JP4717720B2 - Image processing apparatus and method, and program - Google Patents

Description

  The present invention relates to an image processing apparatus and method for processing two image data acquired with different sensitivities for the same subject, and a program for causing a computer to execute the image processing method.

  In recent years, digital cameras are equipped with functions such as AE (automatic exposure) and AF (automatic focus adjustment) so that photographing can be performed more easily. Center-weighted metering is generally known as the AE metering method. However, when photographing with a composition in which the main subject is not in the center, center-weighted metering can provide an appropriate exposure according to the main subject. There is no problem. For this reason, exposure control is also performed by so-called multi-pattern photometry in which the amount of light is measured at a plurality of points. According to multi-pattern metering, since average exposure control is performed over the entire frame, it is possible to solve the problem in the case where the person who is the main subject is not in the center as described above. However, when a person is photographed with backlight, the AE is determined to be bright overall and exposure control is performed to reduce the amount of light regardless of the composition, and the person's face becomes dark.

  For this reason, exposure control is also performed by spot photometry that fixes the exposure to the main subject. If exposure control using spot metering is used, the release button is pressed halfway to adjust the exposure to the main subject, and if the angle of view is moved to achieve the desired composition, the brightness of the main subject in the desired composition can be adjusted. It can be appropriate. However, when the angle of view is changed while the release button is in a half-pressed state, there is a possibility that the release button is accidentally fully pressed or the half-press is released.

  Here, in an image in which a subject to be photographed is a person, in particular, since the photographing state of the person's face affects the performance of the image, it is desired to make the person's face appropriate brightness. For this reason, various methods for extracting a human face from an image and correcting the image so that the extracted face has a desired brightness have been proposed (see Patent Documents 1 to 3). By using these methods, it is possible to correct the brightness of the person to be appropriate.

  By the way, a CCD, which is an imaging means used in a digital camera, has a narrow dynamic range as compared with a silver salt film, so that overexposure and blackout of an image are likely to occur. For this reason, in order to obtain image data with a wide dynamic range, a technique for combining a plurality of pieces of image data captured under different exposure conditions is known.

In addition, a high-sensitivity image obtained from a main pixel using a CCD in which a high-sensitivity main pixel (S pixel) and a sub-pixel (R pixel) that has a smaller area than the main pixel but is less sensitive but less saturated are arranged. A digital camera capable of securing a wide dynamic range by combining data and low-sensitivity image data obtained by sub-pixels and obtaining composite image data having good reproducibility in a wide range including a high-luminance part. Is provided.
JP 2004-153315 A JP-A-2005-311484 JP 2005-51407 A

  However, when the methods described in Patent Documents 1 to 3 are used, the brightness of the face can be corrected to be appropriate, but the brightness of portions other than the face is also corrected accordingly. For this reason, when correction is performed to brighten the face when the face is dark, the high-luminance portion included in the image is saturated, and there is a possibility that overexposure occurs.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to make the brightness of a specific subject such as a person included in an image suitable and to prevent overexposure of the image.

An image processing apparatus according to the present invention processes first image data captured with high sensitivity with respect to the same subject and second image data captured with sensitivity lower than the first image data. In
Detecting means for detecting a maximum dynamic range of the subject;
Luminance correction means for correcting the first and second image data so that the luminance of a specific object included in the subject becomes a predetermined luminance;
Wherein according to the correction of the brightness the predetermined luminance of the specific object included in the subject, a correction coefficient calculating means for calculating a correction coefficient for correcting the maximum dynamic range,
Dynamic range correction means for correcting the maximum dynamic range by the correction coefficient;
The image processing apparatus includes a combining unit that combines the corrected first and second image data in accordance with the corrected maximum dynamic range to obtain combined image data.

  In the image processing apparatus according to the present invention, the correction coefficient calculation means may be means for calculating the correction coefficient based on the first image data.

  In the image processing apparatus according to the present invention, the synthesizing unit selects a gradation conversion characteristic according to the corrected maximum dynamic range from a plurality of gradation conversion characteristics prepared in advance according to various dynamic ranges. In addition, the first and second image data may be subjected to gradation conversion and composition based on the selected gradation conversion characteristics.

The image processing apparatus according to the present invention may further include face detection means for detecting a human face as the specific object from the images represented by the first and second image data. .

