JP2005080007A - Digital camera - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a digital camera capable of obtaining proper gradation reproducibility and enhancing the degree of freedom of gradation reproduction. <P>SOLUTION: Many light receiving parts composed of photodetectors with high sensitivity and those with low sensitivity are arrayed on a CCD image sensor 16. An image processing part 20 adds high sensitivity image data obtained from the photodetectors with high sensitivity and low sensitivity image data obtained from the photodetectors with low sensitivity to generate an image with a wide dynamic range. In adding the individual image data, the operation of an operating part 8 changes an addition multiplication factor by which the low sensitive image data are multiplied. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a digital camera, and more particularly to a digital camera capable of photographing an image having a wide dynamic range using an image sensor in which a large number of light receiving portions each having a relatively high light receiving element and a low light receiving element are arranged. Is.

  Digital cameras using image sensors such as CCD image sensors are widely used. This image sensor generally has a narrow dynamic range that represents the reproduction ability of gradation (brightness and darkness) as compared with a photographic film. For this reason, when shooting a scene with a large contrast between light and dark, the so-called whiteout, in which the gradation of the bright portion (high luminance region) is not reproduced even if the gradation of the dark portion (low luminance region) is reproduced well. In some cases, even if the bright gradation is reproduced well, the dark gradation is not reproduced and the image is crushed black.

  In order to eliminate the inconveniences described above, a high-sensitivity light-receiving element and a low-sensitivity light-receiving element are combined into a matrix on the light-receiving surface. A device that obtains a wide dynamic range by mixing each charge obtained from the element with corresponding ones and then converting it to a photographic signal and outputting it is known (for example, see Patent Document 1). In addition, the shooting signals obtained from the high-sensitivity and low-sensitivity light receiving elements are output separately from the image sensor, and the high-sensitivity shooting signals sliced at a predetermined slice level are clipped at a predetermined clip level and then amplified. By adding the low-sensitivity imaging signal with an adder, it is possible to obtain a wide dynamic range while preventing the occurrence of image pattern noise due to uneven saturation of the high-sensitivity light receiving element. (For example, refer to Patent Document 2).

Japanese Patent Laid-Open No. 3-117281 JP-A-9-205589

  By the way, when the charges obtained from the high sensitivity light receiving element and the low sensitivity light receiving element are mixed as described above, the charge mixing (addition) ratio of the high sensitivity and low sensitivity light receiving elements is high. Since the sensitivity is constant according to the sensitivity ratio of each light receiving element having low sensitivity, appropriate gradation reproducibility may not be obtained. In addition, when the addition ratio of each of the high-sensitivity and low-sensitivity shooting signals is adjusted in advance using an image sensor that outputs the shooting signals separately based on the light reception results of the high-sensitivity and low-sensitivity light-receiving elements. However, similarly, appropriate gradation reproducibility may not be obtained. Furthermore, in any case, the degree of freedom is poor in terms of gradation reproduction.

  An object of the present invention is to provide a digital camera capable of obtaining appropriate gradation reproducibility and having a high degree of freedom in gradation reproduction.

  In order to solve the above-mentioned problem, the invention described in claim 1 comprises setting means for setting an addition magnification used when adding a low-sensitivity image signal to a high-sensitivity image signal. The low-sensitivity image signal increased or decreased by the addition magnification set by the setting means is added to the corresponding high-sensitivity image signal.

  According to the second aspect of the invention, there is provided a setting unit that is operated from the outside and sets a lower limit value of the low-sensitivity image signal to be added to the high-sensitivity image signal, and the image processing unit includes the lower limit value set by the setting unit. The above low sensitivity image signal is added to the corresponding high sensitivity image signal.

  According to the third aspect of the present invention, the image processing unit adds the magnitude of the low-sensitivity image signal relative to the lower limit value set by the setting means to the corresponding high-sensitivity image signal.

  According to a fourth aspect of the invention, there is provided display means for displaying an image generated by the image processing unit.

  According to the present invention, the setting means operated from the outside is provided to set the addition magnification used when adding the low-sensitivity image signal to the high-sensitivity image signal, and the low-sensitivity image signal increased or decreased by the set addition magnification. Is added to the high-sensitivity image signal, and setting means is provided to set the lower limit value of the low-sensitivity image data to be added, and the low-sensitivity image signal equal to or higher than the lower limit value is added to the high-sensitivity image signal. In addition, an image with a wide dynamic range can be taken, and the degree of freedom of gradation reproducibility can be increased.

