JP2013044938A - Imaging apparatus and imaging method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform peripheral darkening correction of a photometric value so that exposure of a face is appropriate in flash photography.SOLUTION: Preliminary light emission is performed before main light emission in flash photography. A photometric part 32 measures a reflected light of a subject and transmits a photometric signal. A face detecting part 36 detects a face image area on the basis of the photometric signal. A photometric value calculating part 38 calculates a photometric value of the face image area detected by the face detecting part 36 before the preliminary light emission by using the preliminary light emission photometric signal obtained from photometric means at the preliminary light emission, and a preliminary light emission photometric value of a photometric area, respectively. A controlling part 41 obtains a first photometric value in which a normal light component is removed from the photometric value of the face image area, and a second photometric value in which the normal light component is removed from the photometric value of the photometric area, and performs peripheral darkening correction of the obtained first and second photometric values on the basis of lens information, and then calculates the quantity of light emission at the main light emission on the basis of the first and second photometric values in which the correction has been performed.

Description

  The present invention relates to an imaging apparatus and an imaging method.

  Conventionally, based on the image captured during preliminary flash photography, it is detected whether a human face area exists in the image, and then a light control area is determined according to the detected face area. There has been proposed an imaging apparatus that calculates a main light emission amount according to a photometric value at the time of preliminary light emission in the determined light control region (Patent Document 1).

JP 2005-184508 A

  However, in the invention described in Patent Document 1, since it is TTL photometry, it depends on lens characteristics of the photographing lens, for example, peripheral dimming in which the amount of light in the peripheral portion falls with respect to the central portion of the optical axis of the image, photographing magnification, and photographing distance. Depending on the characteristics such as the change in the amount of light, the photometric value changes depending on the position of the face region, which may prevent the flash light from being correctly controlled.

  An aspect of the imaging apparatus illustrating the present invention includes a photometry unit that measures a reflected light of a subject and sends a photometric signal, a main subject detection unit that detects a main subject region based on the photometric signal, and the preliminary light emission A photometric value acquisition unit that acquires a first photometric value obtained by removing a stationary light component from a photometric value of a main subject area detected by the main subject detection unit, using a preliminary emission photometric signal obtained from the photometric unit; And a photometric value correcting means for performing peripheral light reduction correction on the first photometric value based on information on characteristics of an optical system that guides reflected light of the subject.

  According to the present invention, it is possible to prevent the photometric value from changing according to the position of the main subject area.

1 is a block diagram illustrating an outline of a single-lens reflex electronic camera according to an embodiment of the present invention. It is a block diagram which shows the structure of a control part. It is a flowchart explaining the operation | movement procedure of the moving image shooting mode of a single-lens reflex electronic camera. 4 is a flowchart for explaining a continuation of the operation procedure described in FIG. 3. It is a timing chart which shows the operation | movement procedure of a single-lens reflex electronic camera. It is explanatory drawing for demonstrating the shape of the peripheral light reduction with respect to the image height in a photometry surface. It is explanatory drawing explaining the optical system for guide | inducing object light to the photometry surface of a photometry sensor. It is explanatory drawing which shows the pixel arranged in the matrix form on the photometry surface of the photometry sensor. It is explanatory drawing which shows each photometry area | region which performs division | segmentation photometry at the time of preliminary light emission. 6 is a graph for determining a weighting coefficient between a face area reflected light amount photometric value (photometric value B) and a full screen reflected light amount photometric value (photometric value A) used in calculating the main light emission amount according to the face size. It is explanatory drawing which demonstrates virtually the face detection frame which scanned the full screen of the photometry signal and detected the face image area | region.

  A single-lens reflex electronic camera (imaging device) 10 exemplifying one embodiment of the present invention includes a replaceable photographing lens 11, an aperture 12, a main mirror 13, a sub mirror 14, a focusing plate 15, a condenser lens 16, a pentaprism 18, an eyepiece. Lens 19, focal plane shutter (hereinafter referred to as “shutter”) 20, lens driving mechanism 22, aperture driving mechanism 23, mirror driving mechanism 24, distance measuring unit 25, shutter driving mechanism 26, imaging unit 21, and A / I for imaging D27, imaging buffer memory 28, imaging image processing unit 29, recording unit 30, operation unit 31, photometry unit 32, information acquisition unit 33, photometric A / D 33, photometric buffer memory 34, photometric Image processing unit 35, face detection unit 36, memory 37, photometric value calculation unit 38, flash control unit 39, flash light emitting unit 40, ROM 46, etc. With which, it is generally controlled by the control unit 41. The control unit 41, the image processing unit 29 for photographing, the recording unit 30, the image processing unit 35 for photometry, the face detection unit 36, the memory 37, and the photometric value calculation unit 38 are connected to the bus 42.