In the photographing apparatus according to the present invention, a high-sensitivity pixel that performs high-sensitivity imaging on the same subject and a low-sensitivity pixel that is lower in sensitivity than the high-sensitivity pixel are arranged, and the first image is formed by the high-sensitivity pixel. Imaging means for obtaining data and obtaining second image data by the low-sensitivity pixels;
An image processing apparatus according to the present invention;
And recording means for recording the composite image data.

An image processing method according to the present invention processes first image data captured with high sensitivity for the same subject and second image data captured with lower sensitivity than the first image data. In
Detecting the maximum dynamic range of the subject,
Correcting the first and second image data so that a specific object included in the subject has a predetermined luminance;
According to the correction of the brightness the predetermined luminance of the specific object included in the subject, calculates a correction coefficient for correcting the maximum dynamic range,
The maximum dynamic range is corrected by the correction coefficient,
The corrected first image data and the second image data are combined according to the corrected maximum dynamic range to obtain combined image data.

  The image processing method according to the present invention may be provided as a program for causing a computer to execute the image processing method.

  According to the present invention, the maximum dynamic range of a subject is detected, the brightness of a specific object included in the subject is detected, and the brightness of the specific object is a predetermined brightness. The first image data imaged with high sensitivity and the second image data imaged with lower sensitivity than the first image data are corrected. Further, a correction coefficient for correcting the maximum dynamic range according to this correction is calculated, and the maximum dynamic range is corrected by the correction coefficient. Then, in accordance with the corrected maximum dynamic range, the first image data and the second image data corrected so that the specific object has a predetermined luminance is combined to obtain combined image data. .

  Therefore, the first image data and the second image data are not saturated according to the corrected maximum dynamic range while correcting the brightness of a specific object included in the subject to a predetermined brightness. Can be synthesized. Therefore, it is possible to obtain an image without overexposure while making the brightness of the specific object suitable.

  Further, by calculating the correction coefficient based on the first image data, the calculation for calculating the correction coefficient is compared with the case where the correction coefficient is calculated using both the first and second image data. Time can be shortened.

  In addition, by selecting a gradation conversion characteristic corresponding to the corrected maximum dynamic range from a plurality of gradation conversion characteristics prepared in advance according to various dynamic ranges, the first can be easily performed without performing complicated calculations. The composite image data can be acquired by converting the gradation of the second image data.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic block diagram showing a configuration of a digital camera which is an embodiment of a photographing apparatus of the present invention. As shown in FIG. 1, the digital camera 1 according to the present embodiment includes an imaging unit 2, an analog signal processing unit 4, a control unit 6, a digital signal processing unit 8, a compression / decompression unit 10, a display unit 12, a recording unit 14, and a memory. 16, an operation unit 18, a face detection unit 20, and a correction value calculation unit 22.

  The imaging unit 2 is an imaging unit including an imaging lens (not shown), a diaphragm, a mechanical shutter, a drive circuit that drives these, and a CCD that photoelectrically converts an optical image formed through the imaging lens. An optical image is formed on the imaging surface of the CCD and exposed for a predetermined time, thereby outputting an analog signal corresponding to the formed image.

  The CCD is an optical sensor having a large number of light receiving elements arranged in a honeycomb shape. FIG. 2 is a partially enlarged view showing the arrangement of the light receiving elements in the CCD. As shown in FIG. 2, in the CCD 40, octagonal light receiving elements 42 corresponding to one pixel of the image are arranged in a honeycomb shape, and each light receiving element 42 includes a main pixel 42S having a large light receiving area and a main pixel 42S. The sub-pixel 42R has a small light receiving area.

  The main pixel 42S saturates earlier than the sub-pixel 42R when receiving the same amount of light because the signal charge generation amount is large and the light receiving sensitivity is increased according to the area ratio compared to the sub-pixel 42R. .

  FIG. 3 is a graph showing the relationship of the output signal level with respect to the incident light amount when the area ratio of the main pixel 42S and the sub-pixel 42R is 4: 1. The main pixel output QS is at a level where the incident light amount is 100%. The subpixel output QR is saturated and the state where the incident light quantity is not saturated to a level of 400% is shown, and the sensitivity ratio is 16: 1. When the sub-pixel output QR is combined with the main pixel output QS, as shown in the characteristic QG, the dynamic range can be expanded so as to reproduce the gradation of the highlight portion.