  The front side of a digital camera embodying the present invention is shown in FIG. 1, and the back side is shown in FIG. On the front surface of the camera body 2, a photographing lens 3, a strobe light emitting unit 4, and a release button 5 are provided. An LCD 7 and an operation unit 8 are provided on the back surface. Further, a lid (not shown) of a memory slot is provided on the side of the camera body 2, and a memory card 9 (see FIG. 3) on which image data is recorded is mounted in the memory slot.

  The operation unit 8 is provided with a power button 10, a cancel button 11, a cross key 12, and an OK button 13. By operating the operation unit 8, it is possible to turn on / off the power, switch between the photographing mode and the reproduction mode, select an image under the reproduction mode, instruct to delete, and perform various settings. Further, adjustment of the addition magnification, which will be described later, is performed by operating the cross key 12 and the OK button 13.

  The LCD 7 constitutes a so-called electronic viewfinder that displays a subject image photographed through the photographing lens 3 in real time, and is used for image reproduction and the like. Further, on the LCD 7, an image shot in response to the pressing operation of the release button 5 in the shooting mode is displayed as a preview image before being recorded on the memory card. The photographer can adjust the addition magnification by operating the cross key 12 and the OK button 13 while confirming the preview image.

  FIG. 3 shows the configuration of the digital camera. An operation signal corresponding to the operation of the release button 5 and the operation unit 8 is input to the system controller 15, and the system controller 15 controls each unit of the digital camera based on the operation signal.

  A CCD image sensor 16 is disposed behind the photographic lens 3. The CCD image sensor 16 is driven by a driver 17 and outputs a photographed subject image as a photographing signal. As will be described later, the CCD image sensor 16 includes a high-sensitivity imaging signal in which one light-receiving unit is composed of a high-sensitivity light-receiving element and a low-sensitivity light-receiving element. And a low-sensitivity photographing signal obtained by photographing a subject image with a low-sensitivity light receiving element. The CCD image sensor 16 outputs, for example, a high-sensitivity shooting signal for one frame and then a low-sensitivity shooting signal for one frame.

  Similarly to the conventional color CCD image sensors, for example, R (red), G (green), and B (blue) color filters are provided in a mosaic pattern in each light receiving portion of the CCD image sensor 16. ing. An imaging signal including R, G, and B color components from the CCD image sensor 16 is input to the analog signal processing unit 18. The analog signal processing unit 18 removes noise by correlated double sampling (CDS), separates the R, G, and B analog signals from the input photographing signal, and separates the separated analog signals from the respective colors. For each color, processing for generating an analog signal for one frame and signal amplification are performed and output.

  Each color analog signal from the analog signal processing unit 18 is sent to an A / D converter 19. The A / D converter 19 digitally converts the analog signals of the respective colors and sends the obtained image data of the respective colors to the image processing unit 20. The processing by the analog signal processing unit 18 and the A / D converter 19 is similarly performed on each of the high-sensitivity imaging signal and the low-sensitivity imaging signal. Therefore, three color image data for one frame (hereinafter referred to as high sensitivity image data) captured by each high sensitivity light receiving element and three color images for one frame captured by each low sensitivity light receiving element. Data (hereinafter referred to as low-sensitivity image data) is sequentially output from the A / D converter 19.

  The image processing unit 20 performs normal processing including white balance correction processing and gamma correction on the image data, and synthesis processing for generating an image having a wide dynamic range from the high sensitivity image data and the low sensitivity image data. The image processing unit 20 is connected to a buffer memory 21 for temporarily storing various image data when performing the composition processing.

  When the LCD 7 operates as a viewfinder, the image processing unit 20 performs normal processing on, for example, sequentially inputted high-sensitivity image data, and sequentially obtains image data of each color to the display control unit 22. By sending the image, the subject image being shot is displayed as a moving image on the LCD 7. Note that when the subject image being photographed is displayed as a moving image on the LCD 7, an image subjected to the synthesis process may be displayed.

