JP2010072619A - Exposure operation device and camera - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of finding an exposure amount at which a main subject and a background are well-balanced in lightness in a scene having a large luminance difference between the main subject and background. <P>SOLUTION: An exposure operation device includes a photometry unit, a target setting unit, a correction unit, and an operation unit. The photometry unit measures luminous flux from a subject to find a first photometric value, and also finds a second photometric value associated with a part of the subject. The target setting unit sets a range of a predetermined luminance value based upon the second photometric value as a target range of the first photometric value. The correction unit corrects the first photometric value based upon the target range to find a third photometric value. The operation unit finds an exposure value for the luminous flux from the subject based upon the third photometric value obtained by the correction unit. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an exposure calculation device and a camera.

  2. Description of the Related Art Conventionally, there is known a camera that detects a main subject from a shooting screen and controls exposure by paying attention to the brightness of the main subject. As an example, Patent Document 1 detects the position of a person's face in a shooting screen by preliminary imaging, and shoots a recording image with an exposure amount that darkens the brightness of the face. A configuration example of a camera that appropriately adjusts the brightness of the face and background by gradation conversion processing is disclosed.

JP 2007-74328 A

  However, with the conventional technology, for example, when the brightness of the main subject and the background becomes unbalanced in an over-order scene where a person on a dark background is illuminated, the overall image looks worse There was room for improvement in that.

  Therefore, an object of the present invention is to provide means capable of obtaining an exposure amount in which the brightness of the main subject and the background is balanced in a scene where the luminance difference between the main subject and the background is large.

  An exposure calculation apparatus according to one aspect includes a photometry unit, a target setting unit, a correction unit, and a calculation unit. The photometry unit measures the light flux from the subject to obtain the first photometric value, and obtains the second photometric value for some of the subjects. The target setting unit sets a predetermined luminance value range based on the second photometric value as a target range of the first photometric value. The correcting unit corrects the first photometric value based on the target range to obtain a third photometric value. The calculation unit obtains an exposure amount for the light flux from the subject based on the third photometric value obtained by the correction unit.

  The exposure calculation apparatus according to the one aspect may further include a subject detection unit that detects a part of the subject image from the subject image. The target setting unit may set the target range based on the second photometric value for the detection result of the subject detection unit.

  In the one aspect described above, the photometry unit may measure light by dividing a part of a subject into a plurality of regions. Further, the photometry unit may obtain the second photometry value based on a plurality of photometry values obtained for each of the plurality of regions. At this time, the photometric unit may obtain the second photometric value based on the maximum value among the plurality of photometric values. The photometry unit may obtain a plurality of photometric values for each of a plurality of groups obtained by grouping a plurality of regions.

  In the one aspect described above, the target setting unit may determine the target range according to the type of a part of the subject.

  In the one aspect described above, the target setting unit may determine the target range according to the size of a part of the subject. The target setting unit may determine the target range based on a subject having the largest size among some subjects when a plurality of some subjects exist. The target setting unit may determine the target range based on a value obtained by summing the sizes of some of the subjects when there are a plurality of some subjects.

  In the one aspect described above, the correction unit may limit the difference between the third photometric value and the first photometric value by a predetermined value. At this time, the correction unit may determine the predetermined value according to the type of a part of the subject. Further, the correction unit may determine the predetermined value according to the size of a part of the subject. Further, the correction unit may determine the predetermined value based on a subject having the largest size among some subjects when there are a plurality of subjects. Further, the correction unit may determine the predetermined value based on a value obtained by summing up the sizes of some of the subjects when there are a plurality of some subjects.

  In the one aspect described above, the target setting unit, when there are a plurality of partial subjects, sets the photometric value for the subject with the largest size among the partial subjects as the second photometric value, and sets the target range May be set.

  In the above aspect, when there are a plurality of some subjects, the target setting unit uses, as the second photometric value, a value obtained by weighted averaging the photometric values for each of the subjects according to the size of the subject. A target range may be set.

  Note that a camera including the exposure calculation device according to the one aspect described above is also effective as a specific aspect of the present invention.

  In the present invention, even in a scene where the luminance difference between the main subject and the background is large, an exposure amount in which the brightness of the main subject and the background is balanced can be obtained.

1 is a block diagram illustrating a configuration example of an electronic camera according to an embodiment. 6 is a flowchart illustrating an operation example of a shooting mode in the electronic camera of the embodiment. The figure which shows the example of the division of the block in a photography screen The figure which shows typically how to obtain | require the value of BvObj in S103 of FIG. The figure which shows the example of the range which calculates | requires representative luminance value BvObj with respect to a face area | region. The figure which shows the example of the division | segmentation metering of a face area FIG. 2 is a flowchart showing an operation example of the correction calculation subroutine in S104 of FIG. Explanatory drawing which shows the relationship between the target range and exposure amount in one Embodiment The figure which shows an example of the function of the weighting coefficient WtWd when the main subject is a person. The figure which shows an example of the function which calculates | requires the upper limit and lower limit when a main subject is a person The figure explaining the structural example of the electronic camera in other embodiment. Flowchart showing an example of the operation of the shooting mode in the electronic camera of another embodiment The flowchart which shows another example of operation | movement of the imaging | photography mode in the electronic camera of other embodiment.

<Description of One Embodiment>
FIG. 1 is a block diagram illustrating a configuration example of an electronic camera according to an embodiment. One embodiment shows an example in which an exposure calculation device is incorporated in a so-called lens-integrated electronic camera.

  The electronic camera of one embodiment includes an imaging optical system 11 and a lens driving unit 12, an aperture 13 and an aperture driving unit 14, an imaging element 15, an AFE 16, a CPU 17, a first memory 18, and a recording I / F. (Interface) 19, monitor 20, release button 21 and operation member 22, and second memory 23. Here, the lens driving unit 12, the aperture driving unit 14, the imaging device 15, the AFE 16, the first memory 18, the recording I / F 19, the monitor 20, the release button 21, the operation member 22, and the second memory 23 are connected to the CPU 17, respectively. Has been.

  The imaging optical system 11 includes a plurality of lens groups including a zoom lens and a focusing lens. The lens position of the imaging optical system 11 is adjusted in the optical axis direction by the lens driving unit 12. For simplicity, the imaging optical system 11 is illustrated as a single lens in FIG. The diaphragm 13 adjusts the amount of light per unit time incident on the image sensor 15. The aperture of the aperture 13 is adjusted by the aperture drive unit 14 in accordance with an instruction from the CPU 17.

