JP2006042168A - Imaging apparatus, and method for calculating white balance control value - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To properly correct the white balance of a main subject area in an image which is photographed by performing light control. <P>SOLUTION: The imaging apparatus comprises: a speed light (138); an imaging element (101) for converting an incident subject optical image into an electric signal and outputting image data; a main subject area detecting part (140) for determining the main subject area including a main subject in the image data which is picked-up by the imaging element after performing the light control with the speed light; and an achromatic color part detecting part (112) and a WB gain calculating part (114) for detecting an achromatic color part in the main subject area from the image data and calculating a white balance control value, based on partial image data corresponding to the achromatic color part. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an imaging device and a white balance control value calculation method, and more particularly, to a white balance control value calculation method in the case of shooting with light control and an imaging device to which the method is applied.

  FIG. 7 is a diagram illustrating a configuration example of a conventional digital camera.

  In FIG. 7, a subject optical image that has passed through a photographing lens (not shown) is formed on an image sensor 301 and converted into electric charges corresponding to the amount of light. The image sensor 301 is covered with, for example, R (red), G (green), and B (blue) color filters as shown in FIG. Note that the filter array shown in FIG. 8 is generally called a Bayer array, and is configured as a set of four pixels in which two G filters having a high contribution to the luminance signal are arranged. In the process described later, considering the case where a readout amplifier is used in which the row including R and the row including B are different due to the circuit configuration of the image sensor, G in R row is set to G1, and G in B row is set to G1. Since G1 and G2 are handled as different color components as G2, they are described separately in FIG. Each color filter has a spectral sensitivity around the wavelength band of each color, and a photoelectric conversion element provided corresponding to each color filter photoelectrically converts light in the band that has passed through each color filter.

  The electric charge converted by each photoelectric conversion element is output as an electric signal from the image pickup element 301 to the A / D conversion unit 303 and converted into a digital signal (image data) by A / D conversion processing.

  The digital signal output from the A / D conversion unit 303 is sent to the auto white balance (AWB) processing unit 305 for gain correction, and simultaneously sent to the chromaticity coordinate conversion unit 310.

  In the case of auto white balance that automatically obtains a white balance control value suitable for a photographed image from photographed image data, for example, a white balance gain value (white balance control value) is obtained as follows.

First, the chromaticity coordinate conversion unit 310 obtains R: B and (R + B) :( G1 + G2) in the combination of adjacent R, G1, G2, and B in the image data as shown in FIG. 9, plotted on two-dimensional coordinates as shown in FIG. 9, the achromatic color portion detection unit 312 determines a combination of R, G1, G2, and B located within the frame of the coordinate range 801 in the vicinity of the blackbody radiation locus 802. It is determined as an achromatic region. Then, the WB gain calculation unit 314 sequentially integrates the determined combination signal for each color component to obtain integration values SumR, SumG1, SumG2, and SumB of each color component, and the ratio of SumR: SumG1: SumG2: SumB is G. The white balance control values WbR, WbG1, WbG2, and WbB, which are 1: 1: 1: 1, are determined as shown in the following equation (1) with reference to the components.
WbR = (SumG1 + SumG2) / (2 x SumR)
WbG1 = (SumG1 + SumG2) / (2 x SumG1)
WbG2 = (SumG1 + SumG2) / (2 x SumG2)
WbB = (SumG1 + SumG2) / (2 × SumB) (1)

  The AWB processing unit 305 determines that the white balance control value obtained as described above in the WB gain calculation unit 314 is a control value for the optimum color temperature of the light source in this image, and out of all the image data. By multiplying WbR for the pixel signal of the R filter, WbG1 for the pixel signal of the G1 filter, WbG2 for the pixel signal of the G2 filter, and WbB for the pixel signal of the B filter, respectively. Perform balance calculation processing.