  In addition, when the release button 5 is pressed, the image processing unit 20 performs normal processing on the high-sensitivity image data and the low-sensitivity image data obtained in response to the operation, and then stores them in the buffer memory 21. Once written, the high-sensitivity image data and the low-sensitivity image data are sequentially read out from the buffer memory 21 to perform the combining process, and the added image data obtained by the combining process is sent to the display control unit 22 to the LCD 7. Display a preview image.

  The synthesis process includes an addition process and a gradation width compression process. In the addition process, high-sensitivity image data and low-sensitivity image data corresponding to each other, that is, addition image data obtained by adding high-sensitivity image data and low-sensitivity image data of the same pixel are calculated. In this addition processing, the low-sensitivity image data multiplied by the addition magnification n is added to the high-sensitivity image data. The gradation width compression process compresses the gradation width of the added image data for one frame that is expanded by adding high-sensitivity image data and low-sensitivity image data to a predetermined gradation width (for example, a gradation width of 10 bits). To do.

  The addition magnification n used in the addition process is increased or decreased by the system controller 15 in response to the operation of the cross key 12 of the operation unit 8. Whenever the addition magnification n is changed, the image processing unit 20 performs a composition process at the changed addition magnification n, and sends the result to the display control unit 22. As a result, a preview image based on the changed addition magnification n is displayed on the LCD 7. In this way, the result by the addition magnification n set by the user can be confirmed before saving to the memory card 9.

  When the OK button 13 of the operation unit 8 is pressed while the preview image is displayed, the image processing unit 20 changes the data format, for example, for the added image data synthesized using the addition magnification n at that time, for example, After conversion to JPEG format and data compression, the data is written to the memory card 9.

  The display control unit 22 displays the image on the LCD 7 by driving the LCD 7 based on the input image data. Further, when displaying the preview image, the display control unit 22 displays the operation guidance and the addition magnification n on the LCD 7 on the LCD 7 under the control of the system controller 15.

  The timing generator 24 sends clock signals to the driver 17, the analog signal processing unit 18, the A / D converter 19, and the image processing unit 20 to synchronize the operations of these units.

  The configuration of the CCD image sensor 16 is schematically shown in FIG. The CCD image sensor 16 is a so-called honeycomb CCD, and each light receiving portion 30 has an octagonal shape. Each light receiving unit 30 includes a pair of light receiving elements 31 and 32. In this example, the light receiving area of the light receiving element 31 is increased and the light receiving element 32 has a smaller light receiving area, so that the light receiving element 31 has a relatively high sensitivity and the light receiving element 32 has a low sensitivity. The sensitivity may be varied depending on the method.

  A vertical transfer path 33 is provided for each column of the light receiving units 30, and a horizontal transfer path 34 is provided at the end of each vertical transfer path 33 in the transfer direction. Each vertical transfer path 33 distinguishes between charges accumulated in the light-sensitive element 31 having high sensitivity and those accumulated in the light-sensitive element 32 having low sensitivity, and moves them to the vertical transfer path 33. A transfer electrode for moving the charged charges toward the horizontal transfer path 34 is provided. The horizontal transfer path 34 is provided with transfer electrodes for moving the charges transferred from the vertical transfer paths 33 along the transfer paths.

  By applying a voltage to each transfer electrode at a predetermined timing, the charges accumulated in the light receiving elements 31 and 32 are serially read from the horizontal transfer path toward the output amplifier. Each charge is converted into a voltage corresponding to the amount of charge by the output amplifier 35 and output as a photographing signal. This charge reading is first performed from the high-sensitivity light receiving element 31, and after the charge reading of all the light receiving elements 31 is completed, the charge reading of the low sensitivity light receiving element 32 is performed. As a result, a high-sensitivity shooting signal and a low-sensitivity shooting signal are output frame by frame.

  Note that the configuration of the CCD image sensor is not limited to the above, and it is sufficient that the CCD image sensor includes a high-sensitivity and a low-sensitivity light-receiving element, and the imaging signal of each sensitivity can be output in a separable manner. Each photographing signal may be output. For example, the high-sensitivity imaging signal and the low-sensitivity imaging signal may be separated and output in parallel from the corresponding output terminals. In this case, two analog signal processing units and A / D converters may be provided to perform signal processing in parallel, and high-sensitivity image data and low-sensitivity image data may be input in parallel to the image processing unit. Alternatively, a high-sensitivity imaging signal and a low-sensitivity imaging signal may be output alternately for each line.

