JP4719453B2 - Imaging apparatus and control method thereof - Google Patents

Description

  The present invention relates to an imaging apparatus and a control method thereof, and more particularly, to an imaging apparatus using an imaging means whose sensitivity changes depending on, for example, an F value of an optical system, and a control method thereof.

  2. Description of the Related Art Conventionally, in an imaging apparatus, a phenomenon is known in which the sensitivity of an imaging element changes depending on the F value. In particular, it is generated in combination with a microlens provided for each light receiving sensor of the image sensor, and has a characteristic that the light sensitivity is decreased and the actual sensitivity is decreased as the F value is decreased.

  For example, in photometry, the subject brightness value Bv0 when the sensitivity is Sv0, the aperture value is Av0, the shutter speed value is Tv0, the brightness value of the exposed screen is Y0, and the appropriate exposure brightness value is Yref is expressed by the following formula ( Photometry is performed in consideration of the sensitivity that varies depending on the F value according to 1) to (3).

  Here, dsv is a function for obtaining the sensitivity that decreases with the F value using the aperture value as an argument. Further, the aperture value Av and the shutter speed Tv at the time of the main exposure are determined from the photometric subject luminance value Bv0 and the set sensitivity Sv by the program diagrams represented by the equations (4) and (5).

  However, at this time point, an aperture value and a shutter speed value that do not take into account the decrease in sensitivity due to the F value are obtained. Therefore, if the main exposure is performed with the aperture value Av, the shutter speed value Tv, and the sensitivity Sv, the sensitivity is increased. When the main exposure is performed with an F value that decreases, the exposure becomes underexposed.

  As means for solving such a problem, as disclosed in Patent Document 1, means for correcting exposure by correcting the aperture value or shutter speed value at the time of main exposure for the sensitivity reduced by the F value, As disclosed in Japanese Patent Application Laid-Open No. 2004-260, there is known means for correcting exposure by controlling a gain for an image signal in accordance with an F value.

JP 2002-185822 A JP 2002-330334 A

  However, in the method of correcting the sensitivity that decreases at the aperture value in accordance with the F value, the aperture cannot be opened from the open position to the sensitivity decrease at the open aperture position, and the exposure cannot be made appropriate. In the method of correcting the sensitivity that decreases with the shutter speed value, the rate of camera shake increases due to a decrease in the shutter speed expected by the user, and shooting with a high-speed shutter expected by the user is not possible. There was a problem.

  Further, in the case of correcting the exposure by controlling the gain for the image signal in accordance with the F value, the amount of information is reduced by digitally increasing the signal obtained by shooting, and the image quality is reduced. There was a problem that deterioration would occur.

  Therefore, an object of the present invention is to perform image processing that effectively uses image information without reducing the amount of image information.

An imaging apparatus according to the present invention includes an imaging unit that captures an image, a luminance value calculation unit that calculates a subject luminance value based on a luminance value of the exposed imaging unit and a preset appropriate luminance value , and a predetermined value. And determining the aperture value from the sensitivity of the imaging means and the subject luminance value set, and controlling the exposure of the imaging means based on the aperture value determined by the determining means. An exposure control unit to perform , a determination unit that determines a degree of sensitivity reduction of the imaging unit based on the aperture value determined by the determination unit, and a degree of sensitivity reduction of the imaging unit that is determined by the determination unit based on the gamma selecting means for selecting one from a gamma curve of a plurality of non-linear, based on the gamma curve selected by the gamma selecting device, the exposure control of the exposure control means And having an image processing means for performing image processing for more image information obtained.

According to the present invention, without reducing the information amount of images information, it becomes possible to perform image processing effectively using the image information.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments to which the invention is applied will be described in detail with reference to the accompanying drawings.

FIG. 7 is a block diagram showing the overall configuration of the imaging apparatus according to an embodiment of the present invention.
In FIG. 7, reference numeral 100 denotes an imaging device. Reference numeral 10 denotes a photographing lens, 12 denotes a shutter having a diaphragm function, 14 denotes an image sensor that converts an optical image into an electric signal, and 16 denotes an A / D converter that converts an analog signal output from the image sensor 14 into a digital signal.

