JP2020077938A - Imaging apparatus, control method of the same, and program - Google Patents

Abstract

To photograph a starry sky in consideration of a change in a field angle due to zooming.SOLUTION: The imaging apparatus includes: specifying means for specifying a photographing field angle; detecting means for detecting a star in a photographed image; and image processing means for performing a predetermined image processing on the star detected by the detection means. The image processing means performs the predetermined image processing with a first parameter when the photographing field angle specified by the specifying means is a first field angle and performs the predetermined image processing with a second parameter different from the first parameter when the photographing field angle specified by the specifying means is a second field angle wider than the first field angle.SELECTED DRAWING: Figure 8

Description

  The present invention relates to a technique for photographing astronomical objects such as a starry sky.

  2. Description of the Related Art In recent years, digital cameras equipped with a function capable of easily shooting astronomical objects have been distributed. For example, there is proposed a mode in which a camera automatically performs long-time shooting to obtain a starry sky image (hereinafter referred to as a starry night view mode) so that a starry sky can be captured beautifully. Furthermore, a digital camera having a mode (hereinafter referred to as a star trail mode) in which a star trail is continuously captured at predetermined intervals and the star trail images are combined to obtain a star trail as one image has been proposed. There is.

  Further, in the technique of photographing such a starry sky, Patent Document 1 is disclosed as a technique for displaying an image of a celestial body in an emphasized manner for the purpose of improving the visibility of constellations.

JP2012-89944A

  However, in the example of the starry sky photography as described above, the appearance of the image is greatly influenced by the number of stars within the angle of view. In an image pickup apparatus equipped with a zoom lens, the angle of view can be changed by a zoom operation, but it has not been conventionally made to adjust a captured image in consideration of this angle of view.

  Therefore, it is an object of the present invention to obtain a great effect in photographing a point light source such as a starry sky as described above even if the angle of view is changed according to the focal length.

  The photographing device according to the present invention is a photographing device capable of photographing a starry sky, and includes a specifying unit that specifies a photographing angle of view, a detecting unit that detects a star in a captured image, and a detecting unit that detects the star. Image processing means for performing a predetermined image processing on a star, wherein the image processing means uses the first parameter to determine the predetermined angle when the photographing angle of view specified by the specifying means is the first angle of view. When the photographing field angle specified by the specifying unit is a second field angle wider than the first field angle, the predetermined image processing is performed using a second parameter different from the first parameter. It is characterized by performing.

  According to the present invention, in shooting a point light source such as a starry sky, a great effect can be obtained even if the angle of view is changed according to the focal length.

Flowchart of Starry Night View Mode Shooting Flowchart diagram of star trail mode shooting Block diagram showing the functional configuration of the digital camera Figure showing an example of reduction of a starry sky image Diagram showing region detection in a starry sky image Figure showing an example of a starry sky image (starry night view) Figure showing an example of a starry sky image (star trail) Diagram showing correspondence table of zoom position and image quality parameters Diagram showing correspondence table of zoom position and image quality parameters Diagram showing correspondence table of zoom position and image quality parameters

[First Embodiment]
<Structure of imaging device>
FIG. 3 is a block diagram showing a configuration example of a digital camera which is an example of the image pickup apparatus according to the present embodiment. The digital camera of this embodiment is a digital camera capable of shooting still images and moving images. Other examples of the imaging device include a mobile phone and a tablet device having a so-called camera function, as well as devices and systems for academically and industrially capturing and observing and analyzing the starry sky. Therefore, in the embodiment, an example will be described in which a digital camera alone realizes the below-described functions. May be realized.

  The operation unit 101 serves as a user interface for the user to input and set various commands to the digital camera 100. For example, the input device is composed of mechanical switches and buttons having various command setting functions. Alternatively, a touch panel type display device such as a liquid crystal may be formed with buttons having the same function to display the buttons. The operation unit 101 is used for turning the power on / off, setting and changing shooting conditions and shooting modes, checking shooting conditions, checking shot images, and the like.

