JP2013040997A - Exposure calculation unit and camera - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stabilize exposure for a whole scene in a photographic mode in which a plurality of images to be watched as one scene are consecutively acquired.SOLUTION: An exposure calculation unit includes: a photometric section for obtaining a first photometric value by performing photometry of luminous flux from a subject, and also obtaining a second photometric value related to a part of the subject; a target setting section for setting a prescribed luminance value range based on the second photometric value as a target range of the first photometric value; a correction section for obtaining a third photometric value by correcting the first photometric value on the basis of the target range; and a calculation section for obtaining an exposure amount for the luminous flux from the subject on the basis of the third photometric value obtained by the correction section. The calculation section obtains the exposure amount on the basis of the first photometric value, in a first photographic mode in which a plurality of images to be watched as one scene are consecutively acquired, and obtains the exposure amount on the basis of the third photometric value, in a second photographic mode different from the first photographic mode.

Description

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

  2. Description of the Related Art Conventionally, there has been known a camera that detects the face of a person as a main subject from a shooting screen and controls exposure by paying attention to the brightness of the face. As an example, Patent Document 1 discloses an example in which the exposure value obtained from the luminance distribution of the entire screen is corrected so that the exposure of the face approaches a target value having an allowable width depending on the size of the face. .

  Patent Document 1 discloses an example in which the largest face is a correction target when a plurality of faces are detected, and a weighted average obtained by multiplying the brightness of each face by a weight corresponding to the size of each face. An example in which a value is a correction target is disclosed.

JP 2010-72619 A

  By the way, in the exposure calculation in the case of acquiring a plurality of images continuously, the exposure amount may change in each still image depending on the presence or absence of a person and the size of a person's face even if the brightness of the background is the same. is there. In the above case, the optimum exposure amount can be obtained for each still image, but when viewing these still images as one scene, the exposure amount of each still image is different, so the exposure is unstable in the entire scene. There is a risk of seeing.

  An exposure calculation apparatus according to one aspect of the present invention includes a photometry unit, a target setting unit, a correction unit, and a calculation unit. The photometric unit measures a light flux from the subject to obtain a first photometric value, and obtains a 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. Then, the calculation unit obtains the exposure amount based on the first photometric value in the first shooting mode in which a plurality of images viewed as one scene are continuously acquired. Further, the calculation unit obtains the exposure amount based on the third photometric value in the second shooting mode different from the first shooting mode.

  For example, the first shooting mode may be a shooting mode in which a predetermined number of images acquired at a constant time interval in one scene period are recorded as a moving image. In addition, the first shooting mode may be a shooting mode in which a predetermined number of still images acquired at a constant time interval in one scene period are individually recorded.

  A camera provided with the above exposure calculation device is also effective as a specific aspect of the present invention.

  According to the present invention, in a shooting mode in which a plurality of images viewed as a scene are continuously acquired, it is possible to obtain an appropriate exposure for the entire scene.

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 [i] in S104 of FIG. The figure which shows the example of the range which calculates | requires luminance value BvObj [i] with respect to a face area | region. The figure which shows the example of the division | segmentation metering of a face area The figure which shows the case where a plurality of faces are detected FIG. 2 is a flowchart showing an operation example of the correction calculation subroutine 1 in S105 of FIG. FIG. 8 is a flowchart showing an operation example in the correction calculation subroutine 2 in S205 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

<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 for focus adjustment. 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 operation mode switching operations 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 exposure calculation unit 27 determines whether or not the first shooting mode for continuously acquiring a plurality of images to be viewed as one scene is selected. If the above requirement is satisfied (YES side), the process proceeds to S107. On the other hand, if the above requirement is not satisfied (in the case of the second shooting mode different from the first shooting mode: NO side), the process proceeds to S104.

  Here, examples of the first shooting mode include “stop motion shooting mode” and “interval timer shooting mode”.

  The stop motion shooting mode is a shooting mode in which a predetermined number of images acquired at a constant time interval in one scene period are recorded as a moving image. The CPU 17 in the stop motion shooting mode records a plurality of still images for one scene as one moving image file.

  The interval timer shooting mode is a shooting mode for individually recording a predetermined number of still images acquired at a fixed time interval in one scene period. The CPU 17 in the interval timer shooting mode individually records a plurality of still images for one scene as still image files.