  The image sensor 15 photoelectrically converts a subject image formed by a light beam that has passed through the imaging optical system 11 and the diaphragm 13 to generate an analog image signal. The output of the image sensor 15 is connected to the AFE 16. Note that the charge accumulation time and signal reading of the image sensor 15 are both controlled by the CPU 17.

  Here, in the photographing mode of the electronic camera, the image sensor 15 captures a still image for recording (main image) in response to a full pressing operation of the release button 21. Further, the imaging element 15 in the shooting mode continuously takes images for observation (through images) at predetermined intervals even during standby for shooting. Here, the data of the through image acquired in time series is used for moving image display on the monitor 20 and various arithmetic processes by the CPU 17.

  The AFE 16 is an analog front end circuit that performs analog signal processing on the output of the image sensor 15. The AFE 16 performs correlated double sampling, image signal amplification, and image signal A / D conversion. The image signal output from the AFE 16 is input to the CPU 17. The CPU 17 can adjust the imaging sensitivity corresponding to the ISO sensitivity by adjusting the gain of the image signal in the AFE 16.

  The CPU 17 is a processor that comprehensively controls the operation of the electronic camera. The CPU 17 functions as an image processing unit 24, a face detection unit 25, a focus adjustment unit 26, and an exposure calculation unit 27 by executing a program stored in the second memory 23.

  The image processing unit 24 performs various types of image processing (color interpolation processing, gradation conversion processing, contour enhancement processing, white balance adjustment, etc.) on the digital image signal. The image processing unit 24 performs resolution conversion on the through image to generate a view image for monitor display. The image processing unit 24 can also obtain a white balance adjustment value to be applied in the white balance adjustment based on the input image data.

  The face detection unit 25 performs a face detection process on the live view image data to detect a human face area in the shooting screen. This face detection process is performed by a known algorithm. As an example, the face detection unit 25 extracts feature points such as eyebrow, eye, nose, and lip end points from an image by a known feature point extraction process, and based on these feature points, the face in the shooting screen is extracted. Identify the location of the region. Alternatively, the face detection unit 25 obtains a correlation coefficient between the face image prepared in advance and the determination target image, and determines that the determination target image is a face area when the correlation coefficient exceeds a certain threshold. Also good.

  The focus adjustment unit 26 performs autofocus (AF) control by known contrast detection using the through image data.

  The exposure calculation unit 27 performs exposure calculation using the through image data, and executes exposure control of the electronic camera according to the exposure amount obtained by the exposure calculation.

  The first memory 18 is a buffer memory that temporarily stores image data in the pre-process and post-process of image processing by the image processing unit 24. The first memory 18 is constituted by an SDRAM which is a volatile storage medium.

  The recording I / F 19 is formed with a connector for connecting the nonvolatile storage medium 28. The recording I / F 19 executes data writing / reading with respect to the storage medium 28 connected to the connector. The storage medium 28 is composed of a hard disk, a memory card incorporating a semiconductor memory, or the like. In FIG. 1, a memory card is illustrated as an example of the storage medium 28.

  The monitor 20 displays various images according to instructions from the CPU 17. For example, at the time of shooting standby in the shooting mode, the view image is displayed as a moving image on the monitor 20 under the control of the CPU 17.

  The release button 21 receives an instruction input for starting an imaging operation by a full press operation from the user. The operation member 22 includes, for example, a command dial, a cross-shaped cursor key, a determination button, and the like. The operation member 22 receives various inputs such as an operation of switching the operation mode of the electronic camera from the user.

  The second memory 23 is composed of a nonvolatile storage medium such as a flash memory. The second memory 23 stores a program executed by the CPU 17. An example of the exposure calculation process in the shooting mode by this program will be described later.

(Operation example in shooting mode)
Next, an operation example of the shooting mode in the electronic camera of one embodiment will be described with reference to the flowchart of FIG. This shooting mode operation is started when the CPU 17 receives a shooting mode start operation (for example, a power-on operation or a mode switching operation) from the user. In the shooting mode shown in FIG. 2, an example in which exposure control is performed using a human face as a main subject will be described.

  Step S101: The CPU 17 drives the image sensor 15 to acquire a through image. Note that the image processing unit 24 obtains a white balance adjustment value using the output of the through image, and the focus detection unit 45 performs AF control using the output of the through image (in the example of FIG. 2, The calculation of the white balance adjustment value and the AF control are executed in the background, and detailed description is omitted).

  Step S102: The exposure calculation unit 27 uses the output of the through image (acquired in S101) to perform divided photometry of the subject included in the shooting screen. Then, the exposure calculation unit 27 obtains a value representative of the brightness of the subject in the shooting screen (temporary representative luminance value PreBvAns) based on the result of the division photometry.

  As an example, the exposure calculation unit 27 in S102 divides the entire through image (shooting screen) into a plurality of blocks (an example of block division in the shooting screen is shown in FIG. 3). Next, the exposure calculation unit 27 averages output values (gradation values) of a plurality of pixels included in one block, and obtains an average luminance value in each block. Then, the exposure calculation unit 27 obtains a temporary representative brightness value PreBvAns using a plurality of average brightness values obtained from each block. Note that the calculation for obtaining the temporary representative luminance value PreBvAns from the average luminance values of a plurality of blocks is performed by a known method disclosed in, for example, JP-A-2006-106617.

  Step S103: The face detection unit 25 detects the position of the face area of the person from the shooting screen using the output of the through image (obtained in S101). Then, based on the position of the face area detected by the face detection unit 25, the exposure calculation unit 27 obtains a representative luminance value BvObj of the main subject (face) that is a part of the subject in the shooting screen.

  Here, when only one face area is detected from the shooting screen, the exposure calculation unit 27 in S103, for example, represents the representative luminance value of the main subject by any one of the following methods (a) to (f): BvObj is obtained.

  (A) The exposure calculation unit 27 groups a plurality of pixels included in the face area in the through image, and sets the average luminance value of the grouped pixels as the representative luminance value BvObj of the main subject. (See FIG. 4 (a)).

  (B) The exposure calculation unit 27 extracts a block overlapping the face area from the blocks (S102) obtained by dividing the shooting screen, further averages the average luminance value of the extracted block, and represents the representative luminance value of the main subject. BvObj may be obtained (see FIG. 4B). For example, in the case of FIG. 4B, the exposure calculation unit 27 obtains the representative luminance value BvObj of the main subject from the average luminance value of four blocks overlapping the face area.

