JP6148577B2 - Imaging apparatus and control method - Google Patents

Description

  The present invention relates to an imaging apparatus and a control method, and more particularly to an imaging apparatus and a control method capable of controlling imaging sensitivity according to an imaging target.

  Conventionally, there is automatic exposure control (AE) in which shooting is performed with an appropriate exposure by adjusting an aperture value and a shutter speed in accordance with the brightness of a subject in a camera. At this time, in the AE, the exposure is determined according to various conditions such as the presence / absence of a person's face and whether it is a backlight scene.

  In the case of a scene with contrast in which bright and dark parts are mixed in the image, the dark part may be blacked out if the bright part is properly exposed, and the bright part may be blown out if the dark part is properly exposed. is there. In such a scene with contrast, it is difficult to obtain an image in which blackout or whiteout is reduced only by an exposure value determined by the aperture, shutter speed, and ISO sensitivity.

  As a technique for reducing the whiteout phenomenon, dynamic range (D range) correction photography is known. This is done by controlling the exposure amount of the image sensor to prevent the occurrence of overexposure, and adjusting the gamma curve for areas that have already been properly lit or the brightness of the dark areas is insufficient. This is a technique to reduce only the whiteout.

  In addition, there is a known method for improving the ISO sensitivity and compensating for the brightness of a subject when the subject blur is reduced by photographing at a fast shutter speed when photographing a moving subject.

  However, the D range correction by the above-described image processing may cause a significant deterioration in the S / N ratio, and there is a problem in coexistence with an increase in ISO sensitivity that also causes a deterioration in the S / N ratio. .

  Patent Document 1 proposes the following imaging device in order to obtain a wide dynamic range image while suppressing an increase in noise. That is, if the D range can be corrected within the ISO sensitivity range, the correction is performed. If the D range cannot be corrected within the ISO sensitivity range, the ISO sensitivity is reduced within the possible range, and the shortage is compensated by other exposure conditions.

JP 2010-183461 A

  However, in Patent Document 1 described above, priority is given to D range correction, and ISO sensitivity and other exposure conditions are used to realize the target D range correction. However, depending on the setting and the scene, priority is given to ISO sensitivity. May be good.

  The present invention has been made in view of the above problems, and an object of the present invention is to obtain an image with suitable sensitivity in accordance with a scene to be photographed and settings.

In order to achieve the above object, an imaging apparatus according to the present invention includes an imaging unit that captures an image of a subject and outputs an image signal, a photometric unit, an analysis unit that analyzes a luminance distribution of the image signal, and the image signal. and amplifying means for amplifying and processing means for dynamic range control against the images signals, and the amplification factor of the amplifying means, determination means for determining one or priority of the correction amount in the dynamic range control, When giving priority to the amplification factor, the range of values that the correction amount can take is limited to the value that the amplification factor can take, and when giving priority to the correction amount, the value that the correction amount can take A range of values limited by the limiting unit based on a result of photometry by the photometric unit and a result of analysis by the analyzing unit. , And a determination means for determining the amplification factor and the correction amount.

  According to the present invention, an image with suitable sensitivity can be obtained according to the scene to be photographed and the setting.

1 is a block diagram illustrating a schematic configuration of an imaging apparatus according to an embodiment of the present invention. Schematic which shows an example of the external appearance of an imaging device. The figure which shows the concept of the process which adjusts the brightness of the image | photographed image with exposure and gain. The figure which shows the example of a gamma curve. The figure which shows the example of the scene from which a subject's motion amount differs. The figure which shows the example of the scene from which the brightness of a background differs. The figure which shows the example of the scene to image | photograph. The figure for demonstrating the concept of the maximum sensitivity with respect to the amount of motion of a to-be-photographed object, and the maximum D range correction amount. It is a figure which shows the brightness | luminance histogram of the scene shown in FIG.6 (b). The figure which shows an example of the program diagram in embodiment. 6 is a flowchart illustrating imaging processing according to the embodiment. 6 is a flowchart illustrating priority mode determination and control range determination processing according to the embodiment. The flowchart which shows the determination process of AE and DPlus amount. The figure which shows the DPlus control range and priority mode according to DPlus setting. The figure which shows the ISO sensitivity control range and priority mode according to the ISO sensitivity setting at the time of DPlus = Off. The figure which shows the ISO sensitivity control range and priority mode according to the ISO sensitivity setting at the time of DPlus = 200% of fixed. The figure which shows the ISO sensitivity control range and priority mode according to the ISO sensitivity setting at the time of DPlus = fixed 400%. The figure which shows the ISO sensitivity control range and priority mode according to the ISO sensitivity setting at the time of DPlus = Auto. The figure which shows the control range of ISO sensitivity and DPlus in ISOAuto adaptation mode.

