JP2016099598A - Imaging apparatus, method for controlling the same, and control program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a difference between images, when making an exposure time different for each optical system and performing photographing, in an imaging apparatus including a plurality of optical systems.SOLUTION: A camera 1 includes a plurality of optical systems 2a and 2b and imaging elements 6a and 6b which generate the image corresponding to an optical image formed through each of the plurality of optical systems. When controlling an exposure start timing for starting an exposure in each optical system or an exposure finish timing for finishing the exposure, according to the exposure time set for each of the plurality of optical systems, a camera system control part 11 adjusts the exposure start timing or the exposure finish timing, according to the length of the exposure time.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an imaging apparatus, a control method thereof, and a control program, and more particularly to an imaging apparatus that includes a plurality of optical systems and captures a subject through a plurality of optical systems to obtain a plurality of images.

  2. Description of the Related Art Conventionally, an imaging apparatus such as a digital camera is known which has a plurality of optical systems, and shoots a subject simultaneously through the plurality of optical systems under different shooting conditions to obtain a plurality of images. (See Patent Document 1).

  The imaging apparatus described in Patent Literature 1 includes a plurality of optical systems having the same focal length, and the imaging unit provided for each optical system changes its exposure time and simultaneously performs imaging.

  Further, an imaging apparatus including a short focus lens unit (hereinafter simply referred to as a short focus lens) and a long focus lens unit (hereinafter simply referred to as a long focus lens) having different angles of view as an optical system is known (Patent Document 2). reference). This type of imaging device is called a compound eye imaging device.

  In the imaging apparatus described in Patent Document 2, an image is obtained by imaging the same subject using a short focus lens and a long focus lens. That is, in the imaging apparatus described in Patent Document 2, a wide-angle image is acquired by an imaging element on which a subject image (optical image) is formed via a short focus lens. Further, a telephoto image is acquired by an image sensor on which an optical image is formed via a long focal lens. When framing in the shooting operation, if the image obtained by the short focus lens is preferentially displayed on the display unit, the user can also observe the shooting range of the long focus lens.

  In addition, in the compound eye imaging devices described in Patent Document 1 and Patent Document 2, the S / N ratio in the image is obtained by adding and synthesizing the image in the same subject range in the image obtained from the imaging unit for each optical system. In addition, a so-called super-resolution image and an image with an expanded dynamic range can be obtained.

JP 2012-195668 A JP 2005-303694 A

  By the way, in the compound eye imaging device described in Patent Document 1, there are cases where photographing is performed with different exposure times and aperture values for each optical system. And in the compound eye imaging device of patent documents 1, the exposure start timing is arranged for every optical system, and exposure time is varied. In such a case, if an image changes due to camera shake or subject movement during exposure, the exposure time differs for each optical system, and thus the image obtained for each optical system differs.

  That is, an image obtained with an optical system with a short exposure time only coincides with an image obtained with an optical system with a long exposure time immediately after the start of exposure. As a result, the difference between the images may become large, resulting in an image unintended by the user. Furthermore, the image quality deteriorates due to the difference between images during image synthesis.

  Accordingly, an object of the present invention is to provide an imaging apparatus that can reduce differences between images when imaging is performed with different exposure times for each optical system in an imaging apparatus including a plurality of optical systems, and a control method therefor And providing a control program.

  In order to achieve the above object, an imaging apparatus according to the present invention is an imaging apparatus that includes an imaging optical group having a plurality of optical systems and performs imaging through the optical system, and each of the plurality of optical systems is provided. Imaging means for generating an image according to the optical image formed through the exposure, and an exposure start timing or exposure for starting the exposure for the plurality of optical systems in accordance with an exposure time set for each of the plurality of optical systems Control means for adjusting the exposure start timing or the exposure end timing in accordance with the length of the exposure time when controlling the exposure end timing to end.

  The control method according to the present invention controls an imaging apparatus having an imaging optical group having a plurality of optical systems and imaging means for generating an image corresponding to an optical image formed through each of the plurality of optical systems. In the method, the exposure start is performed when controlling the exposure start timing to start exposure or the exposure end timing to end exposure for the plurality of optical systems according to the exposure time set for each of the plurality of optical systems. It has a control step of adjusting the timing or the exposure end timing according to the length of the exposure time.

  A control program according to the present invention is used in an imaging apparatus having an imaging optical group having a plurality of optical systems, and imaging means for generating an image corresponding to an optical image formed through each of the plurality of optical systems. An exposure start timing for starting exposure for the plurality of optical systems in accordance with an exposure time set for each of the plurality of optical systems, or exposure for ending the exposure. When the end timing is controlled, a control step of adjusting the exposure start timing or the exposure end timing according to the length of the exposure time is executed.