  The operation unit 101 also includes a shutter switch, and notifies the system control unit 102 as a first shutter switch SW1 when the shutter switch is half-depressed and as a second shutter switch SW2 when the shutter switch is fully-depressed.

  The system control unit 102 is instructed to start AF processing, AE processing, and the like, which will be described later, by the notification of SW1. On the other hand, SW2 instructs the system control unit 102 as a start command for a series of shooting processing operations. The series of photographing processing operations includes processing operations such as reading of image signals from the image sensor 103, A / D conversion, image processing, conversion processing into an arbitrary recording format, and writing of image data into the image recording unit 112. Refers to.

  The system control unit 102 controls the operation of each unit of the digital camera 100 according to an instruction from the operation unit 101. The system control unit 102 generally includes a CPU, a ROM that stores a program executed by the CPU, and a RAM memory for reading the program and for a work area.

  The system control unit 102 calculates the subject brightness level from the digital image data output from the image processing unit 105, and automatically determines at least one of the shutter speed and the aperture according to the shooting mode. AE) processing is performed.

  The exposure mechanism 108a has a function of a diaphragm and a mechanical shutter. The exposure mechanism 108a is used to operate at an aperture and shutter speed under the control of the mechanical drive unit 108 that has been notified of the above-mentioned AE processing result from the system control unit 102, and thus the optical path between the lens 107a and the image pickup element 103. And the amount of light can be secured. As a result, it becomes possible to expose the subject to the image pickup element 103 under the exposure condition obtained by the above AE processing.

  Further, the system control unit 102 drives the focus lens of the lens optical system 107a by using the lens driving unit 107, detects a change in the contrast of the digital image data output by the image processing unit 105, and based on this, the automatic adjustment is performed. Focus control (AF) processing is performed.

  Further, the operation unit 101 of the present embodiment is also provided with a zoom lever (not shown) for performing a zoom function. The system control unit 102 is notified of a signal for instructing the movement of a predetermined zoom lens of the lens optical system 107a to the zoom position in which the zoom lever is linked with the operation amount. Based on this signal, the system control unit 102 uses the lens driving unit 107 to move the zoom lens of the lens optical system 107a to a desired zoom position. By the control of the lens optical system 107a as described above, it is possible to set the lens arrangement at a desired zoom position, that is, set a field angle with a desired focal length, and shoot.

  In addition, the system control unit 102 notifies the zoom position information of the zoom lens to the image processing unit 105, and based on this information, it is used for various settings in image processing at the time of starry sky night view mode shooting and star trail mode shooting. Be done.

  The system control unit 102 also has a role of notifying the A / D conversion unit 104 of the gain adjustment amount according to the set ISO sensitivity. The set ISO sensitivity may be a fixed sensitivity set by the user or may be an ISO sensitivity dynamically set by the system control unit 102 based on the result of the AE processing.

  Further, the system control unit 102 sets the flash, and depending on the shutter speed and the shooting mode based on the AE processing result from the system control unit 102 described above, whether or not the flash operation of the flash unit 110 is necessary during the main shooting is necessary. To decide. When the flash emission is determined, the system control unit 102 instructs the EF processing unit 109 to execute the flash emission. When the EF processing unit 109 receives a flash light emission execution instruction from the system control unit 102, it controls the flash unit 110 and causes the flash unit 110 to emit light at the timing when the shutter of the exposure mechanism 108 opens.

  The image sensor 103 is a photoelectric conversion device such as a CCD sensor or a CMOS sensor, and converts a subject optical image formed via the lens 107a and the exposure mechanism 108a into an analog electric signal (analog image data) in pixel units.

  The A / D conversion unit 104 performs correlated double sampling, gain adjustment, A / D conversion, and the like on the analog image data output from the image sensor 103, and outputs the digital image data. The gain adjustment amount (amplification factor) to be applied is given by being notified from the system control unit 102, and if the gain is set large, the signal level also increases, but on the other hand, the noise component included in the image also increases.