  The analog signal processing unit 4 is a correlated double sampling circuit (CDS) that removes noise of the analog signal output from the imaging unit 2, an auto gain controller (AGC) that adjusts the gain of the analog signal, and digitally converts the analog signal to It consists of an A / D converter (ADC) that converts it into a signal. The image data converted into the digital signal is CCD-RAW data having R, G, and B density values for each pixel.

  The control unit 6 controls the operation of each unit connected by the bus 30 and performs overall control related to the imaging operation of the digital camera 1 based on the input from the operation unit 18 including the release button 18A and other operation switches. . Specifically, AF processing for determining the focal position based on the pre-image, AE processing for determining the aperture value, shutter speed, and the like based on the subject luminance measured by measuring the subject luminance are performed. When performing these processes, the pre-image may use only one of the first image consisting only of the output of the main pixel 42S and the second image consisting only of the output of the sub-pixel 42R. The second image may be added and used. Note that by using only one of the first and second images, operations for these processes can be performed at high speed. By using the first image obtained from the main pixel 42S having particularly high sensitivity, more accurate AF processing and AE processing can be performed.

  Here, the pre-image is represented by image data obtained by causing the imaging unit 2 to perform pre-photographing by the control unit 6 that has detected the half-press signal S1 generated when the release button 18A is half-pressed. It is an image.

  Further, the control unit 6 calculates the maximum dynamic range of the subject based on the measured subject luminance, and corrects the maximum dynamic range DRmax with the correction coefficient k2 calculated by the correction value calculation unit 22 as will be described later, thereby correcting the dynamic range. Calculate DRrev.

  The face detection unit 20 detects a human face from the analog processed main image. Specifically, an area having a facial feature included in the face (for example, having skin color, having eyes, or having a face shape) is detected as a face area, but the present invention is not limited to this.

  Here, the main image is represented by image data obtained by causing the image pickup unit 2 to perform main shooting when the control unit 6 that has detected the full press signal S2 generated when the release button 18A is fully pressed. It is an image.

  The upper limit of the number of pixels of the main image is determined by the number of pixels of the CCD 40. For example, the number of recorded pixels can be changed by setting such as fine and normal. On the other hand, the number of pre-images is smaller than that of the main image. For example, the pre-image is captured with about 1/16 of the number of pixels of the main image.

  The correction value calculation unit 22 calculates the brightness (luminance value) of the face area detected by the face detection unit 20, and corrects the brightness of the image from the difference between the calculated brightness and a desired appropriate brightness. A correction value k1 for correction and a correction coefficient k2 for correcting the maximum dynamic range DRmax are calculated.

  Hereinafter, calculation of the corrected dynamic range DRrev will be described. FIG. 4 is a diagram for explaining calculation of the corrected dynamic range DRrev. First, in the AE process based on the pre-image, the area within the angle of view represented by the pre-image is divided into 16 as shown in FIG. 4A, and the distribution of subject reflectance in each of the areas A1 to A16 is obtained. Here, as shown in FIG. 4B, when the distribution of the subject reflectance is obtained, the control unit 6 calculates the maximum dynamic range DRmax as 230%.

  On the other hand, as shown in FIG. 4C, the face detection unit 20 detects a face area F1 from the analog processed main image.

  Further, the correction value calculation unit 22 calculates the average luminance Ym of the face area F1. Then, a correction value k1 = Yp−Ym for correcting the average luminance Ym to a desired luminance Yp is calculated. Further, the correction value calculation unit 22 calculates a correction coefficient k2 for correcting the maximum dynamic range DRmax by the following equation (1).

k2 = Yp / Ym (1)
Here, when Yp = 50 and Ym = 30, k2 = 5/3. Therefore, when the subject reflectance in each of the areas A1 to A16 is corrected by the correction coefficient k2, the result is as shown in FIG. Therefore, when the maximum dynamic range DRmax is 230%, the corrected dynamic range DRrev is 383%.

  The digital signal processing unit 8 performs image quality correction processing such as AWB (auto white balance) for automatically adjusting white balance at the time of shooting, brightness correction, gamma correction, gradation conversion processing, and the like on the image data of the main image, and YC processing is performed to convert the CCD-RAW data into YC data composed of Y data that is a luminance signal, Cb data that is a blue color difference signal, and Cr data that is a red color difference signal. In particular, the digital signal processing unit 8 performs brightness correction processing so that the luminance of the face area detected by the face detection unit 20 becomes a desired luminance. The configuration of the digital signal processing unit 8 and the processing performed by the digital signal processing unit 8 will be described later.