  A timing generation circuit 18 supplies a clock signal and a control signal to the image sensor 14, the A / D converter 16, and the D / A converter 26, and is controlled by the memory control circuit 22 and the system control circuit 50.

  An image processing circuit 20 performs predetermined pixel interpolation processing and color conversion processing on the data from the A / D converter 16 or the data from the memory control circuit 22. Further, the image processing circuit 20 performs predetermined calculation processing using the captured image data, and the system control circuit 50 controls the exposure control means 40 and the distance measurement control means 42 based on the obtained calculation result. TTL (through-the-lens) AF (autofocus) processing, AE (automatic exposure) processing, and EF (flash pre-emission) processing are performed.

  Further, the image processing circuit 20 performs predetermined arithmetic processing using captured image data, and also performs TTL AWB (auto white balance) processing based on the obtained arithmetic result.

  A memory control circuit 22 controls the A / D converter 16, the timing generation circuit 18, the image processing circuit 20, the image display memory 24, the D / A converter 26, the memory 30, and the compression / decompression circuit 32.

  The data of the A / D converter 16 is written into the image display memory 24 or the memory 30 via the image processing circuit 20 and the memory control circuit 22 or the data of the A / D converter 16 is directly passed through the memory control circuit 22. It is.

  Reference numeral 24 denotes an image display memory, 26 denotes a D / A converter, 28 denotes an image display unit including a TFT, an LCD, and the like. Display image data written in the image display memory 24 passes through the D / A converter 26. Are displayed by the image display unit 28.

  If the image data captured using the image display unit 28 is sequentially displayed, the electronic viewfinder function can be realized. Further, the image display unit 28 can arbitrarily turn on / off the display according to an instruction from the system control circuit 50. When the display is turned off, the power consumption of the imaging apparatus 100 can be significantly reduced. I can do it.

  Reference numeral 30 denotes a memory for storing captured still images and moving images, and has a sufficient storage capacity to store a predetermined number of still images and a predetermined time of moving images. Thereby, even in the case of continuous shooting or panoramic shooting in which a plurality of still images are continuously shot, it is possible to write a large amount of images to the memory 30 at high speed.

  The memory 30 can also be used as a work area for the system control circuit 50. Reference numeral 32 denotes a compression / decompression circuit that compresses and decompresses image data by adaptive discrete cosine transform (ADCT) or the like, reads an image stored in the memory 30, performs compression processing or decompression processing, and stores the processed data in the memory 30. Write to.

  Reference numeral 40 denotes an exposure control means for controlling the shutter 12 having an aperture function, and has a flash light control function in cooperation with the flash 48.

  Reference numeral 42 denotes a distance measuring control means for controlling the focusing of the photographing lens 10, reference numeral 44 denotes a zoom control means for controlling zooming of the photographing lens 10, and reference numeral 46 denotes a barrier control means for controlling the operation of the protection means 102 as a barrier.

  A flash 48 has an AF auxiliary light projecting function and a flash light control function. The exposure control means 40 and the distance measurement control means 42 are controlled using the TTL method. Based on the calculation result obtained by calculating the captured image data by the image processing circuit 20, the system control circuit 50 performs the exposure control means 40 and the distance measurement. Control is performed on the control means 42.

  Reference numeral 50 denotes a system control circuit that controls the entire imaging apparatus 100, and 52 denotes a memory that stores constants, variables, programs, and the like for operation of the system control circuit 50.

  Reference numeral 54 denotes a display unit such as a liquid crystal display device or a speaker that displays an operation state or a message using characters, images, sounds, and the like in accordance with execution of a program in the system control circuit 50, and an operation unit of the imaging device 100. A single or a plurality of locations are provided in the vicinity where they can be easily seen, and are configured by a combination of, for example, an LCD, an LED, and a sounding element.

  The display unit 54 has a part of its function installed in the optical viewfinder 104. Among the display contents of the display unit 54, what is displayed on the LCD or the like includes single shot / continuous shooting display, self-timer display, compression rate display, recording pixel number display, recording number display, remaining image number display, shutter Speed display, Aperture value display, Exposure compensation display, Flash display, Red-eye reduction display, Macro shooting display, Buzzer setting display, Clock battery level display, Battery level display, Error display, Multi-digit number information display and recording There are a display state of the media 200 and 210, a communication I / F operation display, a date / time display, and the like.