  The image processing unit 105 performs various image processing on the digital image data output from the A / D conversion unit 104. For example, image processing (developing processing) such as white balance correction, edge enhancement processing, noise removal processing, pixel interpolation processing, gamma correction processing, and color difference signal generation is performed, and YUV image data is output as processed digital image data. Perform processing.

  The image processing unit 105 also performs image processing corresponding to various shooting modes. The starry night view mode and the star trail mode described in this embodiment are also one of the shooting modes, and will be described in detail later.

  The EVF display unit 106 includes a display device such as an LCD, and displays an image after D / A conversion processing (not shown) on the digital image data processed by the image processing unit 105 described above.

  The format conversion unit 111 generates a data file for recording conforming to, for example, DCF (Design rule for Camera File System) for the digital image data output from the image processing unit 105. The format conversion unit 111 performs encoding into a JPEG format or a Motion JPEG format, a file header, and the like in the process of generating a data file.

  The image recording unit 112 records the data file generated by the format conversion unit 111 in a built-in memory of the digital camera 100, a removable medium mounted in the digital camera 100, or the like.

  The external connection unit 113 is an interface for connecting the digital camera 100 to an external device such as a PC (personal computer) or a printer. The external connection unit 113 communicates with an external device in accordance with a general standard such as USB or IEEE1394 to exchange image data and the like, and utilize the function of each external device.

  Next, the operation of the digital camera 100 of this embodiment will be described.

  When the user turns on a power switch (not shown) which is one of the operation units 101, the system control unit 102 detects this and supplies power to each component of the digital camera 100 by a battery or AC input (not shown). To supply.

  The digital camera 100 of the present embodiment is configured to start an EVF display operation when power is supplied. First, when power is supplied, the mechanical shutter provided in the exposure mechanism 108a opens and the image sensor 103 is exposed. The charges accumulated in each pixel of the image sensor 103 are sequentially read at a predetermined frame rate and output to the A / D conversion unit 104 as analog image data. As described above, in the present embodiment, an EVF display image is acquired by sequentially reading at a predetermined frame rate, that is, by continuously capturing an image using a so-called electronic shutter.

  As described above, the A / D conversion unit 104 performs correlated double sampling, gain adjustment, A / D conversion, and the like on the analog image data output from the image sensor 103, and outputs the digital image data. Here, the gain adjustment will be described below.

  In the image sensor 103, the output signal level of the analog electric signal changes depending on the exposure amount. For a bright subject, the amount of exposure increases, so that the output signal level becomes large. On the other hand, for a dark subject, the amount of exposure decreases, so the output signal level also becomes small. When the analog electric signal having the above-described level fluctuation is input to the A / D conversion unit 104 and is output without gain adjustment, the output digital electric signal also has the level fluctuation.

  On the other hand, in general, a digital camera has a gain that keeps the output signal level of the digital electric signal from the A / D conversion unit 104 constant regardless of the brightness of the subject (output signal level of the analog electric signal). , Is set according to the brightness of the subject.

  The above gains are changed and adjusted according to the setting of ISO sensitivity which is one of the shooting conditions. That is, the gain is set to a higher value when the subject has a high ISO sensitivity than when the subject has a low ISO sensitivity. Therefore, the noise component becomes worse at the time of high ISO sensitivity due to the amplification effect by the high gain.

  The ISO sensitivity setting related to the gain setting of the A / D conversion unit 104 as described above may be the fixed ISO sensitivity set by the user, or may be based on the result of the AE processing from the system control unit 102. The ISO sensitivity may be set to a specific value.

  The image processing unit 105 performs various processes on the digital image data output from the A / D conversion unit 104, and outputs, for example, YUV image data as image processed digital image data.

