JP2017220799A - Imaging apparatus, and method and program for controlling the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an imaging apparatus capable of robust exposure control for characteristics and noise of colors of a subject.SOLUTION: The imaging apparatus comprises: acquisition means that, on the basis of pixel information obtained from imaging devices, acquires pixel-unit color information as a photometric value; estimation means that, on the basis of a photometric value obtained by smoothing luminance values of low chroma pixels in a predetermined region and a photometric value of the low chroma pixels, estimates a noise amount included in the photometric value of the low chroma pixels; noise reduction means that uses, as a new photometric value, any of pieces of color information on the pixels; and control means that executes exposure control by using the new photometric value.SELECTED DRAWING: Figure 4

Description

  The present invention relates to an imaging apparatus, a control method thereof, and a program.

  2. Description of the Related Art Conventionally, imaging apparatuses such as a digital still camera and a digital camcorder having an exposure control function for controlling the brightness of an image to be taken are known. In such an imaging apparatus, there is an apparatus that calculates a brightness value from a photometric value acquired from each pixel value of an image sensor and performs exposure control using the brightness value. In exposure control based on luminance values, the ratio of the R and B components is small in the luminance generation formula for calculating the luminance value from the RGB components of the pixel values, so that depending on the color characteristics of the subject (for example, when the R and B components occupy most of the subject) May be calculated with a low luminance value. In such a case, when controlling the exposure, the exposure is controlled in the direction of brightening the image, resulting in brighter than the appropriate exposure such as occurrence of whiteout. Therefore, a photometric method (hereinafter referred to as RGB maximum value photometry) that approximates the contribution rate to the exposure control of each RGB color by acquiring the maximum value of the color component from the RGB of each pixel of the image sensor as the photometric value of that pixel. An imaging device to be used is also known.

  By the way, since the photometric value obtained from each pixel of the image sensor includes a noise component such as a dark current according to the temperature of the image sensor, a technique for performing exposure control after reducing the noise component in the photometric value is proposed. Has been. Patent Document 1 pays attention to the fact that noise has periodicity, obtains a photometric value obtained at a certain timing and a photometric value obtained by smoothing the noise by averaging in a time series direction, and the photometric value is low (dark). In this case, a technique using a photometric value obtained by smoothing noise is proposed.

JP-A-6-160935

  However, the technique proposed in Patent Document 1 cannot be applied when the imaging apparatus uses RGB maximum value photometry that is robust to the color characteristics of the subject. This is because the noise component is not smoothed even if the RGB maximum values are averaged in time series or space domain. In other words, when the imaging device uses RGB maximum value photometry, noise components are superimposed on the photometric values when high-sensitivity shooting is performed or when the gain of a specific color component is amplified by white balance, and exposure control is performed. May not be performed properly. For this reason, there is a demand for a technique that appropriately controls exposure by reducing noise components when using RGB maximum value photometry that is resistant to the color characteristics of a subject.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide an imaging apparatus capable of robust exposure control with respect to color characteristics and noise of a subject, and a control method and program thereof. .

  In order to solve this problem, for example, an imaging apparatus of the present invention has the following configuration. That is, based on pixel information obtained from the image sensor, acquisition means for acquiring color information for each pixel as a photometric value, and a photometric value and a low chroma obtained by smoothing the luminance value of a low saturation pixel in a predetermined area Based on the photometric value of the degree pixel, an estimation means for estimating the amount of noise included in the photometric value of the low saturation pixel, and any color of the color information of each pixel with the estimated noise amount reduced It is characterized by having noise reduction means that uses information as a new photometric value, and control means that performs exposure control using the new photometric value.

  According to the present invention, exposure control that is robust to color characteristics and noise of a subject can be performed.

1 is a block diagram illustrating an example of a functional configuration of a digital camera as an example of an imaging apparatus according to an embodiment of the present invention. The figure explaining the photometry value acquired in the exposure control process which concerns on Embodiment 1. FIG. FIG. 6 is a diagram for explaining an example of a noise amount estimation table referred to in exposure control processing according to the first embodiment. 7 is a flowchart showing a series of operations of exposure control processing according to the first embodiment. 8 is a flowchart showing a series of operations of exposure control processing according to the second embodiment.