  A ROM 46 and a RAM 47 are connected to the control unit 41, and the ROM 47 stores a control program and the like that are referred to when the control unit 41 performs various controls. The control unit 41 controls each unit (circuit) using the RAM 47 as a temporary storage work area according to a control program stored in the ROM 46, and activates the function of each unit (circuit) of the electronic camera 10.

  In addition, the control unit 41 drives the information acquisition unit 33 at the time of lens replacement or after the replacement until shutter release is performed, and optical information (optical profile) from the photographing lens (interchangeable lens) 11 side. To get. This optical information is information for correcting optical characteristics such as distortion, aberration, and peripheral dimming of the photographing lens 11, and these information are stored in advance in a lens ROM 48 provided for each interchangeable lens. Yes. Further, information on the shooting distance acquired in response to the half-pressing operation of the release button and the magnification position (shooting magnification) acquired in response to the zoom operation are respectively acquired, and the acquired information is updated in the RAM 47. And remember.

  The operation unit 31 includes a power switch, a release button, a zoom operation unit, a mode selection operation unit, and the like. The mode selection operation unit is for selecting either the normal shooting mode or the flash shooting mode. In flash photography mode, preliminary light emission is performed before the main light emission.

  The flash control unit 39 controls preliminary light emission and main light emission based on the result of the preliminary light emission. The flash light emitting unit 40 and the flash control unit 39 constitute a built-in flash that compensates for the amount of light when light such as natural light is insufficient. This built-in flash can adjust the light emission amount of the flash. In flash photography, the control unit 41 calculates the main light emission amount based on the reflected light amount of the subject obtained during preliminary light emission, transmits a flash light emission signal including information on the main light emission amount to the flash control unit 39, and the flash control unit 39. However, the flash light emitting unit 40 emits light with the light emission amount to brighten the subject.

  The mirror driving mechanism 24 has a mirror-up position where the subject light passing through the photographing lens 11 is imaged on the imaging surface of the imaging unit 21 and a focusing plate disposed on a focal plane conjugate with the imaging surface in the finder optical path. The main mirror 13 is moved between the mirror-down position where the image is formed on the mirror 15.

  The lens driving mechanism 22 moves the photographing lens 11 in the optical axis direction to focus on the subject. A part of the main mirror 13 is a half mirror. The sub mirror 14 reflects the subject light beam incident from the half mirror and guides it to the distance measuring unit 25. The distance measuring unit 25 detects a phase difference signal from the incident subject luminous flux and sends the phase difference signal to the control unit 41 as a defocus amount with respect to the subject distance. The control unit 41 controls the lens driving mechanism 22 based on the defocus amount to move the photographing lens 11 to the in-focus position. The sub mirror 14 retracts from the optical axis in conjunction with the movement of the main mirror 13 to the mirror up position.

  The imaging unit 21 is an imaging sensor (CMOS sensor or CCD sensor) for capturing an image for recording. As is well known, the image sensor is provided with a Bayer array color filter (single-plate color filter) in front of the imaging surface.

  The imaging unit 21 captures a subject image and sends an image signal to the imaging A / D 27. The imaging A / D 27 converts the image signal into a digital image signal and temporarily stores it in the imaging buffer memory 28. The image signal read from the buffer memory 28 is sent to the image processing unit 29 for imaging. The image processing unit 29 performs processing such as white balance, RGB pixel interpolation, and YUV conversion on the image signal to generate recording image data, and sends the recording image data to the recording unit 30. The recording unit 30 records image data for recording.

  The photometric unit 32 includes an imaging optical system including an imaging lens 43, a prism 44, and the like, and a photometric sensor 45, which are arranged on the pentaprism 18. The imaging optical system re-images the subject image formed on the focusing screen 15 on the photometric surface of the photometric sensor 45. The subject image that passes through the photographing window 57 and the photographing lens 11 in order is formed on the focusing screen 15 after being reflected by the main mirror 13 set at the mirror down position. The subject image formed on the focusing screen 15 is transmitted through the pentaprism 18 through the condenser lens 16 to be converted into an erect image, magnified by the eyepiece lens 19, and observed through the viewfinder eyepiece window 58. The subject image formed on the focusing screen 15 forms an image on the photometric surface of the photometric sensor 45 via the condenser lens 16, the pentaprism 18, and the imaging optical systems 43 and 44.

