JP2017215529A - Imaging apparatus and control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an imaging apparatus capable of accurately calculating light amount change characteristics of light from a light metering object depending on imaging circumstances.SOLUTION: The imaging apparatus includes: photometric means for obtaining photometric values in each of plural photometric areas in an imaging area; setting means that sets weighting to each photometric value in the plural photometric areas obtained by using the photometric means; and calculation means that calculates light amount change characteristics of the light metering object of the photometric means based on the brightness value based on each of photometric values in the plural photometric areas and the weighting set by the setting means. The setting means sets the weighting depending on the imaging circumstances.SELECTED DRAWING: Figure 6

Description

  The present invention relates to an imaging apparatus, and more particularly to a technique for calculating a light quantity change characteristic of light from a photometric object.

  In recent years, the sensitivity of imaging devices such as digital cameras and mobile phones has been increasing. For this reason, even in a relatively dark environment such as a room, it has become possible to acquire a bright image with reduced blur by shooting with a high shutter speed (short exposure time).

  In addition, fluorescent lamps that are widely used as indoor light sources cause flicker, which is a phenomenon in which illumination light periodically fluctuates due to the influence of the commercial power supply frequency. When shooting with such a flickering light source (hereinafter referred to as a flicker light source) at a high shutter speed, exposure unevenness or color unevenness occurs in one image, or a plurality of images shot continuously. Variations in exposure and color temperature may occur between images.

  In order to solve such a problem, Patent Document 1 detects a flicker state of illumination light, and adjusts the imaging timing so that the center of the exposure time substantially coincides with the timing at which the amount of illumination light exhibits a maximum value. Has been proposed.

JP 2006-222935 A

  However, Patent Document 1 does not consider the case where exposure unevenness occurs only in a part of the imaging region such as an environment where natural light and artificial light are mixed. In an environment where natural light and artificial light are mixed, it is difficult to accurately calculate the light amount change characteristics of the region irradiated with artificial light due to the influence of natural light when the entire imaging region is evaluated.

  In view of the above, an object of the present invention is to make it possible to accurately calculate a light amount change characteristic of light from a photometric object in accordance with a photographing environment.

  In order to achieve the above object, an imaging apparatus according to the present invention includes a photometric unit for obtaining a photometric value of each of a plurality of photometric areas in an imaging region, and the plurality of photometric areas obtained by using the photometric unit. Based on a luminance value based on a setting means for setting a weight for each photometric value, and a photometric value for each of the plurality of photometric areas and a weight set by the setting means, a light quantity change characteristic of the photometric object of the photometric means Calculating means, wherein the setting means sets weighting according to the shooting environment.

  According to the present invention, it is possible to accurately calculate the light quantity change characteristic of light from a photometric object in accordance with the shooting environment.

1 is a schematic diagram of an imaging system according to an embodiment of the present invention. It is a figure which shows the structural example of the sensor for focus detection. It is a figure which shows the relationship between the photometry area of the sensor for photometry, and the focus detection position of the sensor for focus detection. 1 is a block diagram of an imaging system according to an embodiment of the present invention. It is a figure which shows the operation | movement regarding the light emission imaging | photography of the imaging system which concerns on the 1st Embodiment of this invention. It is a figure which shows the flicker detection process which concerns on the 1st Embodiment of this invention. It is a figure which shows the weighting of each photometry area when calculating the to-be-photographed object brightness | luminance value according to imaging | photography environment. It is a figure which shows the operation | movement regarding the light emission imaging | photography of the imaging system which concerns on the 2nd Embodiment of this invention. It is a figure which shows the flicker detection process which concerns on the 2nd Embodiment of this invention. It is a figure which shows the flicker detection process which concerns on the 3rd Embodiment of this invention.

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

(First embodiment)
FIG. 1 is a schematic diagram of an imaging system according to an embodiment of the present invention. The imaging system of FIG. 1 includes a camera body 1 that is an imaging device, an interchangeable lens 2 that is an interchangeable lens that can be attached to and detached from the camera body 1, and a camera. 1 has a flash 3 which is a detachable illumination device.

  In the camera body 1, 10 is a mechanical shutter, 11 is an optical low-pass filter, and 12 is an image sensor made up of an area storage type photoelectric conversion element such as a CMOS or CCD. The image sensor 12 is exposed by retracting the mechanical shutter 10 from the optical path.

  Reference numeral 13 denotes a semi-transparent main mirror, and reference numeral 14 denotes a first reflecting mirror. Both the main mirror 13 and the first reflecting mirror 14 jump upward to be withdrawn from the optical path during photographing.

