JP2008083243A - Photographing device and exposure control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photographing device capable of performing optimum exposure control and setting of photographing sensitivity, especially, for a subject in a short distance when performing flash photography, and to provide an exposure control method. <P>SOLUTION: When a photographing switch is half depressed (S1 on), AE processing and AF processing are performed (steps S10 and S12), the photographing sensitivity is set to high sensitivity (step S14), and a pre-light emission image is fetched (step S16). Next, the integrated value of an image signal of every divided area of the pre-light emission image is acquired (step S18), and the number LF of the divided areas whose integrated value is larger than a threshold A is counted (steps S22 to S28). When LF is equal to or under a threshold B (No in step S30), photographing sensitivity, exposure value and light emitting time in normal light emission are calculated and set based on the pre-light emission image (steps S32 and S34), and normal light emission photography is performed (step S36). Meanwhile, when LF is larger than the threshold B (Yes in step S30), the photographing sensitivity is made low (Yes in step S38, and step S40), and pre-light emission is performed again. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a photographing apparatus and an exposure control method, and more particularly to a technique for controlling exposure during flash photography.

  Conventionally, when flash photography is performed, the distance to the subject is measured, and when the measured distance is greater than the distance at which the amount of main flash is underexposed, the video signal gain is increased accordingly. It has been proposed to correct image quality degradation due to insufficient exposure (for example, Patent Documents 1, 2, and 4).

  In Patent Document 3, preliminary light emission of a certain amount of light is performed a plurality of times, the output signal of the image sensor obtained for each preliminary light emission is amplified with different amplification factors, and the average level of the amplified output signals is within a predetermined range. A strobe device that calculates the amount of light emission based on a certain one is disclosed. Patent Document 3 discloses a strobe device that measures the distance to a subject and controls the amount of preliminary light emission based on the measured distance.

Patent Document 5 discloses an imaging device that controls strobe light emission means based on the detection result of a human face (whether the face occupies the screen or whether it is backlit). Further, in Patent Document 6, a light control area is determined according to a face area detected from a captured image, and imaging is performed to calculate a main light emission amount according to a photometric value at the time of pre-light emission in this light control area. An apparatus is disclosed.
JP-A-6-121225 JP 11-41515 A JP-A-11-84489 JP 2000-134533 A JP 2003-107567 A JP 2005-184508 A

  Recently, the sensitivity of electronic cameras has been increasing. However, when flash photography is performed with the photographing sensitivity set to high sensitivity, a phenomenon called white stripes occurs in which a subject having a certain brightness or more (particularly, a subject at a short distance) is completely white.

  In the above Patent Documents 1, 2, and 4, the amplification factor of the output signal is controlled by the distance information to the subject. However, when the shooting environment is dark and the distance information to the subject cannot be measured, the distance information is There was a problem that it was not possible to obtain an appropriate amplification factor. Further, in Patent Document 3, since the light amount of the main light emission is calculated based on the average level of the amplified output signal, the average of the output signal is averaged if part of the image is white and other parts are dark. There is a problem that the light amount of the main light emission cannot be controlled so that the level falls within a predetermined range and avoids white stripes. Further, Patent Documents 5 and 6 do not consider the setting of photographing sensitivity.

  The present invention has been made in view of such circumstances, and provides a photographing apparatus and an exposure control method capable of performing optimum exposure control and photographing sensitivity setting particularly for a subject at a short distance during flash photographing. The purpose is to do.

  In order to solve the above-described problems, a photographing apparatus according to the first aspect of the present invention includes a photographing unit that photographs a subject image, an illumination unit that emits light during photographing to illuminate the subject, and the illumination unit prior to the main flash photographing. Pre-flash control means for performing pre-flash photography with the photographing means, and dividing the pre-flash image obtained by the pre-flash photography into predetermined divided areas, and integrating image signals for each divided area A calculating unit that calculates a value, a determining unit that determines whether to perform pre-flash shooting again based on the integrated value, and a previous pre-flash when the determination unit determines that pre-flash shooting is to be performed again When the shooting sensitivity is lowered from the time of shooting and the pre-flash control means performs pre-flash shooting, and when the determination means determines that pre-flash shooting is not performed again, Characterized in that it comprises and exposure control means for performing exposure control at the time of the flash shooting based on previous pre-emission image acquired by the pre-flash photography.

  According to the first aspect of the present invention, the pre-light emission is performed with the photographing sensitivity lowered until the integrated value of the divided areas calculated from the pre-light emission image becomes a preferable value, so that a subject at a close distance is particularly overexposed. Can be prevented.

  The photographing apparatus according to the second aspect of the present invention includes a photographing unit that captures an image of a subject, an illuminating unit that emits light at the time of photographing to illuminate the subject, and pre-lights the illuminating unit prior to the main flash photographing, and the photographing device Pre-flash control means for performing pre-flash shooting by means, and a calculation means for dividing the pre-flash image acquired by the pre-flash shooting into predetermined divided areas and calculating an integrated value of the image signal for each divided area; A determination unit that determines whether to perform pre-flash photography again based on the integrated value, and a light emission amount of the illumination unit from the previous pre-flash photography when the determination unit determines to perform pre-flash photography again. And the control unit that performs pre-flash shooting by the pre-flash control unit, and the previous pre-flash shooting when the determination unit determines that the pre-flash shooting is not performed again. Characterized in that it comprises and exposure control means for performing exposure control at the time of the flash shooting based on more acquired pre-emission image.

  According to the second aspect of the present invention, the pre-emission is performed by reducing the light emission amount (emission time or emission intensity) of the illumination unit until the integrated value of the divided areas calculated from the pre-emission image becomes a preferable value. It is possible to prevent a subject at a distance from being overexposed.

  Invention 3 of the present application is the imaging device according to Invention 1 or 2, wherein the determination means again when the number of divided areas in which the integrated value calculated from the pre-flash image exceeds a predetermined value is equal to or less than the predetermined number. The pre-flash photographing is determined not to be performed.