  The best mode for carrying out the present invention will be described below in detail with reference to the accompanying drawings.

  FIG. 1 is a block diagram illustrating a schematic configuration of an imaging apparatus 100 according to the present embodiment.

  The lens unit 10 is composed of a plurality of lenses, and the focal point and the angle of view can be adjusted by driving part or all of the lens unit 10 along the optical axis direction by the mechanical drive circuit 14. It is also possible to perform camera shake correction by driving a part of the lens unit 10 in a direction other than the optical axis direction according to camera shake. Note that the camera shake correction can be similarly realized by moving the imaging unit 20. The amount of light that has passed through the lens unit 10 can be adjusted by the light amount adjusting mechanism 12. There are various methods for adjusting the amount of light, such as a diaphragm that changes the aperture, an ND filter that reduces the amount of light transmission, and a mechanical shutter that transmits and blocks light by opening and closing, depending on the application.

  The light that has passed through the lens unit 10 and the light amount adjustment mechanism 12 is received by the imaging unit 20. The imaging unit 20 operates in accordance with a drive instruction from the imaging drive circuit 22 and accumulates charges in an imaging element typified by a CCD or a CMOS sensor, reads out the accumulated charges, amplifies / attenuates the read charges (image signal), A / D conversion of the image signal is performed. Image data output from the imaging unit 20 is input to the image processing circuit 40 or stored in a temporary storage memory (RAM) 46.

  The image processing circuit 40 performs various processes such as image processing and image analysis of image data input directly from the imaging unit 20 or via the temporary storage memory 46. First, in automatic exposure control (AE: AutoExposure) and automatic focus adjustment (AF: AutoFocus) at the time of shooting, luminance components and frequency components are extracted from image data sequentially output from the imaging unit 20, and these are used as evaluation values. Thus, AE and AF can be performed. Further, the image processing circuit 40 can develop the image data obtained from the imaging unit 20 to adjust the image quality, and appropriately set the hue, gradation, brightness, and the like to finish the photograph suitable for viewing.

  Further, the image processing circuit 40 can detect a subject such as a person's face from the input image, and obtains information on the position, size, inclination, and likelihood of the face of the person in the image. be able to. In addition, it is possible to extract the feature information of the detected face of the person and authenticate whether the person is a specific individual. In the authentication, the personal feature information stored in the ROM 48 is read out, the feature information is compared by the image processing circuit 40, and matching processing is performed to check whether it matches the registered individual. Further, the image processing circuit 40 can perform detailed analysis of a person's face, for example, by analyzing the eyes of the person and detecting the line-of-sight direction.

  Further, the image processing circuit 40 calculates the amount of movement of the subject based on the change in the position of the subject between the images that are continuously input.

  The display device 50 such as an LCD can display an image developed by the image processing circuit 40 and can transmit information to the user by displaying characters and icons. By displaying an image obtained by the imaging unit 20 at a predetermined cycle, it can be used as an electronic viewfinder (EVF).

  Further, the external memory 90 can be inserted into the imaging apparatus 100 via the external memory I / F 52, or the external device 92 can be connected via the external device I / F 54. By connecting the external memory 90 and the external device 92, it is possible to exchange images, exchange command information for operating the devices, and the like.

  The system control unit 42 controls each component of the imaging apparatus 100, and the user can input an operation instruction via the operation unit 44. In response to an instruction from the light emission control circuit 32, the flash 30 emits light toward the main subject, so that when the main subject is dark, a sufficient amount of light can be obtained by causing the flash 30 to emit light. And a suitable image can be obtained.

