JP2014098768A - Imaging device and exposure control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately detect only a certain part within a screen even in a backlight scene like only the certain part is bright, and to enable a correct exposure to be obtained.SOLUTION: The imaging device comprises: correction means that corrects a luminance value of the area in which the main subject exists to a small value on the basis of a luminance value of a plurality of reference areas adjacent to an area in which a main subject exists in a light metering area; luminance value calculation means that calculates an average luminance value of an area including the area in which the main subject exists and the plurality of reference areas, using the luminance value corrected by the correction means; detection means that detects a luminance value of a high luminance area in the area having the average luminance value calculated; and correction value calculation means that calculates an exposure correction value on the basis of the corrected luminance value of the area in which the main subject exists, the average luminance value and the luminance value of the high luminance area.

Description

  The present invention relates to an exposure control technique in a digital camera, a digital video camera, or the like.

  The following devices have been put into practical use as photometric devices such as cameras or exposure control devices. That is, a plurality of luminance information is obtained by dividing the photographing screen into a plurality of areas. Then, by using a predetermined algorithm based on the plurality of pieces of luminance information, a proper exposure is obtained by performing so-called backlight scene discrimination in which the brightness of the main subject is significantly darker than the brightness of the background.

  For example, according to Japanese Patent Application Laid-Open No. H10-228561, the photographing screen is divided into a plurality of blocks, and the photometric value data is obtained from the accumulated data for each block and the maximum value in the screen. In addition, it is possible to change the photometric reference value by determining whether the central part of the screen is in the backlit state or the over-ordered state, and by performing iris control, it is possible to shoot with an appropriate iris operation even under backlighting conditions. It is said.

  Patent Document 2 discloses a method for determining a backlight scene based on a luminance average of each photometric area divided into a plurality of areas and a main focus point luminance difference. Even in a backlit scene where only a part of the screen is bright, it is possible to control the exposure of the camera so that this is accurately detected and the exposure is appropriate.

JP-A-6-225205 JP 2002-296635 A

  A typical example of a condition generally referred to as backlight is a situation where the luminance of the main subject is low and the luminance of the other background is high. In Patent Document 2, exposure correction is performed by accurately detecting brightness and darkness in the screen based on a luminance difference between each luminance average of a photometric area divided into a plurality of areas and a weighted main distance measuring point. According to this technique, there is a high possibility that the exposure accuracy of the main ranging point can be improved in a backlight scene where only a certain part of the screen is bright.

  However, due to the difference in sensitivity distribution characteristics (spot diameter) of the photometric optical system such as the condenser lens and the shooting composition, the main focus point, which should originally have low brightness, may be affected by bright light such as the background around the focus point. If received, the photometric brightness at the main focus point may be raised. In this case, there is a high possibility that the backlight is not determined in spite of the backlight scene because the brightness and darkness in the screen is weak, or the exposure correction amount is weak. For this reason, a photograph in which the subject at the main distance measuring point is blacked out due to underexposure is obtained.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to accurately detect even a backlight scene where only a part of the screen is bright so as to obtain an appropriate exposure. Is to do.

  An imaging apparatus according to the present invention includes a correction unit that corrects the luminance value of a region where the main subject exists to a small value based on the luminance values of a plurality of reference regions adjacent to the region where the main subject exists in the photometric region. A luminance value calculating unit that calculates an average luminance value of an area including the main subject and an area including the plurality of reference areas, using the luminance value corrected by the correcting unit; and calculating the average luminance value. Based on the brightness value of the area where the corrected main subject exists, the average brightness value, and the brightness value of the high brightness area, the detection means for detecting the brightness value of the high brightness area in the area Correction value calculation means for calculating.

  According to the present invention, even in a backlight scene where only a part of the screen is bright, it is possible to accurately detect this and obtain an appropriate exposure.

1 is a side sectional view of an imaging apparatus according to a first embodiment of the present invention. The figure which showed arrangement | positioning of the light-receiving sensor part in a focus detection sensor. The figure which shows the division | segmentation state of a light-receiving sensor part. The figure showing the corresponding position relationship between the focus detection position and the photometric sensor in the shooting screen. FIG. 2 is a block diagram illustrating an internal configuration of the imaging apparatus and the interchangeable lens according to the first embodiment. 6 is a flowchart showing the overall operation of shooting in the imaging apparatus. 6 is a flowchart illustrating an exposure calculation operation in the imaging apparatus. The figure which shows the example of a backlight scene. The figure which showed the numerical example of the luminance information corresponding to a backlight scene. The figure which shows the example of the photometry sensitivity distribution in 2nd Embodiment. The figure which shows the example of the correction coefficient in 2nd Embodiment.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

(First embodiment)
FIG. 1 is a side sectional view showing the arrangement of optical members in a camera which is an image pickup apparatus according to the first embodiment of the present invention. FIG. 1 shows a configuration of a so-called digital single-lens reflex camera that can exchange lenses.