  According to the third aspect of the present invention, the pre-light emission is performed by reducing the photographing sensitivity or the light emission amount of the illumination unit until the number of divided areas having a high integrated value is equal to or less than the predetermined value. Can be prevented.

  Invention 4 of the present application is the imaging apparatus of Invention 3 of the present application, wherein the exposure control means is a divided area where the integrated value exceeds a predetermined value in a pre-flash image acquired by setting the imaging sensitivity to a minimum sensitivity that can be set. If the number is greater than the predetermined number, exposure control during main flash photography is performed based on the pre-flash image acquired with the minimum sensitivity.

  In the fourth aspect of the present invention, when the number of integrated values does not become a predetermined value or less even when the photographing sensitivity is minimized, the exposure control during the main flash photographing is performed based on the pre-flash image acquired with the minimum sensitivity. Is.

  The photographing apparatus according to the fifth aspect of the present invention includes a photographing unit that captures an image of a subject, an illuminating unit that emits light during photographing to illuminate the subject, and the illumination under a setting of different photographing sensitivity prior to the main flash photographing. A pre-flash control means for performing pre-flash photography with the photographing means, and a plurality of pre-flash images obtained by the pre-flash photography are each divided into predetermined divided areas, A calculation unit that calculates an integrated value of image signals for each area, a selection unit that selects a pre-emission image used for exposure control among the plurality of pre-emission images based on the integration value, and a selection unit that is selected by the selection unit. Exposure control means for performing exposure control during main flash photography based on the pre-flash image.

  According to the fifth aspect of the present invention, by performing exposure control using a pre-emission image having a preferable integrated value of divided areas, it is possible to prevent a subject at a particularly short distance from being overexposed.

  A sixth aspect of the present invention is the photographing apparatus according to the fifth aspect of the present invention, wherein the selecting means selects a pre-flash image captured with the highest photographing sensitivity among pre-flash images not including a divided area where the integrated value exceeds a predetermined value. It is characterized by that.

  According to the sixth aspect of the present invention, the maximum value of the integrated values of the divided areas obtained from the pre-emission image is equal to or less than a predetermined value, that is, the pre-emission image that does not include the divided area that has reached the peak value or saturated. By performing exposure control based on the image captured with the highest imaging sensitivity among them, it is possible to prevent a subject at a particularly short distance from being overexposed.

  Invention 7 of the present application is the imaging apparatus according to Inventions 1 to 6 of the present application, wherein the exposure control means controls at least one of photographing sensitivity, exposure value, light emission time or light emission intensity of the illumination means at the time of main flash photography. It is characterized by.

  The exposure control method according to the eighth aspect of the present invention includes: a photographing step for photographing an image of a subject; a pre-flash control step for performing pre-flash photographing by pre-lighting the illumination unit prior to the main flash photographing; and the pre-flash photographing. A calculation step of dividing the acquired pre-flash image into predetermined divided areas and calculating an integrated value of the image signal for each divided area, and a determination for determining whether to perform pre-flash photography again based on the integrated value And a control step in which the pre-flash photography is performed again at a lower sensitivity than the previous pre-flash photography when it is determined that the pre-flash photography is performed again in the determination step, and the pre-flash photography is performed again in the determination step. An exposure control step of performing exposure control during main flash photography based on a pre-flash image acquired by the previous pre-flash photography when it is determined that shooting is not performed. And butterflies.

  The exposure control method according to the ninth aspect of the present invention includes a photographing step for photographing an image of a subject, a pre-flash control step for performing pre-flash photographing by pre-lighting the illumination unit prior to the main flash photographing, and the pre-flash photographing. A calculation step of dividing the acquired pre-flash image into predetermined divided areas and calculating an integrated value of the image signal for each divided area, and a determination for determining whether to perform pre-flash photography again based on the integrated value And a control step of performing pre-flash shooting by the pre-flash control step when the pre-flash shooting is determined to be performed again in the determination step, and the amount of light emitted from the illuminating unit is decreased from the previous pre-flash shooting. When it is determined that the pre-flash photography is not performed again in the determination step, the exposure control during the main flash photography is controlled based on the pre-flash image acquired by the previous pre-flash photography. Characterized in that it comprises a Cormorant exposure control process.

  Invention 10 of the present application is the exposure control method of Invention 8 or 9, wherein, in the determination step, the number of divided areas where the integrated value calculated from the pre-emission image exceeds a predetermined value is equal to or less than a predetermined number, It is characterized in that it is determined not to perform pre-flash photography again.

  Invention 11 of the present application is the exposure control method according to Invention 10 of the present application, wherein in the exposure control step, in the pre-flash image obtained by setting the photographing sensitivity to a minimum settable sensitivity, the integrated value exceeds a predetermined value. When the number of areas is greater than a predetermined number, exposure control during main flash photography is performed based on the pre-flash image acquired with the minimum sensitivity.

  In the exposure control method according to the present invention 12, the pre-flash shooting is performed by pre-flashing the illuminating means a plurality of times under the setting of different shooting sensitivities prior to the shooting process of shooting the subject image and the main flash shooting. A light emission control step, a calculation step of dividing each of the plurality of pre-flash images acquired by the pre-flash photography into predetermined divided areas, and calculating an integrated value of the image signal for each of the divided areas; and A selection step of selecting a pre-flash image to be used for exposure control from among the plurality of pre-flash images, and an exposure control step of performing exposure control during main flash photography based on the pre-flash image selected in the selection step It is characterized by providing.

  Invention 13 of the present application is the exposure control method of Invention 12 of the present application, wherein in the selection step, a pre-emission image photographed with the highest imaging sensitivity is selected from pre-emission images not including divided areas in which the integrated value exceeds a predetermined value. It is characterized by doing.

  Invention 14 of the present application is the exposure control method of Inventions 8 to 13 of the present application, wherein in the exposure control step, at least one of photographing sensitivity, exposure value, light emission time or light emission intensity in the illumination step is controlled. It is characterized by that.