  Step S104: 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). When a plurality of faces are detected, the face detection unit 25 numbers the face areas in order of importance in exposure determination. As an example, the face detection unit 25 includes (I) the size of the face area, (II) the distance between the center of the shooting screen and the face area, (III) the distance between the distance measurement area (AF area) and the face area, ( IV) Each evaluation value of reliability in the face detection calculation is added, and the importance of each face area may be determined by comprehensive evaluation of these evaluation values.

  At this time, in (I) above, the greater the face area, the higher the importance of the face area. In (II) above, the closer the face area is to the center of the shooting screen, the higher the importance of the face area. In (III) above, the closer the face area is to the distance measurement area, the higher the importance of the face area. In the above (IV), the higher the reliability in the face detection calculation, the higher the importance of the face area.

  Then, based on the position of the face area detected by the face detection unit 25, the exposure calculation unit 27 obtains the luminance value BvObj [i] of the main subject (face) that is a part of the subject in the shooting screen. Here, “i” is an argument indicating the number of the face numbered in the order of importance described above. In the example of FIG. 7, when a plurality of faces (two) are detected in the shooting screen, the luminance value BvObj [i] corresponding to each face area is obtained.

  Here, when a face area is detected from the shooting screen, the exposure calculation unit 27 in S104, for example, the subject brightness value BvObj for each face area by any of the following methods (a) to (f): [I] is obtained respectively.

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

  (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 obtains the luminance value BvObj of the main subject. [I] may be obtained (see FIG. 4B). For example, in the case of FIG. 4B, the exposure calculation unit 27 obtains the luminance value BvObj [i] 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 brightness value BvObj [i] is obtained from the above, there are cases where the appropriate face brightness cannot be obtained due to the influence of the background.

  Therefore, the exposure calculation unit 27 may obtain the luminance value BvObj [i] from an area inscribed in the contour of the person's face (area FA1 shown in FIG. 5A). Alternatively, the exposure calculation unit 27 may obtain the luminance value BvObj [i] 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 brightness 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 brightness value is based on the average brightness value of the face area. When BvObj is obtained, the bright part of the face may be overexposed. Therefore, the exposure calculation unit 27 performs photometry by dividing the face of the main subject into a plurality of areas, and obtains the luminance value BvObj [i] based on the plurality of photometric values obtained for each of the plurality of areas. Good.

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 photometry values of each division area (FA41-FA44) as the luminance value BvObj by the following formula | equation (1).
BvObj [i] = 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 luminance value BvObj [i]. 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 [i] = Max (BvFaceUp, BvFaceDown, BvFaceLeft, BvFaceRight) (6)
(F) As another example of the above (d), the exposure calculation unit 27 may calculate the luminance value BvObj [i] 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 luminance value BvObj [i].
BvObj [i] = Σ (BvX [j] × Wt [j]) (7)
Here, “j” in the above equation (7) takes an integer of 1-4. In addition, “Σ ()” in Expression (7) is a function that returns a product-sum operation result using the variable j. Further, “Wt [j]” 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 obtained by Expressions (2)-(5)) in the above expression (7). Substituting as [4], the luminance value BvObj [i] may be obtained.

  Step S105: The exposure calculation unit 27 executes the correction calculation subroutine 1 (the contents of the correction calculation subroutine 1 will be described later). In this correction calculation subroutine 1, the exposure calculation unit 27 calculates a corrected representative luminance value BvAns based on the luminance value BvObj [i] of the main subject (obtained in S104).

  However, if no face area is detected, the exposure calculation unit 27 in S105 sets the temporary representative luminance value PreBvAns to the corrected representative luminance value BvAns (BvAns = PreBvAns).

  Step S106: The exposure calculation unit 27 calculates an exposure amount by a known exposure calculation based on the corrected representative luminance value BvAns, and controls exposure based on the exposure amount (parameters such as shutter speed and aperture value). Adjust). After the process of S106, the process proceeds to S108.

Step S107: The exposure calculation unit 27 obtains a corrected representative luminance value BvAns from the provisional representative luminance value PreBvAns (obtained in S102).
BvAns = PreBvAns (8)
Then, the exposure calculation unit 27 in S107 calculates an exposure amount by a known exposure calculation based on the corrected representative luminance value BvAns, and performs exposure control (shutter time, aperture value, etc.) based on this exposure amount. Adjust each parameter).

  Step S108: 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 a display indicating the position of the face area detected in S104 and selected in the correction calculation subroutine 1 on the view image (illustration of a display example of the view image is omitted).