  In the present embodiment, there is a mechanism for changing the image processing control amount of the image processing unit 105 according to the zoom lens arrangement that correlates with the angle of view in the starry night view mode shooting and the star trail mode shooting. Regarding the details of this mechanism Will be described later.

  Further, the EVF display unit 106 sequentially displays images that have been subjected to D / A conversion processing (not shown) using the digital image data output by the image processing unit 105.

  The system control unit 102 repeats the execution of the EVF display process described above unless SW1 (first shutter switch, half-press notification) is received from the operation unit 101.

  When the system control unit 102 receives the notification of SW1, AF processing and AE processing are performed using the latest captured image at the time of receiving the notification, and the focus position and the exposure condition are determined.

  While the notification of SW1 from the operation unit 101 continues, the system control unit 102 continues to wait without receiving a shooting operation until it receives a notification of SW2 (a notification of the second shutter switch or full press). On the other hand, if the notification of SW1 is interrupted before the notification of SW2 is received, the system control unit 102 operates to restart the EVF display process.

  In the actual shooting process after receiving the notification from SW2, a subject optical image is formed on the image sensor 103 and exposed under the shooting conditions after the AF process and AE process in SW1. After that, an analog electric signal in pixel units from the image sensor 103 is converted into digital image data by the A / D conversion unit 104, and the image processing unit 105 performs image processing using this data. Then, this image-processed digital image data is converted into a data file format for recording by the format conversion unit 111, and is recorded on the recording medium by the image recording unit 112.

  The above is the configuration and basic operation of the digital camera described in the present embodiment. Next, the astronomical shooting mode, which is a feature of the present invention, will be described in detail.

<Outline of astronomical shooting mode>
The digital camera 100 of the present embodiment is provided with a starry sky night view mode for expressing stars as bright spots and a starry sky locus mode for expressing diurnal motion of stars as a locus as astronomical shooting modes. .. The user can operate the operation unit 101 to select one of these astronomical photography modes. When the user selects this celestial object shooting mode, the system control unit 102 writes the mode information in the memory and stores the mode selected by the user.

  FIG. 1 and FIG. 2 are flowcharts showing operation flows in the starry night view mode and the star trail mode, respectively. Each step is executed by the system control unit 102 or each component according to an instruction from the system control unit 102.

  The user presses the shutter switch of the operation unit 101, the AF operation and the AE operation by the counter-pressed SW1 are performed, and the system control unit 102 receives the notification of the fully-pressed SW2. Then, the shooting mode stored in advance in the memory of the system control unit 102 is read out, and if the shooting mode is the astronomical shooting mode, shooting is performed in the designated astronomical shooting mode (starry night view mode or starry sky trajectory mode). ..

  When the celestial object photography mode stored in the memory is the starry night view mode, the processing is performed by each component according to the flow shown in FIG.

  In S101, the user determines the angle of view and sets the zoom magnification in advance. At this time, zoom magnification information (that is, zoom position information of the zoom lens) that correlates with the angle of view is notified to the image processing unit 105 via the system control unit 102, and is used in the subsequent development processing in S104. .. Details will be described later.

  In S102, the aperture, shutter speed, and ISO sensitivity are set based on the photometric result of the AE operation, and in S103, a still image is shot based on the exposure control set in S102.

  In S106, a region discrimination is performed to discriminate between the starry sky region and other regions, and the region discrimination information output here is used in the subsequent development process in S104 to perform the development process. Details will be described later.

  Then, in S104, the image processing unit 105 is used to perform development processing on the captured image. Since S104 is a characteristic process of the present invention, details will be described later.

  After that, in step S105, the format conversion unit 111 generates a data file in a predetermined format for the image developed by the image processing unit 105, and writes the image data to the recording medium mounted in the digital camera 100. An example of a conventional image taken in the starry night view mode is shown in FIGS. 7 (a) and 7 (b).

  On the other hand, when the shooting mode stored in the memory of the system control unit 102 is the star trail mode, the processing is executed according to the flowchart of FIG. In step S201, the user sets the zoom magnification and the total shooting time in advance.

