JP4842639B2 - camera - Google Patents

Description

  The present invention relates to a still image shooting camera and a moving image shooting camera having a human face detection function.

Conventionally, in snapshot shooting in which a person is captured, the position of the person is inferred from framing rules of thumb and autofocus information, and the brightness level of the entire image is corrected so that the brightness level of the person is appropriate. ing. In addition, a skin color region is detected so that the color of the region is close to a predetermined skin color (for example, Patent Document 1), or a face region detected using the face detection function is used as a target. Focusing on color balance, it is used for exposure control and white balance control (for example, see Patent Documents 2 to 5), or when a part of the detected face is shaded, a strobe is emitted. (For example, refer to Patent Document 6).
JP 2005-176028 A JP 2003-189325 A JP 2003-107555 A Japanese Patent Laying-Open No. 2005-086682 JP 2005-027277 A Japanese Patent Laid-Open No. 2001-2222048

  However, when shooting outdoors, the contrast tends to be strong, so if part of the face is shaded or if the sunlight is different depending on the person, part of the face may be crushed black, On the contrary, there is a problem that it may fly white.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a camera capable of obtaining an appropriate captured image.

The present invention has been made to solve the above-described problems, and one aspect of the present invention is a camera including a gamma correction unit that performs gamma correction on an input image. A face detection unit that detects a face and calculates a luminance change evaluation value in a face region including the face, and determines gradation characteristics so that the larger the luminance change evaluation value calculated by the face detection unit is, the softer the tone is and a gamma correction control means for said gamma correction means uses the gradation property of the gamma correction control means decides, have rows gamma correction on the input image, the face detection means, a plurality When the face is detected, the brightness difference is obtained for each detected face, and the largest one is selected as the brightness change evaluation value from the obtained brightness differences for each face. It is.

  According to the present invention, the gradation characteristics of the gamma correction are changed according to the luminance change evaluation value, so that even if a part of the face is shaded or the sun is different, There is an effect that it is possible to prevent flying white and obtain an appropriate photographed image.

  Further, according to the present invention, when the continuous shooting mode is designated, the gradation characteristic used for gamma correction is set to one frame if the amount of change between the image one frame before and the current image is smaller than a predetermined value. Since it is the same as the previous image, even if the face cannot be detected in the middle of continuous shooting, there is an effect that a stable contrast is obtained between the continuous shooting frames, and an appropriate captured image can be obtained.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the overall configuration of a camera according to an embodiment of the present invention. In the present embodiment, a digital camera will be described as an example of the camera according to the present invention.

  The digital camera of this embodiment includes a zoom lens 1, an iris (aperture) 2, a focus lens 3, an image pickup device (CCD) 4, a zoom motor 5, an iris motor 6, a focus motor 7, a timing generator 8, and a CDSAMP circuit 9. Have. Here, the zoom lens 1, the iris 2, the focus lens 3, and the imaging element 4 constitute imaging means for imaging a subject.

  The iris motor 6 forms a diaphragm variable unit that changes the opening degree of the iris 2. The timing generator 8 forms a shutter speed variable unit that changes the shutter speed. A CDSAMP (Corelated Double Sampling Amplifier) circuit 9 constitutes a gain variable unit that varies the degree of amplification with respect to the output of the image pickup device 4 that forms the output of the image pickup means. The iris motor 6, the timing generator 8, and the CDSAMP circuit 9 constitute an exposure changing unit that changes the exposure state in the imaging unit.

  The position of the zoom lens 1 can be moved by a zoom motor 5. The opening degree of the iris 2 can be controlled by the iris motor 6. The position of the focus lens 3 can be controlled by the focus motor 7. The subject image light that has passed through the zoom lens 1, the iris 2, and the focus lens 3 forms an image on the light receiving surface of the image sensor 4.

  The image sensor 4 photoelectrically converts subject image light imaged on its light receiving surface. As the image sensor 4, a CCD (Charge Coupled Device) image sensor, a CMOS (Complementary MOS) image sensor, or the like is used. Color filters are arranged on the front surface of the image sensor 4. The arrangement of the color filters includes R (red), G (green), and B (blue) primary color filters, and Cy (cyan), Mg (magenta), and Ye (yellow) complementary color filters. May be used. The image sensor 4 is driven by a timing signal from the timing generator 8.