  According to the present invention, by performing exposure control using a pre-emission image having a preferable integrated value of divided areas, it is possible to prevent a subject at a particularly short distance from being overexposed.

  Hereinafter, preferred embodiments of a photographing apparatus and an exposure control method according to the present invention will be described with reference to the accompanying drawings.

[First Embodiment]
FIG. 1 is a block diagram showing the main configuration of the photographing apparatus according to the first embodiment of the present invention. An imaging apparatus 1 shown in FIG. 1 is an electronic camera having a function of recording and reproducing still images and moving images, and the overall operation of the imaging apparatus 1 is controlled by a central processing unit (CPU) 10. The CPU 10 functions as a control means for controlling the camera system according to a predetermined program, and performs various calculations such as automatic exposure (AE) calculation, automatic focus adjustment (AF) calculation, and white balance (WB) adjustment calculation. Functions as a means. The power supply circuit 12 supplies power to each block of the camera system.

  A ROM (Read Only Memory) 16 and an EEPROM (Electronically Erasable and Programmable Read Only Memory) 18 are connected to the CPU 10 via a bus 14. The ROM 16 stores programs executed by the CPU 10, various data necessary for control, and the like, and the EEPROM 18 stores CCD pixel defect information, various constants / information related to camera operation, and the like.

  A memory (SDRAM, Synchronous Dynamic Random Access Memory) 20 is used as a program development area and a calculation work area for the CPU 10, and is also used as a temporary storage area for image data and audio data. A video random access memory (VRAM) 22 is a temporary storage memory dedicated to image data, and includes an A area and a B area. The memory 20 and the VRAM 22 can be shared.

  The photographing apparatus 1 is provided with operation switches 24 such as a mode selection switch, a photographing switch, a menu / OK key, a cross key, and a cancel key. Signals from these various operation switches are input to the CPU 10, and the CPU 10 controls each circuit of the photographing apparatus 1 based on the input signals. For example, lens driving control, photographing operation control, image processing control, image data recording / recording Playback control, display control of the image display device 26, and the like are performed.

  The mode selection switch is an operation means for switching between the shooting mode and the playback mode. The photographing switch is an operation button for inputting an instruction to start photographing, and includes a two-stroke switch having an S1 switch that is turned on when half-pressed and an S2 switch that is turned on when fully depressed. The menu / OK key is an operation having both a function as a menu button for instructing to display a menu on the screen of the image display device 26 and a function as an OK button for instructing confirmation and execution of selection contents. Key. The cross key is an operation unit for inputting instructions in four directions, up, down, left, and right, and functions as a button (cursor moving operation means) for selecting an item from the menu screen or instructing selection of various setting items from each menu. To do. The up and down keys of the cross key function as a zoom switch for shooting or a playback zoom switch for playback, and the left and right keys function as a frame advance (forward / reverse feed) button in playback mode. To do. The cancel key is used to delete a desired target such as a selection item, cancel an instruction content, or return to the previous operation state. The flash button functions as a button for switching the flash mode, and the flash mode is set to each mode of flash emission / emission prohibition by pressing the flash button under the shooting mode.

  The image display device 28 is composed of a liquid crystal monitor capable of color display. The image display device 26 can be used as an electronic viewfinder for checking the angle of view at the time of shooting, and is used as a means for reproducing and displaying a recorded image. The image display device 26 is also used as a display screen for a user interface, and displays information such as menu information, selection items, and setting contents. In addition to the liquid crystal monitor, other types of display devices such as organic EL (electro-luminescence) can be used as the image display device 26.

  The photographing apparatus 1 has a media socket (media mounting portion) 28, and a recording medium 30 can be mounted on the media socket 28. The form of the recording medium 30 is not particularly limited, and various types such as a xD picture card (registered trademark), a semiconductor memory card represented by smart media (registered trademark), a portable small hard disk, a magnetic disk, an optical disk, a magneto-optical disk, etc. Media can be used. The media controller 32 performs necessary signal conversion in order to transfer input / output signals suitable for the recording medium 30 mounted in the media socket 28.

  The photographing apparatus 1 also includes an external connection interface unit (external connection I / F) 34 as communication means for connecting to a personal computer and other external devices. The imaging device 1 can exchange data with the external device by connecting the imaging device 1 and the external device using a USB cable (not shown). Note that the communication method between the photographing apparatus 1 and the external device is not limited to USB, and IEEE1394, Bluetooth (registered trademark), and other communication methods may be applied.

[Shooting mode]
Next, the photographing function of the photographing apparatus 1 will be described. When the photographing mode is selected by the mode selection switch, power is supplied to the photographing unit including the color CCD solid-state imaging device 36 (hereinafter referred to as CCD 36), and the photographing is ready.

  The lens unit 38 is an optical unit including a photographing lens 44 including a focus lens 40 and a zoom lens 42, and a diaphragm / mechanical shutter 46. Focusing of the photographic lens 44 is performed by moving the focus lens 40 by the focus motor 40A, and zooming is performed by moving the zoom lens 42 by the zoom motor 42A. The focus motor 40A and the zoom motor 42A are driven and controlled by the focus motor driver 40B and the zoom motor driver 42B, respectively. The CPU 10 controls the focus motor driver 40B and the zoom motor driver 42B by outputting control signals.

  The diaphragm 46 is a so-called turret-type diaphragm, and changes the diaphragm value (F value) by rotating a turret plate in which diaphragm holes of F2.8 to F8 are formed. The diaphragm 46 is driven by an iris motor 46A. The iris motor 46A is driven and controlled by an iris motor driver 46B. The CPU 10 controls the iris motor driver 46B by outputting a control signal.