  Among the display contents of the display unit 54, what is displayed in the optical viewfinder 104 includes in-focus display, camera shake warning display, flash charge display, shutter speed display, aperture value display, exposure correction display, and the like. Reference numeral 56 denotes an electrically erasable / recordable nonvolatile memory such as an EEPROM.

  Reference numerals 60, 62, 64, 66, 68 and 70 are operation means for inputting various operation instructions of the system control circuit 50, and may be a single unit such as a switch, a dial, a touch panel, pointing by line-of-sight detection, a voice recognition device, or the like. Consists of multiple combinations.

  Here, a specific description of these operating means will be given. Reference numeral 60 denotes a mode dial switch, which can switch and set various function modes such as power-off, automatic shooting mode, shooting mode, panoramic shooting mode, playback mode, multi-screen playback / erase mode, and PC connection mode.

  Reference numeral 62 denotes a shutter switch SW1 which is turned on during the operation of the shutter button (half-press of the shutter button), and AF (auto focus) processing, AE (auto exposure) processing, AWB (auto white balance) processing, EF (flash pre-flash). ) Instruct the start of operations such as processing.

  Reference numeral 64 denotes a shutter switch SW2, which is turned on when the operation of the shutter button is completed (the shutter button is fully pressed), and a signal read from the image sensor 12 is transferred to the memory 30 via the A / D converter 16 and the memory control circuit 22. Exposure processing for writing image data, development processing using operations in the image processing circuit 20 and the memory control circuit 22, reading out image data from the memory 30, compression in the compression / decompression circuit 32, and image data on the recording medium 200 or 210 An instruction to start the operation of a series of processing called recording processing to be written is given.

  Reference numeral 66 denotes an image display ON / OFF switch that can set ON / OFF of the image display unit 28. With this function, when photographing using the optical viewfinder 104, it is possible to save power by cutting off the current supply to the image display unit composed of TFT, LCD, and the like.

  Reference numeral 68 denotes a quick review ON / OFF switch, which sets a quick review function for automatically reproducing image data taken immediately after photographing. In the present embodiment, in particular, a function for setting a quick review function when the image display unit 28 is turned off is provided.

  Reference numeral 70 denotes an operation unit composed of various buttons, a touch panel, etc., a menu button, a set button, a macro button, a multi-screen playback page break button, a flash setting button, a single shooting / continuous shooting / self-timer switching button, menu movement + (plus) Button, menu movement-(minus) button, playback image movement + (plus) button, playback image-(minus) button, shooting image quality selection button, exposure compensation button, date / time setting button, image deletion button, image deletion cancel button Etc.

  Reference numeral 80 denotes a power supply control means, which includes a battery detection circuit, a DC-DC converter, a switch circuit for switching a block to be energized, etc., and detects the presence / absence of a battery, the type of battery, the remaining battery level, and the detection result In addition, the DC-DC converter is controlled based on an instruction from the system control circuit 50, and a necessary voltage is supplied to each unit including the recording medium for a necessary period.

  82 is a connector, 84 is a connector, and 86 is a primary battery such as an alkaline battery or a lithium battery, a secondary battery such as a NiCd battery, NiMH battery or Li battery, an AC adapter, or the like.

  90 and 94 are interfaces with a recording medium such as a memory card or a hard disk, 92 and 96 are connectors for connecting to a recording medium such as a memory card or a hard disk, and 98 is a recording medium 200 or 210 attached to the connector 92 or 96. Recording medium attachment / detachment detecting means for detecting whether or not the recording medium is present.

  In the present embodiment, it is assumed that there are two interfaces and connectors for attaching the recording medium. Of course, the interface and the connector for attaching the recording medium may have a single or a plurality of systems, any number of systems. Moreover, it is good also as a structure provided with combining the interface and connector of a different standard.

  The interface and the connector may be configured using a PCMCIA card, a CF (Compact Flash (registered trademark)) card, or the like based on a standard.