  The digital camera of this embodiment includes an A / D converter 10, an image input controller 11, an image signal processing circuit 12, an image compression / decompression circuit 13, a video encoder 14, an image display device 15, and motor drivers 16, 17, and 18. CPU 19, AF detection circuit 20, AE and AWB detection circuit 21, memory 22, VRAM 23, media controller 24, recording medium 25, and face detection circuit 26. In addition, the digital camera of this embodiment includes a shutter switch SW1, a recording / reproducing switch SW2, a zoom switch SW3, a strobe switch SW4, and a shooting mode selection switch SW5.

The A / D converter 10 digitizes the image signal output from the image sensor 4 and input via the CDSAMP circuit 9. The image input controller 11 supplies the image signal output from the A / D converter 10 to the CPU 19.
The image signal processing circuit 12 includes a gamma correction control unit 27 and performs image processing such as gamma correction, edge enhancement, and white balance on the input image signal. The parameters for performing these image processes are set by the CPU 19. Regarding gamma correction, there is selection of gradation characteristics as a parameter set by the gamma correction control unit 27 based on the luminance change evaluation value received from the CPU 19. As shown in FIG. 2, the image signal processing circuit 12 has a standard tone characteristic L1, a slightly soft tone characteristic L2, a soft tone characteristic L3, and a strong soft tone. Gamma correction processing is performed by the gamma correction control unit 27 using the gradation characteristics set before the input of the image signal.
The image compression / decompression circuit 13 compresses and encodes the input image signal. For example, JPEG (Joint Photographic Experts Group) is used as the image data compression method. JPEG is a standard for compressing images using DCT (Discrete Cosine Transform). Note that the image data compression method is not limited to JPEG.
A VRAM (Video RAM) 23 is a memory for storing image data to be displayed on the image display device 15.
The video encoder 14 reads the image data stored in the VRAM 23, forms a component color video signal based on the image data, and outputs the component color video signal to the image display device 15. The image display device 15 is a display such as an LCD (Liquid Crystal Display) that displays a color image based on an input component color video signal.

  The AF (Automatic Focus) detection circuit 20 is for performing AF based on the output of the image sensor 4. The AF detection circuit 20 detects the high frequency component level of the image signal in order to perform focus control. That is, at the focal point, the high-frequency component level of the image signal increases. Therefore, the in-focus state can be determined by detecting the high-frequency component level of the image signal. The high-frequency component level of the image signal is detected by the AF detection circuit 20, and the high-frequency component level of the image signal is integrated during a predetermined focus area to obtain an AF evaluation value. The obtained AF evaluation value is supplied to the CPU 19.

  The face detection circuit 26 detects face detection areas (area A1 and area A2 in FIG. 3) included in the image signal output from the image sensor 4, and calculates a luminance evaluation value by the following procedure. First, the face detection circuit 26 extracts a skin color region from the image signal. Next, contour extraction is performed on the previously extracted region based on the luminance change, and it is confirmed whether or not both eyes and mouth exist in an arrangement where the positions of both eyes and mouth are relatively located. When both eyes and mouth exist, a rectangular area surrounding the area is detected as a face detection area. Further, the face detection circuit 26 divides the face detection area into four equal parts by the middle line of each side (here, the area A1 is divided into areas A1a to A1d and the area A2 is divided into areas A2a to A2d). Skin color pixels are extracted from the area, and the average value of the luminance is calculated for each divided area (here, the average value of the area A1a is H1a, the average value of the area A1b is H1b, and the average value of the area A1c is H1c,..., The average value of the area A2d is H2d). The face detection circuit 26 extracts the maximum value and the minimum value from these average values of luminance, and outputs the difference as a luminance change evaluation value to the CPU 19.

In order to perform exposure and white balance, the AE and AWB detection circuit 21 forms an exposure control signal and a white balance control signal according to the following procedure on the basis of the image signal output from the image pickup device 4, and outputs these signals to the CPU 19. Output to.
The exposure control signal is a luminance evaluation value indicating the brightness of the image. The AE and AWB detection circuit 21 calculates the average value of the luminance of the entire image for the input image signal, and uses this as the luminance evaluation value. At this time, an average luminance value may be calculated by weighting the face detection area detected by the face detection circuit 26.