  15 is a paraxial imaging plane conjugate with the imaging surface of the imaging device 12 by the first reflecting mirror 14, 16 is a second reflecting mirror, 17 is an infrared cut filter, 18 is a diaphragm having two openings, Reference numeral 19 denotes a secondary imaging lens, and 20 denotes a focus detection sensor (AF sensor). The focus detection sensor 20 is composed of an accumulation type photoelectric conversion element in an area such as a CMOS. FIG. 2 is a diagram illustrating a configuration example of the focus detection sensor 20. As illustrated in FIG. 2, two pairs of light receiving sensor units 20 </ b> A and 20 </ b> B are divided into a plurality of light receiving sensor units corresponding to the two openings of the diaphragm 18. It is the composition of the area. In addition to the light receiving sensor units 20A and 20B, a signal storage unit, a signal processing peripheral circuit, and the like are mounted as an integrated circuit on the same chip. The configuration from the first reflection mirror 14 to the focus detection sensor 20 enables focus detection by a phase difference detection method at a plurality of positions in the imaging region.

  21 is a focusing plate having diffusivity, 22 is a pentaprism, 23 is an eyepiece lens, 24 is a third reflecting mirror, 25 is a condensing lens, and 26 is a photometric sensor (AE sensor) for obtaining information on the luminance of the subject. ). The focus plate 21, the pentaprism 22 and the eyepiece lens 23 constitute a finder optical system. Of the light beam reflected by the main mirror 13 and diffused by the focus plate 21, part of the light metering sensor 26 is incident outside the optical axis.

  The photometric sensor 26 is composed of an accumulation type photoelectric conversion element in an area such as a CMOS. FIG. 3A is a diagram showing a configuration example of the photometric sensor 26. As shown in FIG. 3A, the luminance information and color information of the subject for each area (photometric area) obtained by dividing the light receiving area into a plurality of areas. Can be output. In this example, a plurality of divided areas are divided into 35 rows of 7 columns × 5 rows, and the 35 divided areas are referred to as PD1 to PD35. Although not shown, each divided region of PD1 to PD35 is further divided into light receiving unit pixels, and each pixel is provided with a color filter in a fixed arrangement. Subject detection information can be obtained based on the output information of the photometric sensor 26 having such a configuration. The subject detection information may be human face detection information based on the detailed light receiving unit pixel output of the photometry sensor 26 or main subject color information based on the color detection information of the photometry sensor 26. FIG. 3B is a diagram showing the relationship between the photometry area of the photometry sensor 26 and the focus detection position of the focus detection sensor 20. In this example, the focus detection position in the imaging region by the focus detection sensor 20 is 11 points from FA10 to FA26, and each focus detection position matches the PD10 to PD26 portion of the photometry area by the photometry sensor 26. It is supposed to be.

  Reference numeral 27 denotes a mount portion for attaching the interchangeable lens 2, 28 denotes a contact portion for performing information communication with the interchangeable lens 2, and 29 denotes a connection portion to which the flash 3 is attached.

  In the interchangeable lens 2, 30 a to 30 e are optical lenses constituting the photographing lens, 31 is a diaphragm, 32 is a contact portion for performing information communication with the camera body 1, and 33 is a mount portion for being attached to the camera body 1. is there.

  In the flash 3, 34 is a xenon tube as a light source, 35 is a reflecting member that reflects light emitted from the light source in a predetermined direction, and 36 is a Fresnel lens that collects light from the xenon tube 34 and light reflected by the reflecting member 35. It is. Reference numeral 37 denotes a monitor sensor for monitoring the light emission amount of the xenon tube 34, and 38 denotes an attachment portion for attaching the flash 3 to the camera body 1.

  4 is a block diagram of the imaging system shown in FIG. 1, and the same reference numerals as those in FIG.

  In the camera body 1, for example, 41 is a one-chip microcomputer (microcomputer) incorporating an ALU, ROM, RAM, A / D converter, timer, serial communication port (SPI), etc., and performs overall control of the camera imaging system. .

  Output signals of the focus detection sensor 20 and the photometry sensor 26 are connected to an A / D converter input terminal of the microcomputer 41. A timing generator 42 generates a timing signal for controlling accumulation and reading of the photometric sensor 26.

  A signal processing circuit 43 controls the image sensor 12 according to an instruction from the microcomputer 41 and inputs an image signal output from the image sensor 12 while performing A / D conversion to obtain an image signal. Further, when recording the obtained image signal, necessary image processing such as compression is performed. Reference numeral 44 denotes a memory such as a DRAM, which is used as a work memory when the signal processing circuit 43 performs various signal processing, or used as a VRAM when displaying an image on the display unit 45 described later. Reference numeral 45 denotes a display unit that is configured by a liquid crystal panel or the like and displays various types of shooting information and captured images, and lighting control is performed according to instructions from the microcomputer 41. Reference numeral 46 denotes a storage means such as a flash memory or an optical disk, which stores a captured image signal inputted from the signal processing circuit 43.