  In addition, when the interfaces 90 and 94 and the connectors 92 and 96 are configured using a PCMCIA card, a CF (Compact Flash (registered trademark)) card, or the like, a LAN card, a modem card, a USB card, IEEE1394. Image data and management information attached to image data are transferred to and from peripheral devices such as other computers and printers by connecting various communication cards such as cards, P1284 cards, SCSI cards, and PHS communication cards. I can meet each other.

  Reference numeral 102 denotes protection means that is a barrier that prevents the imaging unit from being soiled or damaged by covering the imaging unit including the lens 10 of the imaging device 100.

  Reference numeral 104 denotes an optical viewfinder, which can take an image using only the optical viewfinder without using the electronic viewfinder function of the image display unit 28. In the optical viewfinder 104, some functions of the display unit 54, for example, a focus display, a camera shake warning display, a flash charge display, a shutter speed display, an aperture value display, an exposure correction display, and the like are installed.

  A communication unit 110 has various communication functions such as RS232C, USB, IEEE1394, P1284, SCSI, modem, LAN, and wireless communication.

  Reference numeral 112 denotes a connector for connecting the imaging apparatus 100 to another device by the communication unit 110 or an antenna in the case of wireless communication.

  Reference numeral 200 denotes a recording medium such as a memory card or a hard disk. The recording medium 200 includes a recording unit 202 composed of a semiconductor memory, a magnetic disk, and the like, an interface 204 with the imaging device 100, and a connector 206 that connects to the imaging device 100. Reference numeral 210 denotes a recording medium such as a memory card or a hard disk.

  The recording medium 210 includes a recording unit 212 composed of a semiconductor memory, a magnetic disk, and the like, an interface 214 with the imaging device 100, and a connector 216 that connects to the imaging device 100.

FIG. 8 is a perspective view of an electronic camera to which the present imaging device is applied.
2-1 is a button for power ON / OFF. Reference numeral 2-2 denotes a mode switching lever which can switch and set each function mode such as a shooting mode, a playback mode, a moving image shooting mode, and a still image shooting mode. Reference numeral 2-3 denotes a shutter button. An image captured by the camera is displayed on an image display unit, which is usually referred to as an LCD since it normally uses an LCD (liquid crystal display). A screen for reproducing a still image and / or a moving image is also displayed on the LCD 2-4. Reference numeral 2-5 denotes a MENU button which is used to enter and exit a menu screen for changing shooting parameters and camera settings. 2-6 is a SET button, which is used for determining a menu. A delete button 2-7 can designate deletion of an image. Reference numeral 2-8 denotes a DISP button which is used to switch presence / absence of display on the LCD 2-4. Reference numeral 2-9 denotes a cross button, which is used to move items on the menu screen using the up / down / left / right buttons.

Next, the functional configuration and operation flow of the imaging apparatus according to the present embodiment will be described with reference to FIG.
When the shutter switch SW1 of the imaging apparatus 100 is pressed, the photometry unit 101 performs a photometry operation. The photometric operation is obtained by using the average luminance signal value Y of the entire screen exposed to the CCD, the aperture value Av0 and the shutter speed Tv0 at which the signal is exposed. A specific method for obtaining the subject brightness will be described below. When the luminance value of the entire screen is Y and the appropriate exposure luminance value set in advance is Yref, it is possible to determine how much the exposure differs from the current screen luminance value from the appropriate value by Equation (6). . When the aperture value at this time is Av0, the sensitivity decrease ΔSv0 indicating how much the sensitivity is decreased due to the F-value luminance dependency is obtained by Expression (7). For reference, the characteristic of the function dsv of the equation (7) is shown in FIG. This function can be realized by a polynomial or a lookup table, but in this embodiment, conversion using a lookup table is used.

  In this way, the subject brightness value Bv0 is obtained by using the following equation (8) in consideration of the sensitivity that varies depending on the F value.

  The subject luminance value Bv0 obtained by the photometry unit 101 and the set value of the sensitivity Sv0 of the imaging device are sent to the AF program diagram 102, and an aperture value Av1 and a shutter speed value Tv1 for performing the AF operation are obtained. Desired.