  Further, the image sensor may not be a honeycomb CCD, but may be other than a CCD image sensor. Furthermore, in this example, the high-sensitivity image data and low-sensitivity image data obtained by digitally converting each photographic signal as described above are added, but similar processing may be performed using an analog signal.

  The display state of the preview image is shown in FIG. When the preview image 35 is displayed on the LCD 7, an addition magnification display 36 and an operation guide 37 are displayed on top of each other. The addition magnification display 36 indicates the set addition magnification n. The operation guide 37 includes a display 37a showing a key for increasing the addition magnification n, a display 37b showing a key for reducing the addition magnification n, and a display 37c showing a key for confirming the addition magnification n and instructing data storage. Consists of. In this example, the addition magnification n is increased by the up operation of the cross key 12, and the addition magnification n is decreased by the down operation. Further, the addition magnification n is determined by operating the OK button 13, and the added image data that has been subjected to the synthesis process is recorded in the memory card 9.

  In FIG. 6, symbol H is an input / output characteristic on the high sensitivity side, and indicates the relationship between the amount of light incident on the light receiving unit 30 and the gradation indicated by the high sensitivity image data. Reference numeral L is an input / output characteristic on the low sensitivity side, and indicates the relationship between the amount of light incident on the light receiving unit 30 and the gradation indicated by the low sensitivity image data. Further, symbols A, B, and C indicate input / output characteristics when the addition processing is performed with the addition magnification n set to “2.0”, “1.0”, and “0.5”, respectively. Note that the amount of light incident on the light receiving unit 30 corresponds to the subject brightness, but the relationship between the amount of incident light and the subject brightness varies depending on the aperture value at the time of the shutter speed.

  The charge accumulation amount of the high-sensitivity light receiving element 31 is saturated with the incident light quantity Q1, and even if more light quantity enters the light receiving unit 30, the high-sensitivity image data H has a constant value and does not change. That is, the gradation is not reproduced in a high luminance area brighter than the subject luminance corresponding to the incident light quantity Q1. The charge accumulation amount of the other low-sensitivity light receiving element 32 does not saturate the incident light amount Q2 larger than the incident light amount Q1, and the gradation is reproduced with the low-sensitivity image data up to the high luminance region corresponding to the incident light amount Q2. . Note that the high-sensitivity imaging signal may be limited to a predetermined level in order to prevent the occurrence of pattern noise due to variations in the saturation charge amount of each high-sensitivity light receiving element 31.

  By adding the high-sensitivity image data obtained from each of the light-receiving elements 31 and 32 to the low-sensitivity image data, it is possible to reproduce gradations in a high luminance region that cannot be reproduced by the high-sensitivity light-receiving elements 31 alone. In this addition, by adding the low-sensitivity image data multiplied by the addition magnification n set by the user, the relationship between the change amount of the gradation with respect to the change amount of the incident light amount in the high luminance range, that is, the input By changing the output characteristics, the gradation reproducibility in the high luminance range can be arbitrarily set according to the user's preference and intention.

  For example, as the addition magnification n is increased, the contrast in the high luminance area can be increased and the gradation width allocated to the high luminance area can be increased. Conversely, the smaller the addition magnification n, the weaker the contrast in the high luminance region, and the narrower the gradation width assigned to the high luminance region, the more important is the gradation reproducibility in the lower luminance region. Can do.

  For example, as shown in the figure, when the addition magnification n is “2”, the contrast in the high luminance region is stronger than that in the case where the addition magnification n is “1”, and the gradation width assigned to the high luminance region is larger. Become wider. By increasing the addition magnification n in this way, it becomes possible to highlight the image portion in the high luminance region. On the other hand, when the addition magnification n is “0.5”, the contrast in the high luminance region is weaker than in the case where the addition magnification n is “1”, and the gradation width allocated to the high luminance region is reduced. Accordingly, the gradation width assigned to the lower luminance range is increased accordingly.

  It should be noted that the addition magnification n may be set to a value of “0” or more from the viewpoint of improving the gradation reproducibility in the high luminance region, but a negative value may be selected.

  Next, the operation of the above configuration will be described. When the release button 5 is pressed in the shooting mode, the electronic shutter of the CCD image sensor 16 is opened in response to this, and exposure for one frame is performed. That is, photoelectric conversion is performed by the high sensitivity light receiving elements 31 and the low sensitivity light receiving elements 32 of the CCD image sensor 16, and charges corresponding to the amount of incident light are accumulated.