  (C) When the luminance of the main subject and the background are extremely different (for example, a scene of backlight or excessive light), an area wider than the face area (area FA0 in FIGS. 5A and 5B) When the representative luminance value BvObj is obtained from the above, there are cases where the appropriate face luminance cannot be obtained due to the influence of the background.

  Therefore, the exposure calculation unit 27 may obtain the representative luminance value BvObj from an area inscribed in the outline of the person's face (area FA1 shown in FIG. 5A). Alternatively, the exposure calculation unit 27 may obtain the representative luminance value BvObj from an area (area FA2 shown in FIG. 5B) that is smaller than the area circumscribing the outline of the person's face.

  Here, FIG. 5B shows an example in which the center of gravity of the area FA2 is arranged so as to overlap the center of gravity of the area FA0. However, the center of gravity of the area FA2 may be shifted below the center of gravity of the area FA0 in order to make it less susceptible to the influence of hair (illustration is omitted in this case). FIG. 5B shows an example in which the size of the area FA2 is set to 1/2 the size of the area FA0. However, the size of the area FA2 can be appropriately set within a range not affected by the background.

  (D) When the luminance difference in the face area is large (for example, a half-backlit scene in which light is applied to half of the face and half of the face is dark), the representative luminance is based on the average luminance value of the face area. When the value BvObj is obtained, the bright part of the face may be overexposed. Therefore, the exposure calculation unit 27 may divide the face of the main subject into a plurality of areas and perform photometry, and obtain the representative luminance value BvObj based on a plurality of photometric values obtained for each of the plurality of areas.

As an example, the exposure calculation unit 27 divides the face area into four so as to be 2 × 2 vertically and horizontally as shown in FIG. 6. And the exposure calculating part 27 is good also considering the maximum value among the photometric values of each division area (FA41-FA44) as the representative luminance value BvObj by the following formula | equation (1).
BvObj = Max (BvFA41, BvFA42, BvFA43, BvFA44) (1)
Here, in this specification, “BvFA41-44” indicates an average luminance value of each divided area (FA41-44) of the face area. In this specification, “Max (A, B)” means a function that returns the maximum value of A and B.

(E) As another example of the above (d), the exposure calculation unit 27 groups each region (FA41-FA44) into four in the vertical and horizontal directions, and sets the maximum photometric value obtained in each of the four groups. The value may be the representative luminance value BvObj. Specifically, the exposure calculation unit 27 may sequentially perform the calculations of the following formulas (2) to (6).
BvFaceUp = (BvFA41 + BvFA42) / 2 (2)
BvFaceDown = (BvFA43 + BvFA44) / 2 (3)
BvFaceLeft = (BvFA41 + BvFA43) / 2 (4)
BvFaceRight = (BvFA42 + BvFA44) / 2 (5)
BvObj = Max (BvFaceUp, BvFaceDown, BvFaceLeft, BvFaceRight) (6)
(F) As another example of the above (d), the exposure calculation unit 27 may obtain a representative luminance value BvObj by weighted averaging of the luminance values (BvFA41-44) of each region.

For example, in the following formula (7), the exposure calculating unit 27 may substitute BvFA41-44 as BvX [1] -BvX [4] in descending order to obtain the representative luminance value BvObj.
BvObj = Σ (BvX [i] × Wt [i]) (7)
Here, “i” in the above formula (7) takes an integer of 1-4. In addition, “Σ ()” in Expression (7) is a function that returns the product-sum operation result by the variable i. Further, “Wt [i]” in Expression (7) is a predetermined weighting coefficient. As an example, in one embodiment, Wt [1] = 0.6, Wt [2] = 0.3, Wt [3] = 0.1, Wt [4] = 0 are set. The coefficient is not limited to the above example.

  Note that the exposure calculation unit 27 calculates BvX [1] −BvX in the descending order of BvFaceUp, BvFaceDown, BvFaceLeft, BvFaceRight (photometric values of each group determined by Expressions (2) to (5)) in the above expression (7). Substituting as [4], the representative luminance value BvObj may be obtained.

  On the other hand, when a plurality of face regions are detected from the shooting screen, the exposure calculation unit 27 in S103 obtains the representative luminance value BvObj of the main subject by the following method (G) or (H), for example.

  (G) The exposure calculation unit 27 sets the largest face area of the plurality of face areas detected by the face detection unit 25 as the calculation target face area, and the above-described (I) ) To (f) to obtain the representative luminance value BvObj of the main subject. This is because, in general, in a scene where a person is photographed, the user performs photographing so that the person as the main subject becomes the largest.

  (H) First, the exposure calculation unit 27 obtains a luminance value corresponding to each face area by any one of the methods (A) to (F). Then, the exposure calculation unit 27 finally obtains the representative luminance value BvObj of the main subject by weighting and averaging the plurality of luminance values obtained for each face area in accordance with the size of each face area. In this case, exposure control can be performed in consideration of the brightness of a plurality of faces in the shooting screen.

  Step S104: The exposure calculation unit 27 executes a correction calculation subroutine (the details of the correction calculation subroutine will be described later). In this correction calculation subroutine, the exposure calculation unit 27 calculates a luminance correction amount dBvObj based on the representative luminance value BvObj of the main subject (obtained in S103).

  When the brightness of the main subject and the background is extremely different, such as in backlighting or excessively forward light, the exposure of the main subject is too dark or too bright when the exposure amount is obtained directly from the temporary representative brightness value PreBvAns There is. Therefore, in one embodiment, the luminance value is corrected by the luminance correction amount dBvObj so that the balance between the main subject and the background becomes an appropriate exposure amount.

Step S105: The exposure calculation unit 27 uses the provisional representative luminance value PreBvAns (obtained in S102) and the luminance correction amount dBvObj (obtained in S104) to calculate the corrected representative luminance value BvAns using the following formula. Obtained by (8).
BvAns = PreBvAns + dBvObj (8)
Then, the exposure calculation unit 27 in S105 calculates the exposure amount by a known exposure calculation based on the corrected representative luminance value BvAns, and also performs exposure control (shutter time, aperture value, etc.) based on this exposure amount. Adjust each parameter).

  Step S106: The CPU 17 displays a view image generated from the above-described through image (obtained in S101) on the monitor 20. Accordingly, the user can perform framing for determining the shooting composition with reference to the view image on the monitor 20. At this time, the CPU 17 may overlay the display indicating the position of the face area detected in S103 on the view image (illustration of a display example of the view image is omitted).