  Av1 and Tv1 are sent to the AvTv control unit 103 to set the aperture and electronic shutter speed of the imaging apparatus. When the aperture and electronic shutter speed for performing AF are set, the AF processing unit 104 performs an AF operation. Although the AF operation is not described in detail here, the focus position is moved by a plurality of steps, the image is exposed, the exposed image is subjected to frequency analysis, and the focus position is set to the step having the highest frequency component.

  Next, the aperture value Av2 and the shutter speed value Tv2 for performing the main exposure are determined in the Capture program diagram 105 based on the subject luminance value Bv0 and the sensitivity Sv0 obtained by the photometry unit 101. The determined Av2 and Tv2 are sent to the AvTv control unit 106, and the aperture value Av2 and the mechanical shutter speed Tv2 are set.

  When Av2 and Tv2 are set, the capture unit 107 performs main exposure photography. In addition, the gamma selection unit 108 performs selection determination of gamma used by the image processing unit 109 based on the aperture value Av2 determined by the Capture program diagram 105.

  Here, a gamma selection determination method will be described. The gamma selection unit 108 is provided with a plurality of gammas as shown in FIG. The gamma selection unit 108 is provided with five gammas in which the luminance value of the appropriate luminance level changes from 0 to 0.5 level every 0.1 level. ΔSv1 is obtained from the Av2 used in the main exposure by using the equation (7) for obtaining the sensitivity decrease ΔSv used in the photometry unit 101, and gamma is selected based on the value of ΔSv1 obtained here.

  In actual selection, if -0.1 <ΔSv1 ≦ 0.0, normal gamma is set, and if -0.2 <ΔSv1 ≦ −0.1, the luminance value of the appropriate luminance level is set to be 0.1 level brighter. The selected gamma is selected, and if -0.3 <ΔSv1 ≦ −0.2, the gamma with the brightness value of the appropriate brightness level set to 0.2 steps brighter is selected. When the gamma used for image processing is selected and determined, the image processing unit 109 sends the image data to the image processing unit 109, and the image processing unit 109 performs image processing on the image data obtained by the main exposure in the capture unit 107. Here, the image processing performed by the image processing unit 109 will be described.

FIG. 2 is a diagram illustrating a functional configuration of the image processing unit 109 and a processing flow.
1 is sent to the white balance processing unit 201 in FIG. 2 to obtain the white ballast coefficient and the color temperature of the light source so that white in the image becomes a white signal. It is done. Here, the method for obtaining the white balance coefficient will not be described in detail, but white balance processing is performed so that white in an image is generally a white signal. The white balance processed image data is sent to the luminance signal processing unit 208 and the interpolation processing unit 202. In the interpolation processing unit 202, the surface data of the R, G1, G2, and B signals is obtained from the pixel arrangement of the single-plate CCD as shown in FIG. 5 using the pixels at the R, G1, G2, and B positions, respectively, by interpolation calculation. Create

  The matrix calculation unit 203 performs color conversion for each pixel using Expression (9).

  The CCD digital signal that has been subjected to matrix calculation processing is gained by the color difference gain calculation processing unit 204. In the calculation, the Rm, Gm, and Bm signals are converted into Y, Cr, and Cb signals by Expression (10), and the gain is applied to the Cr and Cb signals by Expression (11), and Expression (12) (the inverse of Expression 9). Is converted into Rg, Gb, and Bg signals by matrix operation.

  The CCD digital signal subjected to the color difference gain calculation process is sent to the first gamma processing unit 205. The first gamma processing unit 205 uses the gamma selected by the gamma selection unit 108 in FIG. 1 and performs data conversion using the following equations (13) to (15). However, GammaTable is a one-dimensional lookup table.

  The gamma-processed image data is sent to the hue correction calculation processing unit 206. In the calculation, the Rt, Gt, and Bt signals are converted into Y, Cr, and Cb signals by Expression (16), and the Cr and Cb signals are corrected by Expression (17), and Expression (18) (the inverse of Expression (16)) is performed. Is converted into Rh, Gh, and Bh signals.

  The image data subjected to the hue correction calculation process is sent to the color difference signal conversion processing unit 207. In the color difference signal conversion processing unit 207, a UV signal is created using Expression (19).

  On the other hand, a luminance signal is created based on the image data sent from the white balance processing unit 201 to the luminance signal processing unit 208. The luminance signal creation method will be described below.