  The light that has passed through the lens unit 38 forms an image on the light receiving surface of the CCD 36. A number of photodiodes (light receiving elements) are two-dimensionally arranged on the light receiving surface of the CCD 36, and red (R), green (G), and blue (B) primary color filters corresponding to the respective photodiodes. They are arranged in a predetermined arrangement structure. The CCD 36 has an electronic shutter function for controlling the charge accumulation time (shutter speed) of each photodiode. The CPU 10 controls the charge accumulation time in the CCD 36 via a timing generator (TG) 48. In addition, the CPU 10 controls the potential of an OFD (Overflow Drain) with respect to the CCD 36 to adjust the upper limit value of the signal charge accumulated in the photodiode constituting the CCD 36.

  The subject image formed on the light receiving surface of the CCD 36 is converted into signal charges of an amount corresponding to the amount of incident light by each photodiode. The signal charge accumulated in each photodiode is sequentially read out as a voltage signal (image signal) corresponding to the signal charge based on a drive pulse (readout pulse, vertical transfer clock, horizontal transfer clock) given from the TG 48 according to a command from the CPU 10. It is.

  The image signal read from the CCD 36 is sent to an analog processing unit (CDS / AMP) 50, where the R, G, B signals for each pixel are sampled and held (correlated double sampling processing) and amplified. It is added to the A / D converter 52. The dot sequential R, G, B signals converted into digital signals by the A / D converter 52 are stored in the memory 20 via the image input controller 54. The amplification gains of the R, G, and B signals in the analog processing unit 50 correspond to shooting sensitivity (ISO sensitivity), and the CPU 10 sets the shooting sensitivity by adjusting the amplification gain. A method for controlling the photographing sensitivity will be described later.

  The image signal processing circuit 56 includes a synchronization circuit (a processing circuit that converts a color signal into a simultaneous expression by interpolating a spatial shift of the color signal associated with the color filter array of a single CCD), a white balance adjustment circuit, a gradation It functions as an image processing means including a conversion processing circuit (for example, a gamma correction circuit), a contour correction circuit, a luminance / color difference signal generation circuit, and the like, and the R stored in the memory 20 is used while utilizing the memory 20 in accordance with a command from the CPU 10. , G and B signals are subjected to predetermined signal processing.

  The R, G, and B signals input to the image signal processing circuit 56 are converted into a luminance signal (Y signal) and a color difference signal (Cr, Cb signal) by the image signal processing circuit 56, and a gradation conversion process (for example, , Gamma correction) and the like are performed. The image data processed by the image signal processing circuit 56 is stored in the VRAM 22.

  When a captured image is output to the image display device 26 on a monitor, image data is read from the VRAM 22 and sent to the video encoder 58 via the bus 14. The video encoder 58 converts the input image data into a predetermined video signal for display (for example, an NTSC color composite image signal) and outputs the video signal to the image display device 26.

  Image data representing an image for one frame is rewritten alternately between the A area and the B area of the VRAM 22 by the image signal output from the CCD 36. Of the A area and B area of the VRAM 22, the written image data is read from an area other than the area where the image data is rewritten. In this way, the image data in the VRAM 22 is periodically rewritten, and an image signal generated from the image data is supplied to the image display device 26, whereby the image being captured is displayed on the image display device 26 in real time. Is done. The photographer can check the shooting angle of view from the video (through movie image) displayed on the image display device 26.

  When the photographing switch is pressed halfway and S1 is turned on, the photographing apparatus 1 starts AE and AF processing. That is, the image signal output from the CCD 36 is input to the AF detection circuit 60 and the AE / AWB detection circuit 62 via the image input controller 54 after A / D conversion.

  The AE / AWB detection circuit 62 includes a circuit that divides one screen into a plurality of divided areas (for example, 8 × 8 or 16 × 16) and integrates R, G, and B signals for each divided area. A value is provided to the CPU 10. The CPU 10 detects the brightness of the subject (subject brightness) based on the integrated value obtained from the AE / AWB detection circuit 62, and calculates an exposure value (shooting EV value) suitable for shooting. The CPU 10 determines an aperture value and a shutter speed according to the obtained exposure value and a predetermined program diagram, and controls the electronic shutter and iris of the CCD 36 according to this to obtain an appropriate exposure amount.

  Further, the CPU 10 sends a command to the flash control circuit 64 to operate it when the flash emission mode is set. The flash control circuit 64 includes a main capacitor for supplying a current for causing the flash light emitting unit 66 (discharge tube) to emit light. In accordance with a flash light emission command from the CPU 10, the main capacitor charging control and the flash light emitting unit 66 are performed. The discharge (light emission) timing and discharge time are controlled. As the flash light emitting means, it is also possible to use an LED instead of the discharge tube.

  Further, the AE / AWB detection circuit 62 calculates an average integrated value for each color of the R, G, and B signals for each divided area during automatic white balance adjustment, and provides the calculation result to the CPU 10. The CPU 10 obtains an integrated value of R, an integrated value of B, and an integrated value of G, obtains a ratio of R / G and B / G for each divided area, and calculates R / G and R / G of the values of B / G. The light source type is determined based on the distribution in the color space of the G and B / G axis coordinates, and the gain value (white balance gain) for the R, G, and B signals of the white balance adjustment circuit is determined according to the determined light source type. Control and correct the signal of each color channel.

  For example, contrast AF that moves the focus lens 40 so that the high-frequency component of the G signal of the image signal is maximized is applied to the AF control in the photographing apparatus 1. In other words, the AF detection circuit 60 cuts out a signal in a focus target area set in advance in a high-pass filter that passes only a high-frequency component of the G signal, an absolute value processing unit, and a screen (for example, the center of the screen). An area extraction unit and an integration unit that integrates absolute value data in the AF area are configured.

  The integrated value data obtained by the AF detection circuit 60 is notified to the CPU 10. The CPU 10 calculates a focus evaluation value (AF evaluation value) at a plurality of AF detection points while moving the focus lens 40 by controlling the focus motor driver 40B, and adjusts the lens position where the calculated focus evaluation value is maximized. Determine as the focal position. Then, the CPU 10 controls the focus motor driver 40B so as to move the focus lens 40 to the obtained in-focus position. The calculation of the AF evaluation value is not limited to a mode using the G signal, and a luminance signal (Y signal) may be used.