  When a predetermined shutter time elapses and the electronic shutter is closed, the charge of each highly sensitive light receiving element 31 is read, and a highly sensitive photographing signal is output from the CCD image sensor 16. Subsequently, the charge of each light receiving element 32 with low sensitivity is read, and a low sensitivity photographing signal is output from the CCD image sensor 16.

  The high-sensitivity photographing signal output from the CCD image sensor 16 is converted into an analog signal of three colors via the analog signal processing unit 18, and each analog signal is digitally converted by the A / D converter 19 to obtain high-sensitivity image data. It is said. Then, high-sensitivity image data for one frame from the A / D converter 19 is input to the image processing unit 20, subjected to normal processing by the image processing unit 20, and written to the buffer memory 21.

  After the high-sensitivity image data is written in the buffer memory 21, a low-sensitivity shooting signal is output from the CCD image sensor 16, and the low-sensitivity shooting signal is analog signal processing unit 18 and A / D converted in the same manner as the high-sensitivity shooting signal. The low-sensitivity image data for one frame is sent to the image processing unit 20 via the device 19. The low-sensitivity image data is written in the buffer memory 21 after being subjected to normal processing by the image processing unit 20.

  After the high-sensitivity image data and the low-sensitivity image data are written in the buffer memory 21 as described above, the high-sensitivity image data and the low-sensitivity image data are sequentially read out by the image processing unit 20, and the low-sensitivity image data is read. The data is multiplied by an initial value of a preset addition magnification n, for example, “1.0”, and high sensitivity image data corresponding to the multiplied low sensitivity image data is added to obtain addition image data.

  When the above addition processing is completed, the image processing unit 20 compresses the gradation width of each addition image data so that the gradation width of the addition image data for one frame examined during the addition processing becomes a gradation width of, for example, 10 bits. Process. In this way, the added image data obtained by the synthesizing process including the adding process and the gradation width compressing process is written in the buffer memory 21 and sent to the display control unit 22.

  When the added image data is sent to the display control unit 22, a preview image 35 based on the added image data is displayed on the LCD 7 as shown in FIG. And an operation guide 37 are displayed. In FIG. 7, the addition magnification display 35 has the addition magnification n of “1.25”, but if the addition magnification n is set to “1.0” as described above, the addition magnification display 35 is “N: 1.0 times”.

  The photographer observes the photographing preview image 35 displayed on the LCD 7 and confirms the reproducibility of the gradation in the high luminance region, the balance with other luminance regions, and the like. If the desired gradation reproducibility is not achieved, the up / down operation of the cross key 12 is performed to increase or decrease the addition magnification n. When the up operation is performed here, the addition magnification n increases in a predetermined step. When the down operation is performed, the addition magnification n decreases in a predetermined step, and the value is displayed on the addition magnification display 35. If high sensitivity image data is to be recorded as it is, “0” may be designated as the addition magnification n.

  When the above operation is performed, the addition magnification n designated by the operation is sent from the system controller 15 to the image processing unit 20, and the addition processing and gradation width compression are performed by the same procedure as described above using the addition magnification n. A composition process consisting of processes is performed. Then, the addition image data in the buffer memory 21 is updated to the newly obtained addition image data, and the new addition image data is sent to the display control unit 22. As a result, an image that has been subjected to the composition process using the changed addition magnification n is displayed on the LCD 7 as a preview image 35.

  In this way, while observing the preview image 35 displayed on the LCD 7, the cross key 12 is operated to change the addition magnification n, and if the desired gradation reproducibility is obtained, the OK button 13 is operated. And instruct to save.

  When the OK button 13 is operated, the image data for one frame recorded in the buffer memory 21 at that time is read out by the image processing unit 20, converted into JPEG format, and subjected to data compression. To the memory card 9. As a result, an image created at the addition magnification n set by the user and having an expanded dynamic range is recorded on the memory card 9. Since the addition magnification n can be arbitrarily set in this way, the user's preference. An image with the intended gradation reproducibility can be obtained.

  The example shown in FIGS. 7 and 8 shows an example in which the addition start point as the lower limit value to be added to the low-sensitivity image data to be added to the high-sensitivity image data can be designated by the user's operation. The configuration of the digital camera is the same as that of the above embodiment except that the function of an image processing unit described below is different.

