JP2017126959A - Imaging device, control method for the same and program therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an imaging device which allows a user to understand a guide for obtaining a dynamic range required in a specific point or area.SOLUTION: An imaging device includes: imaging means for imaging a subject and outputting image data; expansion means for expanding a dynamic range of the imaging means by lowering exposure of the imaging means; acquisition means for acquiring user operation to specify a photometric value acquisition area in an image for acquiring a signal value; detection means for detecting the signal value of the photometric value acquisition area in the image of the imaging means, by expanding the dynamic range by a predetermined amount by the expansion means; control means outputting a guide for changing to a dynamic range where the photometric value acquisition area has gradation, on the basis of the difference of the signal value of the photometric value acquisition area detected by the detection means and a predetermined reference value; and display control means for displaying the guide.SELECTED DRAWING: Figure 5

Description

  The present invention relates to an imaging apparatus, a control method thereof, and a program.

  Conventionally, there is a known method for expanding the dynamic range by controlling the brightness of images shot with exposure lower than the proper exposure (underexposure) by increasing the brightness by gamma correction (gradation correction). It has been. The gamma correction characteristics are changed according to the set dynamic range so that the relationship between the level of incident light and the level of the output signal is a relationship prepared in advance.

  Several methods have been proposed for expanding the dynamic range and changing the gamma correction characteristics. Japanese Patent Application Laid-Open No. 2004-228561 proposes a method of effectively using the gradation of the high luminance part by expanding the dynamic range and smoothing the gradient of the gradation characteristic of the high luminance part. According to this method, even when the dynamic range is low, the gradation of the high luminance part can be effectively used by changing the gradient of the gradation characteristic of the high luminance part.

  Further, in Patent Document 2, there is a method for maintaining the output with respect to the reference incident light amount while shifting the dynamic range according to the maximum reflectance of the incident light amount of the subject and changing the gamma correction to the characteristic corresponding to the maximum reflectance. Proposed. In this method, the gamma value approaches 1 when the maximum reflectance is high, and the gamma value approaches 0 when the maximum reflectance is low. By doing so, the contrast is lowered if the maximum reflectance is high, and the contrast is increased if the maximum reflectance is low.

JP 2004-120511 A JP 2006-81037 A

  By the way, when expanding the dynamic range, the relationship between the level of the incident light and the level of the output signal is maintained by changing the gamma characteristic while photographing underexposed. This is almost the same as signal amplification and causes a decrease in the S / N ratio. Therefore, from the viewpoint of the S / N ratio, it is better not to expand the dynamic range more than necessary. Therefore, for example, when whiteout occurs under certain shooting conditions, the user may desire a minimum dynamic range expansion that can eliminate whiteout. Furthermore, if it is possible to expand to a dynamic range that can eliminate white spots and blackouts of specific points or areas in the image, it is possible to suppress a decrease in the S / N ratio than when all the whiteout that has occurred in the image is eliminated. There is also. However, since the photometric value is saturated at the portion where the whiteout is in the first place, the level of the incident light at the whiteout portion cannot be specified. Therefore, there is a problem that the user cannot know the amount of expansion of the dynamic range necessary for avoiding overexposure.

  The present invention has been made in view of the above-described problems of the prior art, and an imaging apparatus that allows a user to grasp a guideline for obtaining a necessary dynamic range at a specific point or region and its control The object is to provide a method and program.

  In order to solve this problem, for example, an imaging apparatus of the present invention has the following configuration. That is, an imaging unit that captures an image of a subject and outputs image data, an expansion unit that expands a dynamic range of the imaging unit by lowering the exposure of the imaging unit, and a photometric value acquisition in an image for acquiring a signal value An acquisition means for acquiring a user operation for specifying an area, a detection means for expanding a dynamic range by a predetermined amount by an enlargement means, and detecting a signal value of a photometric value acquisition area in the screen of the imaging means, and a detection means Based on the difference between the detected signal value of the photometric value acquisition area and a predetermined reference value, a control means for outputting a standard for changing the photometric value acquisition area to a dynamic range having gradation, and display of the standard And a display control means.

  According to the present invention, it is possible for a user to grasp a guideline for obtaining a necessary dynamic range at a specific point or region.