  According to the present invention, since the exposure start timing or the exposure end timing is adjusted according to the length of the exposure time, the difference between the images when shooting is performed with different exposure times for each optical system. Can be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure for demonstrating the imaging device which has the multi-eye optical group which is an example of the imaging device by the 1st Embodiment of this invention, (a) is the perspective view which looked at the imaging device from the front side, (b) is. It is the perspective view which looked at the imaging device from the back side. It is a block diagram which shows the example about the structure of the camera shown in FIG. FIG. 2 is a diagram for explaining an image obtained as a result of shooting by the camera shown in FIG. 1 and its display; (a) of an image (live view image) displayed on a display unit during framing when performing a shooting operation; The figure which shows an example, (b) is a figure which shows the image image | photographed with the 1st optical system shown to Fig.1 (a), (c) is the image image | photographed with the 2nd optical system shown to Fig.1 (a). FIG. 4D is a diagram showing an image photographed by the third optical system shown in FIG. 1A, and FIG. 4E is a diagram showing an image photographed by the fourth optical system shown in FIG. It is. FIG. 3 is a diagram for explaining an example of an aperture value table in which combinations of aperture values with which the depth of field of the optical system is equal in the camera shown in FIG. 1 are registered, (a) is a diagram showing an aperture value table; (B) shows the relationship between the aperture value of the second to fourth optical systems and the exposure time when the exposure time of the first optical system is set to 1/1000 sec in the pattern “1” shown in (a). FIG. 2 is a timing chart for explaining the operation when the exposure start timings of the first to fourth optical systems are matched in the camera shown in FIG. 1, and (a) is a timing chart showing the operation of the first optical system. (B) is a timing chart showing the operation of the second optical system, (c) is a timing chart showing the operation of the third optical system, and (d) is a timing chart showing the operation of the fourth optical system. . FIG. 3 is a timing chart for explaining an operation when the first to fourth optical systems in the camera shown in FIG. 1 have the same exposure time median value (central time), and FIG. (B) is a timing chart showing the operation of the second optical system, (c) is a timing chart showing the operation of the third optical system, and (d) is a timing chart showing the operation of the fourth optical system. It is a timing chart which shows operation. 3 is a flowchart for explaining a photographing operation in the camera shown in FIG. 2. FIG. 6 is a timing chart for explaining an example of operations of the first to fourth optical systems when the flash photographing mode is set in the camera shown in FIG. 1, and (a) shows the operations of the first optical system. (B) is a timing chart showing the operation of the second optical system, (c) is a timing chart showing the operation of the third optical system, and (d) is a timing chart showing the operation of the fourth optical system. (E) is a timing chart showing the light emission operation of the strobe. FIG. 6 is a timing chart for explaining another example of operations of the first to fourth optical systems when the flash photography mode is set in the camera shown in FIG. 1, and (a) is an operation of the first optical system. (B) is a timing chart showing the operation of the second optical system, (c) is a timing chart showing the operation of the third optical system, and (d) is an operation of the fourth optical system. A timing chart, (e) is a timing chart showing the light emission operation of the strobe. FIG. 6 is a timing chart for explaining still another example of the operation of the first to fourth optical systems when the flash photography mode is set in the camera shown in FIG. 1, and FIG. (B) is a timing chart showing the operation of the second optical system, (c) is a timing chart showing the operation of the third optical system, and (d) is an operation of the fourth optical system. (E) is a timing chart showing the light emission operation of the strobe. It is a timing chart for demonstrating the exposure operation | movement of the 1st-4th optical system at the time of performing several exposure operation | movement with the 1st optical system with the shortest exposure time in the camera by the 2nd Embodiment of this invention. (A) is a timing chart showing the operation of the first optical system, (b) is a timing chart showing the operation of the second optical system, (c) is a timing chart showing the operation of the third optical system, ( d) is a timing chart showing the operation of the fourth optical system. It is a figure for demonstrating an example of the optical system image synthesis | combination performed with the camera by the 2nd Embodiment of this invention, (a) is the image obtained by exposure "51" shown to Fig.11 (a). FIG. 11B shows an image obtained by the exposure “52” shown in FIG. 11A, and FIG. 11C shows an image obtained by the exposure “53” shown in FIG. (D) is a figure which shows the synthesized image obtained as a result of synthesize | combining the image shown to (a)-(c). It is a figure for demonstrating an example of the different optical system image synthesis performed with the camera by the 3rd Embodiment of this invention, (a) shows the image of the state into which the luminance value in all the subjects was in the dynamic range. FIG. 4B is a diagram showing an image when the exposure time is short, and FIG. 4C is a diagram showing an image when the exposure time is long.

  Hereinafter, an example of an imaging apparatus according to an embodiment of the present invention will be described with reference to the drawings.

[First Embodiment]
FIG. 1 is a diagram for explaining an imaging apparatus having a multi-eye optical group which is an example of an imaging apparatus according to the first embodiment of the present invention. FIG. 1A is a perspective view of the imaging device as viewed from the front side, and FIG. 1B is a perspective view of the imaging device as viewed from the back side.

  The illustrated imaging apparatus 1 is, for example, a digital camera (hereinafter simply referred to as a camera), and the camera 1 includes an imaging optical group (also referred to as an imaging optical system) 2 including a plurality of optical systems (lens groups). Yes. A lens located at the forefront of the lens group provided in the imaging optical system 2 is disposed in front of the housing (camera housing) of the camera 1. Also, a release button 16 is provided on the upper surface of the camera casing for issuing a shooting command.

  When the user presses the release button 16 so-called halfway, the camera 1 performs a focus detection operation before photographing. On the other hand, when the user fully presses the release button 16, the camera 1 performs an exposure operation for photographing.

  A display unit 14 for displaying shooting settings and images obtained as a result of shooting is disposed on the back of the camera casing, and a screen operation unit 17 for performing operations related to shooting settings and images. ing.

  In the illustrated example, the photographing optical system 2 has first to fourth optical systems (lens groups) 2a to 2d, and 2 × 2 = 4 optical systems (lenses) 2a to 2 are provided in the camera housing. 2d are arranged in a matrix, and their focal lengths are different. In FIG. 1A, the focal lengths of the first to fourth optical systems 2a to 2d are as follows: first optical system 2a <second optical system 2b <third optical system 2c <fourth optical system. The order is 2d. For example, the focal length of the first optical system 2a = 28 mm, the focal length of the second optical system 2b = 35 mm, the focal length of the third optical system 2c = 50 mm, and the focal length of the fourth optical system 2d = 70 mm. is there.

  FIG. 2 is a block diagram showing an example of the configuration of the camera shown in FIG.

  An imaging optical system 2 provided in the illustrated camera 1 includes a lens driving unit 7 and a shutter driving unit 9 in addition to the first to fourth optical systems 2a to 2d described above. In the illustrated example, only the first optical system 2a and the second optical system 2b are shown for convenience of explanation, but here, the first to fourth optical systems shown in FIG. 2a to 2d are provided. And these 1st-4th optical systems 2a-2d have the same structure.

  The first optical system 2a and the second optical system 2b are also called lens groups, and the first optical system 2a and the second optical system 2b include focus lenses 4a and 4b and diaphragms 5a and 5b, respectively. Then, imaging elements 6a and 6b are arranged through shutters 8a and 8b, respectively, at the subsequent stage of the first optical system 2a and the second optical system 2b.

  The focus lenses 4a and 4b are driven along the optical axes 3a and 3b by the lens driving unit 7 under the control of the camera system control unit 11, respectively. Further, the apertures of the diaphragms 5a and 5b are adjusted by the lens driving unit 7 under the control of the camera system control unit 11, respectively, and thereby the amount of light incident on the imaging elements 6a and 6b is adjusted.

  The focal plane shutters (hereinafter simply referred to as shutters) 8 a and 8 b are controlled to be opened and closed by the shutter drive unit 9 under the control of the camera system control unit 11. That is, the camera system control unit 11 drives the shutters 8a and 8b by the shutter drive unit 9 to control the exposure timing of the image sensors 6a and 6b.