  The white balance control signal refers to B gain and R gain. Here, the B gain is a magnification to be applied to the blue component of each pixel in white balance control, and the R gain is a magnification to be applied to the red component of each pixel. In the white balance control, among the three primary colors of each pixel, the green component is not changed (1 time), and the blue component and the red component are respectively multiplied by the B gain and the R gain to balance the three primary colors. To control. The AE and AWB detection circuit 21 calculates an average value of each of the red, blue, and green components of the entire image, and obtains a value obtained by dividing the average value of the green component by the average value of the blue component as B gain and the average value of the green component. The value divided by the average value of the red component is defined as the R gain.

The CPU 19 is a calculation unit that controls the entire digital camera. Further, the CPU 19 receives input signals from the shutter switch SW1, the recording / reproducing switch SW2, the zoom switch SW3, the strobe switch SW4, the photographing mode selection switch SW5, and the like. Further, the CPU 19 controls the zoom drive signal for moving the zoom lens 1, the focus drive signal for moving the focus lens 3, the iris drive signal for opening and closing the iris 2, and the gain of the CDSAMP circuit 9. The gain control signal is output.
The memory 22 includes a ROM (Read Only Memory) that is a non-volatile memory storing a program for operating the CPU 19, and a RAM (Random Access Memory) that is a volatile memory used as a work memory when the CPU 19 operates. ).

The shutter switch SW1 is a switch that captures an image when pressed in the recording mode.
The recording / playback switch SW2 is a switch for setting the digital camera to a recording mode for capturing an image or a playback mode for displaying the captured image on the image display device 15.
The zoom switch SW3 is a switch for moving the zoom lens 1 in the recording mode.
The strobe switch SW4 is a switch for setting automatic light emission / flash prohibition of a strobe (not shown).
The shooting mode selection switch SW5 is a switch for selecting one shooting mode according to the shooting situation from the self-timer mode, continuous shooting mode, single shooting mode, bracket mode, and the like.

The media controller 24 has a function of reading / writing data from / to the recording medium 25.
The recording medium 25 is a medium on which a compression-coded image signal is recorded as an image file. For example, a card-type removable memory using a flash memory is used. As the recording medium 25, a nonvolatile memory built in a digital camera, a magnetic tape, a magnetic disk, an optical disk, or the like may be applied.

  Next, the operation of the digital camera after the power is turned on will be described. The main power of the digital camera is turned on / off by operating a power switch (not shown). When the power is turned on, the digital camera initializes memory, zooming, DSP, various drivers (16, 17, 18), and the like.

  When the recording / reproducing switch SW2 is set to the recording mode, the image pickup device 4 periodically captures an image even when the image is not taken, and passes through the CDSAMP circuit 9, the A / D converter 10, and the image input controller 11. Thus, an image signal is input to the CPU 19. The CPU 19 outputs this digital image signal to the face detection circuit 26 and also outputs it to the image signal processing circuit 12.

  First, when receiving the image signal of the image as shown in FIG. 3, for example, the face detection circuit 26 that receives the image signal from the CPU 19 detects the area A1 and the area A2 that are face detection areas, Luminance average values H1a to H1d and H2a to H2d of the skin color areas of the divided areas A1a to A1d and areas A2a to A2d are calculated. Next, the maximum value and the minimum value are extracted from the luminance average values H1a to H1d and H2a to H2d, respectively, the difference between them is obtained, and the value having the largest difference is output to the CPU 19 as the luminance change evaluation value x. Upon receiving the luminance change evaluation value x, the CPU 19 outputs this to the gamma correction control unit 27 of the image signal processing circuit 12, and the gamma correction control unit 27 operates according to the flow shown in FIG. First, the gamma correction control unit 27 acquires the luminance change evaluation value x from the CPU 19 (S1). When the luminance change evaluation value x is smaller than the predetermined threshold value l (S2), the gamma correction control unit 27 uses the standard gradation characteristic L1 as the gradation characteristic at the time of gamma correction in the image signal processing circuit 12. Set (S3). When the luminance change evaluation value x is not less than the predetermined threshold value l and less than the predetermined threshold value m (S4), a slightly soft gradation characteristic L2 is set in the image signal processing circuit 12 (S5). When the luminance change evaluation value x is not less than the predetermined threshold value m and less than the predetermined threshold value n (S6), a soft gradation characteristic L3 is set in the image signal processing circuit 12 (S7). In other cases, that is, when the luminance change evaluation value x is greater than or equal to the predetermined threshold value n, a strong soft gradation characteristic L4 is set in the image signal processing circuit 12 (S8).