  The compression / decompression unit 10 compresses the image data of the main image processed by the digital signal processing unit 8 by a predetermined compression method such as the JPEG method, and records it on a recording medium loaded in the recording unit 14 or records it. The image data read from the medium is expanded.

  The display unit 12 is a display for image display composed of a liquid crystal monitor or the like, and is driven by a display control unit (not shown) to perform various displays necessary for images and operations.

  The recording unit 14 records the acquired image data of the main image and tag information for each image data on a recording medium such as a memory card. Specifically, the main image compressed by the JPEG method is provided with a tag storing additional information such as the shooting date and time and recorded on a recording medium.

  The memory 16 stores various constants set in the digital camera 1 and programs executed by the control unit 6. Also, it becomes a work area when the digital camera 1 performs various processes.

  FIG. 5 is a schematic block diagram showing the configuration of the digital signal processing unit 8. As shown in FIG. 5, the digital signal processing unit 8 calculates image data high (hereinafter referred to as main pixel data) of the main pixel generated and input by the main pixel 42S of the CCD 40 to correct the spectral characteristics. An offset processing unit 50S that performs processing, a gain processing unit 52S that performs processing to correct the brightness of the image and adjust white balance (WB) based on the correction value k1, and a γ correction unit 54S that performs γ correction. Is provided.

  Also, the digital signal processing unit 8 calculates the sub-pixel image data low (hereinafter referred to as sub-pixel data) generated and input by the sub-pixel 42R, and performs processing for correcting spectral characteristics and the like. 50R, a gain processing unit 52R that performs processing for correcting the brightness of the image and adjusting white balance (WB) based on the correction value k1, and a γ correction unit 54R that performs γ correction.

  The γ correction units 54S and 54R are circuits for correcting gamma (γ) of the main pixel data high of 14-bit data and the sub-pixel data low of maximum 12-bit data, respectively. The γ correction units 54S and 54R The main pixel data high and the sub-pixel data low represented by, for example, 8 bits are output after being corrected to the gradation corresponding to the processing purpose such as the output form.

  Further, the digital signal processing unit 8 includes a gain calculation unit 56. The gain calculation unit 56 multiplies the main pixel data high with reference to a look-up table (LUT) 58 based on the corrected dynamic range DRrev calculated by the control unit 6 in order to perform a wide dynamic range synthesis process to be described later. A gain h_gain to be multiplied and a gain l_gain to be multiplied by the sub-pixel data low are calculated.

  The gain h_gain calculated by the gain calculation unit 56 is multiplied by the output of the γ correction unit 54S by the multiplication unit 60S. Also, the gain l_gain is multiplied by the output of the γ correction unit 54R by the multiplication unit 60R. Further, the outputs of the multiplying units 60S and 60R are added by the adding unit 62, thereby calculating the composite image data. Here, the multiplying units 60S and 60R and the adding unit 62 constitute a wide dynamic range synthesis processing unit 64. Note that the composite image data obtained in the adding unit 62 is input to a sharpness processing unit, a color correction processing unit, and the like (not shown), where sharpness processing, color correction processing, and the like are performed and output from the digital signal processing unit 8. Is done.

  Here, the LUT 58 and the wide dynamic range synthesis process will be described. The value data of the synthesized image data output from the adding unit 62 by the wide dynamic range synthesis process is calculated by the following equation (2).

data = (high + MIN (high / th, 1) × low) × MAX (-lg (high / th) + 1, p) (2)
＝ MAX (-lg (high / th) + 1, p) × high + (MAX (-lg (high / th) + 1, p) × MIN (high / th, 1)) × low (3)
h_gain = MAX (-lg (high / th) + 1, p) (4)
l_gain = MAX (-lg (high / th) + 1, p) × MIN (high / th, 1)) = h_gain × wl (5)
Then,
data = h_gain × high + l_gain × low (6)
It is.

  Note that p is a gain with respect to the added main pixel data high and sub-pixel data low, and controls the dynamic range. Normally, a value of about 0.8 to 0.9 is used as p. The smaller the value of p, the wider the wide dynamic range, and the larger the value, the narrower the wide dynamic range. More specifically, the scene dynamics are about 0.8 for scenes such as clear midsummer sky with high contrast, about 0.86 for cloudy or shaded scenes, and 0.9 for hearts under indoor fluorescent lights. By changing the value of p according to the range, the 8-bit width of the output data can be used effectively.

  th is a threshold value for controlling the degree of synthesis of the main pixel data high and the sub-pixel data low.

  lg is a parameter for controlling the degree to which the main pixel data high and the sub-pixel data low are combined.

  Here, the LUT 58 defines the parameters p, th, and lg for calculating the gain h_gain and the gain l_gain. FIG. 6 is a diagram showing the configuration of the LUT 58. As shown in FIG. 6, the LUT 58 defines the parameters p, th, and lg for calculating the gain h_gain and the gain l_gain, for example, in seven stages in 100% to 400% as dynamic ranges in increments of 50%.

  With such parameters, h_gain has input / output characteristics as shown in FIG. 7, for example, and l_gain is obtained by multiplying the input / output characteristics shown in FIG. 7 by the input / output characteristics shown in FIG. .

  Next, processing performed in the present embodiment will be described. FIG. 9 is a flowchart showing processing performed in the present embodiment. First, when the half-press signal S1 of the release button 18A is detected (step ST1), AE and AF processing are performed based on the pre-image obtained by pre-photographing (step ST2), and the maximum dynamic The range DRmax is calculated (step ST3). Then, the calculated maximum dynamic range DRmax is temporarily stored in the memory 16 (step ST4).

  Next, when the full-press signal S2 of the release button 18A is detected (step ST5), the main image is taken and the main image composed of pixel data corresponding to the signal charges generated in each of the main pixel 42S and the sub-pixel 42R. Data is processed in the analog signal processing unit 4 and stored in the memory 16 (step ST6).

  Then, the face detection unit 20 detects a face area from the image represented by the main pixel data obtained in the main pixel 42S (step ST7), and the correction value calculation unit 22 calculates the correction value k1 and the correction coefficient k2 ( Then, the control unit 6 corrects the maximum dynamic range DRmax with the correction coefficient k2 and calculates the corrected dynamic range DRrev (step ST9).

  Next, the digital signal processing unit 8 reads the main pixel data and subpixel data stored in the memory 16, and performs offset processing, gain processing, and γ correction processing (step ST10). The gain processing units 52S and 52R perform gain processing based on the correction value k1 so that the brightness of the face becomes a desired brightness.

  Then, the gain calculation unit 56 calculates gains h_gain and l_gain based on the corrected dynamic range DRrev (step ST11), and the wide dynamic range synthesis processing unit 64 performs wide dynamic range synthesis processing using the calculated gains h_gain and l_gain. (Step ST12). Further, the composite image data obtained by performing the wide dynamic range composition processing is subjected to other necessary image processing, and the processed composite image data is recorded on the recording medium by the recording unit 14 (step S1). ST14), the process ends.

  Thus, according to the present embodiment, the main pixel data and the sub-pixel data are subjected to gradation conversion using the gains h_gain and l_gain corresponding to the correction dynamic range DRrev while correcting the facial brightness to a desired brightness. Can be synthesized. Therefore, it is possible to obtain an image without overexposure while making the brightness of the specific object suitable.

  In the above embodiment, the detection of the face area and the calculation of the correction value and the correction coefficient of the face area are performed using the main pixel data high, but the data obtained by adding the main pixel data high and the sub-pixel data low. The face area may be detected and the brightness correction value and the correction coefficient may be calculated.

  The digital camera 1 according to the first embodiment of the present invention has been described above, but a program for causing a computer to perform the process shown in FIG. 9 is also one embodiment of the present invention. A computer-readable recording medium in which such a program is recorded is also one embodiment of the present invention. In these cases, the LUT 58 may be included in the program or the same recording medium, or may be provided from an external device or a separate recording medium.

  By installing such a program in a personal computer, it is possible to perform wide dynamic range composition processing on the CCD-RAW data acquired in the digital camera 1 in the personal computer as in the above embodiment. For example, as shown in FIG. 10A, the CCD-RAW data is expanded and displayed on the processing screen 70, and the maximum dynamic range DRmax is displayed in the dynamic range display area 70A. Then, by clicking the automatic correction button 70B, dynamic range synthesis processing is performed, and the processed image is displayed on the processing screen 70 as shown in FIG. At this time, the corrected dynamic range DRrev is displayed in the dynamic range display area 70A.

  In this case, the maximum dynamic range DRmax, the correction value k1, and the correction coefficient k2 may be calculated using main pixel data included in the CCD-RAW data.

1 is a schematic block diagram showing the configuration of a digital camera that is an embodiment of a photographing apparatus of the present invention. Partial enlarged view showing arrangement of light receiving elements in CCD The graph which shows the relationship of the output signal level with respect to the incident light quantity in case the area ratio of a main pixel and a subpixel is 4: 1. Diagram for explaining the calculation of the corrected dynamic range Schematic block diagram showing the configuration of the digital signal processor Diagram showing LUT configuration Diagram showing input / output characteristics of h_gain The figure which shows the input-output characteristic multiplied by h_gain in order to calculate l_gain A flowchart showing processing performed in the present embodiment Figure showing the program processing screen

DESCRIPTION OF SYMBOLS 1 Digital camera 2 Imaging part 4 Analog signal processing part 6 Control part 8 Digital signal processing part 10 Compression / decompression part 12 Display part 14 Recording part 16 Memory 18 Operation part 20 Face detection part 22 Correction value calculation part 56 Gain calculation part 64 Wide dynamic Range composition processing section

Claims (9)

In an image processing apparatus that processes first image data captured with high sensitivity for the same subject and second image data captured with lower sensitivity than the first image data,
Detecting means for detecting a maximum dynamic range of the subject;
Luminance correction means for correcting the first and second image data so that the luminance of a specific object included in the subject becomes a predetermined luminance;
Wherein according to the correction of the brightness the predetermined luminance of the specific object included in the subject, a correction coefficient calculating means for calculating a correction coefficient for correcting the maximum dynamic range,
Dynamic range correction means for correcting the maximum dynamic range by the correction coefficient;
An image processing apparatus comprising: combining means for combining the corrected first and second image data in accordance with the corrected maximum dynamic range to obtain combined image data.   The image processing apparatus according to claim 1, wherein the correction coefficient calculating unit is a unit that calculates the correction coefficient based on the first image data.   The synthesizing unit selects a gradation conversion characteristic according to the corrected maximum dynamic range from a plurality of gradation conversion characteristics prepared in advance according to various dynamic ranges, and the combination conversion unit selects the gradation conversion characteristic according to the selected gradation conversion characteristic. 3. The image processing apparatus according to claim 1, wherein the image processing apparatus is means for performing gradation conversion and combining the first and second image data. 4. The apparatus according to claim 1, further comprising a face detecting unit that detects a human face as the specific object from the images represented by the first and second image data. 5. The image processing apparatus according to item.   The luminance correction means is means for correcting the first and second image data so that an average luminance of the specific object becomes the predetermined luminance,
  5. The correction coefficient calculating means according to claim 1, wherein the correction coefficient calculating means is means for calculating the correction coefficient by calculating (the predetermined brightness) / (average brightness of the specific object). The image processing apparatus according to item.   The correction coefficient calculation means is means for performing calculation of the correction coefficient based on data obtained by adding the first and second image data. The image processing apparatus described. A high-sensitivity pixel that performs high-sensitivity imaging on the same subject and a low-sensitivity pixel that is lower in sensitivity than the high-sensitivity pixel are disposed, and the first image data is obtained by the high-sensitivity pixel, and the low-sensitivity pixel Imaging means for obtaining second image data by sensitivity pixels;
The image processing apparatus according to any one of claims 1 to 6 ,
An imaging apparatus comprising: recording means for recording the composite image data. In an image processing method for processing first image data imaged with high sensitivity with respect to the same subject and second image data imaged with lower sensitivity than the first image data,
Detecting the maximum dynamic range of the subject,
Correcting the first image data and the second image data so that a specific object included in the subject has a predetermined luminance;
According to the correction of the brightness the predetermined luminance of the specific object included in the subject, calculates a correction coefficient for correcting the maximum dynamic range,
The maximum dynamic range is corrected by the correction coefficient,
An image processing method comprising: combining the corrected first and second image data in accordance with the corrected maximum dynamic range to obtain combined image data. Program for causing a computer to execute an image processing method for processing first image data captured with high sensitivity for the same subject and second image data captured with lower sensitivity than the first image data In
Detecting the maximum dynamic range of the subject;
A procedure for correcting the first and second image data so that a specific object included in the subject has a predetermined luminance;
A step of calculating according to the correction of the brightness the predetermined luminance of the specific object included in the subject, a correction coefficient for correcting the maximum dynamic range,
A procedure for correcting the maximum dynamic range by the correction coefficient;
A program for synthesizing the corrected first and second image data in accordance with the corrected maximum dynamic range to obtain combined image data.

Images