  Step S109: The CPU 17 determines whether or not it is a shooting start timing. For example, in the second shooting mode, the shooting start timing is when the release button 21 is fully pressed. Alternatively, in the first shooting mode, the shooting start timing indicates every predetermined time interval after a period from when the release button 21 is fully pressed until a predetermined period or a predetermined number of shooting operations are performed.

  If the above requirement is satisfied (YES side), the process proceeds to S110. 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 the NO side in S109, the CPU 17 captures a through image based on the exposure amount obtained in S106 (or S107). The view image is displayed as a moving image on the monitor 20 under the control of the CPU 17.

  Step S110: The CPU 17 executes a main image capturing process based on the exposure amount obtained in S106 (or S107). 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.

  Here, in the stop motion shooting mode, a plurality of still images for one scene are recorded as one moving image file under the control of the CPU 17. Further, the CPU 17 in the interval timer shooting mode individually records a plurality of still images for one scene as still image files. Also in the second shooting mode, the CPU 17 records a plurality of still images individually as still image files.

  The description of the operation example of the shooting mode illustrated in FIG.

(Description of correction calculation subroutine 1)
Next, an example of the operation in the correction calculation subroutine in S105 of FIG. 2 will be described with reference to the flowchart of FIG.

  Step S201: The exposure calculation unit 27 determines whether or not the camera state satisfies a predetermined condition. If the above requirement is satisfied (YES side), the process proceeds to S202. On the other hand, if the above requirement is not satisfied (NO side), the process proceeds to S203.

  Here, the exposure calculation unit 27 in S201 determines whether or not any of the following conditions 1 to 3 is satisfied, for example.

  (Condition 1) In the state where the exposure calculation is repeatedly performed (the state where steps 101 to 109 in FIG. 2 are repeatedly performed), it is the first exposure calculation. That is, there is no previous representative luminance value to be compared. For example, the condition 1 corresponds to a case immediately after the power is turned on or a case immediately after switching the metering mode from the known center-weighted metering or spot metering to the multi-segment metering mode.

  (Condition 2) When no face is detected in the previous exposure calculation. That is, it is a case where the last representative luminance value PastBv described later is not correctly calculated.

  (Condition 3) When the focus adjusting unit 26 has a plurality of distance measurement areas in the shooting screen, an arbitrary distance measurement area is manually designated by the user. That is, the user is trying to focus on a certain face. In the above case, the face of the distance measurement area designated among the plurality of faces is the main face, and the exposure should be determined based on the main face. Therefore, in the case of condition 3, the exposure calculation unit 27 avoids keeping the exposure on the face not intended by the user without performing the exposure stabilization process described later.

  However, when the focusing lens is prohibited from being driven even when the distance measurement area is manually designated (during focus lock), the exposure calculation unit 27 determines that the condition 3 is not satisfied in order to stabilize the exposure. To do.

  Step S202: The exposure calculation unit 27 sets the value of a variable n indicating the number of faces to be subjected to correction calculation to 1 (n = 1). In other words, when the predetermined condition of S201 is satisfied, even if a plurality of faces are detected, only one face having the highest importance is subjected to correction calculation. Note that after the process of S202, the process proceeds to S204.

  Step S203: The exposure calculation unit 27 substitutes the number of faces to be corrected into the variable n. For example, when five faces are detected, the exposure calculation unit 27 in S203 may set n = 5.

  In addition, it is inappropriate to include a face of low importance in the correction calculation target. For this reason, when a plurality of faces are detected in the shooting screen, the exposure calculation unit 27 may narrow down the number of faces to be subjected to correction calculation according to the importance of the face area. For example, the exposure calculation unit 27 sets an upper limit value for the value of the variable n (for example, n = 3), and when n or more faces are detected, up to n correction calculation targets in descending order of importance. What is necessary is just to determine the face.

  Step S204: The exposure calculation unit 27 initializes by substituting 1 into the variable i (i = 1).

  Step S205: The exposure calculation unit 27 executes the correction calculation subroutine 2 with the i-th face as a correction target (the contents of the correction calculation subroutine 2 will be described later). In this correction calculation subroutine 2, the exposure calculation unit 27 calculates a luminance correction value dBvObj [i] for each face to be corrected based on the luminance value BvObj [i] of the main subject (obtained in S104).

  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 [i] so that the balance between the main subject and the background becomes an appropriate exposure amount.