  2A and 2B are schematic diagrams illustrating an example of the appearance of the imaging apparatus 100, in which FIG. 2A illustrates the front surface and FIG. 2B illustrates the back surface. The lens unit 10 is disposed on the front surface of the imaging apparatus 100, and the flash 30 is disposed on the same surface. Although not shown in FIG. 2B, a configuration in which a conventional optical finder 204 is also provided can be employed. The EVF that sequentially displays the images obtained from the imaging unit 20 on the display device 50 is easy to realize a high field of view. Depending on the size of the display device 50, the subject is easy to see large. There is a merit that there is no (lux). On the other hand, electric power for operating the image sensor and the display device 50 is required, and there is a concern that the battery will be consumed quickly. For this reason, when a large number of shots are desired while avoiding battery consumption, the electronic viewfinder function can be turned off and the optical viewfinder 204 can be used.

  A display device 50 is arranged on the back surface. Further, by operating the operation members 210, 220, 222, 224, 226, and 228 positioned at a plurality of positions of the imaging apparatus 100, functions corresponding to user operations such as shooting mode switching and various settings are activated. .

  A power ON / OFF switch 200 and a shutter switch 202 are disposed above the image pickup apparatus. The shutter switch 202 is pressed lightly (SW1) to prepare for shooting, and the button is deeply pressed to start shooting.

Next, a method for determining exposure and dynamic range (D range) correction during shooting in the imaging apparatus 100 having the above-described configuration will be described. The factors that determine the exposure are subject brightness Bv, photographing sensitivity Sv, aperture value Av, and shutter speed Tv. In the case of a film camera, the photographing sensitivity Sv is determined by the film to be loaded, the subject brightness Bv is measured by a photometric sensor, and the exposure value Ev can be calculated by equation (1).
Bv + Sv = Ev (1)
The exposure value Ev calculated by the equation (1) is a target value for photographing the subject with appropriate exposure, and determines the combination of the aperture value Av and the shutter speed Tv that realizes this Ev.
Ev = Av + Tv (2)

  Even in the case of a digital camera, the exposure is basically determined by using the equations (1) and (2). However, the difference from the film camera is that the photographing sensitivity Sv can be dynamically changed. is there.

FIG. 3 is a diagram illustrating a concept of processing for adjusting the brightness of an image captured by exposure and gain. When the subject image passes through the lens unit 10, the amount of light is controlled by the aperture value Av303 and received by the image sensor. The light receiving time can be controlled by the shutter speed (charge accumulation time) Tv305. When photoelectric conversion is performed by the image sensor of the imaging unit 20, the basic sensitivity BaseSv307 is determined based on this characteristic. Image data read from the image sensor is gained by an analog gain amplifier 309. The analog gain amplifier 309 can designate an arbitrary value, and can be used as a means for realizing a function for adjusting photographing sensitivity. When the concept of automatic sensitivity control is added to Expression (1) and Expression (2), the following Expression (3) is obtained, and the operation can be performed so as to achieve the target Ev by the aperture value, shutter speed, and gain value.
Bv + BaseSv = Ev = Av + Tv−DeltaGain (3)
The final sensitivity at this time is
Sv = BaseSv + DeltaGain (4)
Equation (3) can be expressed by Equation (5).
Bv + Sv = Ev = Av + Tv (5)

  FIG. 10 shows a program diagram expressing combinations of aperture value, shutter speed, and sensitivity according to the exposure value Ev. The horizontal axis represents the shutter speed Tv, the vertical axis represents the aperture value Av, and a combination corresponding to each exposure value Ev1007 is represented. As an example, FIG. 10 shows an example in which the sensitivity 1005 is increased and the low-brightness object is followed after the aperture value becomes full (Av3 in the figure). An arrow 1013 indicating how much the maximum sensitivity is raised can be expressed by this program diagram, and is designed according to product specifications.