(Embodiment 1)
Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings. In the following description, an example of using an arbitrary digital camera capable of photometry using an imaging device will be described as an example of an imaging apparatus. However, this embodiment is applicable not only to a digital camera but also to any device having an image sensor. These devices include, for example, personal computers, mobile phones including smartphones, game machines, tablet terminals, clock-type and eyeglass-type information terminals, medical devices such as endoscopes and surgery support systems, surveillance cameras, in-vehicle devices, etc. May be included.

(Configuration of digital camera)
FIG. 1 is a block diagram illustrating a functional configuration example of a digital camera 100 as an example of an imaging apparatus according to the present embodiment. One or more of the functional blocks shown in FIG. 1 may be realized by hardware such as an ASIC or a programmable logic array (PLA), or may be realized by a programmable processor such as a CPU or MPU executing software. May be. Further, it may be realized by a combination of software and hardware. Therefore, in the following description, even when different functional blocks are described as the operation subject, the same hardware can be realized as the subject.

  The light reduction unit 1 includes, for example, a diaphragm blade, an ND (Neutral Density) filter, and the like, and adjusts the amount of incident light incident from the outside. The imaging processing unit 2 includes an imaging device, a driver for driving the imaging device, a timing generation circuit, a CDS / AGC circuit, an A / D converter, and the like. The imaging element has a configuration in which a plurality of pixels each having a photoelectric conversion element are two-dimensionally arranged, and photoelectrically converts an object optical image formed by a photographing optical system (not shown) at each pixel. Each pixel of the image sensor includes, for example, one of RGB color filters, and forms a Bayer array. The CDS / AGC circuit samples and amplifies the image signal based on the electric charge stored in each pixel of the image sensor. Note that the CDS / AGC circuit performs, for example, correlated double sampling (CDS) as sampling, and performs automatic gain adjustment (AGC: Auto Gain Control) as amplification, for example. The A / D converter converts the image signal (analog signal) output from the CDS / AGC circuit into a digital signal, and outputs pixel information (image data) including RGB color information in units of pixels. A driver for driving the image pickup device cooperates with the timing generation circuit to supply a drive pulse for driving the image pickup device to the image pickup device to read out an image picked up by the image pickup device and adjust an exposure time. Do.

  The image processing unit 3 performs various signal processing such as AWB (auto white balance) and gamma control on the image data output from the imaging processing unit 2 to generate a captured image.

  The control unit 4 includes, for example, a CPU (MPU), a RAM, a ROM, and the like. The program stored in the ROM is expanded and executed on the RAM to control each unit of the digital camera 100 and data transfer between the blocks. To control. The control unit 4 controls each block of the digital camera 100 in accordance with an operation signal from an operation unit (not shown) that receives an operation from the user.

  The photometric value acquisition unit 5 is configured by a processing circuit or a module, and acquires photometric values of RGB colors in a predetermined region in the captured image generated by the image processing unit 3 (hereinafter, also simply referred to as RGB photometric values). . The RGB maximum value calculation unit 6 is configured by a processing circuit or a module, and among the RGB photometric values acquired by the photometric value acquisition unit 5, the component having the maximum signal intensity is determined as a pixel photometric value (RGB maximum photometric value). ). The luminance value calculation unit 7 includes a processing circuit or a module, and calculates a luminance value from the RGB photometric values acquired by the photometric value acquisition unit 5.

  The achromatic color pixel extraction unit 9 is configured by a processing circuit or a module, and extracts achromatic color pixels or achromatic color regions in the imaging screen generated by the image processing unit 3. For example, when there is an achromatic region such as that shown in FIG. 2A where a specific same subject exists near the center in the captured image, such a region is a detection target of the achromatic pixel extraction unit 9. It becomes. The achromatic color pixel extraction unit 9 specifies an achromatic color pixel or an achromatic color region in the extracted photographed image and outputs it to the luminance average value calculation unit 8.