  In the case of a primary color filter as shown in FIG. 5, the R and B signals are all set to 0, and the two-dimensional filter processing having the coefficients shown in FIG. Further, the luminance signal in the case of the complementary color filter as shown in FIG. 5 is the luminance signal that has been subjected to the two-dimensional filter processing having the coefficients shown in FIG. 6 as it is.

  The luminance signal output from the luminance signal processing unit 208 is subjected to edge enhancement processing by the high frequency enhancement processing unit 209 and further subjected to gamma conversion processing by the second gamma processing unit 210. The gamma processing of the second gamma processing unit 210 uses the gamma determined by the gamma selection unit 108 in FIG. 1 in the same manner as the gamma processing of the first gamma processing unit 205. A Y signal is generated by the gamma conversion processing of the second gamma processing unit 210.

  The U, V, and Y signals created as described above are recorded in the recording unit 110 in FIG.

  In the present embodiment, the method of processing with the look-up table in the first and second gamma processing units 205 and 210 in FIG. 2 has been described, but gamma processing may be performed using a polynomial. In such a case, a plurality of polynomials are prepared for the gamma stored in the gamma selection unit 108 of FIG.

  Further, although the method of selectively determining gamma from the gamma characteristics prepared in advance by the gamma selection unit 108 in FIG. 1 is used, the present invention is not limited to this, and the calculation is performed based on the F value desensitization ΔSv. You may make it obtain | require gamma adaptively. In the above embodiment, the gamma processing performed in the image processing unit 109 in FIG. 1 has been described as being processed using the same gamma in the first and second gamma processing units 205 and 210. The gamma selection unit 108 in FIG. 1 may select and determine gammas used for the first gamma processing unit 205 and the second gamma processing unit 210, respectively. .

  According to the above embodiment, even when the sensitivity is lowered due to the F value, the amount of image data obtained by exposure during the main exposure is reduced by performing image processing using gamma corrected for the sensitivity reduction. Therefore, the information of the image data can be used effectively without making it possible to obtain a high-quality output image.

  Another object of the present invention is to supply a storage medium storing software program codes for realizing the functions of the above-described embodiments to a system or apparatus, and a computer (or CPU or MPU) of the system or apparatus stores the storage medium. Needless to say, this can also be achieved by reading and executing the program code stored in.

  In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiments, and the program code itself and the storage medium storing the program code constitute the present invention.

  As a storage medium for supplying the program code, for example, a flexible disk, a hard disk, an optical disk, a magneto-optical disk, a CD-ROM, a CD-R, a magnetic tape, a nonvolatile memory card, a ROM, or the like can be used.

  Further, by executing the program code read by the computer, not only the functions of the above-described embodiments are realized, but also an OS (basic system or operating system) running on the computer based on the instruction of the program code. Needless to say, a case where the functions of the above-described embodiment are realized by performing part or all of the actual processing and the processing is included.

  Further, after the program code read from the storage medium is written in a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer, the function is determined based on the instruction of the program code. It goes without saying that the CPU or the like provided in the expansion board or function expansion unit performs part or all of the actual processing and the functions of the above-described embodiments are realized by the processing.

It is a figure which shows the function structure and flow of operation | movement of the imaging device which concerns on embodiment of this invention. It is a figure which shows the function structure of an image process part, and the flow of a process. It is a figure which shows the characteristic of a function dsv. It is a figure which shows a gamma characteristic. It is a figure which shows the pixel arrangement | sequence of a single plate primary color CCD. It is a figure which shows the filter characteristic used at the time of luminance signal creation. 1 is a diagram illustrating an overall configuration of an imaging apparatus according to an embodiment of the present invention. 1 is a perspective view of an electronic camera to which an imaging apparatus according to an embodiment of the present invention is applied.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Photometry part 102 AF program diagram 103,106 AvTv control part 104 AF process part 105 Capture program diagram 107 Capture part 108 Gamma selection part 109 Image processing part 110 Recording part 201 White balance process part 202 Interpolation process part 203 Matrix calculation process Unit 204 color difference gain calculation processing unit 205 first gamma processing unit 206 hue correction calculation processing unit 207 color difference signal conversion processing unit 208 luminance signal processing unit 209 high frequency enhancement processing unit 210 second gamma processing unit