  Step S107: The CPU 17 determines whether or not the release button 21 is fully pressed. If the above requirement is satisfied (YES side), the process proceeds to S108. On the other hand, if the above requirement is not satisfied (NO side), the CPU 17 returns to S101 and repeats the above operation. In the case of NO in S107, the CPU 17 captures a through image based on the exposure amount obtained in S105. The view image is displayed as a moving image on the monitor 20 under the control of the CPU 17.

  Step S108: The CPU 17 executes an image capturing process for the main image based on the exposure amount obtained in S105. The data of the main image captured by the image sensor 15 is recorded in the storage medium 28 via the recording I / F 19 after being subjected to predetermined processing by the AFE 16 and the image processing unit 24. The description of the operation example of the shooting mode illustrated in FIG.

(Explanation of correction calculation subroutine)
Next, an operation example of the correction calculation subroutine in S104 of FIG. 2 will be described with reference to the flowchart of FIG.

Step S201: The exposure calculation unit 27 uses the representative luminance value BvObj (obtained in S103) of the main subject to obtain the luminance target value BvTrgt by the following equation (9).
BvTrgt = BvObj−OfsObj (9)
Here, “OfsObj” in this specification means an offset value set in advance for each type of main subject. The value of OfsObj is obtained from the difference between the output value of the gray level in the main image and the output value that is the reproduction target of the main subject in the main image.

  In automatic camera exposure calculation, when shooting an achromatic subject with the same brightness as the main subject, the exposure amount is calculated so that, as a general rule, the above-mentioned achromatic subject is reproduced at the gray level in the main image. The On the other hand, depending on the type of the main subject, it may be preferable to shift the output value of the reproduction target in the main image from the gray level. As an example, if the main subject is a human face, it is preferable to set the output value of the reproduction target in the main image to a value slightly brighter than the gray level. Therefore, the exposure calculation unit 27 in S201 adjusts the luminance value for each type of main subject using OfsObj.

  Hereinafter, an example of the calculation of OfsObj when the main subject is a person's face will be described. In the embodiment, the description will be made on the assumption that the gradation of the main image is 8 bits (output value 0 to 255).

  In this example, the output value of the gray level is 120, and the output value of the face reproduction target in the main image is 150. Therefore, OfsObj in this case is a correction amount for increasing the face output value from 120 to 150 in the main image. In the exposure calculation, as the subject brightness value decreases, the exposure amount on the over side becomes. Therefore, in the above equation (9), the value of OfsObj is subtracted from the value of BvObj to reduce the brightness value.

Further, the output value in the main image is converted into a non-linear state with respect to the output level of the image sensor 15 by the gradation conversion processing in the image processing unit 24. Therefore, the exposure calculation unit 27 can obtain the value of OfsObj by comparing the output value in a state where the output value in the main image is subjected to the reverse gradation conversion process. Note that the value of OfsObj when the human face is the main subject is obtained by the following equation (10).
OfsObj = Log2 (RvG (150) / RvG (120)) (10)
In this specification, “Log2 (A)” means a function that returns the logarithm of A with 2 as the base. Further, in this specification, “RvG (B)” is a function corresponding to inverse gradation conversion, and means a function that returns an input value before gradation conversion with respect to B indicating an output value in the main image. To do.

As another example of S201, an example of the calculation of OfsObj when the main subject is a blue sky will be described. If the output value of the blue sky reproduction target in the main image is 175, the value of OfsObj in this case can be obtained by the following equation (11).
OfsObj = Log2 (RvG (175) / RvG (120)) (11)
Step S202: The exposure calculation unit 27 sets a target range of luminance values based on the target luminance value BvTrgt (obtained in S201). Specifically, the exposure calculation unit 27 in S202 calculates the upper limit value BvUpper of the target range by the following formula (12), and calculates the lower limit value BvLower of the target range by the following formula (13).
BvUpper = BvTrgt + BvSth1 (12)
BvLower = BvTrgt + BvSth2 (13)
Here, “BvSth1” and “BvSth2” are values set for each type of main subject. Therefore, the width of the target range of the brightness value set in S202 can change according to the type of the main subject.

  In S202, the target range of the luminance value is set for the following reason. In scenes where the brightness of the main subject (person's face) and the background are extremely different (for example, in the case of backlight or over-order light), if the exposure is determined based on the brightness of the face, Will appear and the image taken will be unnatural.

  On the other hand, in the above scene, it is rather natural exposure for the entire image when the brightness of the main subject is determined in consideration of the balance with the background. Therefore, the exposure calculation unit 27 can deal with a scene with a large luminance difference by giving a range to the target luminance value by BvUpper and BvLower.

For example, the output value of a human face in the main image in a backlight scene may be 110. Therefore, the value of BvSth1 when the person's face is the main subject can be obtained by the following equation (14). Similarly, the output value of a person's face in an over-order scene may be 180. Therefore, the value of BvSth2 when the person's face is the main subject can be obtained by the following equation (15).
BvSth1 = Log2 (RvG (150) / RvG (110)) (14)
BvSth2 = Log2 (RvG (150) / RvG (180)) (15)
Here, the relationship between the target range and the exposure amount will be described with reference to FIG. BvSth1 obtained by the above equation (14) is a positive correction value with respect to BvTrgt, and the value of BvUpper is larger than BvTrgt. Then, when the exposure amount is obtained based on BvUpper, the exposure is underside than the exposure amount based on BvTrgt. As a result, when the main image is captured with the exposure amount based on BvUpper, the face output value in the main image is lower than the above reproduction target.

  On the other hand, BvSth2 obtained by the above equation (15) is a negative correction value with respect to BvTrgt, and the value of BvLower is smaller than BvTrgt. Then, when the exposure amount is obtained based on BvLower, the exposure is over the exposure amount based on BvTrgt. As a result, when the main image is captured with the exposure amount based on BvLower, the face output value in the main image is higher than the above reproduction target.