  In FIG. 1, 10 is a camera body, and 30 is an interchangeable lens. In the camera body 10, 11 is an optical axis of the photographing lens, 12 is an image sensor, 13 is a semi-transparent main mirror, 14 is a first reflecting mirror, and both the main mirror 13 and the first reflecting mirror 14 are at the top during photographing. Jump up. The imaging element 12 is an area-type storage photoelectric conversion element such as a CMOS sensor or a CCD. 15 is a paraxial image plane conjugate with the imaging element surface 12 by the first reflection mirror 14, 16 is a second reflection mirror, 17 is an infrared cut filter, 18 is a diaphragm having two openings, and 19 is A secondary imaging lens 20 is a focus detection sensor (AF sensor).

  The focus detection sensor 20 is composed of, for example, an area-type storage photoelectric conversion element such as a CMOS sensor or a CCD. As shown in FIG. 2, the light receiving sensor sections 20A and 20B divided into a plurality of parts corresponding to the two openings of the diaphragm 18 are provided. It is the structure by which one pair of these is arrange | positioned. Further, in addition to the light receiving sensor units 20A and 20B, a signal storage unit, a signal processing peripheral circuit, and the like are formed as an integrated circuit on the same chip. The configuration from the first reflecting mirror 14 to the focus detection sensor 20 is described in detail in Japanese Patent Application Laid-Open No. 9-184965 and the like, and focus detection is performed by an image shift method at an arbitrary position in the photographing screen. Is possible.

  Reference numeral 21 denotes a diffusing focusing plate, 22 a pentaprism, 23 an eyepiece lens, 24 a third reflecting mirror, 25 a condenser lens, and 26 a photometric sensor for obtaining information on the luminance of the subject. The photometric sensor 26 is composed of a photoelectric conversion element such as a silicon photodiode, for example, and includes a light receiving sensor section that is divided into a plurality of grids (two-dimensionally arranged) as illustrated in FIG. . In the present embodiment, an example in which the light receiving field is divided into 9 columns × 7 rows = 63 will be described. Each of the 63 light-receiving sections is referred to as PD11 to PD79. It is well known that in addition to the light receiving sensor part, a signal amplifying part, a signal processing peripheral circuit, and the like are formed as an integrated circuit on the same chip.

  FIG. 4 is a diagram showing the corresponding positional relationship between the focus detection position in the shooting screen by the focus detection sensor 20 and the 63 photometric sensors 26 divided into 63 parts. In this example, the focus detection positions in the photographing screen are nine points from S01 to S23, and the focus detection position S01 performs focus detection at a position corresponding to the light receiving unit PD34 of the photometric sensor 26. Further, as shown in the drawing, the focus detection position S02 performs focus detection at a position corresponding to the light receiving portion PD25 of the photometric sensor 26, and the same applies hereinafter, and the focus detection position S23 corresponds to the light receiving portion PD56 of the photometric sensor 26. The focus is detected at.

  Reference numeral 27 denotes a mount portion for attaching the photographing lens, and 28 denotes a contact portion for performing information communication with the photographing lens. In the interchangeable lens 30, 31 is a diaphragm, 32 is a contact portion for performing information communication with the camera body, 33 is a mount portion for mounting on the camera, and 34, 35, and 36 are optical lenses constituting the photographing lens.

  FIG. 5 is a block diagram illustrating a configuration example of an electric circuit of the camera body 10 and the interchangeable lens 30 according to the present embodiment. In the camera body 10, reference numeral 41 denotes a control unit by a one-chip microcomputer having a built-in input / output port such as an arithmetic unit, ROM, RAM, A / D converter, serial communication port, etc. Do.

  A specific control sequence of the control unit 41 will be described later. The focus detection sensor 20 and the photometric sensor 26 are the same as those described in FIGS. Output signals of the focus detection sensor 20 and the photometry sensor 26 are connected to an A / D converter input terminal of the control unit 41.