  In the present embodiment, the achromatic color pixel extraction unit 9 is configured to extract an achromatic color pixel or an achromatic color region in the imaging screen, but is not limited thereto. For example, the achromatic color pixel extraction unit 9 has a low saturation pixel or a small saturation (saturation) in which the saturation in the imaging screen is small (less than a predetermined value) such that the intensity of each RGB photometric value is substantially the same. The configuration may be such that the low region is extracted again when the degree is equal to or less than a predetermined value. For example, a pixel or region in which the difference between other photometric values (for example, G and B) is within 5% with respect to the maximum photometric value (for example, R) among the RGB photometric values is determined as a low saturation pixel. Or, a low saturation region.

  The luminance average value calculation unit 8 is configured by a processing circuit or a module, and uses the achromatic color pixel or the achromatic color region specified by the achromatic color pixel extraction unit 9 included in a predetermined region such as a photometric frame. An average value (average luminance value) of the luminance values calculated by the calculation unit 7 is calculated.

  The noise estimation / removal unit 10 removes (reduces) the amount of noise superimposed on the RGB maximum photometric value by using the average luminance value calculated by the luminance average value calculation unit 8 as a reference signal from which the noise component has been removed. (For example, FIG. 2B). When the noise estimation / removal unit 10 removes (reduces) the noise component from the RGB maximum photometry value, for example, the following two procedures may be used. In the first procedure, first, noise components for RGB colors acquired by the photometric value acquisition unit 5 are calculated and removed (reduced) based on the average luminance value calculated by the luminance average value calculation unit 8 to reduce noise. An RGB maximum photometric value is calculated using the RGB photometric values. In the second procedure, a noise component is calculated and removed (reduced) based on a comparison between the RGB maximum photometric value calculated by the RGB maximum value calculation unit 6 and the average luminance value calculated by the luminance average value calculation unit 8. ) When performing noise reduction of any procedure, it is necessary to make a comparison using the average luminance value of the achromatic color pixel in which the values of the RGB colors match.

  The recording unit 11 stores the captured image generated by the image processing unit 3 in, for example, an internal memory, a memory card such as an SD card or a CF card, or an external storage device such as an external recorder.

  In the embodiment described above, the photometric value acquisition unit 5, the RGB maximum value calculation unit 6, the luminance value calculation unit 7, the luminance average value calculation unit 8, the achromatic color pixel extraction unit 9, and the noise estimation / removal unit 10 are all provided. Although the example comprised independently was shown, the control part 4 may perform all or one part.

(Outline of exposure control in the digital camera 100)
Next, an outline of exposure control in the digital camera 100 will be described. First, image data captured by the imaging processing unit 2 is output, and the image processing unit 3 generates a captured image using the image data.

  The photometric value acquisition unit 5 acquires RGB photometric values from the pixels in the captured image range acquired by the image processing unit 3. In addition, the luminance value calculation unit 7 calculates a luminance value from the RGB photometric values obtained from the photometric value acquisition unit 5 using a predetermined luminance generation formula.

  For example, the achromatic color pixel extraction unit 9 extracts a pixel value that is an achromatic color from the pixel values of the captured image in parallel with the processing of the luminance value calculation unit 7. The achromatic color pixel is used because pixel values having the same RGB value for the same subject are necessary in order to compare the RGB maximum photometric value and the luminance value later.

  The luminance average value calculation unit 8 adds the luminance value of the extracted achromatic pixel when the achromatic color region exists in a predetermined region such as a photometric frame, and also adds the luminance value of the achromatic color pixel. By dividing by the number of pixels, the average value of the luminance values of the achromatic region is calculated. This is because the noise component due to the dark current of the imaging device fluctuates spatially with a predetermined period, and the luminance value of the achromatic pixel is averaged so that the noise component superimposed on the achromatic pixel is reduced. Smoothing (that is, removing). Then, the calculated average brightness value and the RGB photometric values (of the achromatic region) acquired by the photometric value acquisition unit 5 are compared to estimate the noise component. That is, the difference between the RGB photometric value and the average luminance value is the noise component (noise amount) superimposed on the photometric value. Then, the noise amount estimated from the RGB photometric values in the achromatic region is subtracted from the RGB photometric values in other regions (regions other than the achromatic region) in the captured image, thereby removing the noise component of the captured image. can do. The RGB photometric values (or RGB maximum photometric values) in the achromatic region may be values averaged in the achromatic region. In addition, effective pixel values excluding noise components are substantially uniform for achromatic pixels in a predetermined region.