  The shooting switch is half-pressed, AE / AF processing is performed when S1 is turned on, the shooting switch is fully pressed, and the shooting operation for recording starts when S2 is turned on. The image data acquired in response to S2 ON is converted into a luminance / color difference signal (Y / C signal) in the image signal processing circuit 56, subjected to predetermined processing such as gamma correction, and then stored in the memory 20. The

  The Y / C signal stored in the memory 20 is compressed according to a predetermined format by the compression / decompression circuit 68 and then recorded on the recording medium 30 via the media controller 32. For example, still images are recorded as JPEG (Joint Photographic Experts Group) format, and moving images are recorded as AVI (Audio Video Interleaving) format image files.

[Playback mode]
When the playback mode is selected by the mode selection switch, the compressed data of the final image file (last recorded image file) recorded on the recording medium 30 is read. When the image file related to the last recording is a still image file, the read image compression data is expanded to an uncompressed Y / C signal via the compression / decompression circuit 68, and the image signal processing circuit 56 and the video encoder After being converted to a display signal via 58, it is output to the image display device 26. As a result, the image content of the image file is displayed on the screen of the image display device 26.

  Switching the playback target image file by operating the right or left key of the four-way controller during single-frame playback of a still image (including the playback of the first frame of a movie) (forward frame reverse / reverse frame forward) Can do. The image file at the frame-advanced position is read from the recording medium 30, and still images and moving images are reproduced and displayed on the image display device 26 in the same manner as described above.

  In the playback mode, when an external display such as a personal computer or a television is connected to the photographing apparatus 1 via the video input / output terminal 70, the image file recorded on the recording medium 30 is stored in the video output circuit 72. Is processed and reproduced and displayed on the external display.

[Exposure control method]
Next, the flow of processing of the CPU 10 in the exposure control of this embodiment will be described with reference to the flowchart of FIG. First, in the shooting mode, when the flash emission mode is set and the shooting switch is half-pressed (S1 ON), AE and AF processes are executed on the image data output from the CCD 36 (steps S10 and S12). . Then, the shooting sensitivity is set to high sensitivity (for example, the maximum value that can be set for shooting sensitivity) (step S14), pre-emission is performed, and image data (pre-emission image) is captured from the CCD 36 (step S16). .

  Next, as shown in FIG. 3, the image data captured in step S16 is divided into 8 × 8 divided areas (1,..., 64), and image signals (for example, G signal or luminance) of each divided area are divided. Signal) is acquired (step S18).

  Next, in the pre-flash image, the number LF of divided areas where the integrated value (N) is larger than the threshold A is counted (steps S22 to S28). First, the parameter N corresponding to the division area number in FIG. 3 is set to 1 (step S20), and the parameter LF is set to zero. Next, when the integrated value (N) is larger than the threshold A (Yes in step S22), 1 is added to the parameter LF (step S24), 1 is added to the parameter N (step S26), and step S22. Return to. On the other hand, when the integrated value (N) is equal to or less than the threshold value A (No in step S22), 1 is added to the parameter N (step S26), and the process returns to step S22. Then, when the steps S22 to S26 are repeated and the determination of the integrated values of all the divided areas is completed (N = 65, No in step S28), the process proceeds to step S30.

  Next, it is determined whether or not the number LF of divided areas whose integrated value is greater than the threshold A is greater than a threshold B (for example, B = 6 to 10) (step S30). Then, when the number LF of divided areas whose integrated value is larger than the threshold A is equal to or less than the threshold B (No in step S30), the integrated value of the image signal at the time of pre-emission when the shooting sensitivity is set to high sensitivity is used. Then, the photographing sensitivity at the time of main light emission, the exposure value, and the light emission amount (light emission time and light emission intensity) of the flash light emitting unit 64 are calculated and set (steps S32 and S34), and the main light emission photographing is performed (step S36).

  On the other hand, as in the example of FIG. 4A (LF = 45), when the number LF of the divided areas where the integrated value is larger than the threshold A is larger than the threshold B (Yes in step S30), the shooting sensitivity is high. The lower medium sensitivity is set (Yes in step S38, step S40), and the process returns to step S16. Then, pre-light emission is performed again under the setting of medium sensitivity, and image data is captured. After steps S16 to S28, in the pre-light emission image at the time of setting medium sensitivity, the integrated value is larger than the threshold A. It is determined whether or not the number of areas LF is larger than the threshold value B (step S30).

  When the number LF of divided areas where the integrated value is larger than the threshold A is equal to or less than the threshold B (No in step S30), the integrated value of the image signal at the time of pre-emission when the shooting sensitivity is set to the medium sensitivity is used. The shooting sensitivity at the time of light emission, the exposure value, and the light emission amount (light emission time and light emission intensity) of the flash light emitting unit 64 are calculated and set (steps S32 and S34), and the main flash photography is performed (step S36).

  On the other hand, as in the example of FIG. 4B (LF = 11), when the number LF of the divided areas where the integrated value is larger than the threshold A is larger than the threshold B (Yes in step S30), the shooting sensitivity is medium sensitivity. It is set to a lower low sensitivity (for example, the minimum value at which the photographing sensitivity can be set) (No in step S38, Yes in step S42, step S44), and the process returns to step S16. Then, pre-light emission is performed again under the low sensitivity setting, and image data is captured. After the steps S16 to S28, the pre-light emission image at the time of setting the low sensitivity is divided into larger integrated values than the threshold A. It is determined whether or not the number of areas LF is larger than the threshold value B (step S30).

  As in the example of FIG. 4C (LF = 0), when the number LF of the divided areas where the integrated value is greater than the threshold A is equal to or less than the threshold B (No in step S30), the imaging sensitivity is set to low sensitivity. In this case, the integrated value of the image signal at the time of pre-flash is used to calculate and set the shooting sensitivity, exposure value, and light emission amount (light emission time and light intensity) of the flash light emitting unit 64 (steps S32 and S34). ), Real flash photography is performed (step S36). Also, when the number LF of divided areas where the integrated value is greater than the threshold A is greater than the threshold B (Yes in step S30, No in step S38, No in step S42), pre-emission when the imaging sensitivity is set to low sensitivity Using the integrated value of the image signal at the time, the photographing sensitivity, exposure value, and light emission amount (light emission time and light emission intensity) of the flash light emitting unit 64 are calculated and set (steps S32 and S34), and the main light emission is performed. Photographing is performed (step S36).