  Regarding the handling of the zoom magnification, similar to S101 in the starry night view mode, the zoom magnification information having a correlation with the angle of view is notified to the image processing unit 105 via the system control unit 102, and the development processing of S206 to be performed later. Used in the case of. Details will be described later. Regarding the total shooting time, the shooting time is set to a long time when it is desired to take a long trail of a star, and the shooting time is set to a short time when a short trail of a star is taken.

  In S202, the aperture based on the photometric result of the AE operation, the shutter speed for one shot, and the ISO sensitivity are set, and in S203, still images are continuously shot based on the exposure control and shooting settings set in S202. Do it.

  In S204, after the second photographing, comparative bright combination processing with the images photographed up to the previous time is performed. In the case of the first shooting, the image processing unit 105 holds the shot image in the memory for performing the comparative bright combination processing, and proceeds to the next step. In S204, a comparatively bright combination process is performed on the combined image obtained by combining the taken images up to the previous time and the taken image taken this time.

  The comparative bright combination process is a process of comparing pixel levels of corresponding pixels between images and leaving one having a higher pixel level. In this embodiment, synthesizing is performed in the state of RGB signals obtained in the Bayer array, and pixel levels of R, G, and B pixels are compared. However, the present invention is not limited to this, and the RGB signals may be converted into YUV (luminance and color difference) 422 signals and the like, and then the Y and UV signals between the images may be compared with each other.

  When the angle of view by the digital camera 100 is fixed, the stars are constantly moving in the sky due to the diurnal motion, so the positions of the stars are different between the combined images. Therefore, by performing the comparative light combination process, it is possible to obtain an image of a locus of continuous star movement. In S205, it is determined whether or not the time set in advance by the user has elapsed. If the set time is not reached, the process returns to S203 to repeat the shooting / combining process, and if the set time is exceeded, the shooting is completed. , S206.

  In step S208, similar to step S106 in the starry night view mode shooting flow described above, area determination for determining the starry sky area and other areas is performed, and the output area determination information is used in the subsequent development processing in step S206. Details will be described later.

  In step S206, the image processing unit 105 is used to develop the photographed image. Step S206 is the same process as step S104 in the above-mentioned starry night view mode shooting flow, and is a characteristic process of the present invention.

  After that, in step S207, the format conversion unit 111 generates a data file in a predetermined format for the image developed by the image processing unit 105, and writes the image data to the recording medium mounted in the digital camera 100.

  The final image is generated as a trajectory representing the diurnal motion of the stars by the above star trail mode shooting flow. An example of a conventional image taken in the star trail mode is shown in FIGS. 6 (a) and 6 (b).

  The above is a description of the operation flow of the astronomical shooting mode installed in the present embodiment, but hereinafter, the developing process (S104, S206) and each step related thereto in the operation flow will be described in detail. In the present embodiment, the image quality parameter in this developing process is controlled according to the zoom magnification.

<Development processing>
In the developing process (S104, S206), the image processing unit 105 performs various image processes on the digital image data output from the A / D conversion unit 104. For example, image processing such as white balance correction, edge enhancement processing, noise removal processing, pixel interpolation processing, gamma correction processing, and color difference signal generation is performed.

  The image processing circuit for performing these image processing has a set value (so-called image quality parameter) to be set in the image processing circuit in order to operate the circuit optimally for each shooting condition with respect to the target image quality. For example, there is an image quality parameter for optimal edge enhancement processing and noise removal processing for each shooting ISO sensitivity, and by performing image processing using this image quality parameter, a high quality image can be obtained regardless of the shooting ISO sensitivity. Can be obtained.

  In the present embodiment, the image quality parameter is determined by using the zoom position information of the zoom lens output in S101 and S201 in addition to the shooting conditions (ISO sensitivity, aperture, etc.) required in the conventional astronomical shooting mode shooting.