  Then, the RGB maximum value calculation unit 6 calculates the RGB maximum photometric value using the RGB photometric value from which the noise component has been removed. Thereby, the digital camera 100 can perform exposure control based on the RGB maximum photometric values from which noise components have been removed. Note that the calculation of the RGB maximum photometric value is performed by selecting the maximum RGB value for each pixel, or by selecting a specific color component of RGB within the region based on the tendency of the RGB distribution of the subject region (result) The color component having the maximum intensity may be selected as a method).

  On the other hand, when the achromatic color pixel extraction unit 9 does not have an achromatic color pixel, the noise estimation / removal unit 10 removes the noise component according to the noise estimation amount indicated by the noise amount estimation table created in advance. For example, as shown in FIG. 3, the noise amount estimation table is created according to the gain amount set in the digital camera 100 and the temperature of the image sensor. Therefore, the noise estimation / removal unit 10 can select a noise estimation amount corresponding to the gain and temperature by acquiring gain information and temperature information set in the digital camera 100.

  Thereafter, the noise estimation / removal unit 10 subtracts the noise estimation amount from the RGB photometric values acquired by the photometric value acquisition unit 5 to remove noise components. Then, the RGB maximum value calculation unit 6 acquires the RGB maximum photometric value using the RGB photometric value from which the noise component has been removed. In this way, the digital camera 100 can perform exposure control using the RGB maximum photometric value from which noise components have been removed. Also, when the presence of achromatic pixels changes over time, noise components are removed using the average value of luminance values when there are achromatic pixels, and according to the noise amount estimation table when there are no achromatic pixels. Noise component removal is applied to each.

(A series of operations related to exposure control processing)
Next, a series of operations related to the exposure control process will be described with reference to FIG. This process is started when, for example, a recording start button included in an operation unit (not shown) is pressed and a shooting instruction is received from the user. This process is realized by the control unit 4 expanding and executing the program stored in the ROM in the work area of the ROM, and controlling each unit such as the photometric value acquisition unit 5.

  In step S <b> 101, the photometric value acquisition unit 5 acquires RGB photometric values for each pixel based on the image data output from the image processing unit 3. In S102, the achromatic color pixel extraction unit 9 extracts achromatic color pixels based on the photometric value for each pixel acquired in S101. The achromatic color pixel extraction unit 9 extracts, for example, a pixel in which the RGB photometric value of each pixel is R = G = B as an achromatic color pixel. In this embodiment, if the difference between the RGB photometric values of each pixel is within a predetermined range (for example, the error of the output value of the photometric value is within ± 1%), the RGB photometric values of each pixel are R = G. = B is determined. In other words, a configuration may be employed in which pixels in which the RGB photometric values of the pixels are substantially the same (the difference between the photometric values is within a predetermined value) are extracted as achromatic pixels.

  In S103, the achromatic color pixel extraction unit 9 determines whether or not the achromatic color pixel extracted in S102 exists in a predetermined area such as a photometric frame in the captured image (that is, whether there is an achromatic color area). For example, when the number of achromatic pixels extracted in S102 in the predetermined area is equal to or larger than the predetermined number, the achromatic color pixel extraction unit 9 determines that an achromatic color pixel exists (that is, an achromatic color area exists). Determination is made and the process proceeds to S104. On the other hand, if the number of achromatic pixels is less than the predetermined number, it is determined that there are no achromatic pixels in the predetermined area, and the process proceeds to S107.