As another example in S202, a calculation example of BvSth1 and BvSth2 when the main subject is a blue sky will be described. Assuming that the output range of the blue sky reproduction target in the main image is 100 to 200, the value of BvSth1 in this case can be obtained by the following equation (16). Further, the value of BvSth2 in this case can be obtained by the following equation (17).
BvSth1 = Log2 (RvG (175) / RvG (100)) (16)
BvSth2 = Log2 (RvG (175) / RvG (200)) (17)
By the way, in the above example, it has been described that the output of the human face in the main image in the backlight scene may be 110 in consideration of the balance with the background. However, when the area ratio of the human face to the shooting screen (the size of the human face) is large, the brightness of the face determines the impression of the brightness of the main image. Conversely, when the area ratio of the person's face to the shooting screen is small, the brightness of the background determines the impression of the brightness of the main image. Therefore, the exposure calculation unit 27 may adjust the width of the target range of the luminance value according to the area ratio of the main subject to the shooting screen. In this case, the exposure calculation unit 27 obtains values (BvSth1 ′, BvSth2 ′) obtained by weighting the above BvSth1 and BvSth2 by the following equations (18) and (19). Then, the exposure calculation unit 27 may obtain BvUpper and BvLower using BvSth1 ′ and BvSth2 ′.
BvSth1 ′ = BvSth1 × WtWd (18)
BvSth2 ′ = BvSth2 × WtWd (19)
Here, “WtWd” in Expression (18) and Expression (19) indicates a weighting coefficient for the width of the target range. The value of the weighting coefficient WtWd is determined by the exposure calculation unit 27 using a function depending on the area ratio of the main subject to the shooting screen. The weighting coefficient WtWd is a large value when the area ratio of the main subject to the shooting screen is small, and is a small value when the area ratio of the main subject to the shooting screen is large.

  Here, FIG. 9 shows an example of a function of the weighting coefficient WtWd when the main subject is a person. The vertical axis in FIG. 9 indicates the value of WtWd, and the horizontal axis in FIG. 9 indicates the area ratio of the main subject to the shooting screen.

  In the example of FIG. 9, when the area ratio is 5% or less, the value of WtWd is 1.0. Further, in the range where the area ratio is greater than 5% and less than 50%, the value of WtWd decreases in proportion to the size of the area ratio. When the area ratio is 50% or more, the value of WtWd is 0.0.

  That is, when the area ratio of the main subject to the shooting screen is small, the values of BvSth1 'and BvSth2' are large, so the width of the target range of luminance values is large. On the other hand, when the area ratio of the main subject to the shooting screen is large, the values of BvSth1 'and BvSth2' are small, so the width of the target range of luminance values is small.

  When a plurality of main subjects are detected in the shooting screen, the exposure calculation unit 27 determines the area ratio based on the subject having the largest size among the plurality of main subjects, and BvSth1 ′ and The width of the target range of luminance values may be obtained using BvSth2 ′. Alternatively, the exposure calculation unit 27 may determine the area ratio by a value obtained by summing the sizes of a plurality of main subjects, and obtain the width of the target range of luminance values using BvSth1 'and BvSth2'. Note that the function of the weighting coefficient WtWd shown in FIG. 9 is merely an example, and the function of the weighting coefficient WtWd may be changed according to the type of the main subject.

  Step S203: The exposure calculation unit 27 determines whether PreBvAns is larger than BvUpper. If the above requirement is satisfied (YES side), the process proceeds to S207. On the other hand, if the above requirement is not satisfied (NO side), the process proceeds to S204.

  Step S204: The exposure calculation unit 27 determines whether PreBvAns is smaller than BvLower. If the above requirement is satisfied (YES side), the process proceeds to S206. On the other hand, if the above requirement is not satisfied (NO side), the process proceeds to S205.

  Step S205: In this case, if the main image is shot with the exposure amount obtained from the provisional representative luminance value PreBvAns, it can be predicted that the face output value in the main image falls within the range of 110 to 180. Therefore, the exposure calculation unit 27 substitutes a “0” value for the provisional correction amount dBvTrgtToAns when determining dBvOBj. The exposure correction unit 27 moves the process to S208 after S205.

Step S206: In this case, if the main image is captured with the exposure amount obtained from the temporary representative luminance value PreBvAns, it can be predicted that the face output value in the main image will be higher than 180. Therefore, the exposure calculation unit 27 calculates the value of the provisional correction amount dBvTrgtToAns by the following equation (20) in order to set the face output value in the main image to 180.
dBvTrgtToAns = BvLower-PreBvAns (20)
DBvTrgtToAns in the case of S206 corresponds to a correction amount for increasing the luminance value. If the luminance value is corrected in the increasing direction, the exposure amount becomes underside during the exposure calculation, so that a bright face is corrected to be darker in the main image. The exposure correction unit shifts the process to S208 after S206.

Step S207: In this case, if the main image is captured with the exposure amount obtained from the provisional representative luminance value PreBvAns, the face output value in the main image can be expected to be lower than 110. Therefore, the exposure calculation unit 27 calculates the value of the temporary correction amount dBvTrgtToAns by the following equation (21) in order to set the face output value in the main image to 110.
dBvTrgtToAns = BvUpper-PreBvAns (21)
The dBvTrgtToAns in the case of S207 corresponds to a correction amount for reducing the luminance value. If the luminance value is corrected in the direction of decreasing the exposure value, the exposure amount is over during the exposure calculation, so that the dark face is corrected brightly in the main image.

Step S208: The exposure calculation unit 27 limits the provisional correction amount dBvTrgtToAns (obtained in any one of S205, S206, and S207) to a predetermined limit value range, and obtains the luminance correction amount dBvObj. For example, the exposure calculation unit 27 in S208 obtains the luminance correction amount dBvObj by the following equation (22).
dBvObj = Clip (dBvTrgtToAns) (22)
Here, “Clip (A)” in Expression (13) returns a value of A when the value of A is within the limit value range, and returns a limit value when the value of A exceeds the limit value range. Means. An upper limit value and a lower limit value can be set as the limit value in “Clip (A)”. In this case, when the value of A exceeds the upper limit value in “Clip (A)”, the input value of A is replaced with the upper limit value. Further, when the value of A is lower than the lower limit value in “Clip (A)”, the input value of A is replaced with the lower limit value.

  The reason for limiting the value of dBvTrgtToAns in S208 is as follows. In scenes where the brightness of the main subject (person's face) and the background are extremely different, even if the output value of the face in this image is adjusted to the upper or lower limit of the target range, white background or blackout occurs in the background portion. It can happen. Therefore, the exposure calculation unit 27 in S208 limits the value of dBvTrgtToAns within a predetermined range assuming the above case.

  As an example, when a person's face is the main subject, the exposure calculation unit 27 converts the limit value range into an exposure value and sets the range from −1 to +1.5. The subject information is completely lost in the overexposed pixels of the main image, while the remaining subject information may be read by increasing the gain in the blackened pixels. Therefore, from the viewpoint of avoiding white stripes as much as possible while allowing blackening to some extent, in one embodiment, the limit value is set in the above range.