  Then, regarding the area discrimination information from the area discrimination (S106, S208) that is output using the still image captured images in S103 and S203, the area (starry sky) to which the image quality parameter derived from the above-described zoom position information should be applied. Area). By such area discrimination, it is possible to prevent image quality deterioration such as overcorrection due to unnecessary image processing in areas other than the starry sky area.

  FIG. 4 is a diagram illustrating a starry sky region detection method in the region determination (S106, S208). The left side is a schematic diagram of a photographed image of the night sky at the time of low-magnification zoom (the angle of view is the wide-angle side), and the right side is a schematic diagram of the photographed image of the night sky at the time of high-magnification zoom (the angle of view is the telephoto side). Further, the upper part shows a captured image output in still image shooting (S103, S203), while the lower part shows a reduced image of this image.

  Since the purpose of reduction is to obtain an image in which the stars have disappeared from the still image, it is desirable that the reduction ratio be set to the extent that the stars disappear. The left wide-angle image is reduced by 1 / a1 and the right telephoto image is reduced by 1 / a2, which indicates that the star disappears. Further, since the size of the star tends to be larger on the telephoto side at the high-magnification zoom than at the wide-angle side at the low-magnification zoom, there is a relationship of a1 <a2. That is, the reduction rate is changed according to the zoom magnification, and the higher the magnification is, the smaller the reduction rate is set.

  Using the above reduced image, processing such as edge detection is further performed, and the area in which no edge is detected is discriminated as a starry sky area. FIG. 5 is an example of the edge detection result (that is, the starry sky region detection result) of the reduced image.

  As can be seen in FIG. 5, there may be a region where an edge has not been detected other than the starry sky region, and it may be erroneously determined as a starry sky region even though it is not a starry sky region. As a method of preventing such erroneous determination, the attitude state of the image pickup device is detected by the output of a gyro sensor (not shown) built in the image pickup device, and the upper side is the sky region and the lower side is the boundary of the image edge detection region. If is a non-empty area, erroneous determination can be prevented.

  As described above, the starry sky region detection result can be output from the region determination (S106, S208), and this result is used for the subsequent development processing (S104, S206).

  In the developing process (S104, S206), as described above, in addition to the shooting conditions such as the aperture necessary for shooting in the celestial shooting mode, the zoom position information corresponding to the zoom magnification output in S101 and S201 is used to set the image quality parameter. Derive. These image quality parameters are derived by calculation or a correspondence table for each shooting condition and each output information, set in each image processing circuit, and a desired developing process is performed. Hereinafter, the developing process considering the zoom position will be described in detail.

  According to the present invention, the zoom position information and the above-mentioned starry sky region detection result are input during the developing process (S104, S206), and the image processing by the image quality parameter according to the zoom position is applied only to the starry sky region. On the other hand, as for the non-starry region which is not determined to be the starry region, image processing is performed with the image quality parameter based only on the shooting condition such as the aperture as in the conventional case.

  More specifically, in the present embodiment, a map capable of distinguishing a starry sky region from a non-starry sky region is created based on the starry sky region detection result from the region determination (S106, S208), and each region is created using this map. Image processing is performed for each of the image quality parameters. After that, a desired celestial photographic image can be obtained by synthesizing the respective images after the image processing.

  FIG. 8 is a correspondence table of various image quality parameters of the edge enhancement processing with respect to the zoom position in this embodiment. Using such association information, edge enhancement processing is performed only on the starry sky region with the image quality parameter obtained from the zoom position based on the zoom position information.

  In the present embodiment, three types of image quality parameters “strength”, “fineness”, and “threshold value” for controlling sharpness are provided as shown in FIG.

  “Strength” is an image quality parameter corresponding to an edge emphasis control amount that controls the degree of emphasis processing for edges of a captured input image, and is an image quality parameter with three levels of “1: weak, 2: medium, 3: strong”. Is prepared. Regarding the “strength”, an image quality parameter having a larger numerical value improves the clarity as an edge, but also has the adverse effect of increasing the visibility of noise.