  Each of the shutters 8a and 8b has a front curtain and a rear curtain (not shown), and opening and closing of each of the shutters 8a and 8b is performed by running the front curtain and the rear curtain. .

  Subject images (optical images) incident through the first optical system 2a and the second optical system 2b are formed on the image sensors 6a and 6b, respectively. The image sensors 6a and 6b each output an analog signal (image signal) corresponding to the optical image. In the following description, the image signal that is the output of the image sensor 6a is referred to as a first image signal, and the image signal that is the output of the image sensor 6b is referred to as a second image signal.

  In the example shown in FIG. 2, the imaging elements 6a and 6b are provided for the first optical system 2a and the second optical system 2b, respectively, but the first optical system 2a and the second optical system are provided. A single image sensor having a 2b imaging region may be provided, and after imaging, image signals output from these imaging regions may be processed.

  The illustrated camera 1 further includes a camera system control unit 11, an image processing unit 12, a memory unit 13, a display unit 14, and an operation detection unit 15. In the camera 1, the first optical system 2 a and the second optical system 2 b and the imaging elements 6 a and 6 b constitute an imaging system, and the image processing unit 12 constitutes an image processing system. The memory unit 13 and the display unit 14 constitute a recording / reproducing system, and the camera system control unit 11, the operation detection unit 15, the lens driving unit 7, and the shutter driving unit 9 constitute a control system.

  Although not shown, the image processing unit 12 includes an A / D converter, a white balance circuit, a gamma correction circuit, an interpolation calculation circuit, and the like, and receives and records the first and second image signals described above. Image data is generated.

  The memory unit 13 includes a processing circuit necessary for image recording in addition to the recording unit. The memory unit 13 records image data in the recording unit, and generates and stores a display image to be output to the display unit 14 by the processing circuit. Here, the image data obtained as a result of image processing of the first and second image signals are referred to as first and second image data, respectively.

  The memory unit 13 performs compression processing of images (still images), moving images, and sounds using a predetermined recording method, and records these still images, moving images, and sounds. In the camera 1 shown in FIG. 2, a block relating to recording of audio is omitted.

  The camera system control unit 11 controls the entire camera 1. The camera system control unit 11 controls the imaging system, the image processing system, and the recording / reproducing system in accordance with an external operation (that is, a user operation).

  For example, when the operation detection unit 15 detects that the release button 16 shown in FIG. 1A is pressed (for example, fully pressed), the camera system control unit 11 causes the shutter drive unit 9 to open the front curtains of the shutters 8a and 8b. It is made to run so that a light beam may be shielded by a part. Subsequently, the camera system control unit 11 causes the front curtain to run away from the shutter opening. Thereby, exposure of the image sensors 6a and 6b is started. A state in which the front curtain and the rear curtain are retracted from the shutter opening is referred to as an open state.

  Furthermore, the camera system control unit 11 causes the rear curtain to travel so as to close the shutter opening, and ends the exposure of the image sensors 6a and 6b. A state where the shutter opening is shielded by the front curtain or the rear curtain is called a closed state.

  The camera control unit 11 controls the image pickup devices 6a and 6b, and controls the operation of the image processing unit 12, the compression process in the memory unit 13, and the like. Furthermore, the camera system control unit 11 controls display of the display image read from the memory unit 13 on the display unit 14, and controls display of various information related to photographing on the display unit 14.

  Note that, here, photographing the still image by driving the image sensors 6a and 6b according to a preset aperture value, exposure time, and the like when the release button 16 is pressed is referred to as main photographing.

  Further, the camera system control unit 11 performs exposure time control for determining the exposure time in the image sensors 6a and 6b, and performs exposure timing control for controlling the timing for driving the shutters 8a and 8b.

  FIG. 3 is a diagram for explaining an image obtained as a result of photographing by the camera shown in FIG. 1 and its display. FIG. 3A is a view showing an example of an image (live view image) displayed on the display unit during framing when performing a shooting operation, and FIG. 3B is a view shown in FIG. It is a figure which shows the image image | photographed with the 1st optical system 2a. FIG. 3C is a view showing an image photographed by the second optical system 2b shown in FIG. 1A, and FIG. 3D is a third optical system 2c shown in FIG. It is a figure which shows the image image | photographed by. Further, FIG. 3E is a diagram showing an image photographed by the fourth optical system 2d shown in FIG.

  Now, in FIG. 3A, it is assumed that an image photographed by the first optical system 2a (that is, the optical system having the shortest focal length) is displayed on the display unit 14 in a live view (LV). The display unit 14 displays the field angle range of an image captured by the first optical system 2a as the first field angle frame 40a.

  At this time, the camera system control unit 11 sets the field angle ranges of the images captured by the second optical system 2b, the third optical system 2c, and the fourth 2d to the second field angle frame 40b and the third field angle frame, respectively. Are displayed on the display unit 14 by the view angle frame 40c and the fourth view angle frame 40d.

  In this way, if the image obtained by the first optical system 2a having the shortest focal length is displayed in LV, and the first to fourth view angle frames 40a to 40d are displayed in the LV display, the user can Can take a picture by checking the field angle range of the second to fourth optical systems 2b to 2d having other focal lengths.

  In the example illustrated in FIG. 3A, the camera system control unit 11 displays the second to fourth angle-of-view frames 40 b to 40 d related to the second to fourth optical systems 2 b to 2 d on the display unit 14. However, it is not necessary to display all of the second to fourth view angle frames 40b to 40d. Furthermore, the camera system control unit 11 displays only the fourth view angle frame 40d in addition to the first view angle frame 40a, and only a part of the view angle frames other than the first view angle frame 40a. May be displayed.

  When photographing is performed in the state illustrated in FIG. 3A, the image processing unit 12 is respectively illustrated in FIGS. 3B to 3D according to the outputs of the imaging elements corresponding to the first to fourth optical systems 2a to 2d. The image shown in 3 (e) is generated. Since the images shown in FIGS. 3B to 3E are images obtained according to the outputs of the imaging elements corresponding to the first to fourth optical systems 2a to 2d, respectively, enlargement such as an electronic zoom is performed. Unlike processing, the resolution of each image is the same, and a high-definition image can be obtained even for an image obtained by an optical system having a long focal length.

  In the case of LV display or reproduction display after the main photographing, the second to fourth optical systems 2b to 2d are added to the image (first field angle frame 40a) obtained by the first optical system 2a. The image obtained in (1) may be inserted and combined to display a single combined image.