1 is an external view of a digital camera as an example of an imaging apparatus according to an embodiment of the present invention. 1 is a block diagram illustrating a functional configuration example of a digital camera according to a first embodiment. 7 is a flowchart showing a series of operations related to the dynamic range assist function of the first embodiment. 6 is a graph showing an example of gamma correction characteristics related to the dynamic range assist function according to the first embodiment. 7 is a flowchart showing a series of operations related to difference value display processing according to the first embodiment. The figure explaining the example of the photometry value acquisition area | region and display candidate area | region which concern on Embodiment 1. FIG. 8 is a flowchart showing a series of operations related to difference value display processing according to the second embodiment. 6A and 6B are diagrams for explaining examples of photometric value acquisition areas and display candidate areas according to the second embodiment.

(Embodiment 1)
Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings. In the following, an example in which the present invention is applied to an arbitrary digital camera capable of photographing with changing exposure will be described as an example of an imaging apparatus. However, the present invention is not limited to a digital camera having an imaging function, and can be applied to any electronic device that can shoot with changing exposure. These devices may include, for example, a mobile phone, a game machine, a tablet terminal, a personal computer, a clock-type or glasses-type information terminal, a medical device such as a monitoring system or an endoscope system.

(Configuration of digital camera 100)
FIG. 1 is an external view of a digital camera 100 as an example of an imaging apparatus according to the present embodiment. The display unit 28 includes a display panel such as a liquid crystal display, an organic EL display, and electronic paper, and is attached so as to be openable and closable, for example. The display unit 28 displays, for example, a captured image or a captured image read from the recording medium 200 when opened, and also displays a menu screen for the user to operate the digital camera 100.

  The recording switch 61 is a switch for instructing the start and end of moving image recording, and is disposed on the back surface of the digital camera 100, for example. Moreover, you may comprise a part of operation part 70 mentioned later. The mode switch 60 is a switch for switching various modes of the digital camera 100. For example, the digital camera 100 that can be operated when the display unit 28 is opened together with other switches constituting a part of the operation unit 70 described later. It is arranged on the side of the.

  The connector 112 is a connection interface that physically connects a predetermined connection cable and the digital camera 100. When the connection cable is connected, the communication unit 113 can communicate with the connected external device.

  The operation unit 70 includes various members that accept various user operations and operation members such as a cross key. The operation unit 70 includes, for example, a menu display button, a determination button, other cursor keys, a pointing device, a touch panel, and the like.

  The power switch 72 is a switch for switching between power on and power off, and is disposed on the upper surface side of the digital camera 100, for example. The recording medium 200 is a recording medium such as a memory card or a hard disk that can be detached from the digital camera 100. The recording medium slot 201 is a slot for attaching the recording medium 200 to the digital camera 100, and electrically connects the digital camera 100 and the recording medium 200 to enable mutual communication.

  FIG. 2 is a block diagram illustrating a functional configuration example of the digital camera 100 according to the present embodiment. Note that one or more of the functional blocks shown in FIG. 2 may be realized by hardware such as an ASIC or a programmable logic array (PLA), or by executing software by a programmable processor such as a CPU or MPU. May be. Further, it may be realized by a combination of software and hardware. Therefore, in the following description, even when different functional blocks are described as the operation subject, the same hardware can be realized as the subject.

  The imaging optical system 103 includes a lens group including a zoom lens and a focus lens, and forms an object optical image on an imaging element included in the imaging unit 22 according to imaging conditions. The diaphragm 101 is used to adjust the amount of incident light. The ND 104 includes, for example, an ND filter, and reduces the amount of incident light according to the setting.

  The imaging unit 22 includes an imaging element having a configuration in which a plurality of pixels each having a photoelectric conversion element are two-dimensionally arranged. The image sensor photoelectrically converts the subject optical image formed by the photographing optical system 103 at each pixel and outputs an analog image signal. The imaging device may be an imaging device such as a CCD (Charge-Coupled Device) image sensor or a CMOS (Complementary Metal Oxide Semiconductor) image sensor. The imaging unit 22 has functions such as control of accumulated charges using an electronic shutter, control of analog gain, and change of readout speed. The A / D converter 23 converts the analog signal output from the imaging unit 22 into a digital signal (image data). The barrier 102 covers the imaging system including the imaging optical system 103 of the digital camera 100, thereby preventing the imaging system including the imaging optical system 103, the diaphragm 101, and the imaging unit 22 from being dirty or damaged.

  The image processing unit 24 performs predetermined pixel interpolation, resizing processing such as enlargement and reduction, color conversion on the image data output from the A / D conversion unit 23 or the image data output from the memory control unit 15. Processes such as processing, gamma correction, and digital gain addition are applied. In addition, a predetermined calculation process is performed on the image data at the time of imaging, and the calculation result is transmitted to the system control unit 50. The system control unit 50 performs exposure control, distance measurement control, white balance control, and the like based on the calculation result. As a result, TTL (through-the-lens) AF (autofocus) processing, AE (automatic exposure) processing, AWB (auto white balance) processing, and the like can be performed.