Step S206: The exposure calculation unit 27 calculates a temporary corrected representative luminance value TempBv [i] based on the i-th face based on the following equation.
TempBv [i] = PreBvAns + dBvObj [i] (9)
Step S207: The exposure calculator 27 determines whether or not the current value of the variable i is equal to n (i = n). When i = n, the luminance correction amount dBvObj [i] in S205 is obtained for all the faces to be corrected. If the above requirement is satisfied (YES side), the process proceeds to S209. On the other hand, if the above requirement is not satisfied (NO side), the process proceeds to S208.

  Step S208: The exposure calculation unit 27 increments the value of i (i = i + 1), and returns the process to step S205. Through the loop from S205 to S208, provisionally corrected representative luminance values TempBv [i] are obtained for all the faces to be corrected.

  Step S209: The exposure calculation unit 27 determines whether or not the number n of faces to be corrected is 1 (n = 1). If the above requirement is satisfied (YES side), the process proceeds to S210. On the other hand, if the above requirement is not satisfied (NO side), the process proceeds to S211.

  Step S210: The exposure calculation unit 27 substitutes 1 for a variable (selected face number Sel) indicating a face number used in the exposure calculation.

  Step S211: The exposure calculation unit 27 calculates ABS (TempBv [i] -PastBv) for all correction target faces. Then, the exposure calculation unit 27 substitutes i for which ABS (TempBv [i] −PastBv) is the minimum value into the selected face number Sel. In addition, when there are a plurality of i taking the minimum value of ABS (TempBv [i] −PastBv), it is sufficient to substitute i with the smallest i value (that is, higher importance) for Sel.

  Here, “ABS ()” is a function that returns the absolute value of the numerical value in (). “PastBv” is the previous representative luminance value, and a calculation method thereof will be described later.

  Step S212: The exposure calculation unit 27 substitutes the provisional corrected representative luminance value TempBv [i] corresponding to the selected face number Sel into the corrected representative luminance value BvAns (BvAns = TempBv [Sel]).

  Step S213: The exposure calculation unit 27 assigns the representative luminance value BvAns to the previous representative luminance value PastBv, and updates PastBv (PastBv = BvAns). As a result, when the exposure calculation is repeatedly performed, the calculation of S211 is performed using the current representative luminance value BvAns in the next exposure calculation. Above, description of the flowchart of FIG. 8 is complete | finished.

(Description of correction calculation subroutine 2)
Next, an example of the operation in the correction calculation subroutine 2 in S205 of FIG. 8 will be described with reference to the flowchart of FIG.

Step S301: The exposure calculation unit 27 uses the luminance value BvObj (obtained in S104) of the main subject to determine the luminance target value BvTrgt using the following equation (10).
BvTrgt = BvObj−OfsObj (10)
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 S301 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 over exposure amount becomes. Therefore, in the above formula (10), 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. The value of OfsObj when the person's face is the main subject is obtained by the following equation (11).
OfsObj = Log2 (RvG (150) / RvG (120)) (11)
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 in S301, a calculation example 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 (12).
OfsObj = Log2 (RvG (175) / RvG (120)) (12)
Step S302: 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 S302 obtains the upper limit value BvUpper of the target range by the following equation (13) and obtains the lower limit value BvLower of the target range by the following equation (14).
BvUpper = BvTrgt + BvSth1 (13)
BvLower = BvTrgt + BvSth2 (14)
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 S302 can change according to the type of the main subject.

  In S302, 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 (15). Similarly, the output value of a person's face in an over-order scene may be 180. Therefore, the value of BvSth2 in the case where the person's face is the main subject can be obtained by the following equation (16).
BvSth1 = Log2 (RvG (150) / RvG (110)) (15)
BvSth2 = Log2 (RvG (150) / RvG (180)) (16)
Here, the relationship between the target range and the exposure amount will be described with reference to FIG. BvSth1 obtained by the above equation (15) 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 (16) 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 of S302, a calculation example of BvSth1 and BvSth2 when the main subject is a blue sky will be described. If the width of the output value when the blue sky is the reproduction target in the main image is 100 to 200, the value of BvSth1 in this case can be obtained by the following equation (17). Further, the value of BvSth2 in this case can be obtained by the following equation (18).
BvSth1 = Log2 (RvG (175) / RvG (100)) (17)
BvSth2 = Log2 (RvG (175) / RvG (200)) (18)
In the above example, it has been described that the output of the human face in the main image in a 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 BvSth1 and BvSth2 by the following equations (19) and (20). Then, the exposure calculation unit 27 may obtain BvUpper and BvLower using BvSth1 ′ and BvSth2 ′.
BvSth1 ′ = BvSth1 × WtWd (19)
BvSth2 ′ = BvSth2 × WtWd (20)
Here, “WtWd” in Expression (19) and Expression (20) 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. 11 shows an example of a function of the weighting coefficient WtWd when the main subject is a person. The vertical axis in FIG. 11 indicates the value of WtWd, and the horizontal axis in FIG. 11 indicates the area ratio of the main subject to the shooting screen.