  On the other hand, when an image signal is input from the CPU 19, the image signal processing circuit 12 performs gamma correction, edge enhancement, white balance control, etc. with the gradation characteristics set by the gamma correction control unit 27 for the image signal. Image processing is performed, and the resulting image signal is output. This image signal is stored in the VRAM 23 as image data via the CPU 19. The video encoder 14 refers to the image data stored in the VRAM 23, forms a component color video signal, and outputs this component color video signal to the image display device 15. Since the image display device 15 displays the component color video signal, the monitor image being captured is displayed on the image display device 15.

  In this manner, the gamma correction control unit 27 determines the gradation characteristics so that the brightness changes as the luminance change of the skin color portion of the face calculated by the face detection circuit 26 increases. The gamma correction control unit 27 periodically sets the image signal processing circuit 12 so as to perform gamma correction using the gradation characteristics, so that the shadowed portion of the face is crushed in black or on the contrary positive. The image signal processing circuit 12 is always controlled so as to prevent the contact portion from flying white.

  Further, the CPU 19 inputs the digital image signal to the AE & AWB detection circuit 21, and as a result, acquires an exposure control signal and a white balance control signal. Next, the CPU 19 outputs an iris drive signal and a gain setting signal based on the exposure control signal. Then, the iris drive signal is supplied to the iris motor 6 via the motor driver 17, and the opening degree of the iris 2 is controlled so as to have a predetermined signal level. Further, the gain setting signal is supplied to the CDSAMP circuit 9, and the gain of the CDSAMP circuit 9 is controlled so as to have a predetermined signal level. The CPU 19 sets B gain and R gain in the image signal processing circuit 12 based on the white balance control signal. In this way, exposure and white balance are always controlled to an optimum state so that photographing can be performed at any time.

  At this time, when the zoom switch SW3 is operated, the CPU 19 outputs a zoom drive signal accordingly. This zoom drive signal is supplied to the zoom motor 5 via the motor driver 16, and the zoom lens 1 is moved by the zoom motor 5.

  The operation during image shooting will be described. First, the case where the shooting mode selection switch SW5 is selected for single shooting will be described. When the shutter switch SW1 is pressed, the CPU 19 detects this and sends a shutter signal to the timing generator 8, and the image at that time is taken into the image sensor 4. The image sensor 4 outputs the captured image as an analog image signal. The analog image signal is gain-controlled by the CDSAMP circuit 9 and converted into a digital image signal by the A / D conversion 10. This digital image signal is taken into the CPU 19 via the image input controller 11. Thereafter, the captured digital image signal is subjected to image processing such as gamma correction, edge enhancement, white balance, and YC conversion in the image signal processing circuit 12, data compressed in the image compression / decompression circuit 13, and as an image file. It is recorded on the recording medium 25.

  Next, an operation when the shooting mode selection switch SW5 is selected for continuous shooting and shooting is performed in the continuous shooting mode will be described. The continuous shooting mode is a mode in which when the shutter switch SW1 is pressed, a predetermined number of frames is continuously shot. The operation relating to shooting of each frame is performed by the CPU 19 in the single shooting mode. This is the same as the subsequent operation after sending. Here, description of shooting in each frame will be omitted, and operation between frames will be described. In the continuous shooting mode, as shown in FIG. 5, basically after each frame is shot, the gamma correction setting process is performed on the image captured by the image sensor 4 as in the case other than the above-described image shooting. Then, the face detection circuit 26 outputs luminance change evaluation values, and based on these luminance change evaluation values, the gamma correction control unit 27 of the image signal processing circuit 12 gives the gradation characteristics used for gamma correction to the image signal processing circuit 12. Set. However, for the second and subsequent frames, gradation characteristics are set for each frame according to the flow shown in FIG.

  For example, let us consider shooting in the continuous shooting mode in which there is little image change through continuous shooting, a face is captured up to the k-1 frame, and no face is captured from the k frame. In this case, in the first frame, the luminance change evaluation value calculated by the face detection circuit 26 after successful face detection is output, and based on this, the gamma correction control unit 27 uses the image signal processing circuit 12 for gamma correction. Set the gradation characteristics. Thereafter, from the second frame to the k-1th frame, the gamma correction control unit 27 first inputs the image captured by the image sensor 4 to the face detection circuit 26, and the face detection circuit 26 receives the input. Face detection is performed on the image and the calculated luminance change evaluation value is output to the CPU 19, and the CPU 19 outputs the received luminance change evaluation value to the gamma correction control unit 27 of the image signal processing circuit 12 (S11). Next, in step S12, the gamma correction control unit 27 determines whether face detection is successful. Here, in the second frame, since face detection is successful, the process proceeds to step S13. Based on the luminance change evaluation value output from the face detection circuit 26, the gamma correction control unit 27 sets the gradation characteristics used for gamma correction in the image signal processing circuit 12 (S13). The gradation characteristics are set in the same manner for each frame in which the faces up to the (k-1) th frame are shown.