  The memory 32 is a volatile memory such as an SDRAM, and temporarily stores various data such as image data and audio data. The memory 32 inputs the image data output from the A / D conversion unit 23 and the image data to be displayed on the display unit 28 via the image processing unit 24 and / or the memory control unit 15. The memory 32 has a sufficient storage capacity for storing a moving image and sound for a predetermined time, and the memory 32 also serves as a memory (video memory) for displaying images.

  The D / A conversion unit 13 converts the image display data stored in the memory 32 into an analog signal and supplies the analog signal to the display unit 28. The display unit 28 acquires display image data stored in the memory 32 via the D / A conversion unit 13 and displays the acquired analog signal on a display panel such as an LCD.

  As described above, the digital camera 100 functions as an electronic viewfinder, for example, by transferring the digital image data output from the imaging unit 22 and accumulated in the memory 32 to the display unit 28 and displaying the digital image data sequentially. Display can be made.

  The nonvolatile memory 56 is an electrically erasable and recordable memory, and includes, for example, an EEPROM. The non-volatile memory 56 stores constants, programs, and the like for operating the system control unit 50.

  The system control unit 50 controls the entire digital camera 100. By executing the program recorded in the nonvolatile memory 56 described above, each process of the present embodiment to be described later is realized.

  The system memory 52 is a volatile memory, and for example, a RAM is used. In the system memory 52, constants and variables for operation of the system control unit 50, programs read from the nonvolatile memory 56, and the like are expanded. The system control unit 50 also performs display control by controlling the memory 32, the D / A conversion unit 13, the display unit 28, and the like.

  The system timer 53 is a time measuring unit that measures time (timing) used for various controls and the time of a built-in clock.

  The mode switch 60, the recording switch 61, and the operation unit 70 input various operation instructions to the system control unit 50. The mode switch 60 switches the operation mode of the system control unit 50 to any one of a moving image recording mode, a still image recording mode, a reproduction mode, and the like. The modes included in the moving image recording mode and the still image recording mode include, for example, an auto shooting mode, an auto scene discrimination mode, a manual mode, and various scene modes that vary shooting conditions for each shooting scene. The recording switch 61 switches between a shooting standby state and a shooting state. In response to the recording switch 61 being switched to the shooting state, the system control unit 50 starts a series of operations from reading the image signal from the imaging unit 22 to writing the image data to the recording medium 200.

  The operation unit 70 includes each operation member, and also includes various function buttons displayed on the display unit 28, for example. The system control unit 50 displays, for example, icons appropriately assigned functions for each scene, and acts as various function buttons. Examples of the function buttons include an end button, a return button, an image advance button, a jump button, a narrowing button, and an attribute change button. For example, when the menu button is pressed, the system control unit 50 causes the display unit 28 to display a menu screen on which various settings can be made. While confirming the menu screen displayed on the display unit 28, the user can perform various settings by, for example, pressing a cross key and a SET button that can specify four directions, up, down, left, and right.

  The power supply control unit 80 includes, for example, a battery detection circuit, a DC-DC converter, a switch circuit that switches a block to be energized, and the like, and detects whether or not a battery is attached, the type of battery, the remaining battery level, and the like. Further, the power supply control unit 80 controls the DC-DC converter based on the detection result of the remaining battery level and the instruction of the system control unit 50, and supplies a necessary voltage to each unit including the recording medium 200 for a necessary period. .

  The power supply unit 30 includes a primary battery such as an alkaline battery or a lithium battery, a secondary battery such as a NiCd battery, a NiMH battery, or a Li ion battery, an AC adapter, or the like. The recording medium I / F 18 is an interface with the recording medium 200 such as a memory card or a hard disk. The communication unit 113 communicates with an external device by a communication method compliant with a predetermined method. The communication unit 113 performs wired communication with an external device via a connection cable connected to the connector 112, for example, in accordance with an instruction from the system control unit 50. Further, the communication unit 113 may be provided with an antenna to perform, for example, proximity wireless communication, wireless LAN communication, and wireless communication for mobile phones.

  The recording medium 200 is a recording medium such as a memory card for recording image data obtained by photographing, and includes, for example, a semiconductor memory and a magnetic disk.

(Outline of D range assist function)
When shooting a moving image with a video camera, as a method for suppressing overexposure to a high-luminance subject, there is a method of underexposure and increasing the sensitivity by increasing the sensitivity. However, if whiteout occurs in the current exposure, the user can determine how much the dynamic range can be expanded to avoid whiteout, that is, how much underexposure can be used to avoid whiteout. I do not understand. This is because the signal is saturated in the whiteout portion, and the maximum value of the signal level in that portion cannot be detected even on the camera side.