  In the example of FIG. 11, 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 S303: The exposure calculation unit 27 determines whether PreBvAns is larger than BvUpper. If the above requirement is satisfied (YES side), the process proceeds to S307. On the other hand, if the above requirement is not satisfied (NO side), the process proceeds to S304.

  Step S304: The exposure calculation unit 27 determines whether PreBvAns is smaller than BvLower. If the above requirement is satisfied (YES side), the process proceeds to S306. On the other hand, if the above requirement is not satisfied (NO side), the process proceeds to S305.

  Step S305: 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. Note that the processing moves to S308 after S305.

Step S306: In this case, if the main image is taken with the exposure amount obtained from the provisional representative luminance value PreBvAns, it can be expected 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 temporary correction amount dBvTrgtToAns by the following equation (21) in order to set the face output value in the main image to 180.
dBvTrgtToAns = BvLower-PreBvAns (21)
DBvTrgtToAns in the case of S306 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. Note that the process proceeds to S308 after S306.

Step S307: In this case, if the main image is taken with the exposure amount obtained from the provisional representative luminance value PreBvAns, it can be expected that the face output value in the main image will be lower than 110. Therefore, the exposure calculation unit 27 calculates the value of the temporary correction amount dBvTrgtToAns by the following equation (22) in order to set the face output value in the main image to 110.
dBvTrgtToAns = BvUpper-PreBvAns (22)
DBvTrgtToAns in the case of S307 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 S308: The exposure calculation unit 27 obtains the luminance correction amount dBvObj [i] by limiting the temporary correction amount dBvTrgtToAns (obtained in any one of S305, S306, and S307) to a predetermined limit value range. For example, the exposure calculation unit 27 in S308 calculates the luminance correction amount dBvObj [i] by the following equation (23).
dBvObj [i] = Clip (dBvTrgtToAns) (23)
Here, “Clip (A)” in Expression (23) 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 S308 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 S308 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 S308 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. 12 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. 12 represents the limit value converted into the exposure value, and the horizontal axis in FIG. 12 represents the area ratio of the main subject to the shooting screen.

  In the example of FIG. 12, 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.

  Thereafter, the exposure calculation unit 27 ends the correction calculation subroutine 2 and returns to the process of S206 shown in FIG. Above, description of the flowchart of FIG. 9 is complete | finished.

  In the electronic camera of one embodiment, the exposure calculation unit 27 calculates a plurality of corrected temporary representative luminance values (TempBv [i]) based on the detected plurality of faces (S205 to S208). Then, the exposure calculation unit 27 sets a value closest to the previous representative luminance value (PastBv) among the corrected temporary representative luminance values as the current representative luminance value (BvAns) (S212, S213).

  Thereby, in one embodiment, when the exposure calculation is repeatedly performed, the possibility that the exposure value becomes unstable due to the influence of the brightness of a person who is not the main subject is reduced. For example, in a situation where another person crosses in front of the person who is the main subject, the current representative brightness value is set based on the previous representative brightness value of the main subject. It is possible to maintain a stable exposure.

  In the electronic camera of one embodiment, when the camera state satisfies a predetermined condition (conditions 1 to 3), the exposure calculation unit 27 does not perform exposure stabilization processing based on the previous exposure calculation (S201, S202). Therefore, it is avoided that the exposure is continuously adjusted to the face not intended by the user.

  In the electronic camera of one embodiment, when the first shooting mode is selected, the exposure calculation unit 27 obtains a corrected representative luminance value BvAns from the temporary representative luminance value PreBvAns (S103, S107). ).

  Thereby, in one embodiment, the correction of the luminance value by the face is not performed in the first shooting mode in which a plurality of images that are viewed as one scene are continuously acquired. Therefore, in the first shooting mode, the exposure is less likely to fluctuate from image to image depending on the presence or absence of a person and the size of the person's face, and an appropriate exposure can be obtained for the entire scene.