In this example, the addition start point m is increased or decreased by left and right operations of the cross key 13. The addition start point m is specified by a ratio of the incident light amount, for example, where the incident light amount Q2 at which the charge accumulation amount of the low sensitivity light receiving element 32 is saturated is 100%. As shown in FIG. 7, the image processing unit 20 adds only low-sensitivity image data having a value DL ₀ or more of the low-sensitivity image data corresponding to the designated addition start point m to the corresponding high-sensitivity image data. In addition, the image processing unit 20 adds the relative low-sensitivity image data value DL ₁ that sets the value of the low-sensitivity image data corresponding to the addition start point m to “0” to the high-sensitivity image data. To do. Reference sign D indicates the input / output characteristics after the addition process.

  As shown in FIG. 8, the preview image 35 is displayed on the LCD 7 on the LCD 7 as in the above embodiment. When the preview image 35 is displayed on the LCD 7, an addition start point display 41 and an operation guide 42 are displayed on top of each other. The addition start point display 41 indicates the set addition start point m. The operation guide 42 includes a display 42a indicating a key for increasing the addition start point m, a display 42b indicating a key for decreasing the key, and a key for confirming the addition start point m and instructing data storage. Display 42c.

  In this example, the addition start point m is increased by the right operation of the cross key 12, and the addition start point m is decreased by the left operation. Further, the addition start point m is determined by operating the OK key 13, and the added image data that has been subjected to the synthesis process is recorded in the memory card 9.

  According to the above configuration, the gradation reproducibility over the luminance corresponding to the addition start point m can be changed, and the user can arbitrarily set the addition start point m. An image with high gradation reproducibility can be obtained.

  In the above embodiment, the lower limit value of the low-sensitivity image data to be added to the high-sensitivity image data is set. However, the lower limit value and the upper limit value are set, and the low-sensitivity data in a specific range is set to the high sensitivity value. You may add to image data. In each of the above embodiments, the example in which only the addition magnification n and the addition start point m are set has been described. However, both the addition magnification n and the addition start point m may be set.

It is an external view which shows the front side of the digital camera which implemented this invention. It is an external view which shows the back side of a digital camera. It is a block diagram which shows the electrical structure of a digital camera. It is explanatory drawing which shows the structure of a CCD image sensor typically. It is explanatory drawing which shows the display state of a preview image. It is a graph explaining addition of low sensitivity image data and high sensitivity image data. An example in which an addition start point is designated and low sensitivity image data and high sensitivity image data are added is shown. It is explanatory drawing which shows the display state of the preview image in the example shown in FIG.

Explanation of symbols

7 LCD
8 Operation section 16 Image sensor 20 Image processing section 30 Light receiving section 31, 32 Light receiving element 35 Preview image

Claims (4)

An image sensor in which a large number of light receiving portions each composed of a first light receiving element having a relatively high sensitivity and a second light receiving element having a low sensitivity are arranged; a high sensitivity image signal obtained from the first light receiving element; In a digital camera equipped with an image processing unit that generates an image having a wide dynamic range by adding the low-sensitivity image signals obtained from the elements with corresponding ones,
A setting unit configured to set an addition magnification used when the low-sensitivity image signal is added to the high-sensitivity image signal, and is operated from outside; A digital camera characterized by adding a sensitivity image signal to a corresponding high-sensitivity image signal. An image sensor in which a large number of light receiving portions each composed of a first light receiving element having a relatively high sensitivity and a second light receiving element having a low sensitivity are arranged; a high sensitivity image signal obtained from the first light receiving element; In a digital camera equipped with an image processing unit that generates an image having a wide dynamic range by adding the low-sensitivity image signals obtained from the elements with corresponding ones,
A setting unit configured to set a lower limit value of the low-sensitivity image signal to be added to the high-sensitivity image signal, which is operated from the outside, wherein the image processing unit has the low-sensitivity image signal equal to or higher than the lower limit value set by the setting unit; Is added to the corresponding high-sensitivity image signal.   The digital camera according to claim 2, wherein the image processing unit adds the magnitude of the low-sensitivity image signal relative to the lower limit set by the setting unit to the corresponding high-sensitivity image signal.   The digital camera according to claim 1, further comprising display means for displaying an image generated by the image processing unit.

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