  Note that the exposure calculation unit 27 may appropriately adjust the range of the limit value according to the type of the main subject. For example, in the case of another main subject, the exposure calculation unit 27 may convert the range of the limit value into the range of −1 to +1 or may be in the range of −1 to +2.

  Further, the exposure calculation unit 27 in S208 may vary the upper limit value and the lower limit value according to the area ratio of the main subject to the shooting screen (the size of the person's face). The upper limit value and the lower limit value are determined by the exposure calculation unit 27 by a function depending on the area ratio of the main subject to the shooting screen.

  As an example, the exposure calculation unit 27 increases the upper limit value and decreases the lower limit value as the area ratio of the main subject increases. As a result, the range of the limit value increases as the area ratio of the main subject to the shooting screen increases, so that the value of dBvTrgtToAns is less likely to be limited. On the other hand, the exposure calculation unit 27 decreases the upper limit value and increases the lower limit value as the area ratio of the main subject is smaller. As a result, the smaller the area ratio of the main subject to the shooting screen is, the narrower the limit value is, so that the value of dBvTrgtToAns is likely to be limited.

  Here, FIG. 10 shows an example of a function for obtaining an upper limit value and a lower limit value when the main subject is a person. The vertical axis in FIG. 10 represents the limit value converted into the exposure value, and the horizontal axis in FIG. 10 represents the area ratio of the main subject to the shooting screen.

  In the example of FIG. 10, when the area ratio is 5% or less, the upper limit value is 1.5 and the lower limit value is −1.0. In the range where the area ratio is greater than 5% and less than 50%, the upper limit value increases in proportion to the size of the area ratio, and the lower limit value decreases in proportion to the size of the area ratio. And when said area ratio is 50% or more, an upper limit will be 5.0 and a lower limit will be -5.0.

  Here, when the area ratio is 50% or more (upper limit = 5.0, lower limit = −5.0), the exposure calculator 27 corrects the exposure to a maximum of five steps according to the main subject. it can. Therefore, in this case, the probability that the background is white or blacked out increases, and this is the same as the case where the correction is not substantially limited.

  When a plurality of main subjects are detected in the shooting screen, the exposure calculation unit 27 determines the area ratio based on the largest subject among the plurality of main subjects, and sets the upper limit A value and a lower limit value may be obtained. Alternatively, the exposure calculation unit 27 may determine the area ratio by a value obtained by summing the sizes of a plurality of main subjects, and obtain the upper limit value and the lower limit value. The limit value function shown in FIG. 10 is merely an example, and the limit value function may be changed according to the type of the main subject.

  Thereafter, the exposure calculation unit 27 ends the correction calculation subroutine and returns to the process of S105 shown in FIG. Above, description of the flowchart of FIG. 7 is complete | finished.

  In one embodiment, the exposure calculation unit 27 uses the representative luminance value BvObj of the main subject to set a luminance value target range (BvUper, BvLower) according to the type of the main subject (S201, S202). The exposure calculation unit 27 obtains a luminance correction amount dBvObj based on the target range of luminance values and the provisional representative luminance value PreBvAns (S205 to S208). Then, the exposure calculation unit 27 calculates the exposure amount using the corrected representative luminance value BvAns reflecting the luminance correction amount dBvObj (S105).

  As a result, the electronic camera of one embodiment can perform shooting with a preferable exposure amount in which the brightness of the main subject and the background is balanced even in a scene with a large luminance difference between the main subject and the background. Become.

<Description of other embodiments>
FIG. 11 is a diagram illustrating a configuration example of an electronic camera according to another embodiment. Another embodiment shows an example in which an exposure calculation device is incorporated in a single-lens reflex type electronic camera capable of exchanging lenses.

  An electronic camera according to another embodiment includes a camera body 31 and a lens unit 32 that houses an imaging optical system. Here, the camera body 31 and the lens unit 32 are each provided with a pair of mounts. The lens unit 32 is interchangeably connected to the camera body 31 via the mount. Each of the mounts is provided with an electrical contact, and electrical connection between the camera body 31 and the lens unit 32 is established (the illustration of the mount and the electrical contact in FIG. 11 is omitted). ).

  The lens unit 32 includes a focusing lens 33 and a lens driver 34, an aperture 35 and an aperture driver 36, and an in-lens memory 37. The focusing lens 33 is driven by a lens driver 34 in response to an instruction from the camera body 31. The diaphragm 35 is driven by a diaphragm driver 36 in response to an instruction from the camera body 31. The in-lens memory 37 is a memory that stores information on the lens unit 32. The information stored in the in-lens memory 37 is output to the camera body 31.

  The camera body 31 includes a main mirror 41, a mechanical shutter 42, a recording image sensor 43, a sub mirror 44, a focus detection unit 45, a finder optical system (51 to 54), an analysis image sensor 46, and a microcomputer. 47 and a monitor 48. The main mirror 41, the mechanical shutter 42, and the recording image sensor 43 are disposed along the optical axis of the lens unit 32. A sub mirror 44 is disposed behind the main mirror 41. A finder optical system is disposed on the upper part of the camera body 31. Further, a focus detection unit 45 is disposed below the camera body 31.

  The main mirror 41 is pivotally supported by a rotation shaft (not shown) and can be switched between an observation state and a retracted state. The main mirror 41 in the observation state is inclined and disposed in front of the mechanical shutter 42 and the recording image sensor 43. The main mirror 41 in the observation state reflects the light beam that has passed through the lens unit 32 upward and guides it to the finder optical system. The central portion of the main mirror 41 is a half mirror. A part of the light beam transmitted through the main mirror 41 is refracted downward by the sub mirror 44 and guided to the focus detection unit 45. The focus detection unit 45 detects an image shift amount of the subject image divided by a separator lens (not shown), and obtains a defocus amount of the focusing lens 33 from the image shift amount.

  On the other hand, the retracted main mirror 41 is flipped upward together with the sub mirror 44 and is at a position off the photographing optical path. When the main mirror 41 is in the retracted state, the light beam that has passed through the lens unit 32 is guided to the mechanical shutter 42 and the recording image sensor 43.

  The finder optical system includes a focusing screen 51, a condenser lens 52, a pentaprism 53, and an eyepiece lens 54. The focusing screen 51 is positioned above the main mirror 41 and once forms an image of the light beam reflected by the main mirror 41 in the observation state. The light beam formed on the focusing screen 51 passes through the condenser lens 52 and the pentaprism 53, and reaches the user's eyes through the eyepiece 54 from the exit surface having an angle of 90 ° with respect to the incident surface of the pentaprism 53. To do. Further, a part of the light beam imaged by the focusing screen 51 passes through the condenser lens 52 and the pentaprism 53 and enters the analysis imaging element 46 from the reimaging lens 55 disposed in the vicinity of the exit surface of the pentaprism 53. .