  The photometric signal obtained from the photometric sensor 45 is digitally converted by the photometric A / D 33 and then temporarily stored in the photometric buffer memory 34. The photometric signal read from the photometric buffer memory 34 is interpolated into a photometric signal for each RGB by the photometric image processing unit 35, and then a luminance signal is generated from the photometric signal for each RGB. This luminance signal is temporarily stored in the memory 37. Optical information (optical profile) for correcting optical characteristics such as distortion, aberration, and peripheral light reduction of the optical members such as the imaging optical systems 43 and 44 of the photometry unit 32 and the condenser lens 16 is stored in the ROM 46 in advance. It is stored, and is used when the control unit 41 performs light reduction peripheral correction of the photometric value.

  In the photometric sensor 45, photoelectric conversion elements (pixels) composed of, for example, a CMOS or a CCD are two-dimensionally arranged. The photometric sensor 45 is driven according to the control of the control unit 41. The photometric sensor 45 is provided with a Bayer array color filter (single plate color filter) in front of the photometric surface. The photometric signal output from the photometric sensor 45 is converted into a digital photometric signal by the photometric A / D 33 and then temporarily stored in the buffer memory 34. The photometric signal read from the buffer memory 34 is sent to the image processing unit 35 for photometry. As the photometric signal output from the photometric sensor 45, a photometric signal obtained from a pixel in a photometric area of a small size except for the periphery of the photometric surface, which is substantially the same as the imaging area, is used. The photometric signal obtained from the pixels in the photometric area is converted into a digital photometric signal by the photometric A / D 33 and then temporarily stored in the buffer memory 34. The photometric signal read from the buffer memory 34 is sent to the image processing unit 35 for photometry.

  The photometric image processing unit 35 interpolates the Bayer array photometric signals into RGB photometric signals and performs processing such as extracting a luminance signal (Y) from the RGB photometric signals. The face detection unit 36 detects a human face image region (main subject region) based on the luminance signal (Y) described above. Instead of the luminance signal, face detection may be performed based on a photometric signal of one color component, for example, a G color component, among the three color components of RGB. As the color filter in this case, a color filter including two G filters in each column and each row constituting the matrix is preferable.

  In the memory 37, information such as the photometric signal and luminance signal for each RGB obtained from the photometric image processing unit 35, and the position and size (size) of the face image area detected by the face detecting unit 36 are updated. Remembered. The photometric value calculation unit 38 calculates a photometric value based on the luminance signal stored in the memory 37.

  When the release button is fully pressed in the flash photographing mode, the control unit 41 controls the flash control unit 39 to perform preliminary light emission. The control unit 41 causes the photometric sensor 45 to perform an accumulation operation in accordance with the preliminary light emission of the flash light emitting unit 40. The signal obtained by the accumulation operation is input to the photometric A / D 33 as described above.

  The control unit 41 controls the main flash for the flash control unit 39 based on the TTL dimming calculation result. Hereinafter, the charge accumulation operation performed by the photometric sensor 45 during preliminary light emission is referred to as preliminary light emission photometry. Further, the charge accumulation operation performed by the photometric sensor 45 when no light is emitted is referred to as steady-state photometry.

  As shown in FIG. 2, the control unit 41 includes a calculation unit 50, a determination unit 51, a main light emission amount calculation unit 52, a main light emission amount correction unit 53, and a re-preliminary light emission processing unit 54. In order to calculate the main light emission amount corresponding to the subject reflected light amount, the calculation unit 50 performs an operation of removing (subtracting) the steady light amount, that is, the steady light metering value representing the steady light component of the subject, from the preliminary light metering value ( Subtraction process). The photometric value obtained after the subtraction process is called the reflected light amount photometric value.

  Based on the optical information read from the ROM 46 and the RAM 47 and information such as the photographing distance and the photographing magnification acquired from the photographing lens 11, the photometric value correcting unit 56 reflects the amount of reflected light metering value so that the peripheral dimming characteristic becomes flat. Correct. This dimming peripheral correction is an optical system for guiding subject light to the photometric surface of the photometric sensor 45, that is, peripheral dimming in the photographing lens 11, condenser lens 16 and imaging optical systems 43 and 44, photographing magnification, This is a correction that takes into account the dimming associated with the shooting distance and the aberrations and distortions of the optical system.

