JP7229728B2 - Imaging device, its control method, and program - Google Patents

Description

The present invention relates to astrophotography technology such as a starry sky.

2. Description of the Related Art In recent years, digital cameras equipped with a function that enables easy astrophotography have been distributed. For example, a camera has been proposed that has a mode (hereinafter referred to as a starry sky night view mode) in which the camera automatically performs long-exposure photography to obtain an image of the starry sky so that the starry sky can be captured beautifully. Furthermore, a digital camera has been proposed that has a mode (hereinafter referred to as a star trail mode) in which the starry sky is continuously photographed at predetermined intervals, and the star trails are obtained as a single image by synthesizing the respective starry sky images. there is

Further, in the technology of photographing such a starry sky, Japanese Patent Application Laid-Open No. 2002-200301 discloses a technique of emphasizing and displaying an imaged celestial body for the purpose of improving the visibility of constellations.

JP 2012-89944 A

However, in the case of 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 conventionally, adjustment of a captured image has not been made in consideration of this angle of view.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to obtain a large dramatic effect even if the angle of view is changed according to the focal length in photographing a point light source such as a starry sky as described above.

A photographing apparatus according to the present invention is a photographing apparatus capable of photographing a starry sky, and includes specifying means for specifying a photographing angle of view, detecting means for detecting stars in the photographed image, and stars detected by the detecting means. and image processing means for performing predetermined image processing on the stars, wherein the image processing means determines parameters for the predetermined image processing using zoom position information, and performs shooting specified by the specifying means. When the angle of view is the first angle of view, the predetermined image processing is performed with the first parameter, and the shooting angle of view specified by the specifying means is the second angle of view wider than the first angle of view. In this case, the predetermined image processing is performed using a second parameter different from the first parameter.

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

Flowchart for shooting in starry sky nightscape mode Flow chart for shooting in star trail mode Block diagram showing the functional configuration of a digital camera A diagram showing an example of a reduced starry sky image Diagram showing region detection in a starry sky image A diagram showing an example of a starry sky image (starry sky night view) A diagram showing an example of a starry sky image (star trail) Diagram showing correspondence table between zoom position and image quality parameter Diagram showing correspondence table between zoom position and image quality parameter Diagram showing correspondence table between zoom position and image quality parameter

[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 an imaging device according to this embodiment. The digital camera of this embodiment is a digital camera capable of capturing still images and moving images. Other examples of imaging devices include mobile phones and tablet devices having a so-called camera function, as well as devices and systems for photographing, observing, and analyzing the starry sky for academic and industrial purposes. Therefore, in the embodiments, an example in which a single digital camera implements the functions described later will be described. may be realized.

An 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 that have various command setting functions. Further, it may be configured by forming and displaying buttons having similar functions on a display device such as a touch panel type liquid crystal. An operation unit 101 is used for turning on/off the power, setting and changing imaging conditions and imaging modes, confirming imaging conditions, confirming images that have been photographed, and the like.

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

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

A system control unit 102 controls operations of each unit of the digital camera 100 according to instructions from the operation unit 101 . The system control unit 102 generally includes a CPU, a ROM for storing programs executed by the CPU, and a RAM memory for reading the program and for a work area.

In the system control unit 102, the subject brightness level is calculated from the digital image data output from the image processing unit 105, and automatic exposure control ( AE) Processing.

The exposure mechanism 108a has functions of a diaphragm and a mechanical shutter. Using this exposure mechanism 108a, the optical path between the lens 107a and the image sensor 103 is controlled by operating at the aperture and shutter speed controlled by the mechanical driving unit 108, which receives notification of the AE processing result from the system control unit 102. And the amount of light can be secured. As a result, it becomes possible to expose the subject to the image sensor 103 under the exposure conditions obtained by the above-described AE processing.

Further, the system control unit 102 uses the lens driving unit 107 to drive the focus lens of the lens optical system 107a, detects changes in the contrast of the digital image data output from the image processing unit 105, and performs automatic matching based on this. Focus control (AF) processing is performed.

Further, the operation unit 101 of this 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 instructing the movement of a predetermined zoom lens of the lens optical system 107a to a zoom position that interlocks with the operation amount of the zoom lever. 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 controlling the lens optical system 107a as described above, it is possible to set the lens arrangement at a desired zoom position, that is, set the angle of view according to the desired focal length, and photograph.