  A shutter 42 is connected to the output terminal of the control unit 41 and controlled. A first motor driver 43 is connected to and controlled by the output terminal of the control unit 41 and drives a first motor 44 for driving the main mirror 13 and the like.

  A sensor 45 detects the posture of the camera, and an output signal thereof is connected to an input terminal of the control unit 41. The control unit 41 can input information of the posture detection sensor 45 to obtain information such as whether shooting is performed in a horizontal position or shooting in a vertical position at the time of shooting. Reference numeral 46 denotes an AF light source that projects infrared light or the like onto a subject when focus detection is performed by the distance measuring sensor 20 under low illuminance conditions, and emits light according to an output signal of the control unit 41.

  A flash 47 emits light at the time of photographing when the luminance of the subject is insufficient, and is emitted according to an output signal from the control unit 41. Reference numeral 48 denotes a first display that is composed of a liquid crystal panel or the like and displays the number of shots, date information, shooting information, and the like. Each segment is controlled to be turned on in accordance with an output signal from the control unit 41. Reference numeral 49 denotes various switches including a release button and various setting buttons. Reference numeral 28 denotes a contact portion described in FIG. 1, to which an input / output signal of a serial communication port of the control unit 41 is connected.

  In the interchangeable lens 30, a lens control unit 51 includes, for example, a calculator, a memory such as a ROM and a RAM, a serial communication port, and the like. Reference numeral 52 denotes a second motor driver which is connected to and controlled by the output terminal of the lens control unit 51 and drives a second motor 53 for performing focus adjustment. A third motor driver 54 is connected to and controlled by the output terminal of the lens control unit 51 and drives a third motor 55 for controlling the diaphragm 31 shown in FIG. Reference numeral 56 denotes a distance encoder for obtaining information related to the extension amount of the focus adjustment lens, that is, the subject distance, and is connected to the input terminal of the lens control unit 51. Reference numeral 57 denotes a zoom encoder for obtaining focal length information at the time of shooting when the interchangeable lens 30 is a zoom lens, and is connected to an input terminal of the lens control unit 51. Reference numeral 32 denotes a contact portion described in FIG. 1 to which an input / output signal of a serial communication port of the lens control unit 51 is connected.

  When the interchangeable lens 30 is attached to the camera body 10, the contact portions 28 and 32 are connected to each other, and the lens control unit 51 can perform data communication with the control unit 41 of the camera body. The lens-specific optical information necessary for the camera body control unit 41 to perform focus detection and exposure calculation is output from the lens control unit 51 to the camera body control unit 41 by data communication. Similarly, information on the subject distance and focal length information based on the distance encoder 56 or the zoom encoder 57 are also output from the lens control unit 51 to the control unit 41 of the camera body. In addition, focus adjustment information and aperture information obtained as a result of focus detection and exposure calculation performed by the control unit 41 of the camera body are output from the control unit 41 of the camera body to the lens control unit 51 by data communication. The lens control unit 51 controls the second motor driver 52 in accordance with the focus adjustment information, and controls the third motor driver 54 in accordance with the aperture information.

  The optical image of the subject that has passed through the lens is formed on the image sensor 12 and converted into electric charges corresponding to the amount of light. The image sensor 12 is covered with, for example, R (red), G (green), and B (blue) color filters. Each color filter has a spectral sensitivity around the wavelength band of each color, and a photoelectric conversion element provided corresponding to each color filter photoelectrically converts light in the band that has passed through each color filter.

  The electric charge converted by each photoelectric conversion element is output as an electric signal from the image pickup element 12 to the A / D conversion unit of the digital signal processor 60 and converted into a digital signal (image data) by the A / D conversion process. Based on the acquired image data, the digital signal processor 60 performs various signal processing such as image correction processing and image compression processing, acquisition image storage in the RAM 61, image data writing / reading to the external I / F 62, and the like. The RAM 61 is also used as a work memory during signal processing. The ROM 63 stores a signal processing program executed by the digital signal processor 60 and the like. Reference numeral 64 denotes a second display that is configured by a liquid crystal panel such as a TFT and displays a captured image, the number of captured images, date information, shooting information, and the like, and is controlled by an output signal of the digital signal processor 60.

  Hereinafter, a specific operation sequence of the control unit 41 of the camera body and the digital signal processor 60 will be described with reference to a flowchart starting from FIG. When the power switch (not shown) is turned on, the control unit 41 and the digital signal processor 60 become operable, and when the first stroke switch of the release button (not shown) is turned on, the process is executed from step S101 in FIG.