  “Fineness” is an image quality parameter corresponding to the edge width control amount that controls the width of the edge of the captured input image, and image quality parameters of three levels of “1: thin, 2: medium, 3: thick” are prepared. is doing. Regarding the "fineness", the larger the image quality parameter, the wider the width of the line that traces the contour.

  The “threshold” is an image quality parameter corresponding to the base clip control amount for controlling the clip amount of the base clipper with respect to the captured input image signal, and the image quality at three levels of “1: small, 2: medium, 3: large” Parameters are prepared. Pixels having a pixel value equal to or less than the threshold value, which is called a base clip control amount, are not subjected to the sharpening process, and thus noise can be prevented from being emphasized. The larger this threshold is, the higher the effect of preventing noise enhancement is, but instead, the edge of low contrast similar to that of noise is not enhanced. On the contrary, the smaller the threshold value, the more the edge with low contrast can be detected, but this also has the disadvantage that the visibility is increased even for noise having the same contrast.

  In contrast to the above image quality parameters, in the present embodiment, as shown in FIG. 8, when the zoom position is the wide angle position, (strength, fineness, threshold) = (1, 3, 3). On the wide-angle side of the low-power zoom, the size of the star tends to appear small as shown in FIG. 7A of the conventional example, and in particular, the astronomical image tends to be acquired in the direction in which the star image of the high frequency component disappears. It is in. Therefore, in the present embodiment, the setting is “fineness” = 3, which improves the visibility particularly for high frequency components.

  On the other hand, when the zoom position is the telephoto position, (strength, fineness, threshold value) = (3, 2, 1) as shown in FIG. On the telephoto side of the high-power zoom, the angle of view narrows as shown in FIG. 7B, so the number of stars captured tends to decrease. Therefore, in this embodiment, “threshold” = 1 is set in order to obtain a developed image even for a star with low contrast. Regarding "strength", "strength" = 3 is set in order to make low contrast stars more noticeable.

  As described above, even if the angle of view is changed by changing the zoom magnification by shooting the starry sky in the astronomical shooting mode, the effect of the starry sky is sufficient in the starry night view mode and the star trail mode. Images can be obtained.

  In the present embodiment, the image quality parameter of the sharpness is used in order to sufficiently obtain the effect of the starry sky, but the present invention is not limited to this, and any effect that can control the effect of the starry sky may be used. For example, a brightness control amount that controls the brightness of the captured input image, a saturation control amount that controls the saturation of the captured input image, a hue control amount that controls the hue of the captured input image, etc. are also used as image quality parameters of the present invention. be able to.

  Further, in the present embodiment, a correspondence table of various image quality parameters of the edge enhancement processing for the zoom position as shown in FIGS. 9 and 10 is also prepared.

  FIG. 9 is a correspondence table used when the number of stars is small within the shooting angle of view. In the situation where the number of stars is such that the effect of the starry sky cannot be expected, for example, when processing is performed with the image quality parameter of the telephoto position in FIG. 8, only "noise" is affected by "strength" = 3 and "threshold" = 1. A deteriorated image may be obtained. In order to avoid this, when it is determined that the number of stars is less than the predetermined number, the image quality parameters of the correspondence table of FIG. 9 are set and the developing process is performed to prevent the deterioration of noise. Regarding detection of the number of stars, edge detection or the like may be performed only in the starry sky region in the upper image of FIG. 4 used in the region determination (S106, S208). Whether to use the correspondence table of FIG. 8 or the correspondence table of FIG. 9 may be determined based on whether or not the number of stars within the shooting angle of view is smaller than a threshold value held in advance.