  The image data that has been subjected to auto white balance processing is developed in the development processing unit 307. Here, white balance adjusted image data is optimized for output for monitor viewing and print output by giving optimal contrast characteristics with optimal gamma characteristics, color adjustment, sharpness processing, etc. It is converted into image data with characteristics.

  The image data that has been subjected to image processing that is optimal for output by the development processing unit 307 is output as a file in the image data output unit 309. For example, when converting a file format to a JPEG file, the image-processed RGB data is converted into a YPEGCb format by three-dimensional matrix conversion and attached data is attached to the JPEG file format (see, for example, Patent Document 1). ).

JP 07-154814 A

  In the above conventional example, when auto white balance processing is performed, an achromatic color portion is detected from all captured image data, and a gain for making R: G: B of the detected portion 1: 1: 1 is obtained, This is realized by multiplying the gain for each of the R, G, and B color components.

  When shooting is performed with a light control device such as a speedlight attached to a camera that performs white balance processing according to the above method, for example, in the shooting screen 901 shown in FIG. When the light source is a strong reddish light source having a color temperature of about 3000K, such as tungsten light or halogen light, the light source color is significantly different from the bluish speedlight light having a color temperature of about 5500K. In such a photographing screen 901, even if light control is performed so that the exposure amount of the main subject portion 904 is appropriate, the image portion with strong redness that is not dimmed by the conventional method described above. Since the achromatic color portion for obtaining the white balance control value is also detected from 903, the achromatic color portion on the low color temperature side where the redness is strong also affects the white balance result. As a result, the main subject portion 904 with high bluishness on the high color temperature side that is being dimmed and the image portion 902 in the vicinity thereof cannot be properly white balance corrected, resulting in a correction result that remains slightly bluish, resulting in an unsightly image. .

  The present invention has been made in view of the above-described problems, and an object of the present invention is to appropriately perform white balance correction of a main subject region in an image photographed with dimming control.

  In order to achieve the above object, an imaging apparatus according to the present invention includes a light control unit, an imaging unit that converts an incident subject optical image into an electrical signal and outputs image data, and performs light control using the light control unit. In the image data picked up by the image pickup means, a main subject area determination means for determining a main subject area including a main subject, and an achromatic portion in the main subject area is detected from the image data, and the achromatic color is detected. Calculation means for calculating a white balance control value based on partial image data corresponding to the portion.

  Further, the white balance control value calculation method of the present invention includes a determination step for determining whether or not dimming by the dimming unit is necessary, and when dimming is necessary, the dimming unit performs dimming and an incident subject An imaging step for converting an optical image into an electrical signal and outputting image data, a main subject region determination step for determining a main subject region including a main subject in the image data captured in the imaging step, and the image data And calculating a white balance control value based on partial image data corresponding to the achromatic color portion.

  According to another configuration, the imaging apparatus of the present invention includes a light control unit, an image pickup unit that converts an incident subject optical image into an electrical signal and outputs image data, and light control by the light control unit. In the image data that has been captured and picked up by the imaging means, a main subject area determination means that determines a main subject area including a main subject, and the image data is divided into a plurality of areas, and the weight of the main subject area is the heaviest The weighting coefficient determining means for assigning a weighting coefficient to each of the plurality of divided areas, and detecting achromatic portions for each of the plurality of divided areas of the image data, and detecting each achromatic color portion detected The corresponding partial image data is weighted by the weighting coefficient assigned to the divided area to which each achromatic color part belongs, and the white balance is based on the obtained value. And a calculating means for calculating a Nsu control value.

  The white balance control value calculation method according to the present invention includes a determination step for determining whether light control by the light control unit is necessary, and, when light control is necessary, performs light control by the light control unit and makes an incident subject An imaging step for converting an optical image into an electrical signal and outputting image data, a main subject region determination step for determining a main subject region including a main subject in the image data captured in the imaging step, and the image data Is divided into a plurality of regions, and a weighting coefficient determining step for assigning a weighting coefficient to each of the plurality of divided regions so that the weight of the main subject region is the heaviest, and the plurality of divided regions of the image data An achromatic color portion is detected for each, and the partial image data corresponding to each detected achromatic color portion is assigned to the divided area to which each achromatic color portion belongs. Was weighted by weighting coefficients, and a calculation step of calculating the white balance control value based on the obtained value.