  Therefore, in this embodiment, the dynamic range is once set to a wide value during shooting. As a result, the portion that has been whitened up to now in the screen is no longer saturated, and the maximum value of the signal in that portion can be detected. That is, the difference between the maximum value of the signal (having gradation) that can be expressed in the dynamic range that has been set up to now and the original maximum value of the signal in the portion that has been overexposed can be obtained. Then, it can be seen that if the dynamic range is expanded by this difference, whiteout can be avoided, and this can be notified to the user.

  In the present embodiment, the digital camera 100 is currently set to the original maximum value of the signal value in the part that is whiteout when a part of the currently captured video is whiteout. The difference between the maximum signal values that can be expressed in the dynamic range can be displayed. The user can know that whiteout of an image can be avoided by expanding the dynamic range by the displayed difference (by underexposure). This function is called a D range assist function. In the following description, the dynamic range is also simply referred to as the D range.

  In the D range assist function according to the present embodiment, the exposure is once lowered and the dynamic range is set to a wide value. After that, a signal that can be expressed by the photometric value and the currently set dynamic range by detecting the original maximum value (photometric value) of the signal value saturated at a plurality of points or regions on the image input by the user. A process of displaying a difference from the maximum value of the above (difference value display process) is performed.

(A series of operations related to D range assist)
First, a series of operations related to the D range assist will be described with reference to FIG. 3, and next, a difference value calculation process that is a part of the D range assist will be described in detail with reference to FIG. This process is realized by the system control unit 50 expanding and executing a program stored in the nonvolatile memory 56 in the work area of the system memory 52.

  In S301, the system control unit 50 determines whether or not the D range assist function is enabled. More specifically, the system control unit 50 determines whether the D range assist function is enabled with reference to, for example, a flag indicating whether the D range assist function is enabled. The flag indicating whether or not the D range assist function is enabled may be set by the system control unit 50 when the D range assist function is enabled or disabled by the user and stored in the system memory 52. When the flag indicates that the D range assist function is enabled, the system control unit 50 proceeds to S302, and when it indicates that the D range assist function is disabled, the system control unit 50 ends the series of operations of this process.

  In step S302, the system control unit 50 calculates an amount for changing the D range (also simply referred to as a D range change amount). In the present embodiment, the D range is changed to Dmax, which is the maximum D range that can be set by the digital camera 100. Dchange, which is the number of steps of the D range change amount, can be calculated according to equation (1), where Dnow is the current D range and Dmax is the changed D range.

Dchange = log ₂ (Dmax / Dnow) (1)
For example, assuming that the maximum D range is 800% and the current D range is 400%, the Dchange is one stage. If the current D range is 300%, the Dchange is about 1.52 stages. Note that the change amount of the D range may be a change amount smaller than the change amount for setting the dynamic range to the maximum D range that can be set by the digital camera 100 as long as a saturated photometric value can be acquired. Good.

  In S303, the system control unit 50 changes the exposure and changes the gamma correction characteristics according to the number of steps of the D range change amount calculated in S302. First, the system control unit 50 changes the exposure by changing the aperture 101, the ND 104, the electronic shutter, the analog gain, and the like in the imaging unit 22. For example, when changing the exposure using an electronic shutter, if the opening / closing speed of the electronic shutter before changing the D range is set to 1/60 seconds and the number of steps of the D range changing amount is 1, The control unit 50 changes the opening / closing speed of the electronic shutter to 1/120 seconds. The method for changing the exposure may be any method other than the above as long as the exposure can be changed before the image signal is output from the image sensor of the imaging unit 22.

  Then, the system control unit 50 changes the gamma correction characteristics of the gamma correction circuit included in the image processing unit 24. This is because underexposure is undertaken in order to expand the D range, the amount of change in exposure is corrected by changing the gamma correction characteristics, and this change in exposure appears in the display image. It is to prevent.

  Assume that the output by the gamma correction circuit for the input X when the D range assist is not enabled (normal time) is Y. The system control unit 50 changes the gamma correction characteristic when the D range assist function is validated so that the output of X × Dnow / Dmax becomes Y.

  Also, in this gamma correction characteristic, assuming that the maximum value of input during normal time is Xmax and the maximum value of output is Ymax, when the D range assist function is enabled, Ymax is output in the case of input Xmax × Dnow / Dmax. The Also, Ymax is always output for input values larger than the input.