  The determination unit 51 determines whether the photometric result of the photometric sensor 45 and the preliminary light emission photometric value satisfy a predetermined condition. When the preliminary light emission metering value exceeds a predetermined threshold value, it is determined that the light emission amount during the preliminary light emission is large, and a re-emission signal is sent to the re-pre-light emission processing unit 54. The re-preliminary light emission processing unit 54 controls the flash control unit 39 so as to reduce the light emission amount and execute the preliminary light emission again. Conversely, when the photometric value is less than the threshold value, the determination unit 51 drives the main light emission amount calculation unit 52. The main light emission amount calculation unit 52 calculates the light emission amount during the main light emission of the flash based on the reflected light amount photometric value.

  By the way, the preliminary light emission is performed with an open aperture. For this reason, the above-described main light emission amount may be different from the aperture value at the time of shooting. The main light emission amount correcting unit 53 corrects the main light emission amount based on the aperture value and ISO sensitivity at the time of shooting. Then, the main light emission amount correcting unit 53 controls the flash control unit 39 to execute the main light emission based on the corrected main light emission amount. Note that preliminary light emission may be performed by driving the aperture to an aperture value with proper exposure.

  Next, the operation of the above configuration will be described with reference to the drawings. 3 and 4 are flowcharts for explaining the operation procedure in the flash photographing mode of the single-lens reflex electronic camera. First, after the power button is turned on (S-1), the flash shooting mode is selected (S-2). Here, it is confirmed in order whether the shutter 20 is set at the closed position and whether the main mirror 13 is set at the mirror-down position. If neither is set, the closed position and the mirror down position are forcibly set.

  FIG. 5 is a timing chart for explaining the drive timing of each part of the single-lens reflex electronic camera. When the flash photographing mode is selected, the control unit 41 drives the photometric sensor 45 at time t1 shown in FIG. Before the release button is fully pressed, that is, before the photographing instruction operation is performed by the user, the photometry sensor 45 performs steady light metering (exposure steady light metering) at predetermined intervals (S-3). A photometric value obtained by this constant light metering is called a steady light metering value. Based on the steady light metering value, the control unit 41 calculates a proper exposure value BVans related to the steady light exposure using a known metering method (multi-pattern metering method or the like), and determines an aperture value and a shutter speed. The steady light metering value and the steady light exposure value BVans are updated every predetermined period and stored in the memory 37.

  The luminance signal is read from the memory 37 and sent to the face detection unit 36. The face detection unit 36 detects the position and size of the face image area based on the luminance signal at time t2. The position and size of the detected face image area are stored in the memory 37. Thereafter, until the shutter release is performed, the series of cycles from the photometry to the face detection / storage described above are repeated at a predetermined cycle (S-3). Therefore, the memory 37 always stores the latest luminance signal and the position / size of the face image area.

  After the face detection, the control unit 41 drives the information acquisition unit 33 to acquire optical information from the lens ROM 48 and store it in the RAM 48. The control unit 41 acquires the optical information of the condenser lens 16 and the imaging optical systems 43 and 44 from the ROM 47 and stores them in the RAM 48. Then, the control unit 41 reads out the optical information, the shooting distance, the shooting magnification, and the like stored in the RAM 48, and calculates the peripheral darkening correction value of each pixel constituting the entire screen of the photometric surface.

  Here, peripheral dimming will be described with reference to FIG. FIG. 5A shows the amount of light incident on the photometric surface of the photometric sensor 45 when there is peripheral light reduction. Peripheral dimming is due to the optical characteristics of the photographic lens 11, the condenser lens 16, the imaging optical systems 43 and 44, etc., and the amount of light at the periphery of the entire screen drops concentrically with respect to the optical axis center L0 of the imaging lens 43. It is a phenomenon that gets darker. In the figure, for the sake of easy understanding, the change in the amount of light is described as being concentrically changed in a staircase pattern, but in actuality, it changes smoothly within the luminance gradation range.

  The graph of FIG. 6B is a graph showing a change in output level (peripheral dimming characteristic 59) when the photometric surface of the photometric sensor 45 is cut by a diagonal line (two-dot chain line A-A ′). In the graph of FIG. 5B, the horizontal axis indicates the image height, and the vertical axis indicates the output level. Here, the image height r at the optical axis center L0 on the photometric surface of the photometric sensor 45 is set to “0” mm, the output level is set to “1.0”, and equidistant positions (images) concentrically extending from the optical axis center L0. When the change of the output level for each (high) is drawn, it becomes like the peripheral dimming characteristic 59, and the output level is lowered toward the periphery of the photometric surface.