  Here, the recording image sensor 43 of another embodiment captures the main image and the through image when the main mirror 41 is in the retracted state. The analysis image sensor 46 captures a through image when the main mirror 41 is in an observation state. Note that the analysis imaging element 46 of another embodiment can capture a through image with a resolution that allows face detection processing.

  The microcomputer 47 is a processor that comprehensively controls the operation of each unit of the electronic camera. The microcomputer 47 performs image processing on the output of the recording image sensor 43 or the analysis image sensor 46. Further, the microcomputer 47 performs the same function as the face detection unit and the exposure calculation unit in the one embodiment described above. The monitor 48 displays various images under the control of the microcomputer 47.

(Operation example 1 of shooting mode in other embodiment)
Next, an example of the operation of the shooting mode in the electronic camera of another embodiment will be described with reference to the flowchart of FIG. The operation in the photographing mode shown in FIG. 12 is started by the microcomputer 47 in response to an instruction to start the AF operation by half-pressing a release button (not shown in FIG. 11). At the start of the flowchart of FIG. 12, the main mirror 41 is in the observation state position.

  Step S301: The microcomputer 47 drives the analysis image sensor 46 to acquire a through image. At this time, the microcomputer 47 executes AF control based on the output of the focus detection unit 45.

  Step S302: The microcomputer 47 uses the output of the through image to execute divided photometry of the subject included in the shooting screen, and obtains a temporary representative luminance value PreBvAns. Note that the processing in S302 corresponds to S102 in FIG.

  Step S303: The microcomputer 47 uses the output of the through image to detect the position of the face area of the person from the shooting screen, and represents the representative luminance value BvObj of the main subject (face) that is a part of the subject in the shooting screen. Ask for. Note that the processing in S303 corresponds to S103 in FIG.

  Step S304: The microcomputer 47 executes a correction calculation subroutine (the processing from S201 to S208 in FIG. 7) to obtain the luminance correction amount dBvObj.

  Step S305: The microcomputer 47 obtains the corrected representative luminance value BvAns using the temporary representative luminance value PreBvAns (obtained in S302) and the luminance correction amount dBvObj (obtained in S304).

  The microcomputer 47 calculates an exposure amount by a known exposure calculation based on the corrected representative luminance value BvAns, and performs exposure control (adjustment of parameters such as shutter speed and aperture value) based on the exposure amount. Do. Note that the processing in S305 corresponds to S105 in FIG.

  Step S306: The microcomputer 47 determines whether or not the release button has been fully pressed. If the above requirement is satisfied (YES side), the process proceeds to S308. On the other hand, if the above requirement is not satisfied (NO side), the microcomputer 47 returns to S301 and repeats the above operation.

  Step S307: The microcomputer 47 drives the main mirror 41 from the observation state position to the retracted position.

  Step S308: The microcomputer 47 executes a main image capturing process based on the exposure amount obtained in S305. The data of the main image captured by the recording image sensor 43 is recorded in a storage medium (not shown) after predetermined image processing is performed by the microcomputer 47. Above, description of the flowchart of FIG. 12 is complete | finished. In the example of FIG. 12 as well, substantially the same effect as the one embodiment described above can be obtained.

(Operation example 2 of shooting mode in other embodiment)
Next, another example of the shooting mode operation in the electronic camera of another embodiment will be described with reference to the flowchart of FIG. FIG. 13 shows an operation example in an operation mode (live view shooting mode) in which a view image is displayed as a moving image on the monitor 48 using a through image of the recording image sensor 43.

  The operation in FIG. 13 is started when the microcomputer 47 receives a start operation (for example, a mode switching operation) in the live view shooting mode. Note that the main mirror 41 is in the observation state at the start of the flowchart of FIG.

  Step S401: The microcomputer 47 drives the main mirror 41 from the observation state position to the retracted position.

  Step S402: The microcomputer 47 drives the recording image sensor 43 to acquire a through image.

  Step S403: The microcomputer 47 detects the position of the face area of the person from the shooting screen using the through image output.

  Step S404: The microcomputer 47 displays the view image generated from the through image on the monitor 48.

  Step S405: The microcomputer 47 determines whether or not the release button has been pressed. If the above requirement is satisfied (YES side), the process proceeds to S406. On the other hand, if the above requirement is not satisfied (NO side), the microcomputer 47 returns to S402 and repeats the above operation.

  Step S406: The microcomputer 47 drives the main mirror 41 from the retracted position to the observation position. Note that the recording image sensor 43 cannot acquire a through image at the time of S406. For this reason, the microcomputer 47 continuously displays the view image acquired immediately before the mirror down on the monitor 48 or temporarily stops the display of the view image on the monitor 48.

  Step S407: The microcomputer 47 drives the analysis image sensor 46 to perform divided photometry in the photographing screen. Then, the microcomputer 47 in S407 obtains a temporary representative luminance value PreBvAns based on the result of the divided photometry. Further, the microcomputer 47 in S407 obtains the representative luminance value BvObj of the main subject (face), which is a part of the subject in the shooting screen, based on the position of the face area (detected in S403).

  Note that the calculation of PreBvAns in S407 is performed in the same manner as the processing in S102 of FIG. Further, the calculation of BvObj in S407 is performed in substantially the same manner as the processing in S103 of FIG. Therefore, a duplicate description of these processes is omitted.

  Step S408: The microcomputer 47 executes a correction calculation subroutine (the processing from S201 to S208 in FIG. 7) to obtain the luminance correction amount dBvObj.

  Step S409: The microcomputer 47 obtains the corrected representative luminance value BvAns using the provisional representative luminance value PreBvAns (obtained in S407) and the luminance correction amount dBvObj (obtained in S408).

  The microcomputer 47 calculates an exposure amount by a known exposure calculation based on the corrected representative luminance value BvAns, and performs exposure control (adjustment of parameters such as shutter speed and aperture value) based on the exposure amount. Do. Note that the processing in S409 corresponds to S105 in FIG.

  Step S410: The microcomputer 47 drives the main mirror 41 from the observation state position to the retracted position.