  For example, the image processing unit 12 synthesizes images obtained by at least two optical systems under the control of the camera system control unit to generate one composite image. Thereby, it is possible to reproduce and display a high-definition image as it goes to the center of the image even though the image has a wide angle of view.

  Further, the image processing unit 12 may perform addition processing on the output of a plurality of images for a range of angle of view that overlaps each other, instead of inset synthesis. As a result, it is possible to generate a composite image in which the dynamic range of the image is expanded and the S / N is improved. In addition, when adding and synthesizing images obtained by optical systems having a plurality of different focal lengths, a correction process for matching the number of pixels to be added is necessary.

  FIG. 4 is a diagram for explaining an example of an aperture value table in which combinations of aperture values with which the depth of field of the optical system is equal in the camera shown in FIG. 1 are registered. FIG. 4A is a diagram showing an aperture value table, and FIG. 4B is an exposure time of 1/1000 sec of the first optical system lens 2a in the pattern “1” shown in FIG. 4A. It is a figure which shows the relationship between the aperture value Fn of the 2nd-4th optical systems 2b-2d at the time of setting, and exposure time SH [sec].

  In the example shown in FIG. 4A, the focal lengths f of the first optical system 2a, the second optical system 2b, the third optical system 2c, and the fourth optical system 2d are 28 mm, 35 mm, and 50 mm, respectively. In addition, the aperture value at the time of 70 mm is shown in 12 combinations (patterns). When the user selects the first optical system 2a as the optical system having the aperture value priority focal length during LV display, the camera system control unit 11 uses the aperture value Fn at which the exposure of the first optical system 2a is appropriate in the actual photographing operation. Is calculated.

  Assuming that the aperture value Fn of the first optical system 2a is “1.8”, the camera system control unit 11 performs the second operation according to the pattern “3” in the aperture value table shown in FIG. The aperture value Fn of the optical system 2b is "2.8", the aperture value Fn of the third optical system 2c is "5.6", and the aperture value Fn of the fourth optical system 2d is "11". Then, the camera system control unit 11 controls the lens driving unit 7 based on the aperture value Fn to adjust the apertures of the first to fourth optical systems 2a to 2d.

  The aperture value related to the aperture value priority focal length optical system may be determined by the camera system control unit 11 so as to achieve proper exposure, or the user may directly select and set the aperture value. Good. When the user selects / sets the aperture value related to the optical system having the aperture value priority focal length, the user selects from the aperture values registered in the table shown in FIG.

  By the way, when photographing using the camera 1, since the focal lengths of the first to fourth optical systems 2a to 2d are different from each other, the exposure time and the aperture for each of the first to fourth optical systems 2a to 2d. The photographing conditions such as the value and ISO sensitivity may be set. For example, when shooting the range of the same subject using the first to fourth optical systems 2a to 2d, the depth of field of the first to fourth optical systems 2a to 2d is to be adjusted. Needs to set an aperture value for each of the first to fourth optical systems 2a to 2d. Furthermore, when the light amounts incident on the imaging elements are adjusted in the first to fourth optical systems 2a to 2d, the exposure time is changed according to the aperture value.

  Therefore, the camera system control unit 11 controls the exposure time of the first to fourth optical systems 2a to 2d as follows.

  The aperture value table shown in FIG. 4A is stored in, for example, the memory unit 13, and the camera system control unit 11 refers to the aperture value table for each of the first to fourth optical systems 2a to 2d. The lens driving unit 7 is controlled. For example, assume that the pattern 1 is selected in FIG. 4A and the exposure time of the first optical system 2a is set to 1/1000 sec. In this case, as shown in FIG. 4 (b), the camera system controller 11 determines the aperture value Fn and the exposure time SH [sec] of the second optical system 2b, the third lens 2c, and the fourth optical system 4d. Set.

  Here, the camera system control unit 11 sets the exposure times of the second optical system 2b, the third optical system 2c, and the fourth optical system 2d to 1/400 sec, 1/100 sec, and 1/25 sec, respectively. To do. In this way, if the aperture value and the exposure time are set for the first to fourth optical systems 2a to 2d, images having substantially the same depth of field in the first to fourth optical systems 2a to 2d are obtained. Can be obtained.

  However, in the case where the exposure times are different for the first to fourth optical systems 2a to 2d, if there is a change in the image such as the subject moving during the exposure time, the first to fourth optical systems 2a to 2d are obtained. Differences occur between the captured images. Further, when the exposure start is at the same timing, the change in the image immediately before the end of exposure is large between the optical system with a short exposure time and the optical system with a long exposure time.

  FIG. 5 is a timing chart for explaining the operation when the exposure start timings of the first to fourth optical systems are matched in the camera shown in FIG. FIG. 5A is a timing chart showing the operation of the first optical system, and FIG. 5B is a timing chart showing the operation of the second optical system. FIG. 5C is a timing chart showing the operation of the third optical system, and FIG. 5D is a timing chart showing the operation of the fourth optical system.

  In FIG. 5, the horizontal axis indicates time, and the vertical axis indicates opening / closing of the shutter. When the shutter is opened, the exposure operation is in progress. In addition, exposure times SHa, SHb, SHc, and SHd indicate exposure times by the first optical system 2a, the second optical system 2b, the third optical system 2c, and the fourth optical system 2d, respectively.

  As shown in FIG. 5, the exposure start timing (exposure start time) by the first to fourth optical systems 2a to 2d is the same, but the exposure time is SHa <SHb <SHc <SHd. As a result of the exposure time being different for each optical system as described above, when the images obtained by the first to fourth optical systems 2a to 2d at the time of reproduction are compared, there is a possibility that the image is not intended by the user. . When these images are combined, the image quality of the combined image is degraded due to the difference in the images.

  Therefore, here, the camera system control unit 11 causes the first to fourth optical systems 2a to match the timings of the median exposure time (central time) in the first to fourth optical systems 2a to 2d. Control the exposure start timing of ˜2d.

  FIG. 6 is a timing chart for explaining the operation of the first to fourth optical systems in the camera shown in FIG. 1 when the median exposure time (central time) is matched. FIG. 6A is a timing chart showing the operation of the first optical system, and FIG. 6B is a timing chart showing the operation of the second optical system. FIG. 6C is a timing chart showing the operation of the third optical system, and FIG. 6D is a timing chart showing the operation of the fourth optical system.

