JP4105933B2 - Digital camera and image generation method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a digital camera.
[0002]
[Prior art]
An image sensor such as a CCD used in a digital camera has a relatively narrow dynamic range. Therefore, if a digital camera is used to shoot a scene with a very large difference between light and dark, for example, a scene in which a person is backlit, the person becomes too dark or the background becomes too bright. In this case, to reduce the difference in brightness between the person and the background, for example, when the flash is turned on and daytime synchro shooting is performed, the white balance of the image is lost due to the color temperature difference between the flashlight and natural light, Unnaturalness may remain in the image.
[0003]
As a means for solving such problems, image data of proper exposure, image data of underexposure, and image data of overexposure are recorded by one shooting, and these image data are recorded according to the luminance difference. It is known to synthesize (see, for example, Patent Document 1). However, in this method, three pieces of image data of proper exposure, underexposure, and overexposure are required, and the synthesis process takes time. In addition, it is difficult to change the shooting conditions depending on the situation of the shooting scene, for example, the difference in brightness, and as a result, there may be a case where the correction effect by image synthesis cannot be obtained greatly.
[0004]
[Patent Document 1]
Japanese Patent Laid-Open No. 11-317905
[0005]
[Problems to be solved by the invention]
The present invention has been made in view of the above-described problems. For example, even when a subject has a large difference in contrast between light and dark as in a case where the subject is backlit, a bright portion is determined according to the difference in brightness. The main purpose is to be able to properly capture both dark and dark areas.
[0006]
[Means for Solving the Problems]
The digital camera according to the present invention includes a photometric unit that divides an observation screen into a plurality of regions and detects a photometric value of a subject to be photographed for each region, and a first photometry having a relatively large value from the photometric value for each region. A photometric value selecting means for selecting a second photometric value having a relatively small value, a first exposure condition is determined in accordance with the first photometric value, and a second in accordance with the second photometric value. An exposure condition determining means for determining the exposure condition, a first photographing means for photographing a photographing object by the first exposure condition and obtaining a first original image, and a photographing object by the second exposure condition, A second imaging unit that obtains a second original image; a first image area having a pixel luminance greater than a predetermined value; and a second image area having a luminance smaller than a predetermined value in the first or second original image. And an image area dividing means for dividing the first image area and the first original image included in the first image area Characterized in that it comprises an image synthesizing means for synthesizing the second original images included in the second image region.
As a result, a natural image can be obtained even when there is a large difference in brightness between the areas to be imaged, such as when the subject is in a backlight state.
[0007]
Preferably, the first photometric value is the maximum photometric value for each region, and the second photometric value is the minimum photometric value for each region.
[0008]
The aperture value in the first and second imaging means is determined according to the second photometric value, and the exposure time in the first and second imaging means is determined according to the first and second exposure conditions and the aperture value. You may make it the structure to carry out. In other words, by making the aperture values of the first photographing means and the second photographing means the same, the second photographing can be instantaneously performed from the first photographing, so that the obtained first and second originals can be obtained. Images can be generated from substantially the same shooting target.
[0009]
When the shutter speed (exposure time) of the first photographing means is longer than the shutter speed of the second photographing means, photographing by the first photographing means is performed before photographing by the second photographing means. Thereby, since the time lag of the second shooting can be reduced, the difference between the shooting targets of the first shooting and the second shooting can be greatly reduced.
[0010]
The exposure condition determining means of the present invention preferably compares the first and second photometric values and is executed only when the difference is greater than a second predetermined value. Thereby, since image composition can be selectively performed, unnecessary image processing can be reduced. Moreover, it is preferable to set an average value of the luminance of the first original image and the luminance of the second original image as a predetermined value.
The first and second imaging means have the same imaging device and the same imaging optical system that forms an optical image to be imaged on the light receiving surface of the imaging device, and there are a plurality of photometric means. It consists of a light receiving sensor that has a divided light receiving surface and can output the amount of light received for each light receiving surface, while the observation screen is at a position different from the light receiving surface of the image sensor and receives light from the image sensor. A surface that is optically equivalent to the surface is preferable. According to this configuration, since the image signal of the image sensor is not used to obtain a photometric value, a photometric target can be measured quickly and accurately.