  In the present embodiment, the operations from step S101 to S109 are repeated while acquiring a plurality of images in the first shooting mode. However, in order to reduce power consumption, a timer (not shown) of the CPU 17 is predetermined. The operation of FIG. 2 may be started when the time comes.

<Description of other embodiments>
FIG. 13 is a diagram illustrating an exemplary configuration 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 is established between the camera body 31 and the lens unit 32 (the illustration of the mount and the electrical contact in FIG. 13 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 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 shooting mode shown in FIG. 14 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. 13). It should be noted 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 analysis imaging element 46 to acquire an analysis image. At this time, the microcomputer 47 executes AF control based on the output of the focus detection unit 45.

  Step S402: Using the output of the analysis image, the microcomputer 47 performs divided photometry of the subject included in the shooting screen and obtains a temporary representative luminance value PreBvAns. Note that the processing in S402 corresponds to S102 in FIG.

  Step S403: The microcomputer 47 determines whether or not the first shooting mode (stop motion shooting mode / interval timer shooting mode) is selected. If the above requirement is satisfied (YES side), the process proceeds to S407. On the other hand, if the above requirement is not satisfied (in the case of the second shooting mode: NO side), the process proceeds to S404.

  Step S404: The microcomputer 47 detects the position of the face area of the person from the shooting screen using the output of the analysis image. When a plurality of faces are detected, the microcomputer 47 numbers the face areas in order of importance in exposure determination based on the size of the face.

  Then, the microcomputer 47 obtains the luminance value BvObj [i] of the main subject (face), which is a part of the subject in the shooting screen, based on the detected position of the face area. Note that the processing in S404 corresponds to S104 in FIG.

  Step S405: The microcomputer 47 executes the correction calculation subroutine 1 (the processing from S201 to S213 in FIG. 8) to obtain the corrected representative luminance value BvAns. However, if no face is detected, the microcomputer 47 sets the provisional representative luminance value PreBvAns to the corrected representative luminance value BvAns (BvAns = PreBvAns).

  Step S406: The microcomputer 47 calculates an exposure amount by a known exposure calculation based on the corrected representative luminance value BvAns, and controls exposure based on this exposure amount (adjusts each parameter such as shutter speed and aperture value). I do. After the process of S406, the process proceeds to S408. Note that the processing in S406 corresponds to S106 in FIG.

  Step S407: The microcomputer 47 obtains a corrected representative luminance value BvAns from the provisional representative luminance value PreBvAns (BvAns = PreBvAns).

  The microcomputer 47 in S407 calculates the exposure amount by a known exposure calculation based on the corrected representative luminance value BvAns, and controls exposure based on this exposure amount (the parameters such as the shutter speed and the aperture value). Adjust).

  Step S408: The microcomputer 47 determines whether it is a photographing start timing. If the above requirement is satisfied (YES side), the process proceeds to S409. On the other hand, if the above requirement is not satisfied (NO side), the microcomputer 47 returns to S401 and repeats the above operation.

  Step S409: The microcomputer 47 drives the main mirror 41 from the observation state position to the retracted position.

  Step S410: The microcomputer 47 executes a main image capturing process based on the exposure amount obtained in S406 or S407. 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. 14 is complete | finished. In the example of FIG. 14 as well, substantially the same effect as in the above-described one embodiment can be obtained.

<Supplementary items of the embodiment>
(Supplement 1) In each of the above embodiments, the example in which the main subject is a person's face 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 analysis image, and the position on the shooting screen, and the brightness of this region The luminance value BvObj of the main subject may be obtained using the information. 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.

  (Supplement 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.

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

  (Supplement 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 elements 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 element in this case is not shown).

  (Supplement 5) In each of the above 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 of course 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 (4)

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 that obtains an exposure amount for the light flux from the subject based on the third photometric value by the correction unit;
The calculation unit obtains the exposure amount based on the first photometric value in a first shooting mode in which a plurality of images viewed as one scene are continuously acquired, and a second shooting different from the first shooting mode. An exposure calculation device for obtaining the exposure amount based on the third photometric value in the mode. In the exposure calculation device according to claim 1,
The first photographing mode is an exposure calculation device that is a photographing mode in which a predetermined number of images acquired at a constant time interval in one scene period are recorded as a moving image. In the exposure calculation device according to claim 1,
The first photographing mode is an exposure calculation device that is a photographing mode for individually recording a predetermined number of still images acquired at a constant time interval in one scene period.   The camera provided with the exposure calculating apparatus of any one of Claims 1-3.

Images