  In FIG. 6, the same elements as those in the example shown in FIG. In the example shown in the drawing, the exposure time is indicated by Tc at the central time in SHa, SHb, SHc, and SHd, and the camera system control unit 11 has the central time Tc in the first to fourth optical systems 2a-2d. The exposure start timing is controlled so as to match.

  Here, with respect to the first optical system 2a, the camera system control unit 11 sets the exposure start timing to the time before the time Sha / 2 from the central time Tc, and the exposure end timing to the time after the time Sha from the central time Tc. Similarly, for the second optical system 2a, the camera system control unit 11 sets the exposure start timing before the time SHb / 2 from the central time Tc and the exposure end timing after the time SHb from the central time Tc. The camera system control unit 11 controls the exposure start timing and the exposure end timing in the same manner for the third optical system 2c and the fourth optical system 2d.

  Thus, in the example shown in FIG. 6, as a result of matching the central times in the exposure times SHa, SHb, SHc, and SHd, the exposure start timing is delayed in the order of the first to fourth optical systems 2a to 2d. The exposure end timing is accelerated in the order of the first to fourth optical systems 2a to 2d.

  As described above, when the exposure start timing and the exposure end timing are controlled, even if the subject moves during the exposure operation, the central times of the exposure times in the first to fourth optical systems 2a to 2d are aligned. Differences between images can be reduced.

  FIG. 7 is a flowchart for explaining a photographing operation in the camera shown in FIG. Note that the processing according to the illustrated flowchart is performed under the control of the camera system control unit 11.

  When shooting is started, the camera system control unit 11 opens the shutter and exposes the imaging elements corresponding to the first to fourth optical systems 2a to 2d for a predetermined time. And the output of the image pick-up element corresponding to the 1st-4th optical systems 2a-2d is processed in the image process part 12, and it is set as 1st-4th image data, respectively. The camera system control unit 11 displays an image corresponding to the first image data obtained by the first optical system 2a having the shortest focal length on the display unit 14 and starts LV display (step S1001). In addition, the period which reads an image signal from an image pick-up element is performed by predetermined frame rates, such as 30 fps, for example.

  Subsequently, the camera system control unit 11 determines whether or not the operation detection unit 15 detects that the release button 16 is half-pressed (S1) (step S1002). If release button S1 is not detected (NO in step S1002), camera system control unit 11 stands by.

  On the other hand, when S1 of the release button is detected (YES in step S1002), the camera system control unit 11 detects the focus state in the first to fourth image data and detects the main state in the first to fourth image data. A subject is determined (step S1003). Here, the camera system control unit 11 detects a subject existing on the camera side (closest side) as a main subject.

  For focus detection, for example, a phase difference focus detection method is used in which focus detection is performed according to the phase difference between a pair of optical images using a separately provided phase difference detection unit. Further, a contrast focus detection method may be used in which focus detection is performed according to the contrast of image data obtained by moving the focus lens along the optical axis by the lens driving unit 7.

  When the main subject is selected, the user may select the main subject by the screen operation unit 17 while confirming the LV display.

  Next, the camera system control unit 11 controls the lens driving unit 7 so that the focus lens 4 provided in the first to fourth optical systems 2a to 2d is used as an optical axis so that the main subject is in focus. Are driven (step S1004). Then, the camera system control unit 11 determines whether or not the release button 16 has been fully pressed (S2) by the operation detection unit 15 (step S1005). If release button S2 is not detected (NO in step S1005), camera system control unit 11 returns to the process in step S1002.

  On the other hand, when the release button S2 is detected (YES in step S1005), the camera system control unit 11 calculates an aperture value and an exposure time for appropriate exposure in the first optical system 2a (step S1006). For example, the camera system control unit 11 determines the aperture value and the exposure time so that the first image data obtained from the image sensor corresponding to the first optical system 2a falls within the dynamic range. Hereinafter, the aperture value and the exposure time are referred to as a first aperture value and a first exposure time.

  Next, the camera system control unit 11 determines the aperture values in the second to fourth optical systems 2b to 2d with reference to the aperture table shown in FIG. 4A according to the first aperture value ( Step S1007). Here, the aperture values in the second to fourth optical systems 2b to 2d are referred to as second to fourth aperture values, respectively. Then, the camera system control unit 11 determines the exposure time by the second to fourth optical systems 2b to 2d so that the exposure amount equivalent to that of the first optical system 2a is obtained at the second to third aperture values. (Step S1008).

  Furthermore, the camera system control unit 11 determines the exposure start time (exposure start timing) in the first to fourth optical systems 2a to 2d so that the central times in the first to fourth exposure times coincide ( Step S1008). Hereinafter, the exposure start timings in the first to fourth optical systems 2a to 2d are referred to as first to fourth exposure start timings, respectively.

  Thereafter, the camera system control unit 11 controls the lens driving unit 7 according to the first to fourth aperture values obtained as described above, and is provided in the first to fourth optical systems 2a to 2d. The diaphragm (also referred to as a diaphragm mechanism) is driven (step S1009).

  Subsequently, the camera system control unit 11 is provided in the first to fourth optical systems 2 a to 2 d by the shutter driving unit 9 based on the first to fourth exposure start timings and the first to fourth exposure times. The shutter is driven and controlled to perform an exposure operation (step S1010). In the exposure operation, the camera system control unit 11 first closes the shutter 6 provided in the first to fourth optical systems 2a to 2d. Then, the camera system control unit 11 drives and controls the shutter driving unit 9 according to the first to fourth exposure start timings and the first to fourth exposure times, and causes the front and rear curtains of the shutter to travel, so that the image sensor Exposure.

  Thereafter, the camera system control unit 11 records the first to fourth image data obtained according to the outputs of the imaging elements corresponding to the first to fourth optical systems 2a to 2d in the memory unit 13, and An image corresponding to the one image data is displayed on the display unit 14 (step S1011). Then, the camera control unit 11 ends the shooting operation.

  In the above-described example, the focal plane shutter is used as the shutter. However, for example, an electronic shutter that controls the exposure time according to the reset timing and reading timing of the image sensor 6 may be used. As the electronic shutter, a so-called rolling electronic shutter that sequentially performs a reading operation from the pixel row at the end of the image sensor or a global electronic shutter that can simultaneously read all the pixels of the image sensor is used.