  For example, as shown in FIG. 7, the peripheral dimming shape includes the incident angle of light incident on the photometric surface of the photometric sensor 45, the diameters of the photographing lens 11, the condenser lens 16, and the imaging optical systems 43 and 44. The aperture diameter (open aperture in this embodiment) S of the diaphragm 12 and the distance from the photometric sensor 45 to the photographing lens 11, the diaphragm 12, the condenser lens 16, and the imaging optical systems 43 and 44 differ. Further, when the photographing lens 11 is a zoom lens, the shape of the peripheral dimming changes according to the zoom position. The control unit 41 calculates the shape of the peripheral dimming based on such optical / photographing information, and based on the shape of the peripheral dimming, the face area reflected light metering value (to be described later in detail) (the first photometry of the present invention). Value) is corrected.

  Specifically, the control unit 41 obtains, for example, a peripheral light amount correction value for each image height based on the above-described optical / photographing information. Then, the peripheral light amount correction value for each pixel is obtained by interpolation from the peripheral light amount correction value for each image height. Since the peripheral light amount correction value for each pixel is a correction value for the pixels of the entire screen, the peripheral light amount correction value for each pixel in the face image area detected immediately before is extracted from the correction values of the pixels of the entire screen, and the face image is extracted. An average value (face area dimming correction value) obtained by averaging the peripheral light amount correction values for each pixel in the area is calculated, and the face area dimming correction value is stored in the RAM 47.

  The control unit 41 monitors the half-press operation of the release button (S-4), and executes the shooting preparation operation in response to the half-press operation being performed (S-5). In the shooting preparation operation, the distance measuring unit 25 is driven, and the lens driving mechanism 22 is controlled based on the defocus amount obtained from the distance measuring unit 25 to move the shooting lens 11 to the in-focus position.

  The control unit 41 monitors whether the full-press operation (shooting instruction operation) is performed as it is from the half-press operation state (S-6), and when the user performs the shooting instruction operation at time t3, the digital camera The ten control units 41 output a preliminary light emission instruction signal for instructing preliminary light emission to the flash control unit 39 (S-7). When the preliminary light emission instruction signal is input, the flash control unit 39 causes the flash light emission unit 40 to perform preliminary light emission at a predetermined preliminary light emission amount at time t4. As a result, as shown in FIG. 5, the flash light emitting unit 40 performs preliminary light emission in the accumulation time Δt.

  When the preliminary light emission instruction signal is output by the flash control unit 39, the control unit 41 causes the photometric sensor 45 to accumulate charges in the period Δt while the flash light emission unit 40 is emitting light. In this case, the photometric sensor 45 emits light from the flash light emitting unit 40, is reflected by the subject, and enters through the photographing lens 11 (subject reflected light amount) and ambient light (steady light) of the subject. A charge signal corresponding to the above is output to the A / D 33. The photometric value calculating unit 38 calculates a preliminary light emission photometric value from the preliminary light emission photometric result (S-8).

  Immediately after the preliminary light metering is performed, that is, after the sweep of the charges accumulated by the preliminary light metering is completed, the control unit 41 causes the photometric sensor 45 to accumulate charges in the period Δt at time t5. In other words, the photometric sensor 45 performs charge accumulation for a period Δt following the preliminary light metering (S-9). The period Δt is the same as the preliminary light metering time. In this case, the photometric sensor 45 sends a charge signal to the A / D 33 according to the amount of light incident through the photographing lens 11 when no light is emitted, that is, the amount of stationary light that is ambient light of the subject. Output. The photometric value calculation unit 38 calculates a steady light photometric value from the steady light photometric result (S-10).

At time t6, the calculation unit 50 calculates the total screen reflected light amount photometric value (photometric value A) (second photometric value of the present invention) and face area reflected light amount photometric value (photometric value B) (first photometric value of the present invention). ) Is calculated.
First, calculation of the full screen reflected light amount photometric value (photometric value A) will be described.
As shown in FIG. 8, since the photometric sensor 45 includes a plurality of pixels (photoelectric conversion elements) arranged in a matrix, the preliminary light-emission photometric value also includes a plurality of data. In this embodiment, the preliminary light emission photometric value is divided into five areas as shown in FIG. These photometric values are referred to as 5-split preliminary emission photometric values (photometric values C [i]). i is 0-4. Each of the five-split preliminary emission photometric values (photometric values C [i]) is calculated from the average value. The number of divided regions is not limited to “5”, and any number of divided regions may be used.