  FIG. 4 shows an example of gamma correction characteristics when the D range assist is enabled and during normal operation. The horizontal axis represents the input bit value of the gamma correction circuit, and the vertical axis represents the output bit value. The gamma correction characteristic when the D range assist is activated shows an example in which, for example, Dnow is 400% and Dmax is 800%. Specifically, since Dnow / Dmax is ½ (= 400% / 800%), there is an output for the normal input X and an output for the input X / 2 when the D range assist is enabled. It becomes the same value. When the D range assist function is validated, the output is Ymax when Xmax / 2, and thereafter Ymax is output.

  In S304, the system control unit 50 performs a difference value display process described later. When the system control unit 50 displays the difference between the photometric value at a plurality of points or regions on the image input by the user and the maximum value of the signal that can be expressed by the currently set dynamic range, the system control unit 50 End the operation.

(A series of operations related to difference value display processing)
Next, the details of the difference value display process will be described with reference to FIG.

  In step S <b> 501, the system control unit 50 receives a user operation for specifying a photometric value acquisition point via the operation unit 70. The photometric value acquisition point refers to a position on the image for the user to include in the D range or measure the photometric value. FIG. 6A shows an example in which the user specifies the positions of the points A and B for the image including the subject. The operation of designating a predetermined position on the image acquires two-dimensional coordinates on the image designated by the user, for example, by detecting a finger contact with a position on the touch panel included in the operation unit 70. Then, the system control unit 50 sets, for example, predetermined pixels in the vicinity of the point A and the point A (for example, 8 pixels centered on the point A) as the display candidate area A based on the photometric value acquisition point. Note that the photometric value acquisition point of the present embodiment may be an area, and conversely, the display candidate area may be only the position (point) where the user touches.

  In S502, the image processing unit 24 acquires a photometric value in the new display candidate region set in S501 in response to an instruction from the system control unit 50. The photometric value is obtained by obtaining the photometric value in a state where the D range (exposure) is changed, and is obtained from the image data before passing through the gamma correction circuit.

  For example, the image processing unit 24 acquires a luminance signal of a pixel included in the display candidate area A as a photometric value in the display candidate area A. The image processing unit 24 calculates, for example, an average value for the luminance signals of the pixels in the display candidate area in order to obtain a photometric value in the display candidate area. However, as long as the brightness of the display candidate region can be calculated, the maximum value or the minimum value of the luminance signal in the display candidate region may be calculated, or the integrated value of the luminance signal in the display candidate region may be obtained. Also, a value that is an index of brightness, such as an EV value, may be used. For example, in the display candidate area A, it is assumed that 3500 is acquired as a photometric value. In step S <b> 503, the image processing unit 24 stores the coordinates of the display candidate region (for example, a photometric value acquisition point) and the acquired photometric value in the system memory 52.

  In step S504, the system control unit 50 determines whether there is a user operation for specifying a new photometric value acquisition point (for example, point B shown in FIG. 6A). When there is an input for a new photometric value acquisition point via the operation unit 70, the system control unit 50 returns the processing to S501 again, and for example, performs the processing of S501 to S503 for the point B in FIG. repeat. For example, it is assumed that 40 is acquired as the photometric value of the display candidate region B. For example, the system control unit 50 receives a user operation for specifying at least two or more predetermined number of photometric value acquisition points, and there is no user operation for specifying a photometric value acquisition point at a predetermined time interval. The process proceeds to S505.

  In S505, the system control unit 50 selects a display candidate area having the largest photometric value (for example, display candidate area A) and a display candidate area having the smallest photometric value (for example, display candidates) from among the plurality of acquired display candidate areas. Region B) is detected. Further, the system control unit 50 causes the display unit 28 to display the display candidate area having the maximum photometric value and the display candidate area having the minimum photometric value. Other display candidate areas may be displayed after determining their necessity according to coordinates and photometric values (for example, determining that they are necessary when they are present near the center in the image).

In step S <b> 506, the system control unit 50 calculates a difference value of the display candidate area having the maximum photometric value (that is, display candidate area A). That is, the system control unit 50 calculates the difference between the photometric values for reference when changing the current D range in the display candidate region having the maximum photometric value. The system control unit 50 presents to the user how much the current D range should be expanded with respect to the display candidate area A having the maximum photometric value, so that the maximum signal value and the photometric value that can be expressed in the current D range are displayed. Is calculated according to the equation (2).