  Further, in the above-described example, the aperture values and the exposure values of the second to fourth optical systems 2b to 2d according to the first aperture value and the first exposure time at which the first optical system 2a has an appropriate exposure amount. Although the time is obtained, for example, the user may set the aperture value and the exposure time related to the first to fourth optical systems on the setting screen displayed on the display unit 14.

  Here, a photographing operation when the camera 1 shown in FIG. 1 includes a strobe that is a light emitting unit that illuminates the subject will be described. Here, the camera system control unit 11 controls the flash emission timing when the flash photography mode is set.

  FIG. 8 is a timing chart for explaining an example of the operation of the first to fourth optical systems when the flash photographing mode is set in the camera shown in FIG. FIG. 8A is a timing chart showing the operation of the first optical system, and FIG. 8B is a timing chart showing the operation of the second optical system. FIG. 8C is a timing chart showing the operation of the third optical system, and FIG. 8D is a timing chart showing the operation of the fourth optical system. Further, FIG. 8E is a timing chart showing the light emission operation of the strobe.

  First, after setting the flash photography mode, the user sets the flash emission timing. For example, as the setting of the light emission timing, there is a so-called trailing curtain sync setting in which the light emission timing of the strobe is adjusted just before the exposure operation is finished. Furthermore, there is a so-called front curtain sync setting that matches the flash emission timing immediately after the start of the exposure operation. In addition, central sync setting may be performed in which the strobe emission timing is adjusted to the central time of the exposure time of the first to fourth optical systems 2a to 2d.

  In the example shown in FIG. 8, the horizontal axis indicates time, and the vertical axis indicates opening / closing of the shutter or light emission of the strobe, respectively. The exposure times by the first optical system 2a, the second optical system 2b, the third optical system 2c, and the fourth optical system 2d are indicated by exposure times SHa, SHb, SHc, and SHd, respectively. . The strobe light emission time is St.

  In FIG. 8, the rear curtain sync setting described above is performed. Here, the camera system control unit 11 makes the exposure end timing in the first to fourth optical systems 2a to 2d coincide with the exposure end time Te. The exposure operation is controlled. Further, the camera system control unit 11 controls the strobe so that the light emission start timing of the strobe is immediately before the exposure end time Te. That is, the camera system control unit 11 matches the flash emission end timing with the exposure end time Te.

  As described above, when the exposure end timing and the light emission start timing are controlled, when a moving main subject and a non-moving background subject are simultaneously shot, an image synchronized with the movement of the trailing curtain is obtained. be able to.

  FIG. 9 is a timing chart for explaining another example of the operation of the first to fourth optical systems when the flash photographing mode is set in the camera shown in FIG. FIG. 9A is a timing chart showing the operation of the first optical system, and FIG. 9B is a timing chart showing the operation of the second optical system. FIG. 9C is a timing chart showing the operation of the third optical system, and FIG. 9D is a timing chart showing the operation of the fourth optical system. Further, FIG. 9E is a timing chart showing the light emission operation of the strobe.

  In the example shown in FIG. 9, the horizontal axis indicates time, and the vertical axis indicates the opening / closing of the shutter or the flash emission, respectively. The exposure times by the first optical system 2a, the second optical system 2b, the third optical system 2c, and the fourth optical system 2d are indicated by exposure times SHa, SHb, SHc, and SHd, respectively. . The strobe light emission time is St.

  In FIG. 9, the above-described front curtain sync setting is performed. Here, the camera system control unit 11 makes the exposure start timing in the first to fourth optical systems 2a to 2d coincide with the exposure start time Ts. The exposure operation is controlled. Further, the camera system control unit 11 controls the strobe so that the light emission end timing of the strobe is immediately after the exposure start time Ts. That is, the camera system control unit 11 matches the strobe light emission start timing with the exposure start time Ts.

  As described above, when the exposure start timing and the light emission end timing are controlled, an image synchronized with the movement of the front curtain can be obtained when a moving main subject and a non-moving background subject are simultaneously photographed.

  FIG. 10 is a timing chart for explaining still another example of the operation of the first to fourth optical systems when the flash photographing mode is set in the camera shown in FIG. FIG. 10A is a timing chart showing the operation of the first optical system, and FIG. 10B is a timing chart showing the operation of the second optical system. FIG. 10C is a timing chart showing the operation of the third optical system, and FIG. 10D is a timing chart showing the operation of the fourth optical system. Further, FIG. 10E is a timing chart showing the light emission operation of the strobe.

  In the example illustrated in FIG. 10, the horizontal axis indicates time, and the vertical axis indicates opening / closing of the shutter or flash emission. The exposure times by the first optical system 2a, the second optical system 2b, the third optical system 2c, and the fourth optical system 2d are indicated by exposure times SHa, SHb, SHc, and SHd, respectively. . The strobe light emission time is St.

  In FIG. 10, the above-described central sync setting is performed. Here, the camera system control unit 11 aligns the central times of the exposure times SHa, SHb, SHc, and SHd with the time Tc, and sets the first to fourth. The exposure operation (that is, exposure start timing) in the optical systems 2a to 2d is controlled. Further, the camera system control unit 11 controls the light emission start timing of the strobe with the central time of the light emission time St as time Tc.

  When the exposure start timing and the light emission start timing are controlled as described above, when the moving main subject and the non-moving background subject are simultaneously photographed, at least the optical system with the shortest focal length is based on the light emission start timing. The exposure start timing in the first to fourth optical systems 2a to 2d can be controlled so that the light emission start timing enters the exposure time of the system (first optical system 2a).

  As described above, in the first embodiment of the present invention, when a camera having a plurality of optical systems having different focal lengths is used, when the exposure times are different for each optical system, the central times of these exposure times coincide. The exposure operation is controlled to do so. Thereby, even if the subject moves during the exposure operation, the difference in the images obtained by the plurality of optical systems is reduced. As a result, not only a sense of incongruity is reduced during image reproduction, but also deterioration in image quality can be reduced during image composition.

[Second Embodiment]
Next, an example of a camera according to the second embodiment of the present invention will be described. The configuration of the camera according to the second embodiment is the same as that of the camera shown in FIGS.

