value is not limited to this.

[0043] In step S204, the first luminance calculation unit 106 obtains the photometric value of the obtained image based on the integral value in step S203. As shown in FIG. 3b, the photometric value is calculated by multiplying the luminance value obtained in each block by a weight for each area to calculate an average luminance value. The difference between this average luminance value and the exposure target luminance is set as ΔBv, and the next target Bv is calculated by adding this to the currently controlled photometric value Bv. In other words, if the currently controlled photometric value is Bv1 and the next target photometric value is Bv2, then the relationship Bv2=Bv1+ΔBv holds.

[0044] In step S205, the control unit 102 determines whether the metering mode type set in the camera 100 is highlight metering or not. In this embodiment, it is assumed that two metering mode types, evaluative metering and highlight metering, can be selected in the UI menu. When highlight metering is not selected, evaluative metering is selected, and in that case, the process proceeds to step S210, where exposure control (AE control) is performed based on the target Bv value described above.

[0045] If it is determined in step S205 that the metering is highlight metering, the process proceeds to step S206, where the upper threshold of the luminance histogram is set. Here, the upper threshold of the luminance histogram may be set by the user via the operation unit 101. For example, the user may set a selectable threshold in advance as shown in FIG. 4. By adopting such specifications, it is possible to use the luminance histogram in a way that suits the purpose of the user. For example, a user who wants to use the luminance gradation in the screen as effectively as possible can select a setting that suppresses blown-out highlights while considering crushing of dark areas by selecting a high luminance threshold such as TH3. A user who considers a high luminance area as the main subject can set the threshold to be lowered to the exposure target luminance (target luminance value) such as TH1. In other words, it is possible to set the threshold to be equal to or higher than the target luminance value. In addition, a user who prioritizes high luminance gradation without lowering it to TH1 and is considering gradation correction of dark and bright areas by digital processing in a PC application or the like after shooting can set it to have a margin on the high luminance gradation side such as TH2.

[0046] In step S207, the second brightness calculation unit 115 acquires a high brightness accumulated value based on the upper limit value of the brightness histogram set in step S206, and in step S208, the exposure correction value calculation unit 116 calculates a correction value using the high brightness accumulated value acquired in step S207.

[0047] Regarding the details of steps S207 and S208, the following flow is assumed in this case.

[0048] First, in step S207, the second luminance calculation unit 115 accumulates the block integral values ​​of the image for each luminance for the current exposure control value to obtain a luminance histogram (FIG. 7). Next, the luminance values ​​in the top 3% of the histogram (corresponding to the dotted line position in FIG. 7(a)), that is, the high luminance accumulated value, is obtained.

[0049] Next, in step S208, the exposure compensation value calculation unit 116 calculates the difference in luminance steps between the luminance (a) in FIG. 7 and the threshold luminance (the luminance value corresponding to (b) in FIG. 7, Y150 in this case) set in step S206 based on the following formula. HilightCmp = LOG2(a / b) Equation (1) The brightness step difference calculated by formula (1) can be used as the correction step (correction value) for the current photometric value. In other words, if the currently controlled photometric value is Bv1 and the next target photometric value is Bv2, then Bv2 = Bv1 + HilightCmp can be calculated.

[0050] In step S209, a new photometric value is calculated by adding the correction step number calculated by the exposure correction value calculation unit 116 in step S208 to the current photometric value.

[0051] In step S210, the control unit 102 feeds back the new photometric value obtained in step S209 to the AE control, thereby executing exposure control.

[0052] In step S211, the control unit 102 determines whether or not a SW1 notification has been received from the shutter switch. If a SW1 notification has not been received, the processes from step 202 to step 210 are repeated. On the other hand, if a SW1 notification has been received, the process proceeds to step S212, where the control unit 102 acquires the final photometric value.