  In step S101, a control signal is output to the focus detection sensor 20, and signal accumulation is started. In step S102, the process waits for the signal accumulation of the focus detection sensor 20 to end. In step S103, A / D conversion is performed while reading the signal accumulated in the focus detection sensor 20. Further, various necessary data corrections such as shading are performed on each read digital data.

  In step S104, lens information necessary for focus detection is input from the lens control unit 51, and the focus state of each part of the shooting screen is calculated from this and digital data obtained from the focus detection sensor 20. A region to be focused in the screen is determined by a method described in, for example, Japanese Patent Application Laid-Open No. 11-190816 from the focus state of each part of the obtained photographing screen. The amount of lens movement for focusing is calculated according to the focus state in the determined area.

  In step S <b> 105, the calculated lens movement amount is output to the lens control unit 51. In accordance with this, the lens control unit 51 outputs a signal to the second motor driver 52 so as to drive the focus adjustment lens, and drives the second motor 53. As a result, the photographing lens is brought into focus with respect to the subject. The distance information to the subject can be obtained by inputting the information on the subject distance based on the distance encoder 56 from the lens control unit 51 after the in-focus state.

  In step S106, a control signal is output to the photometric sensor 26 to start signal accumulation. In step S107, the process waits for the signal accumulation of the photometric sensor 26 to end. In step S108, A / D conversion is performed while reading the signals of the respective light receiving portions PD11 to PD79 accumulated in the photometric sensor 26.

  In step S109, an exposure calculation is performed. The brightness of the subject is obtained by calculation, and the shutter speed and aperture value at which proper exposure is obtained are determined. Also, the backlight scene is determined by a predetermined algorithm. Details of the calculation contents will be described later with reference to the flowchart of FIG.

  In step S110, the process waits for the second stroke switch of the shutter button to be turned on. If it is not turned on, the process returns to step S101. If it is turned on, the process proceeds to step S111.

  In step S111, a control signal is output to the first motor driver, the first motor 44 is driven, and the main mirror 13 and the first reflection mirror 14 are flipped up.

  In step S112, the aperture value information calculated in step S109 is output to the lens control unit 51. In accordance with this information, the lens control unit 51 outputs a signal to the third motor driver 54 so as to drive the diaphragm 31, and drives the third motor 55. As a result, the photographing lens is brought into a narrowed state.

  In step S113, the shutter 42 is controlled according to the shutter speed calculated in step S109, and the image sensor 12 is exposed.

  In step S114, information is output so that the aperture 31 is opened to the lens controller 51 after the exposure is completed. In accordance with this information, the lens control unit 51 outputs a signal to the third motor driver 54 so as to drive the diaphragm 31, and drives the third motor 55. As a result, the photographing lens is brought into an open state.

  In step S115, a control signal is output to the first motor driver, the first motor 44 is driven, and the main mirror 13 and the first reflecting mirror 14 are lowered.

  In step S116, the charges that have already been converted by the photoelectric conversion elements on the image sensor 12 are output from the image sensor 12 to the A / D converter of the digital signal processor 60 as electrical signals, and are digitally converted by A / D conversion processing. It is converted into a signal (for example, uncompressed image data). This completes a series of shooting sequences.

  Subsequently, the detailed contents of the exposure calculation executed in step S109 will be described with reference to the flowchart of FIG.

  In step S151, lens information and the like necessary for performing the exposure calculation are input from the lens control unit 51 to the control unit 41 of the camera body, and are obtained from the light receiving units PD11 to PD79 of the photometric sensor 26 in step S108. Correct digital brightness data. The luminance data corresponding to each of the light receiving parts PD11 to PD79 after correction is referred to as ED11 to ED79, respectively. Further, information on the posture detection sensor 45 is input to obtain camera posture information.

  In step S152, projection data of Y1 to Y7 and X1 to X9 (see FIG. 3) are calculated based on the corrected luminance data ED11 to ED79 of each light receiving unit. The projection data is data obtained by adding and averaging the luminance data ED11 to ED79 in the row direction or the column direction. For example, the Y1 projection data is obtained by adding and averaging the luminance data ED11 to ED19. When calculating the projection data of Y1 to Y7, the calculation range (calculation area) of the projection data is changed according to the information of the area where the focus is detected in step S104. This is because the focus detection position is considered to be basically the position of the main subject, so that the focus area including the position of the main subject is the main photometric area and the values and features in that area are weighted and exposed. This is for performing the calculation.