  The camera according to the second embodiment has a continuous exposure mode in which the exposure operation in the optical system with a short exposure time is performed a plurality of times during the exposure operation in the optical system with a long exposure time. In the continuous exposure mode, when performing an exposure operation a plurality of times with an optical system having a short exposure time, the camera system control unit 11 sets the central time of the exposure time in one exposure operation to the central time of the exposure time in another optical system. Exposure control is performed so that

  Thereafter, the camera system control unit 11 aligns a plurality of images obtained by a plurality of exposure operations by image matching, and then performs image synthesis processing by addition synthesis and averaging processing. Note that a process for combining images obtained by different optical systems is called a different optical system image composition, and a process for combining a plurality of images obtained by the same optical system is called a same optical system image composition.

  FIG. 11 is a view for explaining exposure operations of the first to fourth optical systems when a plurality of exposure operations are performed with the first optical system having the shortest exposure time in the camera according to the second embodiment of the present invention. It is a timing chart. FIG. 11A is a timing chart showing the operation of the first optical system, and FIG. 11B is a timing chart showing the operation of the second optical system. FIG. 11C is a timing chart showing the operation of the third optical system, and FIG. 11D is a timing chart showing the operation of the fourth optical system.

  In the illustrated example, the horizontal axis indicates time, and the vertical axis indicates opening / closing of the shutter. The exposure times by the first optical system 2a, the second optical system 2b, the third optical system 2c, and the fourth optical system 2d are indicated by exposure times SHa, SHb, SHc, and SHd, respectively. . The camera system control unit 11 controls the exposure operation by matching the central time of the exposure times SHa, SHb, SHc, and SHd with the time Tc.

  Further, the camera system control unit 11 performs the exposure operation for the first optical system 2a a plurality of times during the period from the time Td1 that is the exposure start time of the fourth optical system 2d to the time Td2 that is the exposure end time. Then, the camera system control unit 11 matches the central time of the exposure time SHa with the time Tc for one out of a plurality of exposure operations in the first optical system 2a.

  The camera system control unit 11 sets the number of exposure operations in the first optical system 2a to the exposure time SHd of the fourth optical system 2d, the exposure time SHa of the first optical system 2a, and the first optical system 2a. This is determined in consideration of the interval time between exposure operations in the system 2a.

  As described above, the first optical system 2a having the shortest exposure time is exposed a plurality of times to obtain a plurality of images, and the same optical system image synthesis is performed for these images. Thereby, the S / N ratio can be improved for the image obtained by the first optical system 2a.

  Further, if an image obtained by the first optical system 2a is synthesized with an image obtained by another optical system at an exposure time SHa in which the central time is aligned with the time Tc, image quality deteriorates. Can be reduced.

  In the continuous exposure mode, after the optical system image is combined, the different optical system image may be combined using the combined image. That is, a plurality of images obtained by performing a plurality of exposure operations in the first optical system 2a are synthesized with the same optical system image, and the synthesized images are obtained by the second to fourth optical systems 2b to 2d. The obtained image may be combined with the different optical system image.

  FIG. 12 is a diagram for explaining an example of the optical system image synthesis performed by the camera according to the second embodiment of the present invention. FIG. 12A shows an image obtained by the exposure “51” shown in FIG. 11A, and FIG. 12B shows the image obtained by the exposure “52” shown in FIG. FIG. FIG. 12C shows an image obtained by the exposure “53” shown in FIG. 11A, and FIG. 12D shows the images shown in FIGS. 12A to 12C. It is a figure which shows the synthesized image obtained as a result of synthesize | combining.

  12 (a) to 12 (c), the subject has moved to the right side in the figure from time Td1 to time Td2 shown in FIG. 11 (a). The camera system control unit 11 performs matching processing on the images shown in FIGS. 12 (a) to 12 (c). Here, for example, the camera system control unit 11 performs addition synthesis by shifting the images so that the positions of the subjects coincide with each other using the image shown in FIG. 12B as a reference. Thereby, the composite image shown in FIG. 12D is obtained. As a result of improving the S / N ratio for the composite image obtained by the above-mentioned optical system image composition, if the different optical system image composition is performed using the composite image, the resultant composite image is obtained. Will further improve the S / N ratio.

[Third Embodiment]
Next, an example of a camera according to the third embodiment of the present invention will be described. The configuration of the camera according to the third embodiment is the same as that of the camera shown in FIGS. 1 and 2, but in the third embodiment, the focal lengths of the first to fourth optical systems 2a to 2d are Are the same.

  In the third embodiment, for a subject with a large change in luminance value, the exposure time is changed for the first to fourth optical systems 2a to 2d to synthesize images obtained by shooting. For example, the camera system control unit 11 sets the exposure time in the first optical system 2a so that the range of the subject with the highest luminance value falls within the dynamic range of the image sensor. Furthermore, the camera system control unit 11 sets the exposure time in the fourth optical system 2d so that the range of the subject with the lowest luminance value falls within the dynamic range of the image sensor.

  At this time, the camera system control unit 11 sets the exposure time in the fourth optical system 2d to be longer than the exposure time in the first optical system 2a. Then, the camera system control unit 11 sets the exposure time in the second and third optical systems 2b and 2c between the exposure times in the first and fourth optical systems 2a and 2d. Further, the camera system control unit 11 controls the exposure operation in the first to fourth optical systems 2a to 2d so that the central times of the exposure times for the respective optical systems coincide.

  Thereafter, the camera system control unit 11 performs different optical system image composition on the image obtained for each optical system. At this time, the camera system control unit 11 performs normalization by multiplying the luminance value of the image by a predetermined ratio in accordance with the ratio of the exposure time for each optical system.

  For example, when the exposure time of the first optical system 2a is 1 / n times the exposure time of the fourth optical system 2d (n is a number larger than 1), the first optical system 2a obtained The luminance value of the image is multiplied by n. The images obtained by the second and third optical systems 2b and 2c are also normalized by the ratio of the exposure time with reference to the fourth optical system 2d having the longest exposure time.

  Subsequently, the camera system control unit 11 performs addition synthesis and averaging processing on the normalized image. As a result, the range of the subject with the highest luminance does not exceed the range, and further, the range of the subject with the lowest luminance does not have a luminance value of zero, so that an image having an enlarged dynamic range can be obtained. Can do.

  FIG. 13 is a diagram for explaining an example of different optical system image synthesis performed by the camera according to the third embodiment of the present invention. FIG. 13A is a diagram illustrating an image in a state where the luminance values of all subjects are in the dynamic range, and FIG. 13B is a diagram illustrating an image when the exposure time is short. FIG. 13C shows an image when the exposure time is long.