Further, a 5-division stationary light metering value (photometric value D [i]) is calculated from the stationary light metering value acquired immediately after the preliminary light emission. The calculation method is the same as the five-split preliminary light-emission photometric value (photometric value C [i]).
Next, the stationary light component is removed by subtracting the 5-split stationary light photometric value (photometric value D [i]) from the 5-split preliminary emission photometric value (photometric value C [i]). The obtained photometric value is defined as a five-part reflected light amount photometric value (photometric value E [i]).

Further, the photometric value correction unit 56 reads out the peripheral light reduction correction value corresponding to each pixel of the photometric sensor from the RAM 47 at time t7. From the read out peripheral light correction value, the peripheral light correction value KZ5 [i] of the 5-part metering value is calculated.
A full-screen reflected light amount metering value (photometric value A) is calculated from the five-part reflected light amount metering value (metering value E [i]) and the peripheral light reduction correction value KZ5 [i] of the five-part metering value (S-11). In the present embodiment, as described in [Equation 1], (photometric value E [i]) is weighted and calculated by combining.

[Equation 1]
Photometric value A = 0.33 * E [0] * KZ5 [0] + 0.16 * E [1] * KZ5 [1] + 0.16 * E [2] * KZ5 [2] + 0.16 * E [3 ] * KZ5 [3] + 0.16 * E [4] * KZ5 [4]

  The calculation of the face area reflected light amount photometric value (photometric value B) will be described. From the preliminary light emission photometric value, the photometric value in the face image area detected by the face detection unit 36 before the preliminary light emission and the face area preliminary light emission photometric value (photometric value F) are calculated. As the face image area at this time, position information of the face image area detected before the preliminary light emission and stored in the memory 37 is used.

A face area steady light photometric value (photometric value G (third photometric value of the present invention)) is calculated from the steady light photometric value acquired immediately after the preliminary light emission. The calculation method is the same as the face area preliminary light emission photometric value (photometric value F). From the read out peripheral light attenuation correction value, a peripheral area light attenuation correction value KZKao is calculated.
As described in [Equation 2], the face area reflected light amount photometric value (photometric value B) is obtained by subtracting the face area stationary light photometric value (photometric value G) from the face area preliminary light emission photometric value (photometric value F), It is calculated by multiplying the peripheral region darkening correction value KZKao (S-12).

[Equation 2]
Photometric value B = (Photometric value F−Photometric value G) * KZKao

  The determination unit 51 compares the photometric value F corrected for peripheral light reduction with the threshold value H at time t8 (S-13). As a result of the comparison, if the photometric value F exceeds the threshold value H, that is, the face image region When the luminance value is saturated, the re-preliminary light emission processing unit 54 is controlled so as to reduce the light amount and execute the preliminary light emission again (S-14).

  The determination unit 51 drives the main light emission amount calculation unit 52 when the photometric value F is less than the threshold value H, that is, when the luminance value of the face image region is not saturated. The main light emission amount calculation unit 52 reads the full-screen reflected light amount photometric value (photometric value A) stored in the memory 37 at time t9, and based on the read photometric value A and the photometric value B. Then, the main flash amount is calculated (S-15). Here, the reflected light amount photometric value for calculating the main light emission amount used for calculating the main light emission amount is obtained using the equation described in [Equation 3].

[Equation 3]
RMmain = (1.0−K) × RMAll + K × RMKao
RMmain is a reflected light photometric value for calculating the amount of emitted light, RMAll is a photometric value A, RMKao is a photometric value B, and K is a coefficient of “1” or less.

  The reflected light amount photometric value (RMmain) for light emission amount calculation is calculated by changing the coefficient K for weighting the photometric value A and the photometric value B as shown in [Equation 3]. As shown in FIG. 10, the weighting coefficient K is determined according to the size of the face image area (face detection frame 55) detected by the face detection unit. That is, as the face size increases with respect to the photometric area, the value of the coefficient K is brought closer to “1”, and the weight of the photometric value B is set higher than the photometric value A to obtain the reflected light photometric value for calculating the main light emission amount. As a result, it is possible to reliably prevent the face from being overexposed and overexposure during flash photography. The face size at this time is the vertical length of the face detection frame 55 when a face image is detected, as shown in FIG. The coefficient K is “1” when the photometry area and the vertical length of the face detection frame 55 are substantially the same. The coefficient K is a coefficient corresponding to the vertical length of the face detection frame 55 with respect to the photometric area because the face detection frame 55 is square. However, when the face detection frame 55 is circular, rectangular, or triangular, Alternatively, a coefficient corresponding to the horizontal length, area, or the like may be used.