Next, since the face is not shown in the image at the k-th frame as described above, the gamma correction control unit 27 inputs the image captured by the image sensor 4 to the face detection circuit 26. The face detection for the input image fails, and the fact is output to the CPU 19, and the CPU 19 notifies the gamma correction control unit 27 of the image signal processing circuit 12 (S11). Next, in step S12, the gamma correction control unit 27 determines whether face detection is successful. Here, since face detection has failed as described above, the process proceeds to step S14. In step S14, the gamma correction control unit 27 determines whether the image change between frames is small. The determination is made based on whether the following expression (3) holds. For the determination, in addition to using the luminance average value and the like as in Expression (3), white balance gain values such as B gain and R gain may be used.
abs (ave [n] −ave [n−1]) <α and abs (1 − ((R [n] × G [n−1]) / (G [n] × R [n−1]) )) <Β and abs (1-((R [n] × G [n−1]) / (G [n] × R [n−1])) <γ (3)
Here, α, β, and γ are small positive constants, abs (x) is a function that takes the absolute value of x, ave [n] is the luminance average value of the nth frame image, and R [n ], G [n], and B [n] are the average values of the red, green, and blue components of the n-th frame image, respectively.

  Here, since it is assumed that there is little image change between frames, Equation (3) is satisfied, that is, the condition of step S14 is satisfied, and the process proceeds to step S15. In step S15, the gamma correction control unit 27 does not make settings for the image signal processing circuit 12, and the tone characteristics used by the image signal processing circuit 12 during gamma correction remain the previous frame (k-1 frame). . Next, since the face is not shown and the image change between frames is small even after the (k + 1) th frame, the condition is not satisfied in step S12, and the condition is satisfied in step 14 in the same manner. To step 15. In step 15, the tone characteristics used during gamma correction remain the previous frame (kth frame). In this way, when there is little change in the image, even if the face does not appear in the middle, gamma correction is performed on the captured image with the same gradation characteristics through continuous shooting, so the contrast changes greatly between frames, causing inefficiency. It prevents a stable image.

  Next, as another example, a case will be described in which the image changes drastically through continuous shooting, a face is captured up to the k-1 frame, and no face is captured from the k frame. As in the case where the image change is small through the continuous shooting, the face detection circuit 26 succeeds in face detection in the first frame, and based on this, the gamma correction control unit 27 of the image signal processing circuit 12 performs image signal processing. After setting the gradation characteristics to be used for gamma correction in the circuit 12, an image is taken. Thereafter, from the second frame to the k-1th frame, the CPU 19 first inputs the image captured by the image sensor 4 to the face detection circuit 26, and the face detection circuit 26 applies the input to the image. Face detection is performed and the calculated luminance change evaluation value is output to the CPU 19, and the CPU 19 outputs the received luminance change evaluation value to the gamma correction control unit 27 of the image signal processing circuit 12 (S11). Next, in step S12, it is determined whether face detection is successful. Here, in the second frame, since face detection is successful, the process proceeds to step S13. Based on the luminance change evaluation value output from the face detection circuit 26, the gamma correction control unit 27 sets the gradation characteristics used for gamma correction in the image signal processing circuit 12 (S13). The gradation characteristics are set in the same manner for each frame in which the faces up to the (k-1) th frame are shown.

  Next, at the k-th frame, since the face is not shown in the image as described above, the CPU 19 inputs the image captured by the image sensor 4 to the face detection circuit 26, but the face detection circuit 26 receives the input. Face detection for the image fails, and a message to that effect is output to the CPU 19 (S11). Next, in step S12, it is determined whether face detection is successful. Here, since face detection has failed as described above, the process proceeds to step S14. In step S14, it is determined whether the image change between frames is small. The determination is made based on whether the above-described equation (3) holds. For the determination, in addition to using the luminance average value and the like as in Expression (3), white balance gain values such as B gain and R gain may be used. Here, since it is assumed that the image change between frames is severe as described above, Equation (3) does not hold, and it is determined in step S14 that the condition is not satisfied, and the process proceeds to step S16. In step S16, the face detection circuit 26 has failed in face detection in step S11, and the luminance change amount evaluation value cannot be calculated. Therefore, the gamma correction control unit 27 sets standard gradation characteristics in the image signal processing circuit 12. To do.