  Returning to FIG. 3, the analog signal level is determined by the aperture value Av, the shutter speed Tv, and the sensitivity Sv (= BaseSv + DeltaGain), and then A / D conversion is performed. Thereafter, the image processing circuit 40 can apply DeltaDP (DPlus amount) 313 as digital signal conversion. In this conversion, a method for converting an input signal to an output signal can be expressed by a gamma curve, and a conceptual diagram thereof is shown in FIG. The horizontal axis indicates an input signal, and the vertical axis indicates an output signal. A value after conversion can be defined for each level of the input signal. As an example, two types of conversion characteristics of input signal to output signal are shown. As can be seen from FIG. 4, the conversion characteristic 413 has a higher gain increase than the conversion characteristic 411. In addition, since the conversion curve is standing more vertically in the dark portion of the conversion characteristic 413, the gradation after conversion is impaired as compared with the conversion characteristic 411. In this way, it is possible to adjust how much gradation is applied to which input signal level by the conversion curve characteristics. Therefore, it is possible to adjust the dynamics of the image in accordance with how much exposure is secured to the image sensor by the diaphragm and shutter. The range can be controlled.

  How the aperture value, shutter speed, gain, and gamma curve described above are effectively set according to the subject will be described with reference to FIGS. 5, 6, and 7 as an example.

  FIG. 5 is a diagram showing an example of a scene in which the amount of movement of the subject is different, and FIG. 5A shows an example of photographing a stationary person. On the other hand, FIG. 5B shows an example of photographing a running person. When shooting a moving subject, it is more likely that a person will be blurred when shooting at a slow shutter speed. Although depending on the subject brightness, in order to shoot at a fast shutter speed, it is necessary to shoot with increased sensitivity to compensate for it. On the other hand, since a stationary subject has less blur, good image quality can be obtained by shooting with a slow shutter speed and low sensitivity.

  FIGS. 6A and 6B show examples of photographing a still person, but the background (brightness) is different. FIG. 6A shows a scene with a uniform brightness, while FIG. 6B shows a scene where the lower part of the screen is dark and the upper part has a bright contrast. When shooting in FIGS. 6A and 6B with the same exposure, there is a concern that a phenomenon that the bright background in FIG. For this reason, at the time of shooting in FIG. 6B, the overexposure is suppressed by suppressing the exposure amount of the image sensor to a low level, and shooting is performed by adjusting the gamma curve so as to compensate for the low exposure. Can be expected. When the luminance histogram of the scene as shown in FIG. 6B is seen, as shown in FIG. 9, a large number of pixels are distributed in the high luminance region and the low luminance region, and there is a tendency that there is luminance contrast. The method of referring to the brightness histogram is effective for determining whether or not the scene has brightness contrast and dynamic range control is effective.

  FIG. 7 shows an example of a subject running in a background with a contrast difference. In such a case, it is desired to increase the sensitivity in order to reduce the blurring of the subject and take a picture with a high shutter speed, and it is also desirable to control the dynamic range in order to eliminate the difference in brightness. However, when a gamma curve as shown in FIG. 3 is applied in order to increase the dynamic range, the noise component increases and there is a concern about image quality deterioration, and there is a problem in reducing both subject blurring and good image quality.

  As an example for such a problem, FIGS. 8A and 8B show the concept of a method for determining a shooting parameter in accordance with the amount of movement of a subject. 8A, the horizontal axis represents the amount of movement of the subject, and the vertical axis represents the maximum sensitivity. In FIG. 8B, the horizontal axis represents the amount of movement of the subject, and the vertical axis represents the maximum D range correction amount. . When the movement of the subject is small, the maximum sensitivity is limited to ISO 3200 and the maximum D range correction amount can be up to 400%, so that the image quality degradation due to the increase in ISO sensitivity can be assigned to the D range correction and used. . On the other hand, when the amount of movement of the subject is large, the maximum sensitivity is allowed up to ISO12800, aiming at the effect of reducing the blur of the subject, and a parameter that does not perform D range correction so that image quality deterioration due to D range correction does not occur any more Designed.

  As described so far, the appropriate aperture value, shutter speed, gain, and gamma curve differ depending on the scene. it can. As one method, the user may select an arbitrary ISO sensitivity value or D range correction value. In addition, the camera automatically determines the exposure and designates the item to be prioritized in the determination, such as mode A in which sensitivity improvement is prioritized and mode B in which D range correction is prioritized. It is good.