  A first motor driver 47 is connected to and controlled by the output terminal of the microcomputer 41 to control the first mirror 13 and the first reflecting mirror 14 up and down and to charge the mechanical shutter 10. The motor 48 is driven. Reference numeral 49 denotes a release switch for instructing start of photographing.

  Reference numeral 28 denotes a contact portion with the interchangeable lens 2 to which an input / output signal of a serial communication port of the microcomputer 41 is connected. Reference numeral 29 denotes a connection portion with the flash 3, and an input / output signal of a serial communication port of the microcomputer 41 is connected so that communication with the flash 3 is possible. Reference numeral 50 denotes shutter driving means which is connected to the output terminal of the microcomputer 41 and drives the mechanical shutter 10.

  In the interchangeable lens 2, reference numeral 51 denotes a lens microcomputer by a one-chip microcomputer that contains, for example, an ALU, ROM, RAM, timer, serial communication port (SPI), and the like.

  A second motor driver 52 is connected to and controlled by the output terminal of the lens microcomputer 51 and drives a second motor 53 for adjusting the focus. A third motor driver 54 is connected to and controlled by the output terminal of the lens microcomputer 51 and drives a third motor 55 for controlling the diaphragm 31. Reference numeral 56 denotes a distance encoder for obtaining information related to the extension amount of the focus adjustment lens (focus lens), that is, subject distance, and is connected to the input terminal of the lens microcomputer 51. Reference numeral 57 denotes a zoom encoder for obtaining focal length information at the time of photographing when the interchangeable lens 2 is a zoom lens, and is connected to an input terminal of the lens microcomputer 51. Reference numeral 32 denotes a contact portion with the camera body 1 to which an input / output signal of a serial communication port of the lens microcomputer 51 is connected.

  When the interchangeable lens 2 is attached to the camera body 1, the contact portions 28 and 32 are connected to each other, and the lens microcomputer 51 can perform data communication with the microcomputer 41 of the camera body 1. The lens-specific optical information necessary for the microcomputer 41 of the camera body 1 to perform focus detection and exposure calculation is output from the lens microcomputer 51 to the microcomputer 41 of the camera body 1 by data communication. Further, information on the subject distance or focal length information based on the distance encoder 56 or the zoom encoder 57 is output from the lens microcomputer 51 to the microcomputer 41 of the camera body 1 by data communication. Further, focus adjustment information and aperture information obtained as a result of the focus detection and exposure calculation performed by the microcomputer 41 of the camera body 1 are output from the microcomputer 41 of the camera body 1 to the lens microcomputer 51 by data communication. The lens microcomputer 51 controls the second motor driver 52 in accordance with the focus adjustment information, and controls the third motor driver 54 in accordance with the aperture information.

  In the flash 3, 61 is a flash microcomputer by a one-chip microcomputer having an ALU, ROM, RAM, A / D converter, timer, serial communication port (SPI) and the like built therein. A booster 62 includes a capacitor and has a function of generating a high voltage of about 300 V necessary for light emission of the xenon tube 34 and charging the high voltage to the capacitor.

  When the flash 3 is attached to the camera body 1, the connecting portions 38 and 29 are connected to each other, and the flash microcomputer 61 can perform data communication with the microcomputer 41 of the camera body 1. The flash microcomputer 61 controls the booster 62 in accordance with the communication contents from the microcomputer 41 of the camera body 1 to start and stop the light emission of the xenon tube 34, and the detected amount of the monitor sensor 37 to the microcomputer 41 of the camera body 1. Output.

  Next, an operation related to light emission photography of the imaging system of the present embodiment will be described with reference to FIG. FIG. 5 is a diagram showing operations related to light emission photography of the imaging system of the present embodiment. When a power switch (not shown) included in the camera body 1 is turned on and the microcomputer 41 becomes operable, the operation shown in FIG. 5 starts. Is done.

  In step S <b> 101, the microcomputer 41 communicates with the flash microcomputer 61 to operate the booster 62 and instruct the capacitor to be charged so that it is sufficient for the flash 3 to emit light.

  In step S102, the microcomputer 41 communicates with the lens microcomputer 51 to obtain various lens information necessary for distance measurement and photometry.

  In step S <b> 103, the microcomputer 41 outputs a control signal to the focus detection sensor 20. When the signal accumulation of the focus detection sensor 20 is completed, the microcomputer 41 reads out the signal accumulated in the focus detection sensor 20, performs A / D conversion, and needs shading or the like for each read digital data. Various data corrections are performed.