  The main light emission amount correcting unit 53 corrects the main light emission amount according to the aperture value and ISO sensitivity (S-16). At this time, if the aperture value is a value that cannot be set in the aperture 12, the ISO sensitivity is changed. In this case, the main light emission amount correcting unit 53 corrects the main light emission amount according to the changed ISO sensitivity in addition to the aperture value. Then, the flash control unit 39 causes the flash light emitting unit 40 to perform main light emission with the corrected main light emission amount at time t10 (S-17). This flash main light emission is executed in synchronization with the photographing operation (S-18).

  In the photographing operation, the mirror driving mechanism 24 is controlled so as to perform a flip-up operation for moving the main mirror 13 to the mirror-up position for a moment, and during this time, the shutter 20 is driven based on the determined shutter speed (front curtain). Opening and closing of the rear curtain). While the shutter 20 is opened and closed, the imaging unit 21 captures a subject image. The image data acquired by the imaging unit 21 is accumulated in the imaging buffer memory 28 via the imaging A / D 27, and the image data read from the buffer memory 28 is sent to the image processing unit 29, where various kinds of data are obtained. After the image processing is performed, the image data is recorded by the recording unit 30 as recording image data (S-19). Hereinafter, the above-described operation is repeated until the power switch is turned off (S-20).

  In the above embodiment, the face detection unit 36 detects the face image area based on the luminance signal. However, the present invention is not limited to this, and the skin color is based on the luminance signal converted from the RGB signal and the color difference signal. The face image area may be detected by detecting the area.

  In each of the above embodiments, the color filter provided in the photometric sensor 45 is an additive color mixed three primary color RGB color filter, but a primary color mixed CMY color filter may be provided instead. Further, an infrared cut filter that senses only light in the visible light range may be provided before the color filter.

  In each of the above embodiments, the built-in flash has been described. Needless to say, in the present invention, even when an external flash is used, the same procedure as described with reference to FIGS. The external flash is provided with a flash light emitting unit 40 and a flash control unit 39, and the flash control unit 39 is electrically connected to the control unit 41 on the electronic camera side through the terminal of the accessory shoe. When an external flash is used, the built-in flash is prohibited. As a difference in control on the electronic camera side, in the case of external flash photography, preliminary light emission is initially performed with a weak light emission amount, and the determination unit 51 compares the photometric value B with a predetermined threshold value I to obtain a photometric value B. When it is determined that it is less than the threshold value I, that is, when it is determined that the flash light is too weak to reach the subject, the second time is that the preliminary light emission is performed by increasing the light emission amount. However, the photometric value E may be used as the photometric value to be compared with the threshold value I.

  In each of the above embodiments, the imaging unit 21 has been described as a single-plate type imaging sensor, but may be a three-plate type imaging unit having three imaging sensors. The photometric unit 32 may also be a three-plate type photometric unit having three photometric sensors.

  In each of the above-described embodiments, the photometric value may be calculated based on the entire photometric signal screen during the preliminary light emission (the same photometric area as the imaging area). However, in order to simplify the processing, The photometric value may be calculated with respect to a small-sized screen from which a part is cut. In this case, the detection of the face image area and the calculation of the peripheral darkening correction value for each pixel may be performed on a small size screen. If the photometric value is calculated from a small-sized screen with the periphery cut off, the influence of the peripheral dimming can be avoided and the effort for correcting the peripheral dimming can be reduced.

  In each of the above embodiments, a case where one face image area is detected in the screen has been described. However, when a plurality of face image areas are detected in the screen, the face detection unit 36 is located at the center of the screen. A face image region that is positioned or a face image region having the largest face detection frame (face size) is selected as a main subject region, and a photometric value may be acquired from one main subject region selected by the photometric value calculation unit 38. Of course, when a plurality of face image areas are detected near the center of the screen, or when a plurality of largest face detection frames (face sizes) are detected, the face detection unit 36 selects the plurality of face image areas. The photometric value calculation unit 38 may select the main subject area and acquire the photometric value obtained by averaging the photometric values of the face image areas as the photometric value of the main face image area.