The system control unit 102 also notifies the image processing unit 105 of the zoom position information of the zoom lens, and based on this information, it is used for various settings in image processing during starry sky nightscape mode shooting and star trail mode shooting, which will be described later. 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 AE processing.

Furthermore, the system control unit 102 performs flash settings, and determines whether or not the flash unit 110 needs to operate the flash unit 110 during actual shooting, depending on the shutter speed, shooting mode, etc., based on the AE processing result from the system control unit 102 described above. to decide. When flash emission is determined, the system control unit 102 instructs the EF processing unit 109 to perform flash emission. When the EF processing unit 109 receives an instruction to perform flash emission from the system control unit 102, the EF processing unit 109 controls the flash unit 110 so that the flash unit 110 emits light at the timing when the shutter of the exposure mechanism 108 opens.

The imaging element 103 is a photoelectric conversion device such as a CCD sensor or a CMOS sensor, and converts an optical image of a subject formed via a lens 107a and an exposure mechanism 108a into an analog electrical signal (analog image data) for each pixel.

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

An 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 (development 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. process.

The image processing unit 105 also performs image processing corresponding to various shooting modes. The starry sky night view mode and the starry sky trail mode described in this embodiment are also one of the shooting modes, and the details will be described 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 based on, for example, DCF (Design rule for Camera File System) from the digital image data output from the image processing unit 105 . The format conversion unit 111 performs encoding to the JPEG format or Motion JPEG format, and generates a file header in the process of data file generation.

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 attached to the digital camera 100, or the like.

An 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 compliance with general standards such as USB and IEEE1394 to exchange image data and the like, and utilizes the functions 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 powers each component of the digital camera 100 with a battery (not shown) or AC input. supply.

The digital camera 100 of this embodiment is configured to start an EVF display operation when power is supplied. First, when power is supplied, a mechanical shutter provided in the exposure mechanism 108a is opened, and the image sensor 103 is exposed. The charge accumulated in each pixel of the image sensor 103 is sequentially read out at a predetermined frame rate, and output to the A/D converter 104 as analog image data. As described above, in the present embodiment, images for EVF display are obtained by continuously capturing images using a so-called electronic shutter, which sequentially reads out images at a predetermined frame rate.

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 data as digital image data. Here, gain adjustment will be described below.

In the imaging device 103, the output signal level of the analog electrical signal changes depending on the amount of exposure. For a bright subject, the exposure amount increases, so the output signal level also increases. On the other hand, for a dark subject, the exposure amount decreases, so the output signal level also decreases. When an analog electrical signal that causes level fluctuations as described above is input to the A/D converter 104 and is output without gain adjustment, the output digital electrical signal also undergoes level fluctuations.

On the other hand, a digital camera generally has a gain that keeps the output signal level of the digital electric signal from the A/D converter 104 constant regardless of the brightness of the object (the output signal level of the analog electric signal). , is set according to the brightness of the subject.

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

As for the setting of the ISO sensitivity related to the gain setting of the A/D conversion unit 104 as described above, the fixed ISO sensitivity set by the user may be used, or the dynamic ISO sensitivity based on the result of the AE processing from the system control unit 102 may be used. It may be an ISO sensitivity with a typical setting.

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 this 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 is correlated with the angle of view in the starry sky night view mode shooting and the starry sky trail mode shooting. will be described later.

The EVF display unit 106 uses the digital image data output from the image processing unit 105 to sequentially display images that have undergone D/A conversion processing (not shown).

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

When the system control unit 102 receives notification of SW1, it performs AF processing and AE processing using the latest captured image at the time of receiving the notification, and determines the in-focus position and exposure conditions.

While the notification of SW1 from the operation unit 101 continues, the system control unit 102 continues waiting without performing the shooting operation until receiving the notification of SW2 (second shutter switch, full-press notification). On the other hand, if the notification of SW1 is interrupted before receiving the notification of SW2, the system control unit 102 operates to restart the EVF display processing.

In the actual photographing process after receiving the notification of SW2, an optical image of the subject is formed on the image sensor 103 and exposed under the photographing conditions after the AF process and AE process of SW1. After that, the analog electric signal for each pixel 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, the format conversion unit 111 converts the image-processed digital image data into a data file format for recording, and the image recording unit 112 records it on a recording medium.