  Step S411: The microcomputer 47 executes a main image capturing process based on the exposure amount obtained in S409. The data of the main image captured by the recording image sensor 43 is recorded in a storage medium (not shown) after predetermined image processing is performed by the microcomputer 47. Above, description of the flowchart of FIG. 13 is complete | finished. In the example of FIG. 13 as well, substantially the same effect as in the above-described one embodiment can be obtained.

<Supplementary items of the embodiment>
(1) In each of the above embodiments, the example in which the main subject is the face of a person has been described. However, the present invention can also be applied to a case where a subject other than the face is the main subject. As an example, when the blue sky is the main subject, the exposure calculation unit obtains the blue sky region by paying attention to the brightness and color information of the subject in the through image, and the position on the shooting screen, and uses the luminance information of this region. The representative luminance value BvObj of the main subject may be obtained. Further, the exposure calculation unit may determine the type of the main subject in the mode setting (for example, portrait mode, landscape mode, etc.) of the electronic camera.

  (2) In the one embodiment described above, the CPU 17 may start the operation of the shooting mode shown in FIG. 2 by using an AF start instruction by half-pressing the release button 21 as a trigger. Further, in the shooting mode operation in the above-described one embodiment (FIG. 2), if there is a half-press operation before the release button 21 is fully pressed, the CPU 17 changes the focus adjustment state at that time. The exposure parameters may be fixed and the subsequent focus adjustment control and exposure control may be stopped.

  (3) In the above-described other embodiments, the example in which the exposure calculation device is applied to a single-lens reflex type electronic camera has been described. However, the present invention is also applicable to a single-lens reflex type silver salt camera having an observation imaging device 15. it can.

  (4) The image sensor in each of the above embodiments may have a configuration in which the light receiving elements for focus detection are arranged on the same light receiving surface as the light receiving element for capturing the main image and the like. In this case, the light receiving element for focus detection is configured to detect a pattern of the first signal sequence and a pattern of the second signal sequence each having a phase difference. Then, the camera may determine the focus adjustment state of the image pickup optical system from the image shift amounts of these patterns (note that the configuration example of the image pickup device in this case is not shown).

  (5) In each of the above-described embodiments, the example in which the face detection unit and the exposure calculation unit are realized by software has been described. However, these configurations may be realized by hardware by an ASIC or the like.

  From the above detailed description, features and advantages of the embodiments will become apparent. It is intended that the scope of the claims extend to the features and advantages of the embodiments as described above without departing from the spirit and scope of the right. Further, any person having ordinary knowledge in the technical field should be able to easily come up with any improvements and modifications, and there is no intention to limit the scope of the embodiments having the invention to those described above. It is also possible to use appropriate improvements and equivalents within the scope disclosed in.

DESCRIPTION OF SYMBOLS 13 ... Aperture, 15 ... Image sensor, 16 ... AFE, 17 ... CPU, 24 ... Image processing part, 25 ... Face detection part, 27 ... Exposure calculation part, 31 ... Camera body, 32 ... Lens unit, 35 ... Aperture, 42 ... Mechanical shutter, 43 ... Recording image sensor, 46 ... Analysis image sensor, 47 ... Microcomputer

Claims (17)

A photometric unit for measuring a light flux from a subject to obtain a first photometric value and obtaining a second photometric value for a part of the subjects;
A target setting unit that sets a range of a predetermined luminance value based on the second photometric value as a target range of the first photometric value;
A correction unit that corrects the first photometric value based on the target range to obtain a third photometric value;
A calculation unit for obtaining an exposure amount of the light flux from the subject based on the third photometric value by the correction unit;
An exposure calculation device comprising: In the exposure calculation device according to claim 1,
A subject detection unit that detects an image of the part of the subject from the subject image;
The exposure calculation apparatus, wherein the target setting unit sets the target range based on the second photometric value for the detection result of the subject detection unit. In the exposure calculation device according to claim 1 or 2,
The photometry unit divides the part of the subject into a plurality of areas, performs photometry, and obtains the second photometry value based on a plurality of photometry values obtained for each of the plurality of areas. Exposure calculation device. In the exposure calculation device according to claim 3,
The said photometry part calculates | requires a said 2nd photometric value based on the maximum value of these photometric values, The exposure calculating apparatus characterized by the above-mentioned. In the exposure calculation device according to claim 3 or 4,
The exposure metering device, wherein the photometry unit obtains the plurality of photometry values for each of a plurality of groups obtained by grouping the plurality of regions. In the exposure calculation apparatus according to any one of claims 1 to 5,
The exposure calculation apparatus according to claim 1, wherein the target setting unit determines the target range in accordance with a type of the subject. In the exposure calculation device according to any one of claims 1 to 6,
The exposure calculation apparatus, wherein the target setting unit determines the target range according to the size of the part of the subject. In the exposure calculation device according to claim 7,
The exposure calculation apparatus according to claim 1, wherein the target setting unit determines the target range based on a subject having the largest size among the some subjects when there are a plurality of the subjects. In the exposure calculation device according to claim 7,
The target setting unit determines the target range based on a value obtained by summing the sizes of each of the partial subjects when there are a plurality of the partial subjects. In the exposure calculation device according to any one of claims 1 to 9,
The exposure calculation device, wherein the correction unit limits a difference between the third photometric value and the first photometric value by a predetermined value. In the exposure calculation device according to claim 10,
The exposure calculation apparatus according to claim 1, wherein the correction unit determines the predetermined value according to a type of the subject. In the exposure calculation apparatus according to claim 10 or 11,
The exposure calculation device, wherein the correction unit determines the predetermined value according to the size of the part of the subject. In the exposure calculation device according to claim 12,
The exposure calculation apparatus according to claim 1, wherein the correction unit determines the predetermined value based on a subject having the largest size among the some subjects when there are a plurality of the subjects. In the exposure calculation device according to claim 12,
The exposure calculation apparatus, wherein the correction unit determines the predetermined value based on a value obtained by summing the sizes of the partial subjects when the partial subject is present in plural. In the exposure calculation apparatus according to any one of claims 1 to 14,
The target setting unit sets the target range by using, as the second photometric value, a photometric value for a subject having the largest size among the plurality of the partial subjects when there are a plurality of the partial subjects. An exposure calculation device. In the exposure calculation device according to any one of claims 1 to 15,
The target setting unit, when there are a plurality of some of the subjects, sets a value obtained by weighting and averaging a photometric value for each of the some subjects according to the size of the subject as the second photometric value. An exposure calculation device characterized in that   The camera provided with the exposure calculating apparatus of any one of Claims 1-16.

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