Difference value = log ₂ (photometric value / (maximum value × current D range / maximum D range))
... (2)
For example, when the current D range is 400%, the maximum D range is 800%, the maximum allowable value is 4095, and the photometric value of the display candidate area A is 3500, the difference value is about 0.77 steps. . That is, if the D range is changed by 0.77 steps using the maximum value of the signal that can be expressed in the current D range as a reference value and expanded to about 680%, the display candidate area A has the maximum value that can be expressed in the D range. It will be within the range. Then, when the system control unit 50 presents the change in the D range for 0.77 steps to the user, the user understands the possibility that the S / N ratio for 0.77 steps will decrease and the necessity of exposure change. You can also

  In step S <b> 507, the system control unit 50 calculates the difference value of the display candidate area having the minimum photometric value (that is, display candidate area B). That is, in order to determine whether the display candidate region B having the minimum photometric value is included in the dark D range, the system control unit 50 performs 18% gray as a photometric value and an exposure reference according to Equation (3). The difference value from the input value at the time of shooting is calculated.

Difference value = log ₂ (photometric value / input value taken with 18% gray appropriate exposure)
... (3)
For example, when the input value is 737 when 18% gray is captured with appropriate exposure and the photometric value of the display candidate area B is 40, the difference value obtained according to the equation (3) is about −4.2 steps. The input value when photographing with appropriate exposure is acquired in advance by, for example, a camera test by the user and stored in the nonvolatile memory 56 or the like, and is used as a reference such as a sense of noise or gradation when the photometric value is lower than the appropriate exposure. It is done. Further, it is assumed that a reference indicating that the user can accept a range from the appropriate exposure to a minus level as the image quality is acquired in advance and stored in the nonvolatile memory 56 or the like. For example, in the case of the display candidate region B described above, the D range corresponding to the subtraction of 1.8 steps is changed when the user gives a criterion that the range from the proper exposure to −6 steps is acceptable as the image quality. It will be possible.

  In S508, the system control unit 50 causes the display unit 28 to display the calculation results in S506 and S507 in order to assist the user in changing the dynamic range. More specifically, the system control unit 50 displays the difference between the display candidate area having the maximum photometric value (display candidate area A) and the current D range and the display candidate area having the minimum photometric value (display candidate area B). ) And the appropriate exposure value are input to the image processing unit 24 together with the coordinate information. In response to an instruction from the system control unit 50, the image processing unit 24 generates image data in which the reference type and the difference value are superimposed on the image positions corresponding to the coordinates of the display candidate area A and the display candidate area B. To do. The system control unit 50 causes the display unit 28 to display the generated image data via the memory control unit 15 and the D / A 13.

  FIG. 6B shows a display example in this step. FIG. 6B shows a reference 601 and a difference value 602 in the display candidate area A. By displaying the reference 601 and the difference value 602, the user can set the D range corresponding to “+0.77” steps from the “current D range” in order to keep the subject of the display candidate area A within the range of the D range. It is possible to easily grasp that a change is required. FIG. 6B shows the reference 603 and the difference value 604 in the display candidate area B. By displaying the reference 603 and the difference value 604, the user can easily grasp that the exposure difference from the “appropriate exposure” of the subject in the display candidate region B is in the “−4.2” level. The system control unit 50 displays the image data on which the difference reference and the difference value are superimposed, and then returns to the process illustrated in FIG. 3.

  In addition, about the display of the difference value in S508, you may display the difference value of the parameter | index of brightness, such as a photometric value and EV value, instead of displaying the number of steps from D range or appropriate exposure. Moreover, although the example which displays the difference value mentioned above in D range assist mode was demonstrated in this embodiment, the difference value mentioned above may be displayed in modes other than D range assist mode. Further, in the case of the D range assist mode, the difference value between the photometric value and the maximum value of the display candidate area A having the maximum photometric value is displayed, while in the case other than the D range assist mode, from the photometric value and the appropriate exposure. It may be configured to display the difference in exposure.

  As described above, in the present embodiment, the original photometric value of the position of the subject area designated by the user is acquired with underexposure, and the photometric value and the maximum value of the signal that can be expressed in the current D range are obtained. Difference (difference value) is displayed on the display unit 28. By displaying such a difference value, the user can easily grasp how much the D range should be changed without actually changing the D range even in a region saturated in the current D range. Can do. In other words, if the photometric value of the display candidate region having the maximum photometric value is within the maximum D range that can be set in the digital camera 100, the current value may exceed the maximum value that can be expressed by the current D range. The relationship between the D range and the photometric value can be grasped. In addition, by displaying the difference value from the appropriate exposure for the photometric value of the display candidate area having the minimum photometric value, the subject of the display candidate area having the minimum photometric value is set in the D range range defined by the user. It is possible to grasp how much the D range can be changed while including it. Therefore, the user can grasp a guideline for obtaining a necessary dynamic range at a specific point or region.

(Embodiment 2)
Next, Embodiment 2 will be described. In the first embodiment, the example in which one of the display candidate regions having the maximum value or the minimum value of the photometric value is assigned to the photometric value acquisition point designated by the user has been described. However, in this embodiment, an example of specifying a subject included in the D range, such as a person's face or a landscape of a window, in a range, and assigning display candidate areas having the maximum and minimum photometric values in the specified area Will be described. More specifically, in the present embodiment, an example will be described in which a user operation for designating a region for acquiring a photometric value (also simply referred to as a photometric value acquisition region) is received and a small region obtained by dividing the region is used as a display candidate region. . In the present embodiment, the series of operations related to the difference value display process is different from the embodiment, and the configuration of the digital camera 100 and other processes are the same as those in the first embodiment. For this reason, the same configurations and steps are denoted by the same reference numerals, and redundant description will be omitted, and differences will be mainly described.

(A series of operations related to difference value display processing)
With reference to FIG. 7, a series of operations related to the difference value display processing in the present embodiment will be described.

  In step S <b> 701, the system control unit 50 receives a user operation for specifying a photometric value acquisition region. As described above, the photometric value acquisition area refers to an area on the image for the user to include in the D range or measure the photometric value. FIG. 8A shows an example when the user operation for specifying the photometric value acquisition region is a range designation. For example, when an image in live view display is displayed on the display unit 28, the system control unit 50 inputs a circle or rectangle drawn by the user via the operation unit 70 and is included in the circle or rectangle. A range or a range painted by the user is set as a photometric value acquisition region. In the example of FIG. 8A, the region C and the region D are specified as the photometric value acquisition region.

  In step S <b> 702, the system control unit 50 determines whether the user operation on the image is a point designation or a range designation for specifying a photometric value acquisition region. For example, when the user operation range is larger than a predetermined threshold, the system control unit 50 determines that the user operation is a range specification, and when the user operation range is equal to or less than the predetermined threshold, the system control unit 50 determines that the point operation is a point specification. judge. In addition, the system control unit 50 may determine whether the user operation is point designation or range designation based on settings on a separately provided user interface. If the system control unit 50 determines that the user operation is range designation, the system control unit 50 proceeds to step S703. If the system control unit 50 determines that the user operation range is point designation, the system control unit 50 proceeds to step S502.

  In S703, the system control unit 50 divides the input photometric value acquisition area into small areas. In S704, a photometric value is acquired for each divided small region. In the present embodiment, for example, a small area is set as one pixel, and a pixel value in the photometric value acquisition area is scanned, so that a high luminance part (for example, maximum luminance point) or a low luminance part (for example, minimum luminance) in the photometric value acquisition area. Point).

  In step S <b> 705, the system control unit 50 sets an 8-pixel area centered on each of the detected maximum luminance point and minimum luminance point as a display candidate area. Further, the system control unit 50 sets the average value of the pixel values of each display candidate area as the photometric value of the display candidate area. FIG. 8B shows an example of the obtained display candidate area. The system control unit 50 detects the display candidate region Cmax, the display candidate region Cmin, the display candidate region Dmax, and the display candidate region Dmin from the regions C and D, respectively.

  Thereafter, the system control unit 50 performs the processing of S503 to S508 similarly to the first embodiment, and ends a series of operations related to this processing.

  In S506 and S507, the system control unit 50 calculates a difference value between these display candidate areas. At this time, a difference value between each display candidate region and the 18% gray input value may be calculated according to the equation (3). At this time, for example, the photometric values are detected as 3800 for the display candidate area Cmax, 1200 for the display candidate area Cmin, 2600 for the display candidate area Dmax, and 400 for the display candidate area Dmin. For example, assuming that the input value when 18% gray is appropriate exposure is 737, the difference value of the display candidate region Cmax having the maximum photometric value, for example, is approximately 2.36, and the minimum photometric value according to Equation (3). The difference value of the display candidate area Dmin having a value of approximately −0.88.

  When displaying the calculated difference value, the system control unit 50 displays the difference value, for example, as shown in FIG. In FIG. 8C, the difference value of the display candidate area Cmax and the difference value of the display candidate area Dmin are displayed.

  Note that, for the method of dividing the photometric value acquisition area according to the present embodiment, the area is divided by a predetermined arbitrary width to form a small area, and a calculated value such as an average value of pixel values for each small area is measured. It may be a value.

  As described above, in the present embodiment, the display candidate area having the maximum photometry value and the minimum photometry value is detected for each photometry value acquisition area specified by the user, and the difference value of each display candidate area is displayed. I did it. By displaying the difference value of the display candidate area in this way, it is possible to grasp a guideline for obtaining a necessary dynamic range in the subject area intended by the user.

(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.

22 ... Imaging unit, 24 ... Image processing unit, 28 ... Display unit, 50 ... System control unit, 70 ... Operation unit

Claims (13)

Imaging means for imaging a subject and outputting image data;
Expansion means for expanding the dynamic range of the imaging means by lowering the exposure of the imaging means;
Acquisition means for acquiring a user operation for specifying a photometric value acquisition region in an image for acquiring a signal value;
Detecting means for expanding the dynamic range by a predetermined amount by the enlarging means and detecting a signal value of the photometric value acquisition area in the screen of the imaging means;
Control for outputting a standard for changing the photometric value acquisition area to a dynamic range having gradation characteristics based on the difference between the signal value of the photometric value acquisition area detected by the detection means and a predetermined reference value Means,
An image pickup apparatus comprising: display control means for displaying the reference. The control means, for the first photometric value acquisition area having the highest signal value among the plurality of photometric value acquisition areas, the signal value of the first photometric value acquisition area detected by the detection means, Based on the difference from the first predetermined reference value, which is the maximum value of the signal that can be expressed in the dynamic range before being enlarged by the enlargement means, the first photometric value acquisition region has a dynamic range having gradation. Output a guide for change,
The imaging apparatus according to claim 1. The control means further includes a signal value of the second photometric value acquisition area detected by the detection means for a second photometric value acquisition area having the lowest signal value among the plurality of photometric value acquisition areas. , Based on a difference from a second predetermined reference value, which is a predetermined signal value at appropriate exposure, to output a standard for changing the second photometric value acquisition region to a dynamic range having gradation.
The imaging apparatus according to claim 2. In the photometric value acquisition area, the control means is a first predetermined reference that is a maximum signal value that can be expressed by the highest signal value detected by the detection means and the dynamic range before being enlarged by the enlargement means. Based on the difference between the two values, a high brightness portion of the photometric value acquisition area outputs a difference value for changing to a dynamic range having gradation, and the lowest signal value and appropriate exposure in the photometric value acquisition area Based on the difference from the second predetermined reference value, which is a predetermined signal value in, outputs a guideline for changing the low luminance part of the photometric value acquisition region to a dynamic range having gradation.
The imaging apparatus according to claim 1. The acquisition unit acquires, as the user operation, information on points or regions in the image with respect to the image displayed on the display unit.
The imaging apparatus according to any one of claims 1 to 4, wherein the imaging apparatus is characterized in that Gradation correction means for performing gradation correction on the image data;
The acquisition means is configured so that a user specifies the photometric value acquisition region for the tone-corrected image data.
The imaging apparatus according to any one of claims 1 to 5, wherein The display control means displays the gradation corrected image data together with the standard.
The imaging apparatus according to claim 6. The reference is information indicating a difference in signal value with respect to the predetermined reference value.
The imaging apparatus according to claim 1, wherein The display control means further displays the type of the predetermined reference value, and is the type of the predetermined reference value based on a dynamic range before the predetermined reference value is enlarged by the enlargement means? Information indicating whether the exposure is based on proper exposure.
The imaging apparatus according to claim 8.   10. The imaging apparatus according to claim 1, wherein the expansion unit expands the dynamic range to a maximum dynamic range that can be set by the imaging apparatus. 11.   10. The apparatus according to claim 1, wherein the enlargement unit enlarges the dynamic range by a change amount smaller than a change amount for setting the dynamic range to a maximum dynamic range that can be set by the imaging apparatus. The imaging device described. A method for controlling an imaging apparatus including imaging means for imaging a subject and outputting image data,
An enlarging step in which the enlarging unit expands the dynamic range of the imaging unit by lowering the exposure of the imaging unit;
An acquisition step of acquiring a user operation for specifying a photometric value acquisition region in an image for acquiring a signal value;
A detecting step of detecting a signal value of the photometric value acquisition region in the screen of the imaging means by detecting the expanding means by a predetermined amount by the expanding means;
A guide for the control means to change the photometric value acquisition area to a dynamic range having gradation based on the difference between the signal value of the photometric value acquisition area detected by the detection means and a predetermined reference value A control process for outputting
A display control step, wherein the display control means includes a display control step for displaying the reference.   The program for making a computer perform each process of the control method of the imaging device of Claim 12.

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