  In step S153, the control unit 41 performs a differentiation process by weighted averaging from the focus detection position and the average luminance value of the plurality of photometry areas adjacent to the focus detection position in the photometry area of each light receiving unit of the 63 photometry sensor 26. (Differential operation) is performed. Thereby, the luminance value correction calculation of the focus detection position portion is performed. The focus detection position is a main subject region (a region where a main subject exists) such as a focus region based on a focus detection result or a face region by a face detection function.

  When the spot diameter of the condensing lens is wide, it is affected by a high brightness area such as the background adjacent to the focus detection position, and the brightness value at the focus detection position is inherently low, but it is detected high. The luminance difference between the average luminance value in the photometric area and the luminance value at the focus detection position is reduced.

  In the photometry area of i = 1 to 63 in each light receiving part (photometry area) of the 63 divided photometry sensor 26, the control unit 41 determines the focus from the focus detection position and the luminance value for each photometry area in FIGS. The luminance value M (i) of the detection position portion is calculated. In addition, the luminance value R (i) of the reference area adjacent to the focus detection position portion is also calculated, and a differentiation process using weighted averaging is performed to correct the luminance value of the focus detection position portion. In this example, the reference area is four points on the top, bottom, left, and right with respect to one point of the focus detection position part.

  A differentiation process using weighted averaging is performed to calculate a corrected luminance value (Es) at the focus detection position.

Es = (M * 16 + (ΣR (i)) * r_r) / D
Here, “16” is a fixed value that determines the weighting of the distance measuring point luminance, and “D” is 16 + r_r * 4. r_r is a correction coefficient that determines the correction amount. When r_r = 0, the correction amount is zero, and by increasing the negative coefficient, the slope between the brightness of the focus detection position portion and the brightness of the adjacent region of the focus detection position portion is set. Increase the gradient to increase the brightness difference.

  In this way, by correcting the brightness of the focus detection position part, even if the spot diameter of the condenser lens is wide, even if it is affected by the adjacent brightness of the focus detection position part, the brightness difference close to the actual brightness difference Can be obtained. Even in a backlight scene where only a part of the screen is bright, it is possible to accurately detect these luminance differences and obtain an appropriate exposure.

  An example will be described with reference to FIGS. FIG. 9 shows numerical values of the luminance information ED11 to ED79 corresponding to the backlight scene of FIG. 8 according to the arrangement of FIG. In this scene, since it is appropriate to perform focus detection near the face of the person 80 as the main subject, the focus detection position is S12, and the subject area is the spot diameter 81 of the condenser lens in the photometry area. It is a relatively small area. Therefore, the focus detection position portion 82 obtained from the photometric sensor 26 has a high luminance value due to the influence of the high luminance of the adjacent regions 83, 84, and 85 where the bright sky is included in the background among the adjacent regions 83 to 86. End up.

In the case of this example, when the correction coefficient is set to zero and correction is not performed, there is a possibility that backlight detection is not performed and as a result, exposure is insufficient. When the correction coefficient is -1, using the above formula,
Es = (9.1 * 16 + (10.7 + 9.6 + 10.8 + 10.8) *-1) / 12
= 8.6
Thus, -0.5 correction is performed on the luminance 9.1 of the focus detection position portion before correction, and the luminance difference between the luminance of the focus detection position portion and the average luminance of the adjacent region increases. Even in an average luminance value calculation process in step S154, which will be described later, this luminance difference works effectively and an appropriate exposure calculation is possible.

  In step S154, the average of all areas and the weighted average at the focus detection position are calculated according to the information on the focus detection position, and the average brightness obtained by reducing the weight of the area away from the focus detection position with emphasis on the focus detection position. Let it be the value Ea.

  In step S155, the projection data Y1 to Y7 and X1 to X9 indicating the maximum value are detected. Let the maximum value be Eh. When Eh exceeds a predetermined value, a high brightness correction value γ is calculated. When the high luminance correction value γ is calculated, high luminance correction (addition) is performed on the average luminance value Ea calculated in the previous step to obtain Ea (γ).

Ea (γ) = Ea−γ
By performing the high brightness correction, when a certain area in the screen includes a high brightness area such as a backlit sky, the influence of the brightness value of the high brightness portion can be corrected.

  In step S156, an exposure correction value α is calculated when a predetermined condition is satisfied.