  On the other hand, FIG. 10 is a correspondence table of various image quality parameters of the edge enhancement processing with respect to the zoom position, which is used when shooting the starry sky in the astronomical shooting mode at dusk. Since the starry sky at dusk is relatively bright, the contrast will be reduced even as a bright spot for a star. Therefore, when the time is detected by a clock function or the like installed in the image pickup apparatus and when it is determined that it is dusk, the image quality parameter of the coping method in FIG. 10 is set and the developing process is executed. As a result, it is possible to obtain a starry sky captured image with good visibility even for a low-contrast star.

  The correspondence table of various image quality parameters with respect to the above zoom positions is not limited to the above. If the digital camera 100 has a function of detecting the external environment during shooting such as date, temperature, humidity, and position, and if a correspondence table for each detection result is installed in advance, the optimum image quality parameter for each detection result will be obtained. You can get astronomical images with.

[Other Embodiments]
In the above embodiment, the case where the starry sky is imaged has been described, but the applicable range of the present invention is not limited to this. The present invention can be applied to, for example, photographing a point light source in a dark place such as photographing a night view or a firefly.

  The present invention is also realized by executing the following processing. That is, software (program) that realizes the functions of the above-described embodiments is supplied to a system or device via a network or various storage media, and the computer (or CPU, MPU, etc.) of the system or device reads the program. This is the process to be executed.

Claims (12)

A shooting device capable of shooting the starry sky,
Specifying means for specifying the shooting angle of view,
Detection means for detecting stars in the captured image,
Image processing means for performing a predetermined image processing on the star detected by the detection means,
The image processing means performs the predetermined image processing with the first parameter when the shooting angle of view specified by the specifying means is the first view angle, and the shooting view angle specified by the specifying means is the first angle of view. When the second angle of view is wider than the first angle of view, the predetermined image processing is performed with a second parameter different from the first parameter.   The photographing apparatus according to claim 1, wherein the predetermined image processing is processing for sharpening edges. The predetermined image processing is edge enhancement processing,
The image capturing apparatus according to claim 2, wherein the first parameter is a parameter that makes the degree of edge enhancement stronger than that of the second parameter. The predetermined image processing is processing for controlling the edge width,
The imaging device according to claim 2, wherein the first parameter is a parameter having an edge width narrower than that of the second parameter.   The first parameter and the second parameter are parameters indicating a threshold value of a pixel value for sharpening the edge, and the first parameter is smaller than the second parameter. The imaging device according to claim 2.   The photographing apparatus according to claim 1, wherein the predetermined image processing is processing for controlling at least one of brightness, saturation, and hue.   7. The photographing apparatus according to claim 1, wherein the specifying unit specifies the shooting angle of view based on a position of a zoom lens. Further comprising a holding unit that holds correspondence information indicating correspondence between the shooting angle of view and the predetermined image processing parameter,
8. The image processing unit determines the predetermined image processing parameter based on the photographing field angle specified by the specifying unit and the correspondence held by the holding unit. The image capturing apparatus according to any one of 1. The holding unit holds a plurality of pieces of association information, each of which has a different association with the predetermined image processing parameter,
9. The photographing apparatus according to claim 8, wherein the correspondence information used for the predetermined image processing is different according to the number of stars within the photographing field angle specified by the specifying unit. Further has a detection means for detecting information about the external environment in the shooting,
The holding unit holds a plurality of pieces of association information, each of which has a different association with the predetermined image processing parameter,
9. The photographing apparatus according to claim 8, wherein the correspondence information used for the predetermined image processing is different depending on the external environment detected by the detection unit. A method of controlling a photographing device capable of photographing a starry sky,
A specific step of specifying the shooting angle of view,
A detection step of detecting stars in the captured image,
An image processing step of performing a predetermined image processing on the star detected in the detection step,
In the image processing step, when the shooting angle of view specified in the specifying step is a first angle of view, the predetermined image processing is performed using a first parameter, and the shooting angle of view specified in the specifying step is a first angle of view. When the second angle of view is wider than the first angle of view, the predetermined image processing is performed with a second parameter different from the first parameter.   A computer-executable program that causes a computer to function as each unit of the image capturing apparatus according to claim 1.

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