  In step S104, the microcomputer 41 calculates the focus state of each focus detection position in the imaging region based on the lens information obtained in step S102 and the digital data obtained in step S103, and a region in the imaging region to be focused ( A focus target area) is determined. The focus target area may be specified according to an area designated in advance by an operation member (not shown) included in the camera body 1.

  Then, the microcomputer 41 calculates a lens movement amount for focusing according to the focus state in the determined focus target area, and outputs the calculated lens movement amount to the lens microcomputer 51. The lens microcomputer 51 drives the second motor 53 by outputting a signal to the second motor driver 52 so as to drive the focus adjustment lens based on the lens movement amount acquired from the microcomputer 41. As a result, the subject in the focus target area determined is brought into focus. Here, since the information of the distance encoder 56 is changed by driving the focus adjustment lens, the microcomputer 41 communicates with the lens microcomputer 51 and updates various lens information. Further, the microcomputer 41 calculates the focus state of each focus detection position in the imaging region again after the signal in the focus detection sensor 20 is accumulated and read out after the subject in the focus target region is brought into focus. .

  In step S105, the microcomputer 41 controls the timing generator 42 to perform predetermined accumulation control and signal readout control of the photometric sensor 26. Here, first photometric information for exposure calculation for determining subject detection processing and exposure at the time of photographing, and second photometric information for calculating a light quantity change characteristic (light quantity change period and phase) of a photometric object, Control to obtain

  In order to obtain the second photometric information, for example, accumulation control and signal readout control at intervals sufficiently shorter than an assumed light amount change cycle are repeated a plurality of times. The microcomputer 41 sequentially reads the accumulated signal from the photometric sensor 26 a plurality of times, performs A / D conversion, and stores it in the RAM.

  Note that an example in which the accumulation for obtaining the first photometric information and the accumulation for obtaining the second photometric information are performed independently is conceivable, and the photometric information obtained from the accumulation for obtaining the second photometric information is conceivable. It is also possible to add to the stored information for obtaining the first photometric information.

  In step S106, the microcomputer 41 performs subject detection processing and exposure calculation processing based on the first photometric information stored in the RAM. Subject detection processing includes human face detection and subject color detection.For example, during continuous shooting, this information can be fed back at the next focus detection so that the same subject can be focused. is there.

  In the exposure calculation process, for example, the photometric value of each photometric area divided into 35 from the first photometric information is calculated, and for each photometric area based on the subject detection information, the information on the focus target area determined in step S104, and the like. The weighting coefficient is calculated. Then, the subject luminance is calculated by a well-known method such as weighting and averaging each photometric value for each photometric area. Once the subject brightness is calculated, exposure conditions such as a shutter speed, an aperture value, and shooting sensitivity that can perform appropriate shooting for the brightness are determined.

  In step S107, the microcomputer 41 calculates the light amount change characteristic of the photometric target based on the second photometric information. Hereinafter, calculating the light amount change characteristic of the photometric object is referred to as flicker detection. Details of the flicker detection process executed in step S107 will be described later.

  In step S108, the microcomputer 41 waits for the release switch 49 to be turned on. If it is not turned on, the process proceeds to step S101, and if the release switch 49 is turned on, the process proceeds to step S109.

  In step S109, the microcomputer 41 instructs the flash microcomputer 61 to perform preliminary light emission of the flash 3. In accordance with an instruction from the microcomputer 41, the flash microcomputer 61 causes the xenon tube 34 to emit light based on the output signal of the monitor sensor 37 so that the xenon tube 34 emits a predetermined amount of preliminary light emission. In order to obtain subject photometric information (preliminary light metering information) during the preliminary light emission, the microcomputer 41 controls the timing generator 42 to perform predetermined accumulation control and signal readout control by the photometric sensor 26. Do. When the signal accumulation of the photometric sensor 26 is completed, the microcomputer 41 reads the signal accumulated in the photometric sensor 26, performs A / D conversion, and stores it in the RAM. The microcomputer 41 performs a calculation for determining the main light emission amount of the flash 3 by a known method based on the accumulated signal information of the photometric sensor 26 stored in the RAM.

  In step S110, the microcomputer 41 outputs a control signal to the first motor driver 47, drives the first motor 48, and raises the main mirror 13 and the first reflecting mirror 14. Subsequently, the microcomputer 41 outputs the aperture value information calculated in step S <b> 106 to the lens microcomputer 51. In accordance with this information, the lens microcomputer 51 outputs a signal to the third motor driver 54 so as to drive the diaphragm 31 and drives the third motor 55.