The above is the configuration and basic operation of the digital camera described in this embodiment. Next, the astrophotography mode, which is characteristic of the present invention, will be described in detail.

<Overview of Astrophotography 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 trajectory mode for expressing the diurnal motion of stars as trajectories as astrophotography modes. . The user can operate the operation unit 101 to select these astrophotography modes. When the user selects this astrophotography mode, the system control unit 102 writes mode information in the memory and stores the mode selected by the user.

FIGS. 1 and 2 are flow charts showing operation flows in the starry sky night view mode and the starry sky 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, and the system control unit 102 receives the notification of SW2 in the full-press state through the AF operation and the AE operation by SW1 in the half-press state. After that, the photographing mode pre-stored in the memory of the system control unit 102 is read, and if the photographing mode is the astronomical photographing mode, photographing is performed in the designated astronomical photographing mode (starry sky night view mode or starry sky trail mode). .

When the astrophotography mode stored in the memory is the starry sky night view mode, each component performs processing 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, the zoom magnification information (that is, the zoom position information of the zoom lens) correlated with the angle of view is notified to the image processing unit 105 via the system control unit 102, and is used in the development processing of S104 later. . Details will be described later.

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

In S106, area discrimination is performed to discriminate between the starry sky area and other areas, and the area discrimination information output here is used in the subsequent development processing in S104 to perform development processing, which will be described in detail later.

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

After that, in 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 attached to the digital camera 100. 7A and 7B show examples of conventional images shot in the starry night view mode.

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

Regarding the handling of the zoom magnification, as in S101 in the starry sky night view mode, the zoom magnification information correlated with the angle of view is notified to the image processing unit 105 via the system control unit 102, and the development processing in S206 is performed later. Used when Details will be described later. As for the total photographing time, the photographing time is set to a long time when the star trails are to be photographed for a long time, and the photographing time is set to be a short time when the star trails are to be photographed in a short time.

In S202, the aperture, shutter speed for each shot, and ISO sensitivity are set based on the photometric result of the AE operation. In S203, still image shooting is continued based on the exposure control and shooting settings set in S202. do.

In S204, from the second time of photography onwards, lighten composition processing is performed with images that have been photographed up to the previous time. If it is the first time of photographing, the image processing unit 105 holds the photographed image in the memory for performing the lighten compositing process and proceeds to the next step. In S204, a comparatively bright synthesis process is performed on the synthesized image obtained by synthesizing the captured images up to the previous time and the captured image captured this time.

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

When the angle of view of the digital camera 100 is fixed, the stars are constantly moving in the sky due to diurnal motion, so the positions of the stars are different between the images to be synthesized. Therefore, by performing the lighten compositing process, it is possible to obtain an image of the trajectory of the continuous movement of the stars. 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 photographing/compositing process. , to S206.

In S208, as in S106 in the starry sky night view mode shooting flow described above, area discrimination is performed to discriminate between the starry sky area and other areas, and the output area discrimination information is used in the subsequent development processing in S206. Details will be described later.

In S206, the image processing unit 105 is used to develop the captured image. S206 performs the same processing as S104 in the above-described starry sky night view mode shooting flow, and is a characteristic processing of the present invention, so the details will be described later.

After that, in 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 attached to the digital camera 100.

A final image is generated as a trajectory expressing the diurnal motion of stars by the above starry sky trajectory mode photographing flow. An example of a conventional image captured in the star trail mode is shown in FIGS. 6(a) and 6(b).

The above is the description of the operation flow of the astrophotography mode installed in this embodiment. Hereinafter, the development processing (S104, S206) and related steps in the operation flow will be described in detail. In this embodiment, the image quality parameter in this development process is controlled according to the zoom magnification.

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

An image processing circuit that performs such image processing has setting values (so-called image quality parameters) 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 are image quality parameters for optimum edge enhancement processing and noise removal processing for each shooting ISO sensitivity. can be obtained.

In this embodiment, image quality parameters are determined 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 for conventional astrophotography mode shooting.

Then, with respect to the area discrimination information from the area discrimination (S106, S208) output using the still image captured in S103, S203, the area (starry sky) to which the image quality parameter derived from the zoom position information should be applied. area). Such area discrimination can prevent image quality deterioration such as excessive correction due to unnecessary image processing for areas other than the starry sky area.