[0053] In step S213, the control unit 102 determines whether or not to perform main exposure based on the final photometric value by judging whether or not it has received a SW2 notification from the shutter switch. If a SW2 notification has occurred, the process proceeds to step S214, where main exposure is performed and shooting ends. If a SW2 notification has not occurred, the process returns to step S211, where the control unit 102 judges whether or not it has received a SW1 notification. If there is no SW1 notification, the process returns to S202, and if there is a SW1 notification, a new final photometric value is acquired in S212 to prepare for the SW2 notification.

[0054] As described above, by allowing the user to control the high-brightness areas to the intended gradation when highlight metering is selected, appropriate exposure settings can be made for the entire image without under-correcting areas other than high-brightness areas, making it possible to provide the image the user is aiming for.

[0055] [Second embodiment] Hereinafter, the configuration and processing flow of an imaging device according to the second embodiment of the present invention will be described with reference to FIG. 5 and the like. FIG. 5 is a block diagram showing an example of the configuration of an imaging device according to the second embodiment. Note that in this embodiment, a digital camera 500 is exemplified as an imaging device, but the imaging device is not limited to this. For example, the present invention can be applied to any electronic device having an imaging function, such as a smartphone or a tablet.

[0056] (Configuration of imaging device) The parts overlapping with the first embodiment will be omitted here. The second embodiment is characterized by a third luminance calculation unit 518 and an exposure correction calculation unit 516. The second embodiment may also be configured to perform the same processing as the first embodiment. That is, the second embodiment can be realized by modifying the first embodiment shown in FIG. 1 by adding the third luminance calculation unit 518 and the exposure correction calculation unit 516.

[0057] The third luminance calculation unit 518 uses the image signal obtained from the image processing unit 505 to calculate a low luminance evaluation value from a low luminance area equal to or less than a set threshold value.

[0058] An exposure compensation calculation unit 516 calculates an appropriate exposure compensation value using the overall luminance evaluation value, the high luminance evaluation value, and the low luminance evaluation value obtained in the first luminance calculation unit, the second luminance calculation unit, and the third luminance calculation unit.

[0059] (Overview of shooting operation) Next, a flow of a photographing operation using the imaging device of the present invention will be described.

[0060] Here too, the parts overlapping with the first embodiment will be omitted, and only the flow from the first luminance calculation unit to the third luminance calculation unit will be described.

[0061] The first luminance calculation unit 506 calculates an overall luminance evaluation value from the luminance of the entire screen of the image data output from the image processing unit 505. In this embodiment, the overall luminance evaluation value is calculated by dividing the entire screen into lattice-shaped block integrals as shown in Fig. 3(b), and multiplying the luminance value obtained in each block by a weight for each region to obtain an average luminance.

[0062] Next, a high luminance evaluation value is calculated in the second luminance calculation unit 515. Here, a histogram is obtained by accumulating block integrals in the image, and a luminance value that becomes a predetermined ratio is calculated by calculation (accumulation) from the high luminance side, and an evaluation value is calculated from the difference with a set threshold value.

[0063] The threshold here is a setting value that can be selected by the user (Fig. 4). In this case, three threshold setting patterns are assumed; for example, in an 8-bit image, TH1 is 100, TH2 is 150, and TH3 is 230. TH1 assumes a luminance equivalent to the appropriate exposure luminance, TH3 assumes that the luminance gradation within the screen can be used to the maximum extent, and TH2 assumes an intermediate luminance between TH1 and TH3.

[0064] The third luminance calculation unit 518 calculates a low luminance evaluation value. Here, a histogram is obtained by accumulating block integrals in the image, and a luminance value (FIG. 8(c)) that becomes a predetermined ratio is calculated by calculation (accumulation) from the low luminance side, and an evaluation value is calculated from the difference with a set threshold value.