  In S <b> 104, the luminance value calculation unit 7 calculates a luminance value corresponding to each pixel of the achromatic color pixel among the RGB photometric values acquired by the photometric value acquisition unit 5 based on a predetermined luminance generation formula. In S <b> 105, the luminance average value calculation unit 8 calculates the average luminance value by integrating the luminance values of the achromatic pixels in the predetermined region and dividing by the number of pixels. As described above, by performing this processing, it is possible to smooth the noise component superimposed on the luminance value.

  In S106, the noise estimation / removal unit 10 subtracts the amount of noise based on the RGB photometric values acquired by the photometric value acquisition unit 5 and the averaged luminance values calculated by the luminance average value calculation unit 8. To do. Specifically, the noise estimation / removal unit 10 first averages the RGB photometric values of the achromatic pixels among the photometric values acquired by the photometric value acquisition unit 5 and is calculated by the luminance average value calculation unit 8. Subtract the brightness value. That is, the amount of noise superimposed on the RGB photometric values of the achromatic pixel can be obtained. Next, the calculated noise amount is subtracted from the RGB photometric values acquired by the photometric value acquisition unit 5 for pixels other than the predetermined region (for example, pixels of the entire captured image including pixels other than the achromatic region). . By doing so, it is possible to remove noise components superimposed on each color of RGB.

  On the other hand, in S107, the control unit 4 acquires the currently set gain value from the current setting information stored in the ROM or the like or from the imaging processing unit 2, and from a sensor (not shown) or the imaging processing unit. Temperature information indicating the temperature of the image sensor is acquired from 2. The temperature information is not limited to the temperature of the image sensor, and may be the temperature in the vicinity of the image sensor or the inside of the housing of the digital camera 100.

  In S108, the control unit 4 selects a noise estimation amount from a noise amount estimation table created in advance. Specifically, the control unit 4 acquires a noise amount specified based on the gain value and temperature information acquired in S107 in the noise amount estimation table. In this embodiment, the noise amount estimation table using the gain value and the temperature information is described as an example, but the noise amount estimation table may be configured by other items as long as it is an item for referring to noise. Good.

  In S109, the noise amount acquired from the noise amount estimation table is subtracted from the RGB photometric values acquired by the photometric value acquisition unit 5. By doing in this way, the noise component superimposed on the photometric value of each RGB color can be removed.

  In S110, the RGB maximum value calculation unit 6 calculates (selects) the RGB maximum value of each pixel as the photometric value of each pixel using the photometric values of each RGB color from which the noise amount has been removed in S106 or S109. Further, in S111, the control unit 4 performs exposure control using the RGB maximum photometric value calculated by the RGB maximum value calculation unit 6, and thereafter ends the series of operations. That is, the control unit 4 sets the RGB maximum photometry value calculated by the RGB maximum value calculation unit 6 to a new photometry value used for exposure control and performs exposure control, and then ends a series of operations.

  As described above, in this embodiment, the noise amount with respect to the RGB photometric value is calculated and removed using the RGB photometric value of the achromatic pixel and the average luminance value of the achromatic pixel. Then, the RGB maximum photometric value is calculated using the RGB photometric value from which the noise component has been removed, and exposure control is performed using the RGB maximum photometric value. This avoids the problem of the photometric value being calculated to be low due to the color characteristics of the subject, while reducing noise on the RGB maximum photometric value, thus realizing more appropriate exposure control. can do. In other words, exposure control that is robust to the color characteristics of the subject and robust to noise can be realized.

  In addition, with the above-described configuration, it is possible to suppress an increase in the additional cost of a circuit, a processing load, and the like due to enlargement of each pixel of the image sensor or addition of an NR circuit or the like in order to relatively reduce noise. Can do.

(Embodiment 2)
Next, Embodiment 2 will be described. In the first embodiment, the noise amount of the RGB photometric value is excluded based on the comparison between the RGB photometric value and the average luminance value, and then the RGB maximum photometric value from which the noise component is excluded is obtained. The second embodiment is different from the first embodiment in that the RGB maximum photometric value from which noise components are excluded is calculated based on the comparison between the RGB maximum photometric value and the average luminance value, but the other configuration is different from the first embodiment. Are the same. For this reason, the same reference numerals are assigned to the same components, and redundant descriptions are omitted, and differences will be mainly described.