  In each of the above embodiments, the face detection unit 36 is provided. However, the present invention is not limited to this, and a person detection unit is provided instead of the face detection unit 36 so that the person detection unit detects a person as a main subject. It may be configured. In this case, the photometric value calculation unit 38 may acquire the photometric value based on the detected person image area. Of course, instead of the person detection unit, an animal detection unit may be provided so that the detected animal image region is detected as a main subject, and the photometric value calculation unit 38 acquires the photometric value based on the detected animal image region. Good.

  In each of the above embodiments, the calculation unit 50 calculates the total screen reflected light amount photometric value (photometric value A) by split photometry at the time of preliminary light metering and at the time of steady light photometry, but the average that averages the photometric values of all pixels. The photometric value A may be obtained by photometry.

  In each of the above-described embodiments, the main flash emission amount is calculated based on the photometric value A and the photometric value B. However, the present invention is not limited to this, and subject distance information from the photographing lens or focus detection unit is not limited thereto. In consideration of the above, the main light emission amount may be calculated.

  According to the above embodiment, the first photometric value (main subject region reflected light amount photometric value (photometric value B)) at the time of preliminary light emission in which the stationary light of the main subject region for determining the main light emission amount at the time of flash photography is removed. On the other hand, since the peripheral light reduction correction is performed, it is possible to prevent the photometric value from changing according to the position of the main subject region.

DESCRIPTION OF SYMBOLS 10 Single-lens reflex electronic camera 11 Shooting lens 13 Main mirror 15 Focus plate 45 Photometric sensor 36 Face detection part 38 Photometric value calculation part 56 Photometric value correction part

Claims (6)

In an imaging device that performs preliminary light emission before the main light emission during flash photography,
Photometric means for measuring the reflected light of the subject and sending a photometric signal;
Main subject detection means for detecting a main subject region based on the photometric signal;
A photometric value acquisition unit that acquires a first photometric value obtained by removing a stationary light component from a photometric value of a main subject area detected by the main subject detection unit, using a preliminary emission photometric signal obtained from the photometry unit during the preliminary emission. When,
A photometric value correcting unit that performs peripheral light reduction correction on the first photometric value based on characteristics of an optical system for guiding reflected light of the subject to the photometric unit;
An imaging apparatus comprising: The imaging device according to claim 1,
The photometric value acquisition means acquires a second photometric value obtained by removing a stationary light component from a photometric value in a photometric area using the preliminary emission photometric signal during the preliminary emission,
The photometric value correcting means corrects the peripheral light reduction for the second photometric value based on the characteristics of the optical system,
A main light emission amount calculating means for calculating a light emission amount during the main light emission based on the corrected first photometric value and the second photometric value;
An imaging apparatus characterized by that. The imaging device according to claim 1 or 2,
A recording image pickup means for picking up an image of a subject imaged on an image pickup surface by a photographic lens for recording;
The imaging device, wherein the photometric means is a photometric imaging means for imaging a subject image formed on a plane conjugate with the imaging surface at a position different from the imaging means. The imaging device according to any one of claims 1 to 3,
The photometric value acquisition means calculates the first photometric value by subtracting a third photometric value acquired before or after the preliminary light emission from a main subject region preliminary light emission photometric value acquired at the time of preliminary light emission in the main subject region. An imaging apparatus characterized by the above. The imaging device according to claim 2,
The main light emission amount calculating unit weights the corrected first photometric value as the size of the main subject region used when the photometric value acquiring unit acquires the first photometric value is larger than the photometric region. An imaging apparatus, wherein the main light emission amount is calculated by raising the second photometric value. In the imaging method for determining the amount of light emission based on the photometric value at the time of preliminary light emission obtained by performing preliminary light emission at the time of flash photography,
A photometric step of measuring the reflected light of the subject and sending a photometric signal;
A main subject detection step for detecting a main subject region based on the photometric signal;
A photometric value acquisition step of acquiring a first photometric value obtained by removing a stationary light component from a photometric value of a main subject area detected by the main subject detection unit, using a preliminary light metering signal obtained from the photometry unit during the preliminary light emission. When,
A photometric value correction step for performing peripheral light reduction correction on the first photometric value based on characteristics of an optical system for guiding reflected light of the subject to the photometric means;
An imaging method comprising:

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