[0065] The exposure correction value calculation unit 516 operates differently depending on the photometry method previously set by the operation unit. In this embodiment, the method of averaging the photometry of the angle of view is defined as evaluative photometry, and the method of superimposing a correction considering highlights is defined as highlight photometry. When evaluative photometry is selected, the difference between the overall average luminance obtained by the first luminance calculation unit 506 and the exposure appropriate target luminance is calculated, and the exposure step number for correcting this is calculated. Also, when highlight metering is selected, the high luminance ratio calculated by the second luminance calculation unit 515 is used to calculate a correction value for converging this to a desired ratio, and this is added to the exposure step number to set the correction step number for highlight metering. Also, the low luminance evaluation value calculated by the third luminance calculation unit is used to limit the above correction so that the image does not become too underexposed when corrected with the obtained correction step number.

[0066] In the embodiment of the present invention, it is assumed that the ratio of high luminance areas is calculated at the granularity of block integration, but the present invention also assumes that the ratio is calculated on a pixel-by-pixel basis.

[0067] Next, the flow of processing relating to the above-mentioned highlight metering will be described.

[0068] 6 is a detailed flowchart of the above control. This flow is executed by the control unit 502 reading out a program stored in the non-volatile memory, loading it into the RAM, and executing it to control each unit of the camera 500.

[0069] In step S601, first, the user turns on the power of the camera 500. In S601, in response to the power being turned on for the camera 500, the control unit 502 controls each unit of the camera 500 to start preparatory shooting. The control unit 502 maintains a predetermined frame rate, and the camera 500 captures images successively, and displays the captured images on the display unit 507.

[0070] In step S602, the first luminance calculation unit 506 sequentially acquires images (live images) obtained by the imaging in step S601.

[0071] Next, in step S603, the first luminance calculation unit 506 divides the image acquired in step S602 into lattice blocks, acquires an integral value of the luminance of each block, and proceeds to step S604. Note that the method of acquiring the integral value is not limited to this.

[0072] In step S604, the first luminance calculation unit 506 obtains a photometric value based on the integral value in step S603. As shown in Fig. 3b, the photometric value is obtained by multiplying the luminance value obtained for each block by the weight for each region to obtain an average luminance, and the difference between this average luminance value and the exposure target luminance is set as ΔBv, which is added to the currently controlled photometric value Bv to calculate the next target Bv.

[0073] In step S605, the control unit 502 determines whether the metering mode type set in the camera 500 is highlight metering or not. In this embodiment, it is assumed that two metering mode types, evaluative metering and highlight metering, can be selected in the UI menu. When highlight metering is not selected, evaluative metering is selected, and in that case, the process proceeds to step S606, where exposure control (AE control) is performed based on the target Bv value described above.

[0074] If it is determined in step S605 that the metering is highlight metering, the process proceeds to step S607, where the control unit 502 sets the upper threshold (high luminance threshold) and the lower threshold (low luminance threshold) of the luminance histogram. As shown in FIG. 4, these are selectable thresholds that the user sets in advance, and can be used differently depending on the purpose. For example, a user who wants to use the luminance gradation in the screen as effectively as possible can select a setting that suppresses blown-out highlights while considering crushing of dark areas by selecting a high luminance threshold such as TH3. A user who considers the high luminance area to be the main subject can set the threshold to lower the exposure target luminance such as TH1. On the other hand, a user who prioritizes high luminance gradation and considers correcting gradation in dark and bright areas by digital processing in a PC application after shooting can set a margin on the high luminance gradation side such as TH2. As for the lower limit threshold, in this case, as shown in FIG. 6, the threshold 30 is assumed to be set to On / Off, and the amount of highlight correction is limited here. Then, the process proceeds to step S608.

[0075] In step S608, the second luminance calculation unit 515 accumulates the block integral values ​​of the image for each luminance at the current exposure control value to obtain a luminance histogram (FIG. 3). The third luminance calculation unit 518 obtains the luminance value that is in the top 3% of the histogram (FIG. 3(a)), and proceeds to step S609 (obtaining a high luminance accumulated value).