  According to the present embodiment, it is possible to prevent the subject at a short distance from being overexposed by reducing the photographing sensitivity and performing the pre-flash until the number of divided areas having a high integrated value is equal to or less than the threshold value. it can.

  In the present embodiment, the setting of the photographing sensitivity is decreased in the order of high sensitivity, medium sensitivity, and low sensitivity in accordance with the number LF of divided areas where the integrated value is larger than the threshold A, but low sensitivity, medium sensitivity, The exposure at the time of main flash photography may be controlled using the integrated value at the time of setting the highest sensitivity among the settings where the value of LF is lower than the threshold value B in the order of increasing sensitivity.

  Even if the photographing sensitivity is set to low sensitivity, if the value of LF is larger than the threshold value, for example, the light emission time and light emission intensity of the flash light emitting unit 64 may be reduced.

[Second Embodiment]
Next, an exposure control method according to the second embodiment of the present invention will be described with reference to the flowchart of FIG. First, in the shooting mode, when the flash emission mode is set and the shooting switch is half-pressed (S1 ON), AE and AF processes are executed on the image data output from the CCD 36 (steps S50 and S52). . Then, the light emission time of the flash light emitting unit 64 is set to a small light emission (step S54), pre-light emission is performed, and image data (pre-light emission image) is captured from the CCD 36 (step S56).

  Next, the image data captured in step S56 is divided into 8 × 8 divided areas (1,..., 64), and an integrated value of image signals (for example, G signal or luminance signal) in each divided area is acquired. (Step S58).

  Next, the number LF of the divided areas where the integrated value (N) is larger than the threshold A is counted (steps S62 to S68). First, the parameter N corresponding to the division area number in FIG. 3 is set to 1 (step S60), and the parameter LF is set to zero. Next, when the integrated value (N) is larger than the threshold A (Yes in step S62), 1 is added to the parameter LF (step S64), 1 is added to the parameter N (step S66), and step S62. Return to. On the other hand, when the integrated value (N) is equal to or less than the threshold value A (No in step S62), 1 is added to the parameter N (step S66), and the process returns to step S62. When the steps S62 to S66 are repeated and the determination of the integrated values of all the divided areas is completed (N = 65, No in step S68), the process proceeds to step S70.

  Next, it is determined whether or not the number LF of divided areas whose integrated value is greater than the threshold A is greater than a threshold B (for example, B = 6 to 10) (step S70). Then, when the number LF of divided areas whose integrated value is larger than the threshold A is equal to or less than the threshold B (No in step S70), the integrated value of the image signal at the time of pre-emission when the shooting sensitivity is set to high sensitivity is used. The photographing sensitivity, exposure value, and light emission amount (light emission time and light emission intensity) of the flash light emitting unit 64 are calculated and set (steps S72 and S74), and the main flash photographing is performed (step S76).

  On the other hand, as in the example of FIG. 6A (LF = 11), when the number LF of the divided areas whose integrated value is larger than the threshold A is larger than the threshold B (Yes in step S70), the light emission time is small. Shorter light emission is set (Yes in step S78, step S80), and the process returns to step S56. Then, pre-light emission is performed again under the setting of minute light emission, and image data is captured. After steps S56 to S68, in the pre-light emission image at the time of setting minute light emission, the integrated value is larger than the threshold A. It is determined whether the number of areas LF is larger than the threshold value B (step S70).

  As in the example of FIG. 6B (LF = 0), when the number LF of the divided areas where the integrated value is greater than the threshold A is equal to or less than the threshold B (No in step S70), the imaging sensitivity is set to low sensitivity. In this case, the integrated value of the image signal at the time of pre-flash is used to calculate and set the shooting sensitivity, exposure value, and light emission amount (light emission time and light intensity) of the flash light emitting unit 64 (steps S72 and S74). ), Real flash photography is performed (step S76). Even when the number LF of divided areas where the integrated value is larger than the threshold A is larger than the threshold B (Yes in step S70, No in step S78), the image signal at the time of pre-emission when the photographing sensitivity is set to low sensitivity is used. The integrated value is used to calculate and set the shooting sensitivity, exposure value, and light emission amount (light emission time and light emission intensity) of the flash light emitting unit 64 (steps S72 and S74), and the main flash shooting is performed (step S72, S74). Step S76).

  According to the present embodiment, the pre-light emission is performed by shortening the light emission time of the flash light emitting unit 64 until the number of divided areas having a high integrated value is equal to or less than the threshold value, so that a subject at a particularly short distance is overexposed. Can be prevented.

  In the present embodiment, the setting of the light emission time of the flash light emitting unit 64 is shortened in the order of small light emission and minute light emission in accordance with the number LF of divided areas where the integrated value is larger than the threshold value A. The exposure at the time of main flash photography may be controlled by using the integrated value at the time of the setting with the longest light emission time among the settings in which the LF value is equal to or less than the threshold value B in the order of small light emission.

  In addition, even if the light emission time is set to minute light emission, if the value of LF is larger than the threshold value, for example, the light emission amount of the flash light emitting unit 64 and the photographing sensitivity (see the first embodiment) are reduced. Also good.

[Third Embodiment]
Next, an exposure control method according to the third embodiment of the present invention will be described with reference to the flowchart of FIG. First, in the shooting mode, when the flash emission mode is set and the shooting switch is half-pressed (S1 ON), AE and AF processes are executed on the image data output from the CCD 36 (steps S100 and S102). . Next, the photographing sensitivity is set to high sensitivity (step S104), pre-emission is performed, and image data (pre-emission image) is captured from the CCD 36 (step S106). Then, the image data captured in step S106 is divided into 8 × 8 divided areas (1,..., 64), and the integrated value of the image signal in each divided area is acquired (step S108).