  Next, the operation in the present embodiment of the imaging apparatus 100 having the above configuration will be described with reference to FIGS. 11, 12, and 13. 14 to 19 show combinations of D range correction settings and ISO sensitivity (amplification factor) settings in a table.

  FIG. 11 is a flowchart illustrating a shooting process in the imaging apparatus 100 according to the present embodiment. This process is started when the power ON / OFF switch 200 of the imaging apparatus 100 shown in FIG. 2 is turned on. In S103, the system is activated. Here, the basic system is started, such as power supply and clock supply to the CPU and LSI necessary for the operation of the imaging apparatus 100, and initialization of the memory and OS.

  Next, in S105, an imaging system such as an imaging element in the imaging unit 20 is activated, and an optical system such as a lens unit 10 including a focus lens and a zoom lens is activated. Furthermore, the mechanical shutter and the mechanical aperture operate, and external light starts to be guided to the image sensor. Subsequently, in S107, the image processing circuit 40 starts the AE, AF, and AWB processes that measure the brightness, color, and focus state based on the data read from the image sensor and put them in suitable states. . After the AE, AF, and AWB processes are activated, generation of an EVF image is started in S109. The EVF image generated here is displayed on the display device 50, and is also used for detection system processing such as face detection, personal authentication, and line-of-sight detection in S111. After the start-up is completed, the EVF display steady state is entered.

  In the steady state of EVF display, in S113, the system control unit 42 determines whether SW1 is turned on as a shooting preparation instruction button. If not turned on, the EVF display is continued, and if turned on, the process proceeds to S201. In S201, priority mode determination indicating which of ISO sensitivity and D range correction is given priority and a control range of ISO sensitivity and D range correction amount (DPlus) are determined. Details of the processing performed in S201 will be described later with reference to FIG. In step S301, AE processing for determining exposure for shooting and determination of the D range correction amount are performed. In step S115, AF processing for focus control is performed. Details of the processing in S301 will be described later with reference to FIG.

  After the shooting conditions are determined, in S117, the system control unit 42 determines whether SW2 is turned on. If it is not ON, it is determined whether SW1 remains ON in S118. If it is ON, the process of S117 is repeated. If it is not ON, the process returns to S113 and the above process is repeated. On the other hand, when SW2 is turned on, the process proceeds to S119, and shooting is performed according to a predetermined exposure condition. When shooting is completed, the system control unit 42 waits for SW2 to be turned off in S120, and returns to S113 to return to the above. Repeat the process. In the case of continuous shooting, after shooting in S119, the process returns to S117 instead of S120.

  Next, with reference to FIG. 12, the priority mode determination indicating which of the ISO sensitivity and D range correction to be prioritized performed in S201 and the process of determining the control range of the ISO sensitivity and the D range correction amount will be described. .

  First, in S203, the system control unit 42 determines the DPlus control range and the priority mode according to the DPlus setting according to the table shown in FIG. For example, in the example shown in FIG. 4, the DPlus amount is 400% and the DPlus control range value 2 corresponds to the conversion characteristic 413, and the DPlus amount is 200% and the DPlus control range value 1 corresponds to the conversion characteristic 411. To do. Further, the DPlus amount is OFF and the DPlus control range value 0 corresponds to the characteristic indicated by the dotted line in FIG. 4 (ie, input signal = output signal). In the example shown in FIG. 14, it is assumed that the user can select the DPlus setting from four types of OFF / fixed 200% / fixed 400% / Auto. Depending on the selected DPlus setting, the DPlus control range and priority mode are determined. When it is OFF, the DPlus control range is from the minimum (Min) 0 to the maximum (Max) 0, indicating that DPlus does not function in effect. At this time, the priority mode is the ISO sensitivity priority mode, which indicates that the ISO sensitivity determination is performed with priority. DPlus fixed 200% / 400% indicates that the DPlus control ranges are Min1 to Max1 and Min2 to Max2, respectively, and that DPlus actually takes that fixed amount. In the table, the D range correction 200% is expressed as a numerical value with 1 step and 400% as 2 steps. The DPlus setting Auto follows a table shown in FIG.

  Subsequently, in S205, the system control unit 42 determines the ISO sensitivity control range, but determines which table to follow according to the DPlus setting. Depending on one of the four types of DPlus settings OFF / 200% / 400% / Auto, the process proceeds to any one of S211, S221, S231 referring to the corresponding table.