[0076] In step S609, the exposure correction value calculation unit 516 calculates the luminance step difference between the luminance (a) acquired by the second luminance calculation unit 515 in step S608 and the threshold luminance (b) Y150. HilightCmp = LOG2(a / b) This is added to the current photometric value (here, Bv1) to obtain a correction step, and the exposure correction value calculation unit 516 calculates the target photometric value Bv2. Bv2 = Bv1+HilightCmp Then, the process proceeds to step S610, where the exposure correction value calculation unit 516 uses the obtained Bv value (defined as Bv2) to perform feedback to the block integration, recalculate the corrected histogram (dotted line) in FIG. 8, and the process proceeds to step S611.

[0077] In step S611, the third brightness calculation unit 518 obtains the brightness value (Figure 8 (c)) that is in the bottom 10% in the corrected histogram, calculates the brightness step difference (UNDERClip) between this brightness (c) and the threshold brightness (d) Y30, and proceeds to step S612. UNDERClip = LOG2(c / d) In step S612, the exposure correction value calculation unit 516 determines whether the brightness step is below a lower limit threshold (lower limit threshold). In this example, the lower limit threshold is set to 0. If the brightness step is 0 or more, the process proceeds to step S613. If the brightness step is less than 0, the process proceeds to step S614.

[0078] In step S613, the above-mentioned highlight compensation is added directly by the exposure compensation value calculation unit 516, and the process proceeds to step S606. UNDERClip ≧ 0 , Bv = Bv+ HilightCmp On the other hand, in step S614, the exposure correction value calculation unit 516 performs processing to prevent crushed black in low luminance areas by subtracting a correction amount using the following formula, and then the process proceeds to step S606. UNDERClip < 0 , Bv = Bv+ HilightCmp+UNDERClip In step S606, the control unit 502 feeds back the photometric value obtained in step S612 or S613 to the AE control, thereby executing exposure control.

[0079] In step S615, the control unit 502 determines whether or not a SW1 notification has been received from the shutter switch. If no SW1 notification has been received, the processes from step S602 to step S606 are repeated. On the other hand, if a SW1 notification has been received, the process proceeds to step S616, where the control unit 102 acquires the final photometric value.

[0080] Thereafter, the process proceeds to step S617, where the control unit 502 determines whether or not to perform main exposure based on the final photometric value by judging whether or not it has received a SW2 notification from the shutter switch. If a SW2 notification has occurred, the process proceeds to step S618, where main exposure is performed and shooting ends. If a SW2 notification has not occurred, the process returns to S615, where the control unit 502 judges whether or not it has received a SW1 notification. If there is no SW1 notification, the process returns to S602, and if there is a SW1 notification, a new final photometric value is acquired in S612 to prepare for a SW2 notification.

[0081] As described above, the present invention allows the user to control the high brightness area to the desired gradation when highlight metering is selected. Also, by setting a threshold value on the low brightness side, it is possible to set an appropriate exposure for the entire image without under-correcting areas other than the high brightness, and it is possible to provide an image as the user intended.

[0082] [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.

[0083] The invention is not limited to the above-described embodiments, and various modifications and variations are possible without departing from the spirit and scope of the invention. Accordingly, the following claims are appended to apprise the public of the scope of the invention. [Explanation of symbols]

[0084] 101 Operation section 102 Control section 103 Sensor section 104 A / D conversion section 105 Image processing section 106 First brightness calculation section 107 Display section 108 AF processing section 108a Lens 109 AE Processing Section 109a Mechanical Mechanism 110 EF Processing Section 111 Strobe section 112 Encoder section 113 Image recording unit 114 External connection part 115 Second luminance calculation unit 116 Exposure compensation value calculation unit 117 Memory section 501 Operation section 502 Control section 503 Sensor section 504 A / D conversion section 505 Image Processing Unit 506 First brightness calculation section 507 Display section 508 AF processing section 508a Lens 509 AE Processing Section 509a Mechanical Mechanism 510 EF Processing Section 511 Strobe section 512 Encoder section 513 Image Recording Unit 514 External connection part 515 Second Luminance Calculation Unit 516 Exposure compensation value calculation unit 517 Memory section 518 Third Luminance Calculation Unit