  If shooting is performed with appropriate exposure when the dynamic range of the image sensor is large, an image in which the luminance value of the subject is in the dynamic range can be obtained (see FIG. 13A). Here, it is assumed that the subjects 64, 63, 62, and 61 have higher luminance values in this order.

  When the subjects 64, 63, 62, and 61 are photographed with a camera having a small dynamic range of the image sensor, the image shown in FIG. 13B is obtained in the first optical system 2a having the shortest exposure time. On the other hand, in the fourth optical system 2d having the longest exposure time, an image shown in FIG. 13C is obtained.

  In the image shown in FIG. 13B, the luminance values of the subjects 62, 63, and 64 are in the dynamic range, but the subject 61 has an insufficient exposure time, resulting in an appropriate luminance value. In other words, it becomes a so-called blackened state.

  On the other hand, in the image shown in FIG. 13C, the luminance values of the subjects 61, 62, and 63 are in the dynamic range, but the luminance value of the subject 64 is saturated because the exposure time is too long. Thus, a so-called whiteout state is obtained.

  Therefore, the camera system control unit 11 multiplies the luminance values of the entire images shown in FIGS. 13B and 13C by a predetermined coefficient so that the luminance values of the subjects 62 and 64 in the dynamic range are aligned. For example, if the exposure time of the fourth optical system 2d is twice that of the first optical system 2a, the camera system control unit 11 doubles the luminance value of the image obtained by the first optical system 2a. .

  Then, the camera system control unit 11 obtains the luminance value of the subject 61 that is blacked out in FIG. 13B from the image shown in FIG. Further, the camera system control unit 11 obtains the brightness value of the subject 64 that is overexposed in FIG. 13C from the image of FIG. 13B and performs image composition.

  As a result, even when an imaging device with a small dynamic range is used, an image with a pseudo dynamic range can be obtained as shown in FIG.

  As is clear from the above description, in the example shown in FIG. 2, the imaging elements 6 a and 6 b and the image processing unit 12 function as imaging means. The camera system control unit 11 functions as a control unit, and the camera system control unit 11 and the image processing unit 12 function as a synthesis unit.

  As mentioned above, although this invention was demonstrated based on embodiment, this invention is not limited to these embodiment, Various forms of the range which does not deviate from the summary of this invention are also contained in this invention. .

  For example, the function of the above embodiment may be used as a control method, and this control method may be executed by the imaging apparatus. Further, a program having the functions of the above-described embodiments may be used as a control program, and the control program may be executed by a computer included in the imaging apparatus. The control program is recorded on a computer-readable recording medium, for example.

[Other Embodiments]
The present invention supplies a program that realizes one or more functions of the above-described embodiments to a system or apparatus via a network or a storage medium, and one or more processors in a computer of the system or apparatus read and execute the program This process can be realized. It can also be realized by a circuit (for example, ASIC) that realizes one or more functions.

2a to 2d Optical system 4a, 4b Focus lens 5a, 5b Aperture mechanism 6a, 6b Image sensor 7 Lens drive unit 8a, 8b Shutter 9 Shutter drive unit 11 Camera system control unit 12 Image processing unit 16 Release button

Claims (13)

An imaging apparatus that includes an imaging optical group having a plurality of optical systems and that performs imaging through the optical system,
Imaging means for generating an image according to an optical image formed through each of the plurality of optical systems;
When controlling an exposure start timing for starting exposure or an exposure end timing for ending exposure according to the exposure time set for each of the plurality of optical systems, the exposure start timing or the exposure end Control means for adjusting the timing according to the length of the exposure time;
An imaging device comprising:   The control means controls the exposure start timing or the exposure end timing by matching a central time located at the center of an exposure time set for each of the plurality of optical systems. The imaging device described.   The imaging apparatus according to claim 2, wherein at least one of the plurality of optical systems has a focal length different from that of the other optical systems.   The image pickup apparatus according to claim 3, wherein the control unit starts exposure in order from an optical system having the longest focal length among the plurality of optical systems. Having light emitting means for illuminating the subject during shooting,
The control means controls the exposure end timing in accordance with a light emission end timing at which the light emission means ends light emission in a light emission photographing mode in which the light emission means emits light to photograph the subject. The imaging device according to claim 1. Having light emitting means for illuminating the subject during shooting,
The control means controls the exposure start timing in accordance with a light emission start timing at which the light emission means starts light emission in a light emission photographing mode in which the light emission means emits light to photograph the subject. The imaging device according to claim 1. Having light emitting means for illuminating the subject during shooting,
In the light emission photographing mode in which the light emitting means emits light to photograph the subject, the control means starts the light emission means during the exposure time in the optical system having the shortest focal length among the plurality of optical systems. The imaging apparatus according to claim 3, wherein the light emission start timing is controlled.   The control means is configured to perform exposure a plurality of times with an exposure time of the optical system having the shortest focal length and an exposure time of the optical system having the shortest focal length for the optical system having the shortest focal length among the plurality of optical systems. The imaging apparatus according to claim 3, wherein a central time located at a center of the exposure time is made coincident in one of the plurality of exposures.   The imaging apparatus according to claim 8, further comprising a combining unit that combines the images obtained by the plurality of exposures to obtain a first combined image.   The synthesizing unit generates the second synthesized image by synthesizing the image obtained for the other optical system except the optical system with the shortest focal length and the first synthesized image. Item 10. The imaging device according to Item 9.   The imaging apparatus according to claim 1, further comprising a combining unit that combines images obtained for each of the plurality of optical systems to obtain a combined image. An imaging apparatus control method comprising: an imaging optical group having a plurality of optical systems; and imaging means for generating an image according to an optical image formed through each of the plurality of optical systems,
When controlling an exposure start timing for starting exposure or an exposure end timing for ending exposure according to the exposure time set for each of the plurality of optical systems, the exposure start timing or the exposure end A control method comprising a control step of adjusting timing according to the length of the exposure time. A control program used in an imaging apparatus having an imaging optical group having a plurality of optical systems and imaging means for generating an image according to an optical image formed through each of the plurality of optical systems,
In the computer provided in the imaging device,
When controlling an exposure start timing for starting exposure or an exposure end timing for ending exposure according to the exposure time set for each of the plurality of optical systems, the exposure start timing or the exposure end A control program for executing a control step of adjusting timing according to the length of the exposure time.