(Outline of exposure control in this embodiment)
Also in the present embodiment, the luminance value calculation unit 7 calculates the luminance value from the RGB photometric values obtained from the photometric value acquisition unit 5, and the luminance average value for the achromatic pixels extracted by the achromatic pixel extraction unit 9. The calculation unit 8 calculates an average value of luminance values.

  Next, the noise estimation / removal unit 10 compares the calculated average brightness value with the RGB maximum photometry value calculated by the RGB maximum value calculation unit 6 in order to estimate the noise component. At this time, as in the above-described embodiment, the RGB component obtained from the average luminance value and the RGB maximum photometric value can be compared by using the average luminance value of the achromatic color pixels in the predetermined region. The noise estimation / removal unit 10 can obtain the RGB maximum photometry value from which the noise component is removed by subtracting the noise component obtained by the comparison from the RGB maximum photometry value.

  On the other hand, when there is no achromatic pixel, the noise estimation / removal unit 10 removes the noise component using the noise amount indicated by the noise amount estimation table similar to that of the first embodiment. Specifically, the RGB maximum photometry value from which the noise component has been removed is obtained by subtracting the noise estimation amount selected from the noise amount estimation table from the RGB maximum photometry value. In this way, the digital camera 100 can perform exposure control using the RGB maximum photometric value from which noise components have been removed.

(A series of operations related to exposure control processing)
Next, a series of operations related to the exposure control process in the present embodiment will be described with reference to FIG. Similar to the first embodiment, this process is started when a release instruction included in an operation unit (not shown) is pressed and a photographing instruction is received from the user. This process is realized by the control unit 4 expanding and executing the program stored in the ROM in the work area of the ROM, and controlling each unit such as the photometric value acquisition unit 5.

  In S101, the photometric value acquisition unit 5 acquires RGB photometric values for each pixel, as in the first embodiment. Next, in S201, the RGB maximum value calculation unit 6 calculates the RGB maximum value of each pixel as the RGB maximum photometric value of each pixel.

  Then, the control part 4 performs the process of S102-S105 similarly to Embodiment 1. FIG. That is, as a result of extracting the achromatic color pixel, when the achromatic color pixel exists in the predetermined area, the average value of the luminance values of the achromatic color pixel in the predetermined area is calculated.

  In S202, the RGB maximum value calculation unit 6 subtracts the noise amount based on the RGB maximum photometric value of the achromatic color pixel in the predetermined region and the averaged luminance value. Specifically, first, the amount of noise is calculated by subtracting the luminance average value of the achromatic color pixel from the RGB maximum photometric value of the achromatic color pixel in the predetermined region. Then, the RGB maximum value calculation unit 6 subtracts the calculated noise amount from the RGB maximum photometric value of the pixel of the captured image including areas other than the predetermined area, thereby removing the noise component superimposed on the RGB maximum photometric value. To do.

  On the other hand, when the achromatic color region does not exist, the control unit 4 causes the processing of S107 to S108 to be executed as in the first embodiment, and selects the noise amount based on the noise amount estimation table. In S203, the noise estimation / removal unit 10 can remove the noise component superimposed on the photometric value of the RGB maximum value calculation unit 6 by subtracting the noise amount acquired from the noise amount estimation table.

  In S111, the control unit 4 performs exposure control based on the RGB maximum photometric value calculated by the RGB maximum value calculation unit 6, and then ends the series of operations.

  As described above, in the present embodiment, the noise amount of the RGB maximum photometric value is obtained by subtracting the luminance average value of the achromatic pixel in the predetermined area from the RGB maximum photometric value of the achromatic pixel in the predetermined area. Was calculated so that the noise could be removed. By doing so, it is possible to realize the same effect as the above-described embodiment, that is, exposure control that is robust to the color characteristics of the subject and robust to noise. In addition, the configuration of the present embodiment also increases the additional cost of the circuit and the processing load by increasing the size of each pixel of the image sensor or adding an NR circuit to relatively reduce noise. Can be suppressed.

