JP5772064B2 - Imaging apparatus and image generation program - Google Patents

Description

  The present invention relates to an imaging apparatus such as a digital still camera and an image generation program.

  Conventionally, by combining multiple captured images obtained by shooting the same subject with dark and bright areas under different exposure conditions, one composition where the dark areas are not crushed black and the bright areas are not flying white A high dynamic range (hereinafter, referred to as “HDR”) imaging technique capable of generating an image is known (see, for example, Patent Document 1).

  That is, in such a conventional HDR imaging technique, for example, when two captured images having different exposure conditions are obtained, the number of exposure steps is set from the normal exposure condition to the high exposure side (short seconds side) and the low exposure side (long seconds side). One composite image is generated by combining two captured images photographed under different exposure conditions on the high exposure side and exposure conditions on the low exposure side.

JP 2003-319240 A

  By the way, an exposure interlocking range (exposure condition setting range) defined to limit the setting range of the exposure value (exposure condition) is normally set in the imaging apparatus. In addition, the difference in brightness between the bright and dark areas of the subject is generally higher at the upper limit of the exposure interlocking range (in a high-brightness environment) than at the lower limit of the exposure interlocking range (in a low-brightness environment). growing. For this reason, when the difference in the number of exposure steps between the high exposure side and the low exposure side is set so that the HDR processing result near the upper limit side of the exposure interlocking range is optimal, the portion other than the vicinity of the upper limit of the exposure interlocking range ( There has been a problem that overexposure may occur at the center or near the lower limit.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide an imaging apparatus and an image generation program capable of photographing a subject having a dark part and a bright part with high dynamic range under optimum exposure conditions. There is to do.

To achieve the above object, an imaging apparatus of the present invention, a luminance value detecting means for detecting a luminance value by photometry of a subject, based on the detected brightness value by the brightness value detecting means, a first exposure condition , an exposure condition calculating means for calculating a second exposure conditions low-exposure side than the first exposure condition, a first exposure value corresponding to the first exposure condition, a second corresponding to the second exposure condition the difference between the exposure value, than relatively bright scenes, as towards the relatively dark scenes is reduced, and the exposure adjusting means for adjusting the second exposure value, the exposure after adjustment of the exposure adjustment means an exposure condition setting means for setting an exposure condition corresponding to the value as the first exposure condition and the second exposure condition, it is captured in accordance with the set first exposure condition and the second exposure condition by the exposure condition setting means Combine captured images And summarized in that and a synthesized image generating means for generating a single combined image Te.

In the imaging apparatus according to the aspect of the invention, the luminance value detection unit may measure the subject for each of a plurality of divided regions to detect a luminance value for each region, and the exposure condition calculation unit may include the luminance value detection unit. one of the luminance values in a group of high-luminance values including the maximum luminance value among the detected each luminance value as the first luminance value, thereby calculating the first exposure condition based on the first luminance value, the one of the luminance values in a group of low luminance values including a minimum luminance value out of the luminance value as the second luminance value, and summarized in that for calculating the second exposure condition based on the second luminance value.

  In the imaging device of the present invention, the first luminance value is the maximum luminance value in the group of high luminance values, and the second luminance value is the minimum luminance value in the group of low luminance values. This is the gist.

The image generation program of the present invention, the computer, the luminance value detecting step of detecting a luminance value by photometry of a subject, based on the detected brightness value by the brightness value detection procedure, the first exposure condition, the An exposure condition calculation procedure for calculating a second exposure condition on a lower exposure side than the first exposure condition, a first exposure value corresponding to the first exposure condition, and a second exposure value corresponding to the second exposure condition the difference between the, than relatively bright scenes, as towards the relatively dark scenes is reduced, and the exposure adjustment procedure for adjusting the second exposure value, an exposure value after the adjustment of the exposure adjustment procedure an exposure condition setting procedure for setting the corresponding exposure conditions as the first exposure condition and the second exposure condition, taken according to the set the first exposure condition and the second exposure condition by the exposure condition setting procedure imaging image Synthesized and summarized in that to execute the composite image generating step of generating a single composite image.

  According to the present invention, a subject having a dark part and a bright part can be photographed with a high dynamic range under an optimum exposure condition.

1 is a block diagram showing a schematic configuration of a digital still camera according to an embodiment. The screen figure of the to-be-photographed image divided | segmented into the several area | region for every area | region photometry. The flowchart of a HDR imaging | photography process routine. The graph which shows the relationship between the exposure value and luminance value in the digital still camera of this embodiment.