  Next, the shooting sensitivity is set to medium sensitivity (step S110), pre-flash is performed, and a pre-flash image is captured (step S112). Then, the integrated value of the image signal of each divided area of the image data captured in step S112 is acquired (step S114).

  Next, the photographing sensitivity is set to a low sensitivity (step S116), pre-emission is performed, and a pre-emission image is captured (step S118). Then, the integrated value of the image signal in each divided area of the image data captured in step S118 is acquired (step S120).

  Further, an image (non-light-emitting image) when the flash light emitting unit 64 is not emitted is captured, and an integrated value of the image signals of each divided area of the non-light-emitting image is acquired (step S122).

  Next, when the maximum integrated value of each divided area acquired from the pre-emission image at the time of high sensitivity setting (step S108) is smaller than a threshold Y (for example, a value when the integrated value reaches a peak or is saturated), for example, If at least one of the maximum integrated values of R, G, and B is smaller than the threshold Y (Yes in step S124), the main emission is performed using the integrated value of the image signal at the time of pre-emission in the case of high sensitivity. The photographing sensitivity, exposure value, and light emission amount (light emission time and light emission intensity) of the flash light emitting unit 64 are calculated and set (steps S126 and S128), and the main light emission photographing is performed (step S130).

FIG. 8 is a graph illustrating a table showing the relationship between the flash emission time and the ΔEv value. When calculating the flash firing time, first, the integrated value calculated from the pre-flash image: ipre, the integrated value calculated from the non-flash image: ith, the target integrated value: iob, the shooting sensitivity during pre-flash (SV value): Sv_pre, photographing sensitivity at the time of main light emission (SV value): Sv_rec is substituted into the following equation (1) to calculate the ΔEv value:
ΔEv = log {iob / (ipre−ith)} / log2 + (Sv_pre−Sv_rec) (1)
Then, the flash emission time is calculated from the calculated ΔEv value and the table of FIG.

  On the other hand, the maximum integrated value of each divided area acquired from the pre-emission image at the time of setting high sensitivity (step S108) is not less than the threshold Y (No in step S124), and the pre-emission image at the time of setting medium sensitivity (step S124). When the maximum integrated value of each divided area acquired from S114) is smaller than the threshold Y (Yes in step S132), the integrated value of the image signal at the time of pre-emission in the case of medium sensitivity is used during the main light emission. The shooting sensitivity, exposure value, and light emission amount (light emission time and light emission intensity) of the flash light emitting unit 64 are calculated and set (steps S134 and S128), and the main flash photography is performed (step S130).

  On the other hand, when the maximum integrated value of each divided area acquired from the pre-flash image (step S114) at the time of setting the medium sensitivity is equal to or greater than the threshold Y (No in step S132), the pre-flash at the time of low sensitivity is set. Using the integrated value of the image signal, the photographing sensitivity, exposure value, and light emission amount (light emission time and light emission intensity) of the flash light emitting unit 64 are calculated and set (steps S136 and S128), and the main flash photography is performed. Performed (step S130).

  According to the present embodiment, the maximum value of the integrated value of the divided areas obtained from the pre-flash image is equal to or less than the threshold value, that is, the pre-flash image that does not include a saturated split area or the image signal reaches a peak. By performing exposure control based on the image captured with the highest imaging sensitivity, it is possible to prevent a subject at a close distance from being overexposed.

  In the present embodiment, the integrated value is acquired for each photographing sensitivity. However, for example, the integrated value is acquired by changing the light emission time and the light emission amount of the flash light emitting unit 64, and from the first to the above. In each of the third embodiments, the number of divided areas and the threshold value B may be changed according to the image size and the like. For example, when many subjects are included in the image, such as when shooting a distant subject, the number of divided areas is increased according to the zoom position, and the number of subjects occupying the image is as in macro shooting. When there are few, you may make it reduce the number of division areas according to a macro mode setting or a zoom position.

1 is a block diagram showing the main configuration of a photographing apparatus according to a first embodiment of the present invention. The flowchart which shows the exposure control method of the 1st Embodiment of this invention. Diagram showing screen division area A diagram that visually shows the integrated value for each divided area The flowchart which shows the exposure control method of the 2nd Embodiment of this invention. A diagram that visually shows the integrated value for each divided area The flowchart which shows the exposure control method of the 3rd Embodiment of this invention. A graph illustrating a table showing the relationship between the flash emission time and the ΔEv value

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Image pick-up device, 10 ... Central processing unit (CPU), 12 ... Power supply circuit, 14 ... Bus, 16 ... ROM, 18 ... EEPROM, 20 ... Memory (SDRAM), 22 ... VRAM, 24 ... Operation switch, 26 ... Image Display device 28 ... Media socket 30 ... Recording medium 32 ... Media controller 34 ... External connection interface (external connection I / F) 36 ... CCD 38 ... Lens unit 40 ... Focus lens 42 ... Zoom lens , 44 ... photographic lens, 46 ... mechanical shutter combined with aperture, 48 ... timing generator (TG), 50 ... analog processing unit (CDS / AMP), 52 ... A / D converter, 54 ... image input controller, 56 ... image signal processing Circuit 58 ... Video encoder 60 ... AF detection circuit 62 ... AE / AWB detection circuit 64 Flash unit, 66 ... flash control circuit, 68 ... decompression circuit, 70 ... video input and output terminals, 72 ... video output circuit

Claims (14)