Claims

1. Imaging means, A setting means for setting the metering mode, A first brightness calculation means calculates a first brightness evaluation value from the entire region of the image acquired by the imaging means, A second luminance calculation means calculates a second luminance evaluation value from the region in the aforementioned region where the luminance value is equal to or greater than a predetermined threshold, It has a determination means for determining a target brightness value, The aforementioned determination means is If the first mode is set using the setting means, the target brightness value is determined using the first brightness evaluation value. If a second mode different from the first mode is set, the target luminance value is determined using the second luminance evaluation value. An imaging device characterized by the following features.

2. The imaging apparatus according to claim 1, characterized in that the predetermined threshold is a brightness value higher than the target brightness value in the first mode.

3. The imaging apparatus according to claim 1, characterized in that the second luminance calculation means calculates a first luminance value that is obtained by accumulating from the high luminance side to obtain a predetermined ratio, and calculates the difference between the first luminance value and the exposure calculated using the luminance value set as a predetermined threshold as an exposure compensation value.

4. The imaging apparatus according to claim 1, characterized in that the predetermined threshold is greater than or equal to the target brightness value.

5. The imaging apparatus according to any one of claims 1 to 4, further comprising setting means for which a user can set a predetermined threshold.

6. Imaging means, A setting means for setting the metering mode, A first brightness calculation means calculates a first brightness evaluation value from the entire region of the image acquired by the imaging means, A second luminance calculation means calculates a second luminance evaluation value from a high-luminance region above a first threshold from the aforementioned region, A third luminance calculation means calculates a third luminance evaluation value from the region below the second threshold, which is different from the first threshold, within the aforementioned region, as determined by the second luminance calculation means. It has a determination means for determining a target brightness value, The aforementioned determination means is If the first mode is set using the setting means, the target brightness value is determined using the first brightness evaluation value. If a second mode different from the first mode is set, the target luminance value is determined using the first luminance evaluation value, the second luminance evaluation value, and the third luminance evaluation value. An imaging device characterized by the following features.

7. The imaging apparatus according to claim 6, characterized in that the third luminance calculation means calculates a luminance value that is a predetermined ratio by accumulating from the low luminance side, and limits exposure correction by the second luminance evaluation value so that the luminance value does not fall below a preset low luminance threshold.

8. The imaging apparatus according to claim 6 or 7, further comprising setting means that allows a user to set at least one of the first threshold and the second threshold.

9. Imaging step and Setting steps for setting the metering mode, A first brightness calculation step, which calculates a first brightness evaluation value from the entire region of the image acquired in the imaging step, A second luminance calculation step involves calculating a second luminance evaluation value from the region in the aforementioned region where the luminance value is equal to or greater than a predetermined threshold, It includes a determination step for determining a target brightness value, The aforementioned decision step is, If the first mode is set in the setting step, the target brightness value is determined using the first brightness evaluation value. If a second mode different from the first mode is set, the target luminance value is determined using the second luminance evaluation value. A control method for an imaging device, characterized by the following:

10. Imaging step and Setting steps for setting the metering mode, A first brightness calculation step, which calculates a first brightness evaluation value from the entire region of the image acquired in the imaging step, A second luminance calculation step involves calculating a second luminance evaluation value from the high-luminance region above a first threshold in the aforementioned region, A third luminance calculation step in which a third luminance evaluation value is calculated from the region below the second threshold, which is different from the first threshold in the second luminance calculation step, among the region in the aforementioned region, It includes a determination step for determining a target brightness value, The aforementioned decision step is, If the first mode is set in the setting step, the target brightness value is determined using the first brightness evaluation value. If a second mode different from the first mode is set, the target luminance value is determined using the first luminance evaluation value, the second luminance evaluation value, and the third luminance evaluation value. A control method for an imaging device, characterized by the following:

11. A program for causing a computer to execute the control method of the imaging apparatus described in claim 9 or 10.

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