  Next, even after the k + 1 frame, the face is not shown as described above, and the image change between frames is assumed to be severe. Similarly, the condition in step S12 is not satisfied, and the condition in step 14 is also satisfied. First, the process proceeds to step 16. In step S <b> 16, the gamma correction control unit 27 sets standard gradation characteristics in the image signal processing circuit 12 as in the k-th frame. As described above, when the image change is large, if the face is captured, the gradation characteristic of gamma correction is selected based on the face detection area included in the acquired image signal. If the face is not captured, the standard level is selected. A tone characteristic is selected. For this reason, a captured image according to the situation of each frame is obtained.

  When the recording / reproduction switch SW2 is operated to the reproduction side, the reproduction mode is set. In the reproduction mode, the CPU 19 opens the image file on the recording medium 25 via the media controller 24 and reads the image data. The CPU 19 supplies the image data read from the recording medium 25 to the image compression / decompression circuit 13. The image compression / decompression circuit 13 performs image data decompression processing and stores the resulting image data in the VRAM 23. The video encoder 14 refers to the image data in the VRAM 23, generates a component color video signal, and supplies this to the image display device 15. In order to display an image, a reproduced image is displayed on the stored image display device 15 on the recording medium 25.

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and includes a design and the like within the scope not departing from the gist of the present invention.

It is a block diagram which shows the structure of the digital camera by one Embodiment of this invention. It is a figure which shows the gradation characteristic of the gamma correction of the image signal processing circuit 12 in this embodiment. It is a figure which shows the example of the area | region A1 of the face detected by the face detection circuit 26 in this embodiment, A2, and the area | region A1a-A1d and area | region A2a-A2d which each divided | segmented this area | region. It is a flowchart explaining operation | movement of the gamma correction control part 27 in this embodiment. It is a figure explaining the operation | movement in the continuous shooting mode of the camera in this embodiment. It is a flowchart explaining operation | movement of CPU19 in the continuous shooting mode in this embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Zoom lens 2 ... Iris 3 ... Focus lens 4 ... Image sensor 5 ... Zoom motor 6 ... Iris motor 7 ... Focus motor 8 ... Timing generator 9 ... CDSAMP
DESCRIPTION OF SYMBOLS 10 ... A / D conversion 11 ... Image input controller 12 ... Image signal processing circuit 13 ... Image compression / decompression circuit 14 ... Video encoder 15 ... Image display apparatus 16, 17, 18 ... Motor driver 19 ... CPU
DESCRIPTION OF SYMBOLS 20 ... AF detection circuit 21 ... AE & AWB detection circuit 22 ... Memory 23 ... VRAM
24 ... Media controller 25 ... Recording medium 26 ... Face detection circuit 27 ... Gamma correction control unit

Claims (3)

A camera comprising gamma correction means for performing gamma correction on an input image,
Face detection means for detecting a face from an input image and calculating a luminance change evaluation value in a face region including the face;
Gamma correction control means for determining gradation characteristics so as to be softer as the luminance change evaluation value calculated by the face detection means is larger ,
The gamma correction means uses the gradation property of the gamma correction control means decides, have rows gamma correction on the input image,
When detecting a plurality of faces, the face detection means obtains the luminance difference for each detected face, and selects the largest one from the obtained luminance differences for each face as the luminance change evaluation value A camera characterized by that .   The camera according to claim 1, wherein the face detection unit extracts a skin color region of the detected face and calculates a luminance difference in the extracted skin color region as the luminance change evaluation value. A shooting mode specifying means for specifying a shooting mode including a continuous shooting mode;
When the continuous shooting mode is specified by the shooting mode specifying means, the calculation means includes a calculating means for calculating the amount of change between the previous image and the current image,
The gamma correction unit is used for the current image when the face detection unit does not detect a face for the current image and the amount of change calculated by the calculation unit is smaller than a predetermined value. 3. The camera according to claim 1, wherein the gradation characteristic is the same as that used for the image one frame before.

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