  According to the present invention, it is possible to appropriately perform white balance correction of the main subject region in an image photographed with light control.

  The best mode for carrying out the present invention will be described below in detail with reference to the accompanying drawings.

<First Embodiment>
A first embodiment of the present invention will be described.

  FIG. 1 is a block diagram showing a schematic functional configuration of the imaging apparatus according to the first embodiment of the present invention.

  In FIG. 1, 121 is a photographing lens including a focusing lens, 101 is an image sensor such as a CCD or MOS, which receives a subject optical image transmitted through the photographing lens 121 and outputs an electrical signal corresponding to the received light amount, 103 Is an A / D converter that converts an electrical signal output from the image sensor into a digital signal (image data), and 105 is an auto white that performs white balance processing on the image data output from the A / D converter 103. A balance (AWB) processing unit 107, a development processing unit 107 that performs development processing on the image data that has been subjected to white balance processing by the AWB processing unit 105, and an image 109 that outputs image data generated by the development processing as an image file A data output unit. In addition, each said structure performs the processing operation similar to the past.

  The image data output from the A / D conversion unit 103 is also output to the chromaticity coordinate conversion unit 110, the photometry unit 132, and the main subject region detection unit 140. The chromaticity coordinate conversion unit 110 converts the input image data into two-dimensional coordinates as shown in FIG. 9, and the achromatic color portion detection unit 112 converts the achromatic color image data (R within the frame of the coordinate range 801). , G1, G2, B) are detected. The WB gain calculation unit 114 calculates white balance (AWB) control values WbR, WbG1, WbG2, and WbB that are used for white balance processing by the AWB processing unit 105 based on the detected achromatic image data.

  122 is a focus detection unit that detects the focus state, 124 is a lens control unit that controls the photographing lens 121 based on the detection result of the focus detection unit 124, 132 is a photometry unit, and 134 is according to the photometry result of the photometry unit 132. A driving unit for driving the image sensor, 138 is a speed light, and 136 is a speed light control unit that controls light emission of the speed light 138 in accordance with the photometric result of the photometric unit 132. Reference numeral 140 denotes a main subject area detection unit.

  In the imaging apparatus according to the first embodiment having the above-described configuration, the AWB processing unit 105 performs AWB processing using the AWB control value calculated by the WB gain calculation unit 114.

  Next, the calculation procedure of the WB control value in the imaging apparatus of the first embodiment will be described with reference to the flowchart of FIG. This operation is executed, for example, when a preparation for photographing is instructed by operating a shutter button (not shown).

  First, in step S11, it is determined whether dimming with the speedlight 138 is necessary. Here, for example, when the imaging apparatus has a display unit, the brightness of the image immediately before the shutter button operation, which is displayed through on the display unit, can be measured by the photometry unit 132, separately from the photometry unit 132. You may provide the photometry circuit which measures a peripheral light quantity. If dimming is necessary, the process proceeds to step S12. If not, the process proceeds to step S15.

  In step S <b> 12, the speedlight control unit 136 causes the speedlight 138 to emit light before photographing (pre-light emission), and obtain a dimmed image. Here, image data is captured by the image sensor 101 in a pre-emission state, and the image data changed into a digital signal by the A / D conversion unit 103 is sent to the photometry unit 132, the chromaticity coordinate conversion unit 110, and the main subject region detection unit. Entered. The photometric unit 132 performs photometry using the image data acquired here. At this time, as shown in FIG. 3, the photometric unit 132 divides the imaging screen 401 of the image sensor 101 into a plurality of individual photometric areas 402. Find the photometric value.

  In step S <b> 13, the main subject region detection unit 140 determines the main subject region and notifies the achromatic color portion determination unit 112. Here, the distance from the image data output from the A / D conversion unit 103 to each subject located in each region corresponding to each photometric region 402 (referred to as a photometric region for convenience) is calculated, and the focus detection unit 122 is calculated. A photometric area 402 including a subject at a distance matching the focal length of the lens sent from is detected as the main subject area. In addition, as a method for detecting the main subject, a known method other than these may be used, such as defining the closest subject as the main subject without using the focal length of the lens. Thus, by obtaining the main subject area in units of each photometric area, it can be used for exposure amount control. In the example of FIG. 3, the subject 404 is determined as the main subject in this shooting scene, and the region 403 is determined as the main subject region. In the example shown in FIG. 3, one photometric area is the main subject area 403, but the present invention is not limited to one area, and may be a plurality of photometric areas.

  The main subject region detection unit 140 also notifies the photometry unit 132 of the main subject region 403 including the detected main subject 404. The photometric unit 132 passes the photometric value of the main subject area 403 to the speedlight control unit 136 when performing main light emission. The speedlight control unit 136 calculates the light control amount during the main light emission so that the main subject region 403 is in an optimal light control state. By controlling in this way, the main subject 404 can be photographed in an appropriate exposure state.

  At the same time, the speedlight control unit 136 sends a signal indicating that light emission control is to be performed to the achromatic color part detection unit 112 to notify that the light control by the speedlight 138 is to be performed at the time of actual photographing.

  In step S14, the chromaticity coordinate conversion unit 110 converts the image data input from the A / D conversion unit 103 into chromaticity coordinate values for each pixel, and the achromatic color portion detection unit 112 performs the input light emission control. Based on the two signals, i.e., a signal indicating that the main subject area is displayed and a signal indicating the main subject area, only the achromatic color portion included in the main subject area 403 is detected from the chromaticity coordinate values of each pixel, and the corresponding image is detected. Data (R, G1, G2, B) is transferred to the WB gain calculation unit 114. The WB gain calculation unit 114 integrates the image data detected by the achromatic color part detection unit 112 using a method similar to the conventional method, and obtains integrated values SumR, SumG1, SumG2, and SumB for each color.

  On the other hand, if it is determined in step S11 that dimming with the speedlight 138 is not necessary, in step S15, an image is acquired without performing pre-shooting light emission (pre-light emission). In step S16, the chromaticity coordinate conversion unit 110 converts the image data input from the A / D conversion unit 103 into chromaticity coordinate values for each pixel, and the achromatic color portion detection unit 112 detects the absence of the entire captured image. The image data (R, G1, G2, B) corresponding to the chromaticity coordinate value of the chromatic part is passed to the WB gain calculation unit 114, and the WB gain calculation unit 114 integrates each color using a method similar to the conventional method. Integral values SumR, SumG1, SumG2, and SumB are obtained.

  Next, in step S17, the WB gain calculation unit 114 calculates the WB control values WbR, WbG1 according to the above-described equation (1) based on the integral values SumR, SumG1, SumG2, SumB obtained in either step S14 or step S16. , WbG2, WbB are obtained, and the obtained WB control values WbR, WbG1, WbG2, WbB are set in the AWB processing unit 105.

  As described above, according to the first embodiment, when the auto white balance control value at the time of flash control shooting is obtained, there is no image data only for the main subject region used for determining the main light emission control value. By detecting the chromatic part and obtaining the WB control value, the white balance control result of the dimmed main subject becomes an appropriate hue without being affected by the color within the range where the dimming does not reach within the shooting screen. In this way, the processing can be performed.

<Second Embodiment>
Next, a second embodiment of the present invention will be described.

  FIG. 4 is a block diagram showing a schematic functional configuration of the imaging apparatus according to the second embodiment of the present invention. In addition, the same reference number is attached | subjected to the structure similar to FIG. 1 demonstrated in 1st Embodiment, and description is abbreviate | omitted. The configuration shown in FIG. 1 is different from the configuration shown in FIG. 1 in that a weighting coefficient determination unit 240 for weighting each photometric area is added, and the operations of the achromatic color portion detection unit 212, the WB gain calculation unit 214, and the photometry unit 232 change accordingly.

  Hereinafter, the calculation procedure of the AWB control value in the imaging apparatus of the second embodiment having the configuration shown in FIG. 4 will be described with reference to the flowchart of FIG. In the process shown in FIG. 5, the same step number is assigned to the same process as in FIG. 2, and a part of the description is omitted.

  First, in step S11, it is determined whether dimming with the speedlight 138 is necessary. If dimming is necessary, the process proceeds to step S12. If not, the process proceeds to step S15.

  In step S <b> 12, the speedlight control unit 136 causes the speedlight 138 to emit light before photographing (pre-light emission), and obtain a dimmed image. The photometric unit 232 obtains a photometric value for each photometric area shown in FIG. 3 based on the obtained image data.

  Next, in step S21, the chromaticity coordinate conversion unit 110 converts the image data input from the A / D conversion unit 103 into chromaticity coordinate values for each pixel, and the achromatic color portion detection unit 212 performs the measurement for each photometric area. The achromatic portion is detected and the corresponding image data (R, G1, G2, B) is passed to the WB gain calculation unit 214. In the WB gain calculation unit 214, the image data detected by the achromatic color part detection unit 212 is integrated for each photometry region using a method similar to the conventional method, and the integration values SumR (n), SumG1 (n), SumG2 of each color are integrated. (n), SumB (n) (where n is the number of each photometric area).

  In step S22, the main subject area is determined by the weighting coefficient determination unit 240, and in step S23, the weighting coefficient Wt (n) for each photometric area is determined. This operation will now be described.

  First, the main subject area is detected in the same manner as in the first embodiment. In the example shown in FIG. 6A, the area 504 is the main subject. Next, the weighting coefficient determination unit 240 sets the photometry area 503 in which the main subject 504 is located to a weight of 1.0, and the photometry results of each of the peripheral photometry areas are shown in the example of FIG. 6B. As described above, the weighting value is assigned to be smaller as the distance from the photometric area 503 is increased. Note that the weighting method is not limited to this, and the distance to the subject included in each photometry area is obtained for each photometry area, and the weight value decreases as the obtained distance increases from the distance to the main subject. For example, a known method may be used. In the example shown in FIG. 6, one photometry area is the main subject area 503, but the present invention is not limited to one area, and may be a plurality of photometry areas.

  The weighting coefficient determination unit 240 outputs the obtained weighting coefficient to the WB gain calculation unit 214 and also outputs it to the photometry unit 232.

  The photometric unit 232 weights each photometric value with a weighting coefficient, and passes the weighted photometric value to the speedlight control unit 136. The speedlight control unit 130 obtains the optimal light control amount for this shooting scene from each photometric value obtained as a result of performing weighting multiplication for each photometric area as described above.

  At the same time, the speedlight control unit 130 sends a signal indicating that the light emission control is performed to the WB gain calculation unit 214 to notify that the light control by the speedlight 138 is performed at the time of the actual photographing.

  In step S24, a variable i indicating the photometric area number is initialized to 1. In step S25, the integral value SumR (i), SumG1 (i), SumG2 (i), SumB (i) of the i-th photometric area is multiplied by the weighting coefficient Wt (i) of that photometric area, For the photometric area (until YES in step S26), the sums SumR, SumG1, SumG2, and SumB of the weighted integral values for each color are calculated by sequentially adding while increasing i by 1 in step S27.

  On the other hand, if it is determined in step S11 that dimming with the speedlight 138 is not necessary, an image is acquired without performing pre-shooting emission (pre-emission), and based on the acquired image, the entire captured image is acquired in step S16. The integral values SumR, SumG1, SumG2, and SumB of the achromatic portion are obtained.

  Next, in step S17, the WB gain calculation unit 114, based on the integral values SumR, SumG1, SumG2, and SumB obtained in either step S25 or step S16, the WB control values WbR and WbG1 according to the above-described equation (1). , WbG2, WbB are obtained, and the obtained WB control values WbR, WbG1, WbG2, WbB are set in the AWB processing unit 105.

  As described above, in order to obtain the auto white balance control value at the time of light control shooting, the detected achromatic part is weighted to obtain the white balance control value, thereby obtaining an appropriate value mainly for the main subject. White balance control processing can be realized.

  As described above, according to the second embodiment, when obtaining the control value of the auto white balance at the time of light control shooting, each photometry area is determined using the weighting coefficient assigned around the area of the main subject. Each color component integral value obtained for each region corresponding to is weighted and summed, and a WB control value is obtained using the weighted integral value of each color. As a result, it is possible to relatively reduce the influence of the color in the shooting screen that does not reach the dimming range, so that the white balance control result in the vicinity of the dimmed main subject becomes an appropriate hue. Can be processed.

<Other embodiments>
An object of the present invention is to supply a storage medium (or recording medium) in which a program code of software for realizing the functions of the above-described embodiments is recorded to a system or apparatus, and a computer (or CPU or MPU) of the system or apparatus. Needless to say, this can also be achieved by reading and executing the program code stored in the storage medium. In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiment, and the storage medium storing the program code constitutes the present invention. Further, by executing the program code read by the computer, not only the functions of the above-described embodiments are realized, but also an operating system (OS) running on the computer based on the instruction of the program code. It goes without saying that a case where the function of the above-described embodiment is realized by performing part or all of the actual processing and the processing is included. Examples of the storage medium for storing the program code include a flexible disk, hard disk, ROM, RAM, magnetic tape, nonvolatile memory card, CD-ROM, CD-R, DVD, optical disk, magneto-optical disk, MO, and the like. Can be considered. Also, a computer network such as a LAN (Local Area Network) or a WAN (Wide Area Network) can be used to supply the program code.

  Furthermore, after the program code read from the storage medium is written into a memory provided in a function expansion card inserted into the computer or a function expansion unit connected to the computer, the function is based on the instruction of the program code. It goes without saying that the CPU or the like provided in the expansion card or the function expansion unit performs part or all of the actual processing and the functions of the above-described embodiments are realized by the processing.

It is a block diagram which shows the function structure of the imaging device in the 1st Embodiment of this invention. It is a flowchart which shows the calculation procedure of the white balance control value in the 1st Embodiment of this invention. It is a figure for demonstrating main subject detection operation | movement. It is a block diagram which shows the function structure of the imaging device in the 2nd Embodiment of this invention. It is a flowchart which shows the calculation procedure of the white balance control value in the 2nd Embodiment of this invention. It is a figure explaining main subject detection operation and a weighting coefficient. It is a block diagram which shows the function structure of the conventional imaging device. It is a figure which shows an example of the combination of the pixel when calculating the position of the color filter on an image sensor, and chromaticity coordinates. It is a figure showing the black body radiation locus | trajectory on a chromaticity coordinate, and an achromatic color determination area | region. It is a figure which shows the light control range in an imaging | photography screen.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Image pick-up element 103 A / D conversion part 105 Auto white balance process part 107 Development process part 109 Image data output part 110 Chromaticity coordinate conversion part 112,212 Achromatic part detection part 114,214 WB gain calculation part 121 Shooting lens 122 Focus Detection unit 124 Lens control unit 132, 232 Photometry unit 134 Drive unit 138 Speedlight 136 Speedlight control unit 140 Main subject region detection unit 240 Weighting coefficient determination unit

Claims (16)

Dimming means;
Imaging means for converting an incident subject optical image into an electrical signal and outputting image data;
Main subject area determining means for determining a main subject area including a main subject in the image data obtained by performing light control by the light adjusting means and picked up by the imaging means;
An imaging device comprising: a calculation unit that detects an achromatic portion in the main subject region from the image data and calculates a white balance control value based on the partial image data corresponding to the achromatic portion. apparatus.   The calculating means totals the partial image data corresponding to the detected achromatic color part for each color, and calculates a coefficient with which the obtained sum for each color has the same ratio as a white balance control value. The imaging device according to claim 1. Dimming means;
Imaging means for converting an incident subject optical image into an electrical signal and outputting image data;
Main subject area determining means for determining a main subject area including a main subject in the image data obtained by performing light control by the light adjusting means and picked up by the imaging means;
Dividing the image data into a plurality of areas, and weighting coefficient determination means for assigning a weighting coefficient to each of the plurality of divided areas so that the weight of the main subject area becomes the heaviest,
A weighted coefficient assigned to the divided area to which each achromatic color part belongs to the partial image data corresponding to each detected achromatic color part for each of the plurality of divided areas of the image data. An image pickup apparatus comprising: a calculation unit that performs weighting by calculating a white balance control value based on the obtained value.   The said calculation means totals the said weighted partial image data for every color, and calculates the coefficient from which the sum for each obtained color becomes the same ratio as a white balance control value. Imaging device.   The imaging apparatus according to claim 1, further comprising a light control unit that controls the light control unit so that an exposure state of the main subject area is appropriate.   6. The imaging apparatus according to claim 1, further comprising a white balance processing unit that performs white balance correction using the white balance control value calculated by the calculation unit.   The imaging apparatus according to claim 1, wherein the main subject area determination unit determines a closest subject as a main subject based on the image data. A focus detection means;
The imaging apparatus according to claim 1, wherein the main subject area determination unit determines a subject at a focal point as a main subject. A determination step of determining whether light control by the light control means is necessary;
When dimming is necessary, the dimming means performs dimming, converts the incident subject optical image into an electrical signal, and outputs image data; and
A main subject region determination step for determining a main subject region including a main subject in the image data captured in the imaging step;
And calculating a white balance control value based on the partial image data corresponding to the achromatic color portion, and detecting an achromatic color portion in the main subject area from the image data. Balance control value calculation method. The calculation step includes
Summing the partial image data corresponding to the detected achromatic color portion for each color;
And a step of calculating a coefficient with which the sum for each obtained color has the same ratio,
The white balance control value calculation method according to claim 9, wherein the calculated coefficient is used as a white balance control value. A determination step of determining whether light control by the light control means is necessary;
When dimming is necessary, the dimming means performs dimming, converts the incident subject optical image into an electrical signal, and outputs image data; and
A main subject region determination step for determining a main subject region including a main subject in the image data captured in the imaging step;
Dividing the image data into a plurality of areas, and assigning a weighting coefficient to each of the plurality of divided areas so that the weight of the main subject area is the heaviest;
A weighted coefficient assigned to the divided area to which each achromatic color part belongs to the partial image data corresponding to each detected achromatic color part for each of the plurality of divided areas of the image data. And calculating a white balance control value based on the obtained value. A white balance control value calculation method comprising: The calculation step includes
Summing the weighted partial image data for each color;
And a step of calculating a coefficient with which the sum for each obtained color has the same ratio,
The white balance control value calculation method according to claim 11, wherein the calculated coefficient is a white balance control value.   13. The white balance control value calculation method according to claim 9, wherein, in the main subject area determination step, a closest subject is determined as a main subject based on the image data. A focus detection step;
The white balance control value calculation method according to claim 9, wherein, in the main subject area determination step, a subject in focus is determined as a main subject.   15. A program executable by an information processing apparatus, comprising program code for realizing the white balance control value calculation method according to claim 9.   A storage medium readable by an information processing apparatus, wherein the program according to claim 15 is stored.

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