  In step S111, the microcomputer 41 adjusts the exposure timing when flicker is detected by the flicker detection in step S107 (the amount of light to be measured changes at a predetermined cycle). In the exposure timing adjustment, the flicker light source is controlled so that exposure unevenness and color unevenness do not occur in the image due to the change in the light amount of the flicker light source, and exposure and color temperature variations do not occur between multiple images taken continuously. The exposure timing is adjusted to a predetermined phase in the light quantity change. For example, the amount of light quantity change is the smallest in the vicinity of the peak phase among the light quantity changes of the flicker light source. Therefore, in the present embodiment, the exposure timing is adjusted to the peak timing in the light amount change of the flicker light source. As a method for adjusting the exposure timing to the peak timing in the light amount change of the flicker light source, for example, a known method such as a method described in Japanese Patent Application Laid-Open No. 2015-210283 may be used, and detailed description thereof is omitted.

  In step S <b> 112, the microcomputer 41 outputs a signal to the shutter driving unit 50 to open the mechanical shutter 10. As a result, the image sensor 12 enters a state (exposure state) where light transmitted through the interchangeable lens 2 enters. The microcomputer 41 sets the image sensor 12 to the signal processing circuit 43 so that the signal is accumulated with the accumulation time corresponding to the shutter speed calculated in step S106 and the read gain according to the predetermined imaging sensitivity. Give instructions. Further, in order to perform flash photography, a flash 3 main flash instruction is output to the flash microcomputer 61 so that the flash 3 performs main flash in synchronization with the exposure timing. In accordance with the main light emission instruction from the microcomputer 41, the flash microcomputer 61 causes the xenon tube 34 to emit light based on the output signal of the monitor sensor 37 so that the light emission amount corresponds to the main light emission amount calculated in step S109. As described above, imaging accompanied by light emission of the flash 3 is executed.

  When the accumulation time corresponding to the shutter speed calculated in step S106 elapses, the microcomputer 41 outputs a signal to the shutter driving unit 50 to put the mechanical shutter 10 in a light shielding state. As a result, the light transmitted through the interchangeable lens 2 with respect to the image sensor 12 is blocked.

  In step S <b> 113, the microcomputer 41 outputs information to the lens microcomputer 51 so as to open the diaphragm 31. In accordance with the information from the microcomputer 4, the lens microcomputer 51 outputs a signal to the third motor driver 54 so as to drive the diaphragm 31 and drives the third motor 55. Further, the microcomputer 41 outputs a control signal to the first motor driver 47 and drives the first motor 48 to bring down the main mirror 13 and the first reflecting mirror 14.

  In step S114, the microcomputer 41 reads the captured image information from the image sensor 12 while performing A / D conversion, and instructs the signal processing circuit 43 to perform necessary correction processing and interpolation processing.

  In step S115, the microcomputer 41 instructs the signal processing circuit 43 to perform white balance adjustment on the captured image information. Specifically, the image based on the captured image information is divided into a plurality of areas, and the white area of the subject is extracted from the color difference signal for each area. Further, the white balance adjustment is performed by correcting the gain of the red channel and the blue channel of the entire image based on the signal of the extracted region.

  In step S 116, the microcomputer 41 instructs the signal processing circuit 43 to compress and convert the captured image information subjected to white balance adjustment into a recording file format and store it in the storage unit 46. The above is a series of operations related to flash photography.

  Next, the operation relating to the flicker detection process in step S107 will be described with reference to FIGS. FIG. 6 is a diagram illustrating an operation related to flicker detection processing, and FIG. 7 is a diagram illustrating weighting of each photometric area when calculating a flicker detection subject luminance value corresponding to a shooting environment.

  In step S151, the microcomputer 41 calculates the main subject region and the main subject region based on the focus state of each focus detection position in the imaging region, which is calculated again after the subject in the focus target region is brought into focus in step S104. A background area that can be considered far away from the subject is determined. The main subject region is a region corresponding to the subject in the focus target region, and the detection result of the subject detection process in step S106 may be taken into account in determining the main subject region.

  In step S152, the microcomputer 41 determines based on the subject brightness value calculated in step S106 whether the subject brightness is large enough to be regarded as shooting in a high brightness environment such as outdoors during the daytime. Specifically, for example, it is determined whether or not the subject luminance value calculated in step S106 is equal to or greater than a first threshold value set in advance. The determination may be made based on the subject luminance value calculated in step S106 and the exposure condition determined in step S106. If the subject brightness value is less than the first threshold value, the process proceeds to step S153, and if the subject brightness value is greater than or equal to the first threshold value, the process proceeds to step S156.

  In step S153, the microcomputer 41 determines based on the subject brightness value calculated in step S106 whether the subject brightness is large enough to be regarded as shooting in a relatively bright medium brightness environment such as indoors. Specifically, for example, it is determined whether or not the subject luminance value calculated in step S106 is equal to or greater than a second threshold value set in advance. The second threshold value is smaller than the first threshold value. The determination may be made based on the subject luminance value calculated in step S106 and the exposure condition determined in step S106. When the subject brightness value is less than the second threshold value, the process proceeds to step S154, and when the subject brightness value is equal to or greater than the second threshold value, the process proceeds to step S155.

  In the case of shifting to S154, it can be regarded as shooting in a low brightness environment such as outdoors at night. When flash photography is performed in a low-luminance environment, as shown in FIG. 7A, the main subject that the light from the flash 3 reaches is bright, and the background that the light from the flash 3 does not reaches is dark. In this way, when performing flash photography in a low-brightness environment, even if the ambient light source is a flicker light source, there is very little effect on the image, so the detection area for flicker detection is not distinguished between the main subject and the background. . Therefore, in step S154, the microcomputer 41 calculates the subject luminance value for flicker detection by equalizing the weights of the 35 photometry areas divided as shown in FIG. Then, a plurality of flicker detection subject luminance values based on a plurality of second photometric information are compared to calculate a light amount change period of the photometric target. Furthermore, the peak timing of the light quantity in the change in the light quantity of the photometric target is calculated from the change tendency of the subject luminance values for detecting a plurality of flickers. Note that a known method such as the method described in Japanese Patent Laid-Open No. 2015-210283 may be used as a method for calculating the light amount change period and peak timing of the photometric target, and detailed description thereof will be omitted.

  When flash photography is performed in a medium luminance environment, as shown in FIG. 7C, the subject to which the light from the flash 3 reaches is bright as in the low luminance environment. However, the background where the light from the flash 3 does not reach is as follows. It becomes a certain level of brightness due to ambient light. In such a medium luminance environment, the ambient light reaches the subject to which the light from the flash 3 reaches, but the amount of ambient light that reaches the subject is smaller than the light from the flash 3, so the light source of the environmental light is the flicker light source. However, the effect on the subject is small. On the other hand, the background where the light from the flash 3 does not reach is greatly affected if the light source of the ambient light is a flicker light source. Therefore, in step S155, the microcomputer 41 attaches importance to the background area when flicker is detected, and the weighting of the photometry area in the background area is made larger than the photometry area in the main subject area as shown in FIG. The subject luminance value for flicker detection is calculated. The method for calculating the peak timing of the light amount in the change in the amount of light to be measured is the same as that in step S154, and the description thereof is omitted.

  When flash photography is performed in a high-luminance environment, the subject to which the light from the flash 3 reaches is bright as shown in FIG. 7E, which is the same as in the low-luminance environment and the medium-luminance environment. The unreachable background also has a uniform brightness due to ambient light. In such a high brightness environment, the ambient light reaches the subject to which the light of the flash 3 reaches, and the amount of ambient light reaching the subject is larger than the light of the flash 3. Therefore, if the light source of the ambient light is a flicker light source, the influence on the subject to which the light of the flash 3 reaches is large. If the light source of the ambient light is a flicker light source, the influence of the background light from which the light of the flash 3 does not reach is greater because the ambient light reaches more than the medium luminance environment. However, what the photographer wants to take beautifully is the main subject rather than the background. Therefore, in step S156, the microcomputer 41 places importance on the main subject area when flicker is detected, and sets the metering area of the main subject area to be larger than the weighting of the metering area of the background area as shown in FIG. Thus, the subject brightness value for flicker detection is calculated. The method for calculating the peak timing of the light amount in the change in the amount of light to be measured is the same as that in step S154, and the description thereof is omitted.

  As described above, by setting the weighting for each photometry area when calculating the subject brightness value for flicker detection according to the shooting environment, the light quantity change characteristic of the light from the photometry target can be accurately determined according to the shooting environment. Can be calculated. In addition, although the example which sets weighting with respect to each photometry area according to imaging | photography environment was demonstrated using FIG. 7, the value of weighting is not limited to the value shown in FIG. For example, the weighting value of the area where the weighting value is “1” in FIG. 7D or FIG. 7F may be “0”. Setting the weighting value to “0” means that the photometric value of the photometric area is not used when calculating the subject luminance value for flicker detection. That is, setting the weighting for each photometric area when calculating the subject luminance value for flicker detection includes selecting the photometric area to be used when calculating the subject luminance value for flicker detection.

(Second Embodiment)
In the first embodiment, an example has been described in which the main subject region and the background region are discriminated using the focus state information in order to set the weighting for each photometric area when calculating the subject luminance value for flicker detection. . In the second embodiment, an example will be described in which the main subject region and the background region are determined by a method different from the method using the focus state information. Note that the imaging system of the present embodiment is the same as the imaging system of the first embodiment, and thus detailed description thereof is omitted.