(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 2 ... Imaging processing part, 3 ... Image processing part, 4 ... Control part, 5 ... Photometric value acquisition part, 6 ... RGB maximum value calculation part, 7 ... Luminance value calculation part, 8 ... Luminance average value calculation part, 9 ... None Colored pixel extraction unit, 10 ... noise estimation / removal unit

Claims (13)

Based on pixel information obtained from the image sensor, acquisition means for acquiring color information for each pixel as a photometric value;
Based on the photometric value obtained by smoothing the luminance value of the low saturation pixel in the predetermined area and the photometric value of the low saturation pixel, the amount of noise included in the photometry value of the low saturation pixel is calculated. Estimating means for estimating;
Noise reducing means for reducing the estimated noise amount and using any one of the color information of each pixel as a new photometric value;
An image pickup apparatus comprising: control means for performing exposure control using the new photometric value.   The image pickup apparatus according to claim 1, wherein the noise reduction unit sets any color information of the color information of each pixel from which the estimated noise amount is removed as a new photometric value.   The estimation means compares the photometric value obtained by smoothing the luminance value of the low chroma pixel with the photometric value of the low chroma pixel, and thereby includes noise included in the photometric value of the low chroma pixel. The imaging device according to claim 2, wherein the imaging device is configured to estimate a quantity.   The estimation means compares the photometric value obtained by smoothing the luminance value of the low saturation pixel with the color information of any one of the color information of the low saturation pixel, thereby calculating the low saturation pixel. The imaging apparatus according to claim 2, wherein the imaging apparatus is configured to estimate an amount of noise included in the photometric value.   The noise reduction means subtracts the estimated noise amount from each of the color information of each pixel, and the color information of each pixel from which the noise amount has been subtracted is replaced with the new photometric value. The imaging apparatus according to claim 3, wherein the imaging apparatus is configured as follows.   The noise reduction means subtracts the estimated noise amount from any color information of the color information of each pixel, and calculates any color information of each pixel from which the noise amount has been subtracted as the new photometry. The imaging device according to claim 4, wherein the imaging device is configured to be a value.   7. The imaging apparatus according to claim 1, wherein any one of the color information of each pixel is color information having the strongest intensity among the color information of each pixel. .   The estimation means calculates a luminance value of the low saturation pixel in the predetermined area based on color information for each low saturation pixel, and calculates a luminance value of the low saturation pixel in the predetermined area. The imaging device according to claim 1, wherein the imaging device is configured to obtain a photometric value obtained by smoothing a luminance value of the low saturation pixel by averaging. .   The estimation means estimates a noise amount included in the photometric value for each pixel using a noise amount indicated by a predetermined noise amount estimation table when the low saturation pixel does not exist in the predetermined region. The imaging apparatus according to claim 1, wherein the imaging apparatus is configured to be configured as described above.   The image pickup apparatus according to claim 9, wherein the noise amount indicated by the noise amount estimation table is specified based on a gain amount set for the pixel information and a temperature of the image sensor.   The estimation means uses a pixel whose intensity of each color information in the predetermined area is substantially the same as the low saturation pixel, and a photometric value obtained by smoothing a luminance value of the low saturation pixel and the low saturation 11. The imaging apparatus according to claim 1, wherein a noise amount included in the photometric value of the low saturation pixel is estimated based on the photometric value of the pixel. An acquisition step in which an acquisition unit acquires color information for each pixel as a photometric value based on pixel information obtained from an image sensor;
The estimation means includes the photometric value of the low chroma pixel based on the photometric value obtained by smoothing the luminance value of the low chroma pixel in the predetermined area and the photometric value of the low chroma pixel. An estimation step for estimating the amount of noise generated,
The setting means includes a setting step of setting any color information of the color information of each pixel with the estimated noise amount reduced to a new photometric value used for exposure control. Control method of imaging apparatus.   The program for functioning a computer as each means of the imaging device of any one of Claim 1 to 11.

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