If Ea (γ)> Es as the condition,
α = {Es−Ea (γ)} × 0.5
When Ea (γ) <Es and Ea (γ) <0 as conditions,
α = {Es−Ea (γ)} × 0.25
Is calculated as Α = 0 under other conditions.

  Here, Es is a luminance value after correction at the focus detection position coordinates. When Es is smaller than the average luminance value Ea (γ) corrected for high luminance, the luminance of the subject at the focus detection position is increased. Therefore, the exposure correction amount is increased.

  In step S157, the subject brightness value for exposure control is calculated as Ee = Ea (γ) + α. An optimal exposure control factor, that is, an exposure control value such as a shutter speed and an aperture value is determined based on the subject luminance value Ee and the presence or absence of the flash 47.

  In step S157, the subject brightness value Ee for exposure control is calculated using the exposure correction value α calculated in the correction value calculation process in step S156. However, the exposure correction value α is used for exposure control in association with the exposure value. It may be used when calculating the exposure value.

(Second Embodiment)
The sensitivity distribution characteristic (spot diameter) of the photometric optical system such as the condenser lens 25 may vary depending on the position of the photometric area. In this case, the correction coefficient r_r in step S153 is changed depending on the focus detection position. It is also good.

  This embodiment will be described with reference to FIGS. FIG. 10 is a diagram showing a correspondence relationship between a photometric area divided into a plurality of grids and a focus detection position of the focus detection sensor 20. In the present embodiment, an example in which the light receiving field is divided into 9 columns × 7 rows = 63 will be described.

  In the present embodiment, the focus detection positions in the photographing screen are nine points from S01 to S23, and spot diameters 90 to 98 are provided for the respective focus detection positions.

  In general, the spot diameter range at the center of the photometry area is the narrowest, and the spot diameter range in the area away from the center is lost due to sharpness. Therefore, the correction coefficient r_r is set for each focus detection position spot diameter as shown in FIG. That is, the correction coefficient r_r is set such that the closer the position of the region where the main subject exists is to the center of the photometry region, the less the influence of the luminance value of the reference region when correcting the luminance value of the region where the main subject exists. change. In this way, it is possible to change the correction amount by changing the correction coefficient depending on whether the main subject is the central part or the peripheral part of the photometric region.

  As mentioned above, although preferable embodiment of this invention was described, this invention is not limited to these embodiment, A various deformation | transformation and change are possible within the range of the summary.

  For example, in the above-described two embodiments, the light receiving unit of the photometric sensor 26 is described as having 7 × 9 63 divisions, and the number of focus detection positions is nine, but the present invention is in such a case. It is not limited.

Claims (5)

Correction means for correcting the luminance value of the area where the main subject exists to a small value based on the luminance values of a plurality of reference areas adjacent to the area where the main subject exists in the photometry area;
A luminance value calculating means for calculating an average luminance value of an area including the main subject and an area including the plurality of reference areas, using the luminance value corrected by the correcting means;
Detecting means for detecting a luminance value of a high luminance region in the region for calculating the average luminance value;
Correction value calculation means for calculating an exposure correction value based on the corrected luminance value of the region where the main subject exists, the average luminance value, and the luminance value of the high luminance region;
An imaging apparatus comprising:   The imaging apparatus according to claim 1, wherein the area where the main subject exists is an in-focus area or a face area based on a focus detection result.   3. The correction unit according to claim 1, wherein the correction unit changes a correction coefficient used when correcting a luminance value of a region where the main subject exists based on a position of the region where the main subject exists. The imaging device described.   The correction means is such that the closer the position of the area where the main subject exists is to the center of the photometric area, the smaller the influence of the luminance value of the reference area when correcting the luminance value of the area where the main subject exists. The imaging apparatus according to claim 3, wherein the correction coefficient is changed. A correcting step for correcting the luminance value of the area where the main subject exists to a small value based on the luminance values of a plurality of reference areas adjacent to the area where the main subject exists in the photometry area;
A luminance value calculating unit that calculates an average luminance value of an area including the main subject and an area including the plurality of reference areas, using the luminance value corrected by the correcting unit;
A detecting step for detecting a luminance value of a high luminance region in the region for calculating the average luminance value;
A correction value calculating step in which a correction value calculating means calculates an exposure correction value based on the corrected luminance value of the region where the main subject exists, the average luminance value, and the luminance value of the high luminance region;
An exposure control method comprising: