JP2008160190A - Imaging apparatus and method thereof - Google Patents

Abstract

An imaging apparatus capable of performing wide dynamic range imaging even in a bright scene.
An ND filter 81 and an ND filter driver 82 for controlling whether the ND filter is inserted into the imaging optical path or retracted from the imaging optical path are provided. In order to expand the dynamic range by 400%, the proper exposure value is corrected to 2EV underexposure and shooting is performed. At this time, if the control limit of the fastest shutter speed and the maximum aperture of the digital camera 10 is reached and 2EV underexposure cannot be set, the ND filter driver 82 inserts the ND filter 81 into the photographing optical path and Reduce the amount of light received. As a result, even when the shutter speed and the aperture limit reach the control limits and cannot be set, wide dynamic range imaging is possible.
[Selection] Figure 3

Description

  The present invention relates to an imaging apparatus and method thereof, and more particularly to an imaging apparatus and method for imaging with a wide dynamic range.

There is known a method of achieving dynamic range expansion by lifting a darkly photographed image with a highlight gamma. For example, it is possible to realize a dynamic range expansion rate of 400% by shooting 2 EV darker than the appropriate exposure. Patent Document 1 describes a similar method.
JP 2004-120511 A

  However, the above system has a drawback that a bright scene requiring a dynamic range may not be photographed as it is. This is because it is necessary to photograph darker than normal exposure, and there are cases where the shutter speed and aperture for photographing darkly cannot be set due to camera specifications.

  The present invention has been made in view of such circumstances, and provides an imaging apparatus capable of performing wide dynamic range imaging even in a bright scene.

  In order to achieve the above object, an imaging apparatus according to the present invention selects an imaging unit that converts a subject image received through an imaging lens into an image signal, a photometric unit that measures subject luminance, and a wide dynamic range imaging mode. Then, the correction means for correcting the appropriate exposure so that the exposure is under-exposed than the appropriate exposure by the exposure correction according to the enlargement ratio of the dynamic range, and the appropriate exposure or the appropriate exposure according to the measured subject brightness is corrected. Exposure control means for controlling the shutter speed and aperture so as to be exposed, and dimming control means for inserting or retracting an ND filter into the imaging optical path, the dimming control means, At least one of the shutter speed and the aperture by the exposure control means reaches the control limit in the wide dynamic range imaging mode. The case, characterized by inserting the ND filter in the image pickup optical path.

  As a result, even when at least one of the shutter speed and the aperture reaches the control limit, it is possible to take a picture with an exposure with an appropriate exposure corrected so as to be underexposed by dimming using an ND filter. Become.

  Before the actual imaging, the image signal obtained from the imaging unit is integrated for each of the plurality of divided areas, and the integrating unit for calculating the integrated value or integrated average value for each divided area, and the calculated integrated value or integrated average value Dynamic range calculation means for calculating the expansion ratio of the dynamic range based on the maximum value of each of the above, and the dimming control means has a plurality of ND filters each having a different transmittance, and in the wide dynamic range imaging mode, When the shutter speed and the aperture value by the exposure control means reach the control limit, an ND filter having a transmittance corresponding to the calculated dynamic range expansion ratio may be inserted into the imaging optical path.

  As a result, it is possible to perform shooting according to the expansion rate of the dynamic range obtained from the luminance of the subject.

  In order to achieve the above object, an imaging apparatus according to the present invention selects an imaging unit that converts a subject image received through an imaging lens into an image signal, a photometric unit that measures subject luminance, and a wide dynamic range imaging mode. Then, the correction means for correcting the appropriate exposure so that the exposure is under-exposed than the appropriate exposure by the exposure correction according to the enlargement ratio of the dynamic range, wherein at least one of the shutter speed and the aperture by the exposure control means is When the control limit is reached, a corrector that corrects the appropriate exposure so that the enlargement ratio of the dynamic range becomes small, and an exposure that corrects the appropriate exposure or the appropriate exposure based on the photometric subject brightness, Exposure control means for controlling the shutter speed and aperture.

  Thereby, it is possible to perform photographing even when at least one of the shutter speed and the aperture reaches the control limit.

  It is preferable that gradation conversion means for performing gradation conversion of an image signal obtained from the imaging means in the wide dynamic range imaging mode is provided.

  Thereby, gradation conversion suitable for the exposure correction value according to the expansion rate of the dynamic range can be performed, and an image with an expanded dynamic range can be obtained.

  Integration means for integrating the image signals obtained from the imaging means for each of the plurality of divided areas in the wide dynamic range imaging mode and calculating an integrated value or integrated average value for each divided area; and the calculated integrated value or integrated value Dynamic range calculation means for calculating a dynamic range expansion ratio based on the maximum value of the average values, and the gradation conversion section performs gradation conversion according to the calculated dynamic range expansion ratio. Is preferred.

  Thereby, gradation conversion can be performed according to the expansion ratio of the dynamic range calculated from the captured image, and an image with an appropriately expanded dynamic range can be obtained.

  In order to achieve the above object, an imaging method according to the present invention selects an imaging step for converting a subject image received through an imaging lens into an image signal, a photometric step for metering subject luminance, and a wide dynamic range imaging mode. Then, a correction step for correcting the appropriate exposure so that the exposure is under-exposed with respect to the appropriate exposure by correcting the exposure according to the enlargement ratio of the dynamic range, and the appropriate exposure or the appropriate exposure according to the measured subject brightness is corrected. An exposure control step for controlling the shutter speed and aperture so as to be exposed, and a dimming control step for inserting or retracting an ND filter into the imaging optical path, the dimming control step comprising: At least one of the shutter speed and the aperture by the exposure control means in the wide dynamic range imaging mode. If one reaches the control limits, characterized by inserting the ND filter in the image pickup optical path.

  As a result, even when at least one of the shutter speed and the aperture reaches the control limit, it is possible to take a picture with an exposure with an appropriate exposure corrected so as to be underexposed by dimming using an ND filter. Become.

  In order to achieve the above object, an imaging method according to the present invention selects an imaging step for converting a subject image received through an imaging lens into an image signal, a photometric step for metering subject luminance, and a wide dynamic range imaging mode. In this case, the correction means corrects the appropriate exposure so that the exposure is under-exposed rather than the appropriate exposure by the exposure correction according to the enlargement ratio of the dynamic range, and at least one of the shutter speed and the aperture in the exposure control step is When the control limit is reached, a correction step for correcting the appropriate exposure so that the enlargement ratio of the dynamic range becomes small, and an exposure that corrects the appropriate exposure or the appropriate exposure based on the photometric subject brightness, And an exposure control step for controlling the shutter speed and the aperture.

  Thereby, it is possible to perform photographing even when at least one of the shutter speed and the aperture reaches the control limit.

  According to the present invention, wide dynamic range photographing can be performed even in a bright scene where the shutter speed and aperture for photographing darkly cannot be set due to camera specifications.

  Hereinafter, preferred embodiments of an imaging device according to the present invention will be described with reference to the accompanying drawings.

<First Embodiment>
FIG. 1 is a perspective view of a digital camera 10 that is an image pickup apparatus according to a first embodiment of the present invention as seen obliquely from the front. FIG. 1A shows a case in which a lens barrel 12 is retracted into a camera housing. The state where the lens cover 14 is closed is shown, and FIG. 5B shows the state where the lens barrel 12 is extended. FIG. 2 is a perspective view of the digital camera 10 as viewed obliquely from the rear.

  The digital camera 10 has a function of recording and reproducing still images and moving images, and a power button 20, a shutter button 22, and a mode lever 24 are provided on the upper surface. By rotating the mode lever 24, it is possible to set any one of a scene position in which an auto shooting mode, a manual shooting mode, a portrait mode, a landscape mode, a night view mode, and the like can be selected, and a moving image shooting mode. ing.

  A shutter button 22 provided in the center of the mode lever 24 is turned on when the shutter button 22 is half-pressed to perform shooting preparation such as focus lock, photometry, and the like. S2.

  On the back of the digital camera 10, as shown in FIG. 2, a multi-function cross consisting of a zoom key 26, a playback button 28, a photo mode button 30 for displaying a menu screen for setting the number of pixels, sensitivity, and the like, and up / down / left / right keys. A key 32, a menu / OK button 34, a display / return button 36, and a liquid crystal monitor 38 are provided.

  The liquid crystal monitor 38 displays a moving image (through image) and can be used as an electronic viewfinder, and also displays a photographed image before recording (preview image), a reproduced image read from a memory card loaded in the camera, and the like. Can do. The liquid crystal monitor 38 displays various menu screens for manually setting the camera operation mode, white balance, the number of pixels of the image, sensitivity, and the like according to the operation of the menu / OK button 34 or the photo mode button 30. Then, a screen for a graphical user interface (GUI) capable of setting manual setting items in accordance with the operation of the cross key 32 and the menu / OK button 34 is displayed.

  FIG. 3 is a block diagram illustrating an example of the internal configuration of the digital camera 10.

  In the figure, the CPU 50 includes the power button 20, shutter button 22, mode lever 24, zoom key 26, playback button 28, photo mode button 30, cross key 32, menu / OK button 34, and display / return button 36 described above. An input of the operation switch 64 is input via the operation switch interface 63, and controls each circuit in the digital camera 10 based on this input, and executes processing according to the camera control program.

  Control of each circuit of the CPU 50 is performed via the BUS 51. The CPU 50 exchanges necessary data with the RAM 68 and the ROM 69 via the memory interface 67.

  The ROM 69 stores a camera control program, an opening image at start-up, an ending image at stop, a GUI image such as a menu image used for operating the digital camera 10, an image for a screen saver, and a progress display during processing. Audio data indicating an image (such as an hourglass image whose scale changes), a key operation sound (such as a shutter sound), a warning sound, and an error sound are recorded.

  First, when the power button 20 is operated, the CPU 50 detects this, turns on the power in the camera, displays the opening image stored in the ROM 69 for a certain period, and then enters the shooting standby state in the shooting mode. In this photographing standby state, the CPU 50 extends the retractable lens barrel 12 via the motor drive unit 42 (see FIG. 1A), and normally displays a moving image (through image) on the liquid crystal monitor 38.

  A user (photographer) performs framing while viewing a through image displayed on the liquid crystal monitor 38, confirms a subject to be photographed, confirms an image after photographing, and sets photographing conditions.

  When the shutter button 22 is pressed in the shooting standby state, the CPU 50 detects this, performs focus control, photometry, and exposure control, drives the focus lens and diaphragm in the optical unit 41 via the motor drive unit 42, and A subject image is formed on the light receiving surface of the CCD 43 via the optical unit 41. At this time, if necessary, the flash 62 is caused to emit light with the electric charge boosted and charged by the charging unit 61 and used as auxiliary photographing light.

  In the CCD 43, one element corresponds to one pixel of the screen. A large number of photodiodes (light receiving elements) are two-dimensionally arranged on the light receiving surface, and red (R), green (G), and blue (B) primary color filters corresponding to each photodiode are predetermined. It is arranged in the array structure. The CCD 43 has an electronic shutter function for controlling the charge accumulation time (shutter speed) of each photodiode. The CPU 50 controls the charge accumulation time in the CCD 16 via the timing generator 44. Instead of the CCD 43, another type of image sensor such as a MOS type may be used.

  The ND filter 81 is a neutral density filter having a predetermined transmittance. By inserting the ND filter 81 between the optical unit 41 and the CCD 43, the amount of light received by the CCD 43 can be reduced according to the transmittance. The ND filter driver 82 drives the ND filter 81 and inserts the ND filter 81 between the optical unit 41 and the CCD 43 or retracts the ND filter 81 from between the optical unit 41 and the CCD 43 based on a control signal from the CPU 50. .

  The CCD 43 converts the subject image formed on the light receiving surface into a signal charge having an amount corresponding to the amount of light. The signal charges converted in this way are read to the shift register by the read gate pulse applied from the timing generator 44, and sequentially read as a voltage signal corresponding to the signal charge by the register transfer pulse.

  The voltage signal output from the CCD 43 is subjected to analog processing such as correlated double sampling and amplification by the analog signal processing unit 45, and then added to the A / D converter 46 as R, G, and B signals for each pixel. It is done. The A / D converter 46 converts the analog R, G, and B signals sequentially added from the analog signal processing unit 45 into digital R, G, and B signals, respectively. These R, G, and B signals are temporarily stored in the RAM 68.

  The digital signal processing unit 47 reads the R, G, B raw data stored in the RAM 68 and applies a digital gain corresponding to the type of light source to adjust the white balance, and also performs gamma (gradation conversion). Processing, sharpness processing, etc. are performed to generate R, G, B signals. Further, YC signal processing is performed to generate a luminance signal Y and chroma signals Cr and Cb (YC signals), which are stored in the RAM 68 again.

  The YC signal stored in the RAM 68 as described above is compressed into a predetermined format by the compression / decompression processing circuit 70 and then recorded on the memory card 72 detachably attached to the digital camera 10 via the external memory interface 71. .

  When the menu / OK button 34 is pressed while the through image is displayed on the liquid crystal monitor 38, a menu screen is displayed on the liquid crystal monitor 38. While the menu screen is displayed, the cross key 32 is operated to select desired items such as shooting conditions and image sizes, or by pressing the menu / OK button 34 again to confirm the selection items. Execution of processing can be instructed. The display / return button 36 is used to switch the display on the liquid crystal monitor 38 or to return to the previous operation state.

  On the other hand, when the playback mode is selected by operating the playback button 28, the image file of the last frame recorded on the memory card 78 is read out via the external memory interface 71. The compressed data of the read image file is expanded into an uncompressed YC signal via the compression / expansion processing circuit 70.

  The expanded YC signal is converted into a signal format for display by the LCD interface 65 and output to the liquid crystal monitor 38. As a result, the last frame image recorded on the memory card 72 is displayed on the liquid crystal monitor 38.

  Thereafter, when the forward frame advance switch (the right key of the cross key 32) is pressed, the frame is advanced in the forward direction, and when the reverse frame advance switch (the left key of the cross key 32) is pressed, the frame is advanced in the reverse direction. . Then, the image file at the frame position where the frame is advanced is read from the memory card 72, and the image is reproduced on the liquid crystal monitor 38 in the same manner as described above.

  Next, the wide dynamic range imaging mode of the digital camera 10 will be described with reference to FIG. The digital camera 10 according to the first embodiment of the present invention performs imaging by inserting an ND filter into the imaging optical path when the shutter speed and the aperture value reach the control limits in the wide dynamic range imaging mode.

  FIG. 4 is a flowchart showing the operation of the digital camera 10 in the wide dynamic range imaging mode.

  First, the wide dynamic range imaging mode is set using the cross key 7 and the menu / OK button 8 (step S41). In the wide dynamic range shooting mode, the dynamic range is expanded to 400%.

  When the wide dynamic range imaging mode is set, the CPU 50 calculates a shutter speed and an aperture that make 2EV underexposure from the proper exposure (step S42), and the calculated shutter speed and aperture can be set in the specifications of the digital camera 10. Whether or not is determined (step S43).

  Here, the proper exposure refers to a shooting EV value suitable for the brightness of the subject (subject brightness), and the shutter speed and aperture are determined according to a predetermined program diagram. The brightness of the subject can be obtained based on the integrated value by dividing one screen into a plurality of areas and integrating the RGB signals for each divided area, for example.

  If the calculated shutter speed and aperture can be set, shooting is performed with the calculated shutter speed and aperture set (step S46).

  If the maximum shutter speed and the minimum aperture of the digital camera 10 are reached and cannot be set, the CPU 50 inserts the ND filter 81 into the photographing optical path via the ND filter driver 82 (step S44), and the filter is inserted properly. The shutter speed and aperture are recalculated (step S45). Here, the exposure coefficient of the ND filter is 2, and the shutter speed and aperture value calculated in step S42 are reset to two-step overexposure and shooting is performed (step S46).

  When photographing is performed, the output signal of the CCD 43 is subjected to analog processing, A / D conversion, and digital processing as described above. In the digital signal processing unit 47, the dynamic range is expanded according to an expansion rate of 400%. A gradation conversion process is performed (step S47).

  As described above, even when it is impossible to set the under-exposure shooting according to the shutter speed and the aperture specification, the shooting can be performed by using the ND filter.

  The digital camera 10 can shoot with a fixed aperture when, for example, it is desired to shoot with a blurred background by opening the aperture. In this case, when the wide dynamic range imaging mode is set, the setting of underexposure is supported by increasing the shutter speed. At this time, if the shutter speed reaches the set limit, the ND filter 81 may be inserted.

  It is also possible to shoot with a fixed shutter speed, for example, when it is desired to shoot at a low shutter speed in order to pan a subject moving at high speed. In this case, when the wide dynamic range imaging mode is set, the setting for underexposure corresponds to the aperture stop. At this time, the ND filter 81 may be inserted even when the aperture reaches the set limit.

  As described above, the ND filter 81 may be inserted when either of the fastest shutter speed and the minimum aperture has not reached the set limit. In this case, it is possible to perform shooting suitable for the shooting intention.

<Second Embodiment>
In the wide dynamic range imaging mode of the digital camera 10 according to the second embodiment of the present invention, the dynamic range expansion ratio is automatically calculated according to the subject brightness, and the exposure according to the calculated dynamic range expansion ratio. Shoot with. If the shutter speed and aperture value reach the control limits and cannot be set, an appropriate ND filter is inserted into the imaging optical path to perform imaging.

  FIG. 5 is a block diagram illustrating an example of the internal configuration of the digital camera 10. Portions common to those in the block diagram shown in FIG. 3 are denoted by the same reference numerals, and detailed description thereof is omitted. 3 is different from the block diagram shown in FIG. 3 in that an integrated average value calculation unit 83 and a dynamic range expansion rate calculation unit 84 are provided. The filter driver 82 includes a rotary filter device, and can automatically switch between a plurality of ND filters 81 having different transmittances.

  FIG. 6 is a flowchart showing the operation in the wide dynamic range imaging mode of the digital camera 10 according to the second embodiment of the present invention.

  First, the wide dynamic range imaging mode is set using the cross key 7 and the menu / OK button 8 (step S601).

  When the wide dynamic range imaging mode is set, the CPU 50 sets the exposure to 2 EV under the appropriate exposure, and the integrated average value calculation unit 83 integrates the signals obtained from the CCD 43 for each of the divided areas. Calculate the integrated average value. The dynamic range expansion rate calculation unit 84 calculates the expansion rate of the dynamic range based on the maximum value of the integrated average value (step S602).

Here, when a signal amount per pixel and 14 bit processing, since the calculated integration average value 2EV under the maximum value of the signal amount is estimable and 4096 = 2 ^14/4. Therefore, the formula for calculating the automatic dynamic range expansion ratio is (Equation 1)
Enlargement rate (%) = Maximum integrated average value / 4096 x 400
It becomes.

  Next, the calculated enlargement ratio is determined (step S603). When the enlargement ratio is 100% or less, the shutter speed and aperture of the proper exposure are calculated according to the program diagram (step S604), and the ND filter 81 is retracted from the imaging optical path via the ND filter driver 82 (step S607). .

  If the calculated enlargement ratio is greater than 100%, the shutter speed and aperture with underexposure are calculated according to the enlargement ratio rather than the proper exposure (step S605). Next, it is determined whether or not the calculated shutter speed and aperture can be set in the specifications of the digital camera 10 (step S606).

  If it can be set, the shutter speed and aperture are set, and the ND filter 81 is retracted from the photographing optical path via the ND filter driver 82 (step S607).

  If it cannot be set, the shutter speed and aperture are set to the limits of the spec (step S608), and the difference between the exposure set by the shutter speed and aperture and the exposure to be set is calculated as an ND filter value ( Step S609).

  Next, the ND filter 81 having the calculated filter value is inserted into the photographing optical path via the ND filter driver 82 (step S610). When the difference between the exposure set by the shutter speed and the aperture and the exposure to be set is 1 EV, an ND filter with an exposure coefficient of 1 is placed in the photographing optical path. Insert into.

  After these settings are completed, shooting is performed (step S611). As in the first embodiment, after shooting, signal processing is performed on the output signal of the CCD 43. In the digital signal processing unit 47, the enlargement ratio of the dynamic range calculated from the maximum integrated average value The gradation conversion process according to the above is performed (step S612).

  Although the integrated average value is used here, the dynamic range expansion rate may be obtained from the maximum integrated value.

  In this way, the enlargement ratio of the dynamic range is calculated from the maximum value of the integrated average value, and shooting is performed with underexposure according to the enlargement ratio. Even if it is not possible to set underexposure on shutter speed and aperture specifications, it is possible to take a picture by using an appropriate ND filter.

<Third Embodiment>
In the wide dynamic range imaging mode of the digital camera 10 according to the third embodiment of the present invention, when the shutter speed and the aperture value reach the control limits and cannot be set, the dynamic range expansion rate is reduced. Correcting the appropriate exposure, wide dynamic range imaging is performed with an enlargement ratio within a settable range.

  FIG. 7 is a block diagram illustrating an example of the internal configuration of the digital camera 10. Portions common to those in the block diagram shown in FIG. 3 are denoted by the same reference numerals, and detailed description thereof is omitted. 3 is different from the block diagram shown in FIG. 3 in that the ND filter 81 and the ND filter driver 82 are not provided.

  FIG. 8 is a flowchart showing an operation in the wide dynamic range imaging mode of the digital camera 10 according to the third embodiment of the present invention.

  First, the wide dynamic range imaging mode is set using the cross key 7 and the menu / OK button 8 (step S801). In the wide dynamic range imaging mode, the dynamic range is set to be expanded to 400%.

  When the wide dynamic range imaging mode is set, the CPU 50 calculates a shutter speed and an aperture that are under 2EV exposure from the appropriate exposure (step S802), and determines whether the calculated shutter speed and aperture can be set in the specification. This is performed (step S803).

  If it can be set, shooting is performed with the calculated shutter speed and aperture set (step S809).

  If the maximum shutter speed and minimum aperture value of the digital camera 10 have been reached and cannot be set, the CPU 50 calculates a shutter speed and aperture that will be 1 EV underexposure from the proper exposure (step S804), and the calculated shutter speed and aperture. Is determined whether or not can be set (step S805).

  If it can be set here, shooting is performed (step S809) by setting the wide dynamic range imaging mode with an enlargement ratio of 200% (step S806).

  If the setting is impossible, the shutter speed and aperture at the appropriate exposure are calculated (step S807), the normal imaging mode in which the dynamic range is not expanded is set (step S808), and the image is taken (step S809). .

  As before, signal processing is performed on the output signal of the CCD 43 after photographing, but the digital signal processing unit 47 performs gradation conversion processing according to the dynamic range expansion rate of the determined mode. (Step S810).

  As described above, even when underexposure shooting cannot be set on the basis of shutter speed and aperture specifications, wide dynamic range imaging can be realized within a settable range.

  The exposure change when it is impossible to set is not limited to 1 EV, but for example, the shutter speed and aperture are calculated so that the appropriate exposure is close to 1/3 EV, and it is determined whether the shutter speed and aperture can be set. May be.

<Fourth embodiment>
In the wide dynamic range imaging mode of the digital camera 10 according to the fourth embodiment of the present invention, when the shutter speed and the aperture value reach the control limits, the ND filter is inserted into the imaging optical path to perform imaging. The dynamic range expansion ratio is automatically calculated from image data obtained by photographing, and signal processing is performed in accordance with the calculated dynamic range expansion ratio.

  The internal configuration of the digital camera 10 is the same as that of the block diagram of the second embodiment shown in FIG. 5, and includes an integrated average value calculation unit 83 and a dynamic range expansion rate calculation unit 84.

  FIG. 9 is a flowchart showing the operation in the wide dynamic range imaging mode of the digital camera 10 according to the fourth embodiment of the present invention.

  First, the wide dynamic range imaging mode is set using the cross key 7 and the menu / OK button 8 (step S901). When the wide dynamic range imaging mode is set, the CPU 50 sets the exposure under 2 EV from the appropriate exposure, calculates the shutter speed and aperture for this exposure (step S902), and the calculated shutter speed and aperture are in the camera specifications. It is determined whether setting is possible (step S903).

  If it can be set, shooting is performed with the calculated shutter speed and aperture set (step S906).

  If the maximum shutter speed and the minimum aperture value of the digital camera 10 have been reached and cannot be set, the CPU 50 inserts the ND filter 81 into the photographing optical path via the ND filter driver 82 (step S904), and the filter is properly inserted. The correct shutter speed and aperture are recalculated (step S905). Here, the exposure coefficient of the ND filter is 2, and the two-stage overexposure setting is recalculated with respect to the shutter speed and aperture value calculated in step S902, and shooting is performed with the setting (step S906).

  When shooting is performed, the integrated average value calculation unit 83 integrates the signals obtained from the CCD 43 for each of the plurality of divided areas, and calculates an integrated average value for each divided area (step S907). The dynamic range expansion rate calculating unit 84 calculates the dynamic range expansion rate based on the maximum value of the integrated average value (step S908). The expansion rate of the dynamic range can be calculated in the same manner as in the second embodiment.

  Finally, signal processing is performed. In the digital signal processing unit 47, gradation conversion processing is performed in accordance with the dynamic range expansion rate calculated from the maximum integrated average value (step S909).

  Although the integrated average value is used here, the dynamic range expansion rate may be obtained from the maximum integrated value.

  As described above, even when it is impossible to set the under-exposure shooting according to the shutter speed and the aperture specification, the shooting can be performed by using the ND filter. An image with an appropriate dynamic range can be obtained by calculating the enlargement ratio of the dynamic range for the captured image and performing gradation conversion processing according to the enlargement ratio.

FIG. 1 is a perspective view of a digital camera according to the present invention as viewed obliquely from the front. FIG. 2 is a perspective view of the digital camera 10 as viewed obliquely from the rear. FIG. 3 is a block diagram illustrating an example of an internal configuration of the digital camera 10 according to the first embodiment. FIG. 4 is a flowchart showing the operation of the digital camera 10 of the first embodiment in the wide dynamic range imaging mode. FIG. 5 is a block diagram showing an example of the internal configuration of the digital camera 10 according to the second embodiment of the present invention. FIG. 6 is a flowchart showing an operation in the wide dynamic range imaging mode of the digital camera 10 according to the second embodiment of the present invention. FIG. 7 is a block diagram showing an example of the internal configuration of the digital camera 10 according to the third embodiment of the present invention. FIG. 8 is a flowchart showing an operation in the wide dynamic range imaging mode of the digital camera 10 according to the third embodiment of the present invention. FIG. 9 is a flowchart showing an operation in the wide dynamic range imaging mode of the digital camera 10 according to the fourth embodiment of the present invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Digital camera, 22 ... Shutter button, 32 ... Cross key, 34 ... Menu / OK button, 38 ... Liquid crystal monitor, 41 ... Optical unit, 43 ... CCD, 45 ... Analog signal processing part, 46 ... A / D converter, 47 ... Digital signal processing unit, 50 ... CPU, 67 ... Memory interface, 68 ... RAM, 69 ... ROM, 81 ... ND filter, 82 ... ND filter driver, 83 ... Integrated average value calculation unit, 84 ... Dynamic range expansion rate calculation Part

Claims (7)

Imaging means for converting a subject image received through the imaging lens into an image signal;
Metering means for metering subject brightness;
When the wide dynamic range imaging mode is selected, correction means for correcting the appropriate exposure so that the exposure is underexposure than the appropriate exposure by the exposure correction according to the enlargement ratio of the dynamic range;
Exposure control means for controlling the shutter speed and aperture so as to obtain an appropriate exposure according to the subject brightness measured or an exposure obtained by correcting the appropriate exposure;
A dimming control means for inserting an ND filter into the imaging optical path or withdrawing from the imaging optical path, and
The dimming control means inserts the ND filter into the imaging optical path when at least one of a shutter speed and an aperture by the exposure control means reaches a control limit in the wide dynamic range imaging mode. Imaging device. Integration means for integrating the image signals obtained from the imaging means before the main imaging for each of the plurality of divided areas, and calculating an integrated value or an integrated average value for each divided area;
Dynamic range calculation means for calculating the expansion rate of the dynamic range based on the maximum value of the calculated integrated value or integrated average value,
The dimming control means includes a plurality of ND filters each having a different transmittance, and when the shutter speed and the aperture by the exposure control means reach a control limit in the wide dynamic range imaging mode, the calculated dynamics The imaging apparatus according to claim 1, wherein an ND filter having a transmittance corresponding to a range expansion rate is inserted into the imaging optical path. Imaging means for converting a subject image received through the imaging lens into an image signal;
Metering means for metering subject brightness;
When a wide dynamic range imaging mode is selected, a correction unit that corrects the appropriate exposure so that the exposure is underexposure than the proper exposure by exposure correction according to the enlargement ratio of the dynamic range, the shutter speed by the exposure control unit And at least one of the diaphragms reaches a control limit, a correction means for correcting an appropriate exposure so that the enlargement ratio of the dynamic range is reduced,
Exposure control means for controlling the shutter speed and aperture so as to obtain an appropriate exposure based on the measured subject brightness or an exposure obtained by correcting the appropriate exposure;
An imaging apparatus comprising:   The imaging apparatus according to claim 1, further comprising a gradation conversion unit that performs gradation conversion of an image signal obtained from the imaging unit in the wide dynamic range imaging mode. Integration means for integrating the image signals obtained from the imaging means during the wide dynamic range imaging mode for each of a plurality of divided areas, and calculating an integrated value or an integrated average value for each divided area;
Dynamic range calculation means for calculating the expansion rate of the dynamic range based on the maximum value of the calculated integrated value or integrated average value,
The imaging apparatus according to claim 4, wherein the gradation conversion unit performs gradation conversion in accordance with the calculated enlargement ratio of the dynamic range. An imaging step of converting a subject image received through the imaging lens into an image signal;
A metering step for metering subject brightness;
When the wide dynamic range imaging mode is selected, a correction step for correcting the appropriate exposure so that the exposure is underexposure than the appropriate exposure by exposure correction according to the expansion ratio of the dynamic range;
An exposure control step for controlling the shutter speed and the aperture so as to obtain an appropriate exposure according to the measured subject brightness or an exposure obtained by correcting the appropriate exposure;
A dimming control step for inserting an ND filter into the imaging optical path or withdrawing from the imaging optical path, and
In the dimming control step, the ND filter is inserted into the imaging optical path when at least one of a shutter speed and an aperture by the exposure control means reaches a control limit in the wide dynamic range imaging mode. Imaging method. An imaging step of converting a subject image received through the imaging lens into an image signal;
A metering step for metering subject brightness;
When a wide dynamic range imaging mode is selected, the correction means corrects the appropriate exposure so that the exposure is underexposure than the appropriate exposure by exposure correction according to the enlargement ratio of the dynamic range, and the shutter speed by the exposure control step And when at least one of the diaphragms reaches a control limit, a correction step for correcting an appropriate exposure so that an expansion rate of the dynamic range is reduced,
An exposure control step for controlling the shutter speed and the aperture so as to obtain an appropriate exposure based on the measured subject brightness or an exposure obtained by correcting the appropriate exposure;
An imaging method comprising:

Images