FIG. 4 is a diagram explaining a method of detecting a starry sky area in area discrimination (S106, S208). The left side is a schematic diagram of a captured image of the night sky at low zoom (angle of view on the wide-angle side), and the right side is a schematic diagram of a captured image of the night sky at high zoom (angle of view on the telephoto side). In addition, the upper part shows the photographed image output in the still image photographing (S103, S203), while the lower part shows the reduced image of this image.

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

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

As can be seen in FIG. 5, there are cases where edges are not detected in areas other than the starry sky area, and there are cases where an area is erroneously determined to be a starry sky area even though it is not a starry sky area. As a method to prevent such an erroneous determination, the posture state of the imaging device is detected by the output of a gyro sensor (not shown) built in the imaging device, and the upper side of the edge detection area of the image is the sky area, and the lower side is the sky area. is a non-empty area, erroneous determination can be prevented.

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

In the development processing (S104, S206), as described above, image quality parameters are determined using zoom position information corresponding to the zoom magnification output in S101 and S201, in addition to shooting conditions such as aperture necessary for shooting in the astrophotography mode. to derive These image quality parameters are calculated or derived from correspondence tables for each shooting condition and output information, and set in each image processing circuit to perform desired development processing. The development processing considering the zoom position will be described in detail below.

In the present invention, zoom position information and the above-mentioned starry sky area detection result are input during development processing (S104, S206), and image processing is applied only to the starry sky area using image quality parameters according to the zoom position. On the other hand, for non-starry sky regions that have not been determined to be starry sky regions, image processing is performed using image quality parameters based only on imaging conditions such as aperture, as in the conventional art.

More specifically, in this embodiment, based on the starry sky area detection results from the area determination (S106, S208), a map is created that enables discrimination between the starry sky area and the non-starry sky area. , image processing is performed using each image quality parameter. After that, by synthesizing the images after each image processing, a desired astrophotography image can be obtained.

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

In this embodiment, as shown in FIG. 8, three types of image quality parameters "strength", "fineness", and "threshold" are prepared for controlling sharpness.

"Strength" is an image quality parameter corresponding to an edge enhancement control amount that controls the degree of enhancement processing for the edge of the captured input image, and is an image quality parameter with three levels of "1: weak, 2: medium, and 3: strong." are prepared. As for "strength", the larger the numerical value of the image quality parameter, the better the clarity of the edge, but there is also the problem that the visibility of noise also increases.

"Fineness" is an image quality parameter equivalent to the edge width control amount that controls the edge width of the captured input image. are doing. As for "fineness", the larger the numerical value of the image quality parameter, the thicker the line forming 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 for the captured input image signal. I have the parameters. Pixels having a pixel value less than or equal to a threshold, which is called a base clip control amount, are not subjected to sharpening processing, so noise can be prevented from being emphasized. The larger the threshold value, the more effective it is in preventing noise enhancement, but in return, the edge with the same low contrast as noise is not enhanced. Conversely, the smaller the threshold value, the more low-contrast edges can be detected, but it also has the disadvantage of increasing the visibility of noise having a similar contrast.

For 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 a low-power zoom, stars tend to appear smaller in size, as shown in FIG. 7(a) of the conventional example. It is in. Therefore, in the present embodiment, "fineness" is set to 3, which improves the visibility of high frequency components in particular.

On the other hand, when the zoom position is the telephoto position, as shown in FIG. 8, (strength, fineness, threshold)=(3, 2, 1). On the telephoto side of the high-power zoom, the angle of view narrows as shown in FIG. 7B, so the number of captured stars tends to decrease. Therefore, in the present embodiment, "threshold" is set to 1 in order to obtain a developed image even for stars with low contrast. In addition, the "strength" is also set to "strength"=3 in order to make the low-contrast stars stand out more.

As described above, by photographing the starry sky in the astrophotography mode, even if the angle of view is changed by changing the zoom magnification, the starry sky rendering effect is sufficient in the starry sky nightscape mode and the starry sky trail mode. image can be obtained.

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

In this embodiment, correspondence tables of various image quality parameters for edge enhancement processing with respect to zoom positions as shown in FIGS. 9 and 10 are also prepared.