  If the DPlus setting is OFF, the process proceeds to S211 and follows the table shown in FIG. The table shows the ISO sensitivity control range and priority mode for each selectable ISO sensitivity. When DPlus is set to OFF, neither the minimum sensitivity nor the maximum sensitivity is limited. Therefore, the ISO fixed setting can be selected within the range of ISO 100 to 12800 which is the minimum sensitivity and the maximum sensitivity of the imaging apparatus 100. In the example, two types can be selected as the ISOAuto setting. Auto The sensitivity can be selected automatically in the range of ISO 100 to 3200, and Auto extension in the range of ISO 100 to 12800. Auto Normally, the maximum sensitivity is suppressed in consideration of image quality degradation due to increased ISO sensitivity. Auto expansion, on the other hand, is a mode that increases the sensitivity to the highest sensitivity of the camera, without any deterioration in image quality.

  When DPlus is 200%, the process proceeds to S221 and follows the table shown in FIG. The table shows that the lowest ISO sensitivity is ISO200, and ISO100 cannot be realized. This is because the sensitivity has already been increased by one step in realizing DPlus 200%. Also, the highest ISO sensitivity is ISO6400, which indicates that the ISO sensitivity can only be increased to 6400 because of concern about image quality degradation. Here, the ISO 100 and ISO 12800 cannot be set by the user via the operation unit 44 so that the ISO sensitivity that cannot be realized is not set. In the table shown in FIG. 16, the ISOAuto sensitivity control range is also limited. For the same reason, compared to the case where the DPlus setting is OFF, the minimum sensitivity value is ISO200 and the maximum sensitivity value of ISOAuto expansion is lowered to ISO6400. In DPlus200%, all priority modes are DPlus priority, which indicates that DPlus200% is prioritized.

  When DPlus is 400%, the process proceeds to S221 and follows the table shown in FIG. The idea is the same as DPlus200% shown in FIG. 16, and the minimum sensitivity and the maximum sensitivity are limited. The priority mode is a mode that prioritizes DPlus implementation. When DPlus is 400%, the maximum value of ISOAuto is limited to ISO3200, so the sensitivity control range is the same for Auto normal and Auto expansion. That is, when DPlus is 400%, there is no distinction between Auto normal and Auto extension, so the Auto extension does not function effectively, and the table shown in FIG. 17 does not describe the Auto extension. Similarly to the case where DPlus is 400%, similarly to the case where DPlus is 400%, the user cannot set ISO100, ISO200, and ISO12800 via the operation unit 44 so that the ISO sensitivity that cannot be realized is not set. In addition, the Auto extension that doesn't actually work is disabled.

  When DPlus is Auto, the process proceeds to S231 and follows the table shown in FIG. When DPlus is Auto and ISO sensitivity is fixed, priority is given to realizing the ISO sensitivity selected by the user. At this time, ISO400 to 3200 can realize DPlus400% as the minimum sensitivity guarantee and the image quality guarantee, and the DPlus control range is 0 to 2 steps. On the other hand, because ISO200 can only apply 1 step of DPlus, the DPlus control range is 0 to 1 step, and ISO100 cannot apply DPlus, so the DPlus control range is 0 to 0 and DPlus can be applied. Can not. On the other hand, on the high sensitivity side, the ISO 6400 sets the DPlus control range to 0 to 1 in consideration of image quality deterioration, and the ISO 12800 sets the control range to 0 to 0 so that DPlus is not applied.

  The normal combination of DPlusAuto and ISOAuto is the mode that prioritizes DPlus. At this time, in the table, the ISO sensitivity range is ISO100 to 3200, and the range where the minimum ISO sensitivity cannot be realized when DPlus is applied is determined according to the flowchart of FIG.

  The combination of DPlusAuto and ISOAuto expansion is a mode that prioritizes ISO sensitivity. At this time, in the table, the DPlus control range is 0 to 2, which is a range where DPlus cannot be realized when the ISO sensitivity is lower or higher than a predetermined value, but this is determined according to the flowchart of FIG. .