  FIG. 1 shows an embodiment in which the present invention is embodied in a digital still camera (hereinafter referred to as “camera”) as an imaging apparatus and an imaging method in the case of photographing a subject with high dynamic range (HDR) using the camera. Description will be made with reference to FIG.

As shown in FIG. 1, the camera 11 includes a lens unit 12 composed of a plurality of lenses such as a zoom lens (only one lens is shown in FIG. 1 for simplification of the drawing), and object light that has passed through the lens unit 12. A diaphragm 13 that adjusts the amount of light, and an imaging element 14 that forms an image of subject light that has passed through the diaphragm 13 on an incident-side light-receiving surface 14a that serves as an imaging surface. Then, the image sensor 14
An AFE (Analog Front End) 15 and an image processing circuit 16 are connected to the output side, and an MPU (Micro Processing Unit) 17 is connected to the image processing circuit 16 via a data bus 18. Yes.

  In addition, a nonvolatile memory 19 that stores a control program for the camera 11, a RAM 20 that functions as a buffer memory, a liquid crystal display monitor 21 that functions as a display unit, and a memory card 22 that is a recording medium can be inserted into and removed from the MPU 17. A card I / F (Inter-Face) 23 is connected via a data bus 18. Further, on the camera body (not shown), an operation member 24 such as a mode switching button or a release button operated by a user of the camera 11 receives each operation signal (mode switching signal or half-pressed) from the MPU 17. The operation signal is provided so that data communication is possible.

  The imaging element 14 is composed of a complementary metal oxide semiconductor (CMOS) image sensor or a charge coupled device (CCD) image sensor, has an electronic shutter function, and has a large number of light receiving elements (not shown) on its light receiving surface 14a. Dimensionally arranged. The image sensor 14 accumulates signal charges corresponding to the subject image formed on the light receiving surface 14a, and outputs the accumulated signal charges to the AFE 15 as analog signals called pixel signals that are the source of image data.

  The AFE 15 samples a pixel signal of an analog signal input from the image sensor 14 at a predetermined timing (correlated double sampling), and amplifies the signal to a predetermined signal level based on ISO sensitivity, for example. And an A / D converter (not shown) for converting the amplified pixel signal into a digital signal. The AFE 15 outputs image data generated by digitizing the pixel signal of the analog signal by the A / D conversion unit to the image processing circuit 16.

  The image processing circuit 16 performs various image processing on the image data input from the AFE 15 based on a control signal from the MPU 17. Then, the image processing circuit 16 temporarily stores the image data subjected to such image processing in the RAM 20 and displays it on the monitor 21 as a through image. Note that when a composite image is generated in an HDR shooting mode to be described later, a plurality of images stored in the RAM 20 are read and combined, and stored in the RAM 20 again. When the release button is fully pressed, the image corresponding to the image data at that time is displayed on the monitor 21 as a confirmation image, and on the other hand, predetermined image processing such as format processing for JPEG compression is performed. After that, it is recorded as an image file in the memory card 22.

  The non-volatile memory 19 has an exposure interlocking range (exposure condition setting range) defined to limit the setting range of an exposure value (exposure value; EV value) that is an exposure condition in the camera 11 and a control program of the camera 11. An upper limit value RJ and a lower limit value RK, an abnormal threshold value, a stage number threshold value, and a setting threshold value S described later are stored (see FIG. 4).

  The MPU 17 comprehensively controls various processing operations (for example, HDR imaging processing) in the camera 11 based on a control program such as an image generation program stored in the nonvolatile memory 19. The data bus 18 functions as a transmission path for various data accompanying the control of the MPU 17. The mode switching button on the operation member 24 is a button that is operated when the operation mode of the camera 11 is switched. For example, the mode switching button is operated when the shooting mode is switched between the normal shooting mode and the HDR shooting mode. On the other hand, the release button is pressed down when shooting the subject when the operation mode of the camera 11 is the shooting mode.

  In the camera 11, AF (Auto Focus) processing for focusing on the subject and AE (Auto Exposure) processing for exposure adjustment when the release button of the operation member 24 is half-pressed in the normal shooting mode. After that, the image generation process is executed when the release button is fully pressed. On the other hand, in this camera 11, when the release button of the operation member 24 is half-pressed in the HDR shooting mode, the AE processing and synthesis for HDR shooting different from the AE processing and the combined image generation processing in the normal shooting mode are performed. Image generation processing is executed.

  That is, in the HDR shooting mode, the first exposure condition on the high exposure side and the low exposure necessary for HDR shooting of the same subject having a dark part and a bright part like the subject in the image 25 shown in FIG. AE processing for determining the second exposure condition on the side is executed. Incidentally, the image 25 in FIG. 2 has a subject in which the sun 26 is located on the upper left side of the mountain 27 and the surface of the lake 28 at the foot of the mountain is shaded by the trees 29 on the lakeside and becomes dark. It is. Therefore, in this image 25, the area A and the area E in which the bright sun 26 is located in the area are bright parts, while the area P in which the lake surface 28 is located in the area and the standing tree with the sun 26 in the back A region L where 29 is located in the region is a dark part.

  When the light from the subject of the image 25 shown in FIG. 2 is measured for each of the areas A to P and the luminance value is detected for each of the areas A to P, most of the sun 26 is located in the area A in the upper left corner. Therefore, the luminance value of the area A in the upper left corner is the maximum luminance value. Since a part of the sun 26 is located in the region E immediately below the region A, the luminance value of the region E is a high luminance value according to the maximum luminance value. Accordingly, in the subject in the image 25, a group of high luminance values including the maximum luminance value is constituted by the luminance value of the region A and the luminance value of the region E.

  On the other hand, since the lake 28 with a dark lake surface is located in the area P in the lower right corner, the luminance value of the area P in the lower right corner becomes the minimum luminance value. In the region L immediately above the region P, the standing tree 29 on the lakeside is located with the light from the sun 26 in the back (specifically, received from the rear left side). Is a low-brightness luminance value according to the minimum luminance value. Therefore, in the subject in the image 25, a group of low luminance values including the minimum luminance value is constituted by the luminance value of the region P and the luminance value of the region L.

  In the case of the present embodiment, when the first exposure condition and the second exposure condition are determined based on the luminance value for each of the areas A to P in the subject image having the dark part and the bright part, the dark part (area P, L) and the same subject having bright portions (areas A and E) are continuously photographed under the first exposure condition and the second exposure condition. Incidentally, in the case of the present embodiment, the AE process for HDR imaging is executed by adjusting the electronic shutter speed of the image sensor 14. Specifically, the first shutter speed on the high speed side that is the first exposure condition and the second shutter speed on the low speed side that is the second exposure condition are set as the electronic shutter speed for continuous shooting. ing.

  After that, when the release button is fully pressed, the same subject having the dark part (areas P and L) and the bright part (areas A and E) is set to the first shutter speed (first exposure condition) and the second. One composite image is generated by combining two captured images obtained by continuous shooting at the shutter speed (second exposure condition).

  Therefore, next, an outline of an HDR imaging processing routine (image generation program) executed by the MPU 17 when HDR imaging of a subject having a dark part and a bright part using the camera 11 will be described below with reference to the flowchart of FIG. explain.

  When the shooting mode is switched from the normal shooting mode to the HDR shooting mode by operating the mode switching button of the operation member 24 when the operation mode of the camera 11 is the shooting mode, the MPU 17 in FIG. The HDR imaging processing routine shown in the flowchart is started.

  First, in step S11, the MPU 17 determines whether or not the release button of the operation member 24 is half-pressed. When the determination result in step S11 is negative (step S11 = NO), the MPU 17 periodically repeats the determination in step S11. And if the determination result of this step S11 becomes affirmation determination (step S11 = YES), MPU17 will transfer the process to the following step S12.

  In the next step S12, the MPU 17 detects the luminance value for each of the areas A to P in the subject image displayed as a through image on the monitor 21 at that time. Specifically, the luminance signal Y and the color difference signals Cr and Cb are separated from the R, G, and B image data obtained by the image sensor 14, and the luminance signal Y is integrated for each of the regions A to P. Thus, the luminance value for each of the areas A to P is detected. In this respect, the MPU 17 functions as a luminance value detection unit that executes a luminance value detection procedure. When the luminance values in all the areas A to P are detected, the MPU 17 temporarily stores the detected luminance values in the RAM 20 in association with the areas A to P, and then proceeds to the next step S13. To do.

  In the next step S13, the MPU 17 determines whether or not there is an abnormal value in each luminance value for each of the areas A to P detected in the previous step S12. Specifically, an average value of all detected luminance values is calculated, and whether there is a luminance value (abnormal value) whose numerical difference from the average value exceeds an abnormal threshold value stored in advance in the nonvolatile memory 19. Determine whether. And when the determination result of step S13 is affirmation determination (step S13 = YES), MPU17 transfers the process to the following step S14.

  Then, in the next step S14, the MPU 17 excludes the luminance value determined to be an abnormal value in step S13 from the luminance values for each of the areas A to P detected in the previous step S12, and performs the following processing. The process proceeds to step S15. On the other hand, when the determination result of step S13 is negative (step S13 = NO), the MPU 17 directly shifts the process to step S15 without going through step S14.

  Then, in the next step S15, the MPU 17 becomes the first luminance value for determining the first exposure condition and the second exposure condition from the remaining luminance values after being excluded in the previous step S14. A luminance value and a second luminance value are selected. In the case of the present embodiment, one high luminance value having the maximum luminance is selected as the first luminance value among the remaining luminance values after the abnormal value is excluded in the previous step S14, and each remaining luminance value is selected. One low luminance value having the minimum luminance among the luminance values is selected as the second luminance value. Thereafter, the MPU 17 temporarily stores the first luminance value and the second luminance value in the RAM 20, and then proceeds to the next step S16.

  In the next step S16, the MPU 17 determines the first exposure condition and the second exposure based on the first luminance value (for example, the maximum luminance value of the region A) and the second luminance value (for example, the minimum luminance value of the region P). Calculate the condition. In this respect, the MPU 17 functions as an exposure condition calculation unit that executes an exposure condition calculation procedure. Then, when the process of step S16 ends, the MPU 17 proceeds to the next step S17.

  Then, in the next step S17, the MPU 17 determines the first exposure step number and the second luminance value (for example, the region) corresponding to the first exposure condition calculated based on the first luminance value (for example, the maximum luminance value of the region A). Whether the difference in the number of steps from the second number of exposure steps corresponding to the second exposure condition calculated based on the minimum brightness value of P is equal to or greater than the step number threshold value (three steps in the present embodiment) stored in the nonvolatile memory 19 in advance. Determine whether or not. And when the determination result of this step S17 is affirmation determination (step S17 = YES), MPU17 transfers the process to the following step S18.

  Then, in the next step S18, as shown in FIG. 4, the MPU 17 sets the first exposure step number and the second exposure step number on the side where the exposure value is lower than the preset threshold value S stored in the nonvolatile memory 19 in advance. The second exposure step number is adjusted so that the step number difference is less than the step number threshold (two steps in this embodiment). In this respect, the MPU 17 functions as an exposure adjustment unit that executes an exposure adjustment procedure.

  Specifically, the first exposure step number corresponding to the first exposure condition calculated based on the first luminance value is maintained, and the second exposure step number corresponding to the second exposure condition calculated based on the second luminance value is maintained. This is made closer to the first exposure step number between the set threshold S and the lower limit value RK of the exposure interlocking range. Accordingly, in the exposure interlocking range, the difference in the number of steps (two steps) between the first exposure step number corresponding to the first exposure condition and the second exposure step number corresponding to the second exposure condition on the side lower than the set threshold S is set. The difference is smaller than the difference (three steps) between the number of first exposure steps corresponding to the first exposure condition on the side higher than the threshold S and the number of second exposure steps corresponding to the second exposure condition. The setting threshold S is set to one value (EV value 12 in this embodiment) on the higher side than the intermediate value between the upper limit value RJ and the lower limit value RK in the exposure interlocking range.

  After the second exposure step number after the adjustment so that the difference in the step number between the first exposure step number and the second exposure step number is two on the side lower than the set threshold value S is temporarily stored in the RAM 20. The MPU 17 proceeds to the next step S19. On the other hand, if the determination result of the previous step S17 is negative (step S17 = NO), the MPU 17 proceeds directly to step S19 without going through step S18.

  Then, in the next step S19, the MPU 17 determines the first shutter speed and the second shutter speed as the first exposure condition based on the first exposure step number and the second exposure step number in which the step number difference changes with the set threshold value S as a boundary. The second shutter speed as an exposure condition is set as the electronic shutter speed in the image sensor 14 during continuous shooting. In this respect, the MPU 17 functions as an exposure condition setting unit that executes an exposure condition setting procedure. Then, when the process of step S19 ends, the MPU 17 proceeds to the next step S20.

  In the next step S20, the MPU 17 determines whether or not the release button of the operation member 24 has been fully pressed. When the determination result in step S20 is negative (step S20 = NO), the MPU 17 periodically repeats the determination in step S20. And if the determination result of step S20 becomes affirmation determination (step S20 = YES), MPU17 will transfer the process to the following step S21.

  In the next step S21, the MPU 17 uses the image processing circuit 16 to obtain image data of two captured images obtained by continuously photographing the subject at the first shutter speed and the second shutter speed by the electronic shutter function of the image sensor 14. One synthesized image is generated by synthesizing at. In this respect, the MPU 17 and the image processing circuit 16 function as a composite image generation unit that executes a composite image generation procedure. Then, after the composite image generated by such image processing is displayed on the monitor 21 as a confirmation image, the image data of the image is filed and stored in the memory card 22, and the MPU 17 performs the above HDR imaging processing. End the routine.

  When combining a plurality of images in the HDR shooting mode, a shift between images to be combined is detected, and at least one image is shifted and combined so that the subject images match. For example, the displacement between images may be detected by analyzing a motion vector between images, or other methods may be used.

Next, the operation of the camera 11 according to the present embodiment configured as described above will be described below, particularly focusing on an imaging method in the case of subjecting a subject having a dark part and a bright part to HDR imaging.
Note that, as a premise of the description, the image captured by the camera 11 in this case is the landscape image 25 shown in FIG. 2, and as described above, the subject image in the image 25 has a dark part and a bright part. It shall be. And about the brightness | luminance value for every area | region AP in the case where the to-be-photographed image is divided | segmented into 16 area | region AP, the brightness | luminance value of the area | region A of the upper left corner where most of the sun 26 is located in an area | region is maximum brightness | luminance. On the other hand, it is assumed that the luminance value of the area P in the lower right corner where the lake 28 with a dark lake surface is located in the area is the minimum luminance value. Furthermore, it is assumed that the shooting mode is switched from the normal shooting mode to the HDR shooting mode by operating the mode switching button on the operation member 24.

  Under the above premise, when the lens unit 12 of the camera 11 is directed toward the mountain 27 as a subject, the sun 26 rises above the left side of the ridgeline of the mountain 27 where the lake 28 and the standing tree 29 are located at the foot of the mountain. The scenery in the state is displayed on the monitor 21 as a through image. When the release button is half-pressed by the user of the camera 11 in this state, AF processing is executed and at the time of continuous shooting in the image sensor 14 having an electronic shutter function as AE processing for HDR shooting. The shutter speed is set.

  That is, the first shutter speed on the high speed side (first exposure condition on the high exposure side) is set based on the maximum luminance value that is the luminance value of the area A among the luminance values of the areas A to P in the subject image. Further, the second shutter speed on the low speed side (second exposure condition on the low exposure side) is set based on the minimum luminance value that is the luminance value of the area P among the luminance values of the areas A to P in the subject image.

  In this case, if the step difference between the number of exposure steps of the first shutter speed and the number of exposure steps of the second shutter speed is equal to or greater than the step number threshold (three steps), the difference in step number is larger than the set threshold S in the exposure interlocking range. The exposure step number at the second shutter speed is brought closer to the exposure step number at the first shutter speed so that the EV value is less than the step number threshold (two steps) on the low side. Then, each shutter speed corresponding to the number of exposure steps after such adjustment of the step number difference is set as the first shutter speed and the second shutter speed for continuous shooting.

  Here, for example, when the difference in the number of steps between the exposure step number of the first shutter speed and the exposure step number of the second shutter speed is three steps throughout the exposure interlocking range, the set threshold value S in the exposure interlocking range. In the region on the higher side (the luminance value is higher), the appropriate exposure value is obtained, but in the region on the lower side (the luminance value is in the middle to lower side), there is a possibility that the exposure is overexposed. This is because the brightness value of the subject image is moderate to low (the brightness of the subject image) compared to the difference between the bright part and the dark part when the brightness value of the subject image is high (when the brightness of the subject image is bright). This is because the difference between the bright part and the dark part in the case of normal to dark is smaller.

  In this regard, in the present embodiment, as described above, both exposures are performed by bringing the exposure step number of the second shutter speed closer to the exposure step number of the first shutter speed on the side where the EV value is lower than the set threshold value S within the exposure interlocking range. Since the difference in the number of steps is adjusted, overexposure is effectively suppressed even when the luminance value of the subject image is medium to low.

  In addition, regarding the luminance value of each of the areas A to P, which is the basis for calculating the shutter speed (exposure condition), when a luminance value with a numerical difference from the average luminance value of all areas exceeding the abnormal threshold is detected, the luminance value of that area Are excluded as abnormal values that are inappropriate for the basis of calculation of the shutter speed used for HDR imaging. Then, the first shutter speed and the second shutter speed are determined based on the remaining luminance values excluding such abnormal values.

  Then, after the first shutter speed and the second shutter speed are set as described above, when the release button of the camera 11 is fully pressed, the subject image is continuously photographed at the first shutter speed and the second shutter speed. . At that time, since the first shutter speed is a shutter speed that is an exposure condition suitable for the luminance value (maximum luminance value) of the area A that is a bright portion in the subject image, the first shutter speed is the first shutter speed. There is almost no occurrence of overexposure in one captured image. Similarly, since the second shutter speed is a shutter speed that is an exposure condition suitable for the luminance value (minimum luminance value) of the dark area P in the subject image, the second shutter speed photographed at the second shutter speed is used. There is almost no blackening in the captured image.

  Then, one composite image obtained by combining the first captured image and the second captured image obtained by such continuous shooting is generated in the image processing circuit 16 based on the control of the MPU 17. Then, a single composite image is generated in which the dark portion is not blacked out and the bright portion is not overexposed, and the composite image is stored and saved in the memory card 22.

According to the present embodiment as described above, the following effects can be obtained.
(1) The difference between the number of exposure steps at the first shutter speed and the number of exposure steps at the second shutter speed is such that the exposure value (EV value) lower than the setting threshold S has an exposure value lower than the setting threshold S. Adjustment is made by bringing the number of exposure steps of the second shutter speed closer to the number of exposure steps of the first shutter speed so as to be smaller than the higher side. For this reason, by appropriately changing the setting threshold S, HDR shooting can be performed under the optimum exposure condition corresponding to the luminance (brightness) regardless of the luminance level of the subject image having the dark part and the bright part. .

  (2) Since the set threshold value S is set to one value that is set to a higher exposure value than the intermediate value between the upper limit value RJ and the lower limit value RK in the exposure interlocking range, the luminance value of the subject image is Overexposure can be effectively suppressed not only in the case of high but also in the case of medium to low.

  (3) The first shutter speed on the high speed side and the second shutter speed on the low speed side are set as the exposure conditions for HDR shooting based on the actual luminance values (first luminance value and second luminance value) in the image of the subject. Therefore, it is possible to perform HDR imaging of an object having a dark part and a bright part under an optimal exposure condition corresponding to the contrast ratio between the dark part and the bright part.

  (4) After detecting the luminance value for each of the plurality of divided areas A to P in the image of the subject having the dark part (area P) and the bright part (area A), the high-exposure value is obtained based on the luminance value of the bright part. The first exposure condition is set, and the second exposure condition for low exposure is set based on the luminance value of the dark part. Therefore, it is possible to more suitably perform HDR shooting of an object having a dark part and a bright part under an optimal exposure condition corresponding to an actual light / dark ratio between the dark part and the bright part.

  (5) The maximum luminance value, which is the luminance value of the brightest region A, is used as the first luminance value that is the basis for calculating the first exposure condition on the high exposure side, and is the basis for calculating the second exposure condition on the low exposure side. The minimum luminance value that is the luminance value of the darkest region P is used as the second luminance value. Therefore, it is possible to easily set the exposure condition according to the light / dark ratio.

  (6) When the luminance value for each of the regions A to P is detected, if there is an abnormal luminance value greatly deviating from the average luminance value, such abnormal luminance value is excluded, and the remaining luminance values The first and second luminance values that are the basis for calculating the first and second exposure conditions are selected. Therefore, the possibility of setting abnormal exposure conditions can be suppressed.

  (7) In this embodiment, the number of exposure steps is set by the shutter speed among the shutter speed, aperture value, and ISO sensitivity, which are the three elements when determining the exposure value that is the exposure condition. Therefore, in contrast to the case where the exposure condition is set based on the aperture value or ISO sensitivity, the exposure condition can be easily set while suppressing the possibility that the depth of field changes or coloration occurs.

The above embodiment may be changed to another embodiment as described below.
The first exposure condition and the second exposure condition are set to correspond to each exposure step number obtained by adding and subtracting a predetermined exposure step number to the exposure step number (exposure value) corresponding to the average luminance value of the subject image. You may make it do. That is, without actually measuring the luminance values of the dark and bright portions of the subject image, the number of exposure steps of the dark and bright portions of the subject image is mechanically calculated based on the average luminance value of the subject image, and the calculation is performed. The first exposure condition and the second exposure condition may be set based on each exposure step number.

  A high luminance value and a low luminance value other than the maximum luminance value and the minimum luminance value are used as the first luminance value and the second luminance value, which are basic values when the first exposure condition and the second exposure condition are set. Also good. For example, the luminance value of the second brightest region E (high luminance value) in the bright portion is used as the first luminance value, and the luminance value of the second darkest region L in the dark portion is used as the second luminance value. (Low luminance value) may be used. In short, one luminance value in a group of high luminance values including the maximum luminance value is set as the first luminance value, and one luminance value in the group of low luminance values including the minimum luminance value is set as the second luminance value. The first exposure condition on the high exposure side and the second exposure condition on the low exposure side may be set.

  The step of discriminating whether or not there is an abnormal luminance value among the luminance values detected for each of the regions A to P of the subject image may be omitted. That is, step S13 and step S14 may be omitted in the HDR imaging processing routine.

  In step S17 of the HDR imaging processing routine, the step number threshold may be set to an arbitrary number of steps (for example, 3, 4, 6, etc.) other than 3. In this case, the second exposure step number of the second exposure condition that is adjusted with the setting threshold S as a boundary also needs to be set appropriately according to the step number threshold value.

  In step S18 of the HDR imaging processing routine, the second exposure step number of the second exposure condition is gradually brought closer to the first exposure step number of the first exposure condition between the setting threshold value S and the lower limit value RK of the exposure interlocking range. It may be.

  In step S18 of the HDR imaging processing routine, the first exposure under the first exposure condition gradually (linearly) as the second exposure step number of the second exposure condition is moved from the set threshold value S to the lower limit value RK of the exposure interlocking range. You may make it approach the number of steps.

  A plurality of setting threshold values S may be set within the exposure interlocking range. For example, another set threshold value is set to one value (for example, EV value 5) on the lower side than the intermediate value between the upper limit value RJ and the lower limit value RK in the exposure interlocking range, and this further set threshold value and exposure are set. The difference in the number of steps between the first exposure step number of the first exposure condition and the second exposure step number of the second exposure condition may be one step between the lower limit value RK of the interlocking range.

  The setting threshold S is not necessarily set within the exposure interlocking range. That is, the setting threshold value S may be set to a value higher than the upper limit value RJ of the exposure interlocking range, or may be set to a value lower than the lower limit value RK of the exposure interlocking range.

  The subject image may be divided into an arbitrary number of divided areas, and the luminance value may be detected for each divided area. That is, for example, the luminance value may be detected without dividing the subject image at all.

  When determining the exposure condition, the exposure condition may be set based on the aperture value of the aperture 13 and the ISO sensitivity in addition to the shutter speed. That is, the exposure condition can be set by at least one of the shutter speed, aperture value, and ISO sensitivity.

  In the above embodiment, the set threshold value S and the exposure value (EV value) are compared to change the number of exposure steps. However, if the value to be compared is a value indicating brightness, other values ( For example, it may be a BV value indicating external light luminance).

  The image generation program may be stored in advance in an external storage medium such as a memory card, and when the external storage medium is attached to the camera, the image generation program may be taken into the camera from the external storage medium.

  In the above embodiment, the present invention is embodied in a digital still camera which is a kind of imaging apparatus, but may be embodied in other imaging apparatuses such as a digital video camera or a mobile phone with a camera function and an imaging method using them. Good.

  In the above embodiment, the subject image formed on the light receiving surface of the image sensor is photometrically detected to detect the luminance ground. However, the luminance value of the subject is detected using another photometric element instead of the image sensor. It is good.

  In the above embodiment, it is described that when the EV value is lower than the set threshold value, the difference in the number of exposure steps is made smaller than when the EV value is high. However, when the EV value is lower than the set threshold value, the MPU 17 may make the difference between the exposure values smaller than when the EV value is high. In such a case, the MPU 17 sets the difference between the first exposure value corresponding to the first exposure condition and the second exposure value corresponding to the second exposure condition on the side lower than the set threshold value. The second exposure value is adjusted to be smaller than the difference between the first exposure value corresponding to the first exposure condition and the second exposure value corresponding to the second exposure condition on the higher side than the threshold value.

  In the above-described embodiment, it is described that the difference in the number of exposure steps (exposure value) is different depending on whether the threshold is higher or lower than the set threshold. However, other conditions may be used as conditions for differentiating the number of exposure steps (exposure values). For example, the MPU 17 may make the difference in the number of exposure steps (exposure value) smaller in a relatively dark scene than in a relatively bright scene. In this case, the MPU 17 causes the difference between the first exposure value corresponding to the first exposure condition and the second exposure value corresponding to the second exposure condition to be relatively darker than the relatively bright scene. The second exposure value is adjusted so as to decrease. In addition, for example, the MPU 17 has the number of exposure steps (exposure) when the lowest luminance value is lower than a predetermined threshold among the luminance values obtained by the division metering, compared with the case where the lowest luminance value is higher than the predetermined threshold. The second exposure value may be adjusted so that the difference between the two values is small. Further, the MPU 17 is different in the number of exposure steps (exposure value) when the average value of each luminance value obtained by the division photometry is lower than a predetermined threshold value, compared with the case where the average value of each luminance value is higher than the predetermined threshold value. You may adjust a 2nd exposure value so that may become small. The predetermined threshold value may be appropriately changed by the user or according to the shooting scene.

  DESCRIPTION OF SYMBOLS 11 ... Camera (imaging apparatus), 14 ... Imaging device (luminance value detection means), 14a ... Light-receiving surface, 16 ... Image processing circuit (composite image generation means), 17 ... MPU (luminance value detection means, exposure condition calculation means) Exposure adjusting means, exposure condition setting means, composite image generating means, computer), AP ... area, S ... setting threshold (threshold).

Claims (4)

A luminance value detecting means for measuring a subject to measure a luminance value;
Based on the detected brightness value by the brightness value detecting means, a first exposure condition, an exposure condition calculating means for calculating a second exposure conditions low-exposure side than the first exposure condition,
The difference between the first exposure value corresponding to the first exposure condition and the second exposure value corresponding to the second exposure condition is smaller in a relatively dark scene than in a relatively bright scene. Exposure adjusting means for adjusting the second exposure value;
An exposure condition setting means for setting an exposure condition corresponding to the exposure value after the adjustment of the exposure adjustment unit as the first exposure condition and the second exposure condition,
And a synthesized image generating unit configured to synthesize a captured image captured in accordance with the first exposure condition and the second exposure condition set by the exposure condition setting unit to generate one synthesized image. Imaging device. The luminance value detecting means measures the subject for each of a plurality of divided areas to detect a luminance value for each area,
The exposure condition calculating means, one of the luminance values in a group of high-luminance values including the maximum luminance value among the luminance value detected by the luminance value detecting means as a first luminance value, the first luminance value with computing the first exposure condition based on the one of the luminance values in a group of low luminance values including a minimum luminance value of said each luminance value as the second luminance value, based on said second luminance value The imaging apparatus according to claim 1, wherein the second exposure condition is calculated. Wherein the first luminance value is the maximum luminance value in the set of high luminance values, the second luminance value to claim 2, characterized in that the said minimum luminance value in the set of low brightness values The imaging device described. On the computer,
Luminance value detection procedure for photometric measurement of a subject to detect luminance values;
Based on the detected brightness value by the brightness value detection procedure, the first exposure condition, an exposure condition calculating procedure for calculating a second exposure conditions low-exposure side than the first exposure condition,
The difference between the first exposure value corresponding to the first exposure condition and the second exposure value corresponding to the second exposure condition is smaller in a relatively dark scene than in a relatively bright scene. And an exposure adjustment procedure for adjusting the second exposure value;
An exposure condition setting procedure for setting the exposure conditions corresponding to the exposure value after the adjustment of the exposure adjustment procedure as the first exposure condition and the second exposure condition,
Image generation program for executing the composite image generating procedure to generate one synthesized image by synthesizing an image captured in accordance with the set first exposure condition and the second exposure condition by the exposure condition setting procedure .

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