  The operation related to the flash photography of the imaging system of this embodiment will be described with reference to FIG. FIG. 8 is a diagram illustrating an operation related to light emission photographing of the imaging system of the present embodiment. When a power switch (not shown) included in the camera body 1 is turned on and the microcomputer 41 becomes operable, the operation illustrated in FIG. 8 starts. Is done.

  Steps S201 to S206 are the same as steps S101 to S106 in FIG.

  After performing subject detection processing and exposure calculation processing in step S206, the microcomputer 41 waits for the release switch 49 to be turned on in step S207. Steps S207 to S209 are the same as steps S108 to S110 in FIG.

  Thereafter, in step S210, the microcomputer 41 performs flicker detection processing. Details of the flicker detection process executed in step S210 will be described later.

  Steps S211 to S216 are the same as steps S111 to S116 in FIG.

  Next, the operation relating to the flicker detection process in step S210 will be described with reference to FIG. FIG. 9 is a diagram illustrating an operation related to flicker detection processing, and step S251 is different from step S151 in FIG. 6 in comparison with FIG.

  In step S251, the microcomputer 41 determines the main subject area and the background area based on the photometric information of the subject obtained during the preliminary light emission obtained in step S208. For example, based on the photometric information of the subject during the preliminary light emission, the area where the photometric value exceeds a predetermined value in each photometric area is determined as the area where the preliminary light emission has arrived, and is set as the main subject area. Let the region be the background region. Here, by using the difference between the photometric information of the subject during the preliminary light emission and the photometric information of the subject when the preliminary light emission is not performed, the reflected light component of the preliminary light emission can be extracted. The photometric information of the subject may be acquired immediately before or after.

  The subsequent steps S252 to S256 are the same as steps S152 to S156 of FIG.

  As described above, in the present embodiment, the main subject region and the background region are determined based on the photometric information of the subject during the preliminary light emission, and thus the main subject region and the background region are distinguished from each other even in the region where the focus state cannot be obtained. A subject area and a background area can be discriminated.

  In addition, since the preliminary light emission is actually performed and an area brightened by the preliminary light emission is used as the main subject, the main subject region and the background region can be distinguished regardless of the accuracy of the information regarding the focus state.

(Third embodiment)
This embodiment is different from the first embodiment and the second embodiment in the weighting setting method for each photometric area when calculating the subject luminance value for flicker detection. Note that the imaging system of the present embodiment is the same as the imaging system of the first embodiment, and thus detailed description thereof is omitted. The operation related to the flash photography of the imaging system of the present embodiment is different from the second embodiment only in the weighting setting method for each photometric area when calculating the subject luminance value for flicker detection. Descriptions other than the operations related to are omitted.

  Operations related to the flicker detection processing of the present embodiment will be described with reference to FIG. FIG. 10 is a diagram illustrating an operation related to the flicker detection process, and a step (step S352) of calculating the ambient light contribution rate is added as compared with FIG.

  In step S351, the microcomputer 41 determines the main subject region and the background region based on the photometric information of the subject during the preliminary light emission obtained in step S208.

  In step S352, the microcomputer 41 subtracts the subject luminance value calculated in step S206 from the subject luminance value obtained from the exposure condition (shutter speed, aperture value, photographing sensitivity) determined in step S206. Determine the contribution rate.

  If the result of subtracting the subject brightness value calculated in step S206 from the subject brightness value obtained from the exposure conditions at the time of shooting is small (subtraction result), the flash 3 is not fired and only the ambient light is used for shooting. The main subject is photographed with almost appropriate brightness. For example, it corresponds to a case where the flash 3 is emitted in order to put a catchlight in the eyes of a person who is a main subject in a bright shooting environment outdoors during the daytime. In this embodiment, if the subtraction result is less than the first threshold value, the scene has a large environmental light contribution rate.

  On the other hand, when the subtraction result is large, the main subject is photographed darkly when photographing with only ambient light without causing the flash 3 to emit light. In this embodiment, if the subtraction result is greater than or equal to the second threshold value that is greater than the first threshold value, the scene has a low environmental light contribution rate, and if the subtraction result is greater than or equal to the first threshold value and less than the second threshold value, the environment. The scene is in the light contribution ratio. Note that the ambient light contribution ratio may be obtained as a specific value instead of being classified as described above. For example, if the reciprocal of the subtraction result is defined as the ambient light contribution rate, the ambient light contribution rate can be set to a specific value, and the ambient light contribution rate thus obtained may be compared with a threshold value.

  In step S353, the microcomputer 41 determines whether or not the environmental light contribution rate is large. If the environmental light contribution rate is not large, the microcomputer 41 proceeds to step S354. If the environmental light contribution rate is large, the microcomputer 41 proceeds to step S357.

  In step S354, the microcomputer 41 determines whether the environmental light contribution rate is medium. If the environmental light contribution rate is not medium, the microcomputer 41 proceeds to step S355. If the environmental light contribution rate is medium, the microcomputer 41 proceeds to step S356.

  Steps S355 to S357 are the same as steps S154 to S156 in FIG.

  As described above, in the present embodiment, the weighting for each photometric area when calculating the subject luminance value for flicker detection is changed according to the ambient light contribution rate, thereby changing each weight according to the degree of influence of the flicker light source. The weighting for the photometric area can be changed. Therefore, it is possible to accurately calculate the light quantity change characteristic of light from the photometric object according to the environment.

  In this embodiment, the main subject area and the background area are discriminated by the same method as in the second embodiment, but the main subject area and the background area are discriminated by the same method as in the first embodiment. May be.

  In the above-described three embodiments, the example in which the weighting for each photometric area when calculating the subject luminance value for flicker detection is changed in three patterns has been described, but depending on the subject luminance and the ambient light contribution ratio You may make it change with four or more patterns. Alternatively, two of the three patterns (for example, simple average and background emphasis, background emphasis and main subject emphasis, etc.) may be selected according to subject brightness and ambient light contribution rate.

  In the above-described three embodiments, the imaging system in which the illumination device is mounted on the imaging device has been described as an example. However, the imaging device may include the illumination device.

  In the above three embodiments, the light quantity change characteristic of the photometric object is calculated based on the photometric information obtained using the photometric sensor 26, but based on the photometric information obtained by driving the image sensor 12. Thus, the light quantity change characteristic of the photometric object may be calculated. Photometric information obtained by driving the image sensor 12 may also be used in the calculation of the subject luminance value and the determination of the ambient light contribution rate.

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

  For example, the function of the above embodiment may be used as a control method, and this control method may be executed by the imaging apparatus. Further, a program having the functions of the above-described embodiments may be used as a control program, and the control program may be executed by a computer included in the imaging apparatus. The control program is recorded on a computer-readable recording medium, for example.

(Other embodiments)
The present invention supplies a program that realizes one or more functions of the above-described embodiments to a system or apparatus via a network or a storage medium, and one or more processors in a computer of the system or apparatus read and execute the program This process can be realized. It can also be realized by a circuit (for example, ASIC) that realizes one or more functions.

DESCRIPTION OF SYMBOLS 1 Camera body 2 Interchangeable lens 3 Flash 20 Focus detection sensor 26 Photometric sensor 41 Microcomputer 51 Lens microcomputer 61 Flash microcomputer

Claims (8)

A photometric means for obtaining a photometric value of each of a plurality of photometric areas in the imaging area;
Setting means for setting weights for the photometric values of the plurality of photometric areas obtained using the photometric means;
Based on a luminance value based on a photometric value of each of the plurality of photometric areas and a weight set by the setting unit, a light amount change characteristic of a photometric target of the photometric unit, and a calculation unit,
The imaging device according to claim 1, wherein the setting means sets a weight according to a shooting environment.   The imaging apparatus according to claim 1, wherein the setting unit sets weighting according to brightness of a shooting environment.   The imaging apparatus according to claim 1, wherein the setting unit sets weighting according to an environmental light contribution rate. Having a discriminating means for discriminating between the main subject area and the background area in the imaging area;
4. The apparatus according to claim 1, wherein the setting unit changes whether or not the weighting for the photometric value of the main subject area is larger than the weighting for the background area according to a shooting environment. The imaging device described in 1. Having a discriminating means for discriminating between the main subject area and the background area in the imaging area;
The imaging apparatus according to claim 2, wherein the setting unit increases the weighting of the photometric value of the main subject when the brightness of the shooting environment is brighter than when the brightness is dark. Having a discriminating means for discriminating between the main subject area and the background area in the imaging area;
The imaging apparatus according to claim 3, wherein the setting unit increases the weighting for the photometric value of the main subject when the ambient light contribution ratio is large, compared to when the ambient light contribution ratio is small.   7. The determination unit according to claim 4, wherein the determination unit determines the main subject region and the background region based on a focus state of each focus detection position in the imaging region. Imaging device. A photometric step for obtaining a photometric value of each of a plurality of photometric areas in the imaging region;
A setting step for setting weights for the photometric values of the plurality of photometric areas obtained in the photometric step;
Based on a luminance value based on a photometric value of each of the plurality of photometric areas and a weight set in the setting step, and calculating a light quantity change characteristic of a photometric object in the photometric step,
The method of controlling an imaging apparatus, wherein the setting step sets weighting according to a shooting environment.

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