Claims (9)

An imaging means for capturing an image;
A luminance value calculating means for calculating a subject luminance value based on the exposed luminance value of the imaging means and a preset appropriate luminance value;
Determining means for determining an aperture value from the sensitivity of the imaging means to be set and the subject luminance value using a predetermined program diagram;
Exposure control means for performing exposure control of the imaging means based on the aperture value determined by the determination means;
Determination means for determining the degree of sensitivity reduction of the imaging means based on the aperture value determined by the determination means;
Gamma selection means for selecting one of a plurality of nonlinear gamma curves based on the degree of sensitivity reduction of the imaging means determined by the determination means;
An image processing apparatus comprising: an image processing unit that performs image processing on image information obtained by exposure control of the exposure control unit based on a gamma curve selected by the gamma selection unit.   The determining unit determines a shutter speed value in addition to the aperture value from the sensitivity of the imaging unit and the subject luminance value using the predetermined program diagram, and the exposure control unit is configured to determine the aperture value and the subject brightness value. The imaging apparatus according to claim 1, wherein exposure control of the imaging unit is performed based on a shutter speed value.   3. The imaging according to claim 1, wherein the gamma selection unit selects a gamma curve having a higher appropriate luminance level as the determination unit determines that the degree of sensitivity reduction of the imaging unit is larger. apparatus.   In the plurality of gamma curves, when the difference between each luminance level is compared, the difference between the luminance values of the intermediate portion including the appropriate luminance level is larger than the difference between the luminance values of the low luminance portion and the high luminance portion. The imaging device according to any one of claims 1 to 3, wherein An imaging means for capturing an image;
A luminance value calculating means for calculating a subject luminance value based on the exposed luminance value of the imaging means and a preset appropriate luminance value;
Determining means for determining an aperture value from the sensitivity of the imaging means to be set and the subject luminance value using a predetermined program diagram;
Exposure control means for performing exposure control of the imaging means based on the aperture value determined by the determination means;
Determination means for determining the degree of sensitivity reduction of the imaging means based on the aperture value determined by the determination means;
Gamma calculation means for calculating a gamma curve based on the degree of sensitivity reduction of the imaging means determined by the determination means;
An image processing apparatus comprising: an image processing unit that performs image processing on image information obtained by exposure control of the exposure control unit based on a gamma curve calculated by the gamma calculation unit. A method for controlling an image pickup apparatus having an image pickup means for picking up an image,
A luminance value calculating step for calculating a subject luminance value based on the exposed luminance value of the imaging means and a preset appropriate luminance value;
A determination step of determining an aperture value from the sensitivity of the imaging means and the subject luminance value to be set using a predetermined program diagram;
An exposure control step of performing exposure control of the imaging means based on the aperture value determined by the determination step;
A determination step of determining a degree of sensitivity reduction of the imaging means based on the aperture value determined by the determination step;
A gamma selection step of selecting one of a plurality of nonlinear gamma curves based on the degree of sensitivity reduction of the imaging means determined in the determination step;
An image processing step for performing image processing on image information obtained by exposure control in the exposure control step based on the gamma curve selected in the gamma selection step. A method for controlling an image pickup apparatus having an image pickup means for picking up an image,
A luminance value calculating step for calculating a subject luminance value based on the exposed luminance value of the imaging means and a preset appropriate luminance value;
A determination step of determining an aperture value from the sensitivity of the imaging means and the subject luminance value to be set using a predetermined program diagram;
An exposure control step of performing exposure control of the imaging means based on the aperture value determined by the determination step;
A determination step of determining a degree of sensitivity reduction of the imaging means based on the aperture value determined by the determination step;
A gamma calculation step of calculating a gamma curve based on the degree of sensitivity reduction of the imaging means determined in the determination step;
An image processing control method comprising: an image processing step for performing image processing on image information obtained by exposure control in the exposure control step based on the gamma curve calculated in the gamma calculation step. A program for causing a computer to execute the method for controlling an imaging apparatus according to claim 6 . A computer-readable recording medium on which the program according to claim 8 is recorded.

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