  The combination of DPlusAuto and ISOAuto adaptation allows the priority mode to be switched according to the subject's situation. This will be described with reference to the table shown in FIG. The table shown in FIG. 19 is an example in which the control range is adaptively determined in consideration of the case where the subject is moving and the case where there is a light / dark difference in the screen as shown in FIGS. Show. In the table, each control range and priority mode are determined using the result of detecting the amount of movement of the subject as large, medium and small.

  As described above, when DPlus is Auto, the system control unit 42 determines whether ISOAuto adaptation is applied in S233 after S231. If it is not ISOAuto adaptation, the process of S201 is terminated, and if it is ISOAuto adaptation, the process proceeds to S235.

  In S235, the system control unit 42 determines the amount of movement of the subject calculated by the image processing circuit 40, and in S237, based on the calculated amount of movement and the table shown in FIG. DPlus control range and priority mode are determined.

  When the amount of movement of the subject is small, the ISO control range is set to ISO 100 to 3200 because it is not necessary to extremely increase the sensitivity in order to reduce subject blur. The DPlus control range can be set to 0 to 2 stages, and DPlus is given priority, so that priority is given to reducing the contrast. When the amount of movement of the subject is medium, the ISO control range is set to ISO 100-6400, it is relatively resistant to subject blurring, and as the ISO sensitivity increases, the DPlus control range is narrowed so that image quality deterioration does not become noticeable. ing. When the amount of movement of the subject is large, the highest priority is to reduce subject blurring, and the ISO sensitivity control range is ISO12800. In addition, priority mode focuses on reducing blurring as ISO sensitivity priority. Thus, the ISO sensitivity control range, DPlus control range, and priority mode are determined according to the table.

  Next, with reference to FIG. 13, the process for determining the exposure for photographing performed in S301 of FIG. 11 will be described. First, in step S303, the system control unit 42 determines whether a fixed value has already been selected by the user as the DPlus amount (correction amount for dynamic range control) according to the DPlus setting, or whether the imaging device automatically selects Auto. judge. If a fixed value is selected as the DPlus amount, the selected fixed value is confirmed in S305.

  On the other hand, if the DPlus setting is Auto, in S307, the image processing circuit 40 analyzes the amount of whiteout in order to calculate the amount of DPlus corresponding to the scene. There are various methods for analyzing the amount of whiteout, and there is a method of using the luminance histogram shown in FIG. 9 as evaluation data. The luminance distribution in the screen can be read from the luminance histogram, and the amount of whiteout can be calculated from the pixel number distribution on the high luminance side. In step S309, the system control unit 42 calculates how much the exposure amount on the image sensor surface needs to be suppressed in order to suppress the whiteout. This is the DPlus amount. If the exposure is suppressed to underexposure only to suppress overexposure, an already properly exposed area in the screen will be underexposed. In order to prevent this, the gamma curve is adjusted to prevent the luminance region from the dark part to the appropriate exposure from becoming too dark.

  Subsequently, in S311, the system control unit 42 confirms the ISO setting. When the user has selected an ISO fixed value from the settable ISO sensitivity corresponding to the DPlus amount set in S305 or S309 according to the tables shown in FIGS. 15 to 17, the process proceeds to S313 and the ISO sensitivity value is used for shooting. Confirm as sensitivity. On the other hand, if the ISO sensitivity is set to Auto, the lowest ISO sensitivity in the ISO sensitivity control range is redetermined in S315. In S305 or S309, when an effective value as the DPlus amount is confirmed, the ISO sensitivity cannot be lowered at least for the number of steps, and therefore re-determination is performed here. For example, in the ISOAuto normal of the table shown in FIG. 18, the ISO sensitivity control range is ISO100-at this time, but in S315, it is redetermined according to the DPlus amount.

  Subsequently, in S317, the system control unit 42 determines whether or not the priority mode is DPlus priority, and in the case of DPlus priority, the highest ISO sensitivity is determined again in S319. For example, in the table shown in FIG. 18, the highest ISOAuto normal sensitivity is ISO3200, but if there is a concern about image quality degradation due to the combination of the DPlus amount determined in S305 or S309 and the highest sensitivity at this point, the ISO sensitivity Re-determine to further reduce the maximum value. On the other hand, when the priority mode is ISO sensitivity priority, in S320, the DPlus amount is redetermined so as to suppress image quality deterioration by redetermining so as to suppress the already determined DPlus amount.

  With the processing so far, the DPlus amount and the ISO sensitivity control range are determined. If the ISO sensitivity setting is fixed, the ISO sensitivity value is also determined.

  In step S321, the system control unit 42 creates a program diagram in consideration of the ISO sensitivity control range. The program diagram represents a combination of the aperture value, shutter speed, and ISO sensitivity value as shown in FIG. 10, and a program diagram reflecting the ISO sensitivity control range is generated here. In step S323, the system control unit 42 finally determines an aperture value, a shutter speed, and an ISO sensitivity value from the program diagram based on the brightness Bv of the subject that has been separately measured.

  As described above, according to the present embodiment, it is possible to appropriately determine the ISO sensitivity and DPlus value at the time of shooting.

Although the present invention has been described in detail based on preferred embodiments thereof, the present invention is not limited to these specific embodiments, and various forms within the scope of the present invention are also included in the present invention. included. A part of the above-described embodiments may be appropriately combined.
The present invention can also be realized by executing the following processing. That is, software (program) that realizes the functions of the above-described embodiments is supplied to a system or apparatus via a network or various storage media, and a computer (or CPU, MPU, or the like) of the system or apparatus reads the program. It is a process to be executed.

Claims (9)

Imaging means for photographing a subject and outputting an image signal;
Photometric means;
Analyzing means for analyzing the luminance distribution of the image signal;
Amplifying means for amplifying the image signal;
And processing means for dynamic range control against the images signals,
A determination unit that determines which one of the amplification factor in the amplification unit and the correction amount in the dynamic range control is prioritized;
When giving priority to the amplification factor, the range of values that the correction amount can take is limited to the value that the amplification factor can take, and when giving priority to the correction amount, the value that the correction amount can take Limiting means for limiting the range of values that the amplification factor can take;
And determining means for determining the amplification factor and the correction amount within a range of values limited by the limiting means based on the result of photometry by the photometric means and the result of analysis by the analyzing means. An imaging device. Said limiting means, said by the dynamic range control by amplification and the processing means by the amplifying means such that said image signal degradation becomes lower than the predetermined level, the range and the correction amount of the gain possible values The imaging apparatus according to claim 1, wherein a range of values that can be taken is limited. A calculation means for calculating the amount of movement of the subject;
3. The determination unit according to claim 1, wherein the determination unit determines to prioritize the amplification factor if the amount of movement exceeds a predetermined amount of movement, and to prioritize the correction amount if not. The imaging device described. A designating unit for designating the amplification factor and the correction amount;
The imaging apparatus according to claim 3, wherein when the fixed value is specified as the correction amount by the specifying unit, the determination unit determines to prioritize the correction amount regardless of the movement amount. .   When the correction amount is specified so that the dynamic range control is not performed by the specifying unit, the determination unit determines that the amplification factor is given priority regardless of the movement amount. The imaging device according to claim 4.   6. The determination unit according to claim 4, wherein if the correction amount is not specified and the amplification factor is specified, the determination unit determines to prioritize the amplification factor regardless of the amount of movement. Imaging device. A control method in an imaging apparatus having an imaging means for photographing a subject and outputting an image signal, and a photometry means,
An analyzing step for analyzing a luminance distribution of the image signal;
An amplification step in which the amplification means amplifies the image signal;
Processing means, a processing step of performing dynamic range control against the images signals,
A determining step for determining which of the amplification factor in the amplification step and the correction amount in the dynamic range control is prioritized;
When the limiting means gives priority to the amplification factor, the range of values that the correction amount can take is limited to the value that the amplification factor can take, and when the correction amount takes priority, the correction amount takes A limiting step of limiting a range of values that the amplification factor can take with respect to a value to be obtained;
A determining step for determining the amplification factor and the correction amount within a range of values limited in the limiting step based on a result of photometry by the photometric unit and an analysis result in the analyzing step; A control method comprising:   The program for making a computer perform each process of the control method of Claim 7.   A computer-readable storage medium storing the program according to claim 8.

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