Photographing means for photographing an image of a subject;
Illumination means for illuminating the subject by emitting light during shooting;
Pre-flash control means for pre-flashing the illuminating means prior to the main flash photography and performing pre-flash photography with the photography means;
A calculation unit that divides a pre-flash image acquired by the pre-flash shooting into predetermined divided areas, and calculates an integrated value of image signals for each of the divided areas;
Determining means for determining whether to perform pre-flash photography again based on the integrated value;
Control means for lowering the shooting sensitivity from the previous pre-flash shooting and performing pre-flash shooting by the pre-flash control means when it is determined by the determination means to perform pre-flash shooting again;
An exposure control means for performing exposure control during main flash photography based on a pre-flash image obtained by the previous pre-flash photography when it is determined by the determination means that the pre-flash photography is not performed again;
An imaging apparatus comprising: Photographing means for photographing an image of a subject;
Illumination means for illuminating the subject by emitting light during shooting;
Pre-flash control means for pre-flashing the illuminating means prior to the main flash photography and performing pre-flash photography with the photography means;
A calculation unit that divides a pre-flash image acquired by the pre-flash shooting into predetermined divided areas, and calculates an integrated value of image signals for each of the divided areas;
Determining means for determining whether to perform pre-flash photography again based on the integrated value;
A control means for lowering the light emission amount of the illumination means from the previous pre-flash shooting and performing the pre-flash shooting by the pre-flash control means when it is determined by the determination means to perform the pre-flash shooting again;
An exposure control means for performing exposure control during main flash photography based on a pre-flash image obtained by the previous pre-flash photography when it is determined by the determination means that the pre-flash photography is not performed again;
An imaging apparatus comprising:   The determination unit determines that the pre-flash photography is not performed again when the number of divided areas where the integrated value calculated from the pre-flash image exceeds a predetermined value becomes a predetermined number or less. The imaging device according to claim 1 or 2.   In the pre-flash image acquired by setting the photographing sensitivity to a minimum sensitivity that can be set, the exposure control means, when the number of divided areas where the integrated value exceeds a predetermined value is greater than a predetermined number, 4. The photographing apparatus according to claim 3, wherein exposure control at the time of main flash photography is performed based on a pre-flash image acquired with a sensitivity of. Photographing means for photographing an image of a subject;
Illumination means for illuminating the subject by emitting light during shooting;
Prior to the main flash photography, pre-flash control means for performing pre-flash photography by the photographing means by causing the illumination means to pre-light a plurality of times under different photographing sensitivity settings;
A calculation unit that divides each of the plurality of pre-flash images acquired by the pre-flash photographing into predetermined divided areas, and calculates an integrated value of the image signal for each of the divided areas;
Selection means for selecting a pre-emission image used for exposure control among the plurality of pre-emission images based on the integrated value;
Exposure control means for performing exposure control during main flash photography based on the pre-flash image selected by the selection means;
An imaging apparatus comprising:   6. The photographing apparatus according to claim 5, wherein the selecting means selects a pre-flash image captured with the highest photographing sensitivity among pre-flash images not including a divided area where the integrated value exceeds a predetermined value.   7. The exposure control unit according to claim 1, wherein the exposure control unit controls at least one of a photographing sensitivity, an exposure value, a light emission time or a light emission intensity of the illumination unit during main flash photography. Shooting device. A shooting process for shooting an image of the subject;
Prior to the main flash photography, a pre-flash control process in which pre-flash photography is performed by pre-lighting the illumination means;
A calculation step of dividing the pre-flash image acquired by the pre-flash photographing into predetermined divided areas and calculating an integrated value of the image signal for each of the divided areas;
A determination step of determining whether to perform pre-flash photography again based on the integrated value;
When it is determined that pre-flash photography is performed again in the determination step, a control process in which pre-flash photography is performed again with a lower sensitivity than the previous pre-flash photography;
An exposure control step of performing exposure control during main flash shooting based on the pre-flash image acquired by the previous pre-flash shooting when it is determined that the pre-flash shooting is not performed again in the determination step;
An exposure control method comprising: A shooting process for shooting an image of the subject;
Prior to the main flash photography, a pre-flash control process in which pre-flash photography is performed by pre-lighting the illumination means;
A calculation step of dividing the pre-flash image acquired by the pre-flash photographing into predetermined divided areas and calculating an integrated value of the image signal for each of the divided areas;
A determination step of determining whether to perform pre-flash photography again based on the integrated value;
When it is determined that pre-flash photography is performed again in the determination step, a control step of performing pre-flash photography by the pre-flash control process by lowering the light emission amount of the illumination unit from the previous pre-flash photography,
An exposure control step of performing exposure control during main flash shooting based on the pre-flash image acquired by the previous pre-flash shooting when it is determined that the pre-flash shooting is not performed again in the determination step;
An exposure control method comprising:   In the determination step, it is determined that pre-flash photography is not performed again when the number of divided areas where the integrated value calculated from the pre-flash image exceeds a predetermined value is equal to or less than a predetermined number. The exposure control method according to claim 8 or 9.   In the exposure control step, in the pre-flash image acquired by setting the photographing sensitivity to a minimum settable sensitivity, when the number of divided areas where the integrated value exceeds a predetermined value is greater than a predetermined number, the minimum The exposure control method according to claim 10, wherein exposure control during main flash photography is performed based on a pre-flash image acquired with a sensitivity of. A shooting process for shooting an image of the subject;
Prior to the main flash photography, a pre-flash control process in which pre-flash photography is performed by pre-flashing the illumination means a plurality of times under different shooting sensitivity settings
A calculation step of dividing each of the plurality of pre-flash images acquired by the pre-flash shooting into predetermined divided areas, and calculating an integrated value of the image signal for each of the divided areas;
A selection step of selecting a pre-emission image to be used for exposure control among the plurality of pre-emission images based on the integrated value;
An exposure control step for performing exposure control during main flash photography based on the pre-flash image selected in the selection step;
An exposure control method comprising:   13. The exposure control method according to claim 12, wherein, in the selection step, a pre-flash image captured with the highest shooting sensitivity is selected from pre-flash images not including a divided area where the integrated value exceeds a predetermined value. .   14. The exposure control process according to claim 8, wherein at least one of photographing sensitivity at the time of main flash photography, exposure value, light emission time or light emission intensity of the illumination process is controlled. Exposure control method.

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