FIG. 9 is a correspondence table used when the number of stars within the shooting angle of view is small. In a situation where the number of stars is so large that a starry sky effect cannot be expected, for example, when development processing is performed with the image quality parameters of the telephoto position in FIG. Deteriorating images may be obtained. In order to avoid this, when it is determined that the number of stars is less than a predetermined number, image quality parameters in the correspondence table of FIG. 9 are set and development processing is performed to prevent deterioration of noise. As for the detection of the number of stars, it suffices to perform edge detection and the like only in the starry sky region for the image in the upper row of FIG. 4 used in the region determination (S106, S208). Whether to use the correspondence table in FIG. 8 or the correspondence table in FIG. 9 may be determined by whether or not the number of stars within the shooting angle of view is smaller than a pre-stored threshold value.

On the other hand, FIG. 10 is a correspondence table of various image quality parameters for edge enhancement processing with respect to zoom positions, which is used when photographing a starry sky in the astrophotography mode at dusk. Since the starry sky at dusk is relatively bright, the contrast of the luminous point of the star is reduced. Therefore, the time is detected by a clock function or the like installed in the imaging apparatus, and when it is determined that it is dusk, image quality parameters are set according to the corresponding method shown in FIG. 10 and development processing is performed. As a result, it is possible to obtain a starlit sky image with good visibility even for low-contrast stars.

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

[Other embodiments]
In the above-described embodiment, the case of photographing the starry sky has been described, but the scope of application of the present invention is not limited to this. For example, the present invention can be applied to photographing a point light source in a dark place, such as photographing a night scene or fireflies.

The present invention is also realized by executing the following processing. That is, the 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 photographing device capable of photographing a starry sky,
a specifying means for specifying a shooting angle of view;
detection means for detecting stars in the captured image;
and image processing means for performing predetermined image processing on the stars detected by the detection means,
The image processing means determines a parameter for the predetermined image processing using the zoom position information, and when the photographing angle of view specified by the specifying means is a first angle of view, the predetermined and if the photographing angle of view specified by the specifying means is a second angle of view wider than the first angle of view, the predetermined image processing is performed with a second parameter different from the first parameter. A photographing device characterized by: 2. The photographing apparatus according to claim 1, wherein said predetermined image processing is processing for sharpening edges. the predetermined image processing is edge enhancement processing;
3. The photographing apparatus according to claim 2, wherein said first parameter is a parameter for increasing the degree of edge enhancement more than said second parameter. The predetermined image processing is processing for controlling edge width,
4. The photographing apparatus according to claim 2, wherein said first parameter is a parameter that provides an edge width narrower than said second parameter. The first parameter and the second parameter are parameters indicating thresholds of pixel values for sharpening the edge, and the first parameter is smaller than the second parameter. The photographing device according to any one of claims 2 to 4. 2. The photographing apparatus according to claim 1, wherein said predetermined image processing is processing for controlling at least one of lightness, saturation, and hue. 7. The photographing apparatus according to any one of claims 1 to 6, wherein said specifying means specifies said photographing angle of view based on a position of a zoom lens. further comprising holding means for holding association information indicating association between the photographing angle of view and the predetermined image processing parameter;
8. The image processing means determines the parameters of the predetermined image processing based on the photographing angle of view specified by the specifying means and the association held in the holding means. The photographing device according to any one of Claims 1 to 3. The holding means holds a plurality of pieces of association information each different in 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 differs according to the number of stars within the photographing angle of view specified by the specifying means. further comprising detection means for detecting information about the external environment in shooting,
The holding means holds a plurality of pieces of association information each different in association with the predetermined image processing parameter,
9. The photographing apparatus according to claim 8, wherein the association information used for said predetermined image processing differs according to the external environment detected by said detection means. A control method for a photographing device capable of photographing a starry sky,
a specifying step of specifying a shooting angle of view;
a detection step of detecting stars in the captured image;
an image processing step of performing predetermined image processing on the stars detected in the detection step;
In the image processing step, parameters for the predetermined image processing are determined using the zoom position information, and if the photographing angle of view specified in the specifying step is the first angle of view, the predetermined and if the photographing angle of view specified in the specifying step is a second angle of view wider than the first angle of view, the predetermined image processing is performed with a second parameter different from the first parameter. A control method for an imaging device, characterized in that: A computer-executable program that causes a computer to function as each means of the photographing apparatus according to any one of claims 1 to 10.

Images