[0011]
The image generation method according to the present invention includes a photometric value detection step of detecting the photometric value of the imaging target for each region by dividing the observation screen into a plurality of regions, and a first value having a relatively large value from the photometric value for each region. The photometric value, a photometric value selection step for selecting a second photometric value having a relatively small value, a first exposure condition is determined according to the first photometric value, and the second photometric value is determined. An exposure condition determining step for determining a second exposure condition, a first imaging step for capturing an image of the imaging object by the first exposure condition and obtaining a first original image, and an imaging object for the second exposure condition. A second photographing step for photographing and obtaining a second original image; a first image region having a pixel luminance greater than a predetermined value in the first or second original image; and a second having a luminance smaller than the predetermined value. An image area dividing step for dividing the image area into a first image area and a first image Characterized in that it comprises an image synthesizing means for synthesizing the first original image included in the region, the second original image included in the second image region.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a perspective view of a digital camera to which an embodiment of the present invention is applied as viewed from the rear.
[0013]
This digital camera is a single-lens reflex camera, and the interchangeable lens 11 is attached to the camera body 90. An optical viewfinder 91 is provided at the center of the upper portion of the camera body 90, and a liquid crystal panel (image LCD) 46 is provided at the approximate center of the back surface 92. On the liquid crystal panel 46, a moving image obtained by the interchangeable lens 11, a captured still image, or the like is displayed. A mode setting switch 95 is provided beside the liquid crystal panel 46. The mode setting switch 95 is provided for setting various operation modes, and is a jog dial in the illustrated embodiment.
[0014]
When the camera body 90 is viewed from the back, a shutter button 93 and a status display device 56 are provided on the right side of the upper part of the camera body 90. The status display device 56 is composed of a liquid crystal display element, and various setting states of the digital camera are displayed as characters or symbols on the liquid crystal display element. When the shutter button 93 is half-pressed, photometry, distance measurement, etc. are performed, and when fully pressed, a still image is stored in the PC card and displayed on the liquid crystal panel 46.
[0015]
A card slot 96 is formed on the side surface of the camera body 90. The card slot 96 is provided for inserting a PC card into the camera body 90, and a card connector (not shown) into which the PC card is inserted is provided inside the card slot 96.
[0016]
FIG. 2 is a block diagram mainly showing an electrical configuration of the digital camera. The operation of this camera is controlled by a system controller 31 having a microcomputer. That is, under the control of the system controller 31, a moving image or a still image is displayed on the liquid crystal panel 46, and a still image is recorded on the PC card.
[0017]
The interchangeable lens 11 is electrically connected to an electric circuit provided in the camera body 90 (FIG. 1) via the mount pins 12, 13, and 14. In the lens barrel of the interchangeable lens 11, a front group lens 15 and a rear group lens 16 that are photographing optical systems are provided, and a diaphragm 17 is provided between these lenses 15 and 16. Focus adjustment for each of the lenses 15 and 16 is performed by a lens control circuit 18, and a zooming operation is performed by a zoom motor 19. The lens control circuit 18 and the zoom motor 19 operate according to control signals sent from the system controller 31 provided in the camera body via the mount pins 13 and 14. The diaphragm 17 operates in accordance with a control signal sent from the diaphragm drive circuit 32 provided in the camera body via the mount pin 12, and the opening degree of the diaphragm 17 is adjusted. The aperture drive circuit 32 is controlled by the system controller 31.
[0018]
A quick return mirror 21 is provided on the optical axis of the lenses 15 and 16 in the camera body. The mirror 21 is rotatable between the illustrated inclined state and the horizontal state rotated upward. A focus plate 22 is provided above the mirror 21, and a pentaprism 23 is provided above the focus plate 22. The eyepiece 24 of the finder 91 is disposed behind the pentaprism 23.
[0019]
A shutter 25 is provided behind the mirror 21, and an infrared cut filter 26 and an optical low-pass filter 27 are provided behind the shutter 25. A CCD (imaging device) 33 is provided behind the optical low-pass filter 27. That is, the optical low-pass filter 27 and the CCD 33 are disposed on the optical axes of the lenses 15 and 16.
[0020]
The rotation operation of the mirror 21 is driven by a mirror drive circuit 34, and the opening / closing operation of the shutter 25 is driven by a shutter drive circuit 35. The mirror drive circuit 34 and the shutter drive circuit 35 are controlled by the system controller 31.
[0021]
Normally, the mirror 21 is set in an inclined state, and guides light taken from the interchangeable lens 11 to the pentaprism 23 side. The focus plate 22 is located at a position different from the light receiving surface (imaging surface) of the CCD 33 and is disposed at a position optically equivalent to the light receiving surface of the CCD 33, and the user holds the pentaprism 23 and the eyepiece 24. Thus, the optical image on the focus plate can be visually recognized as an observation image, and the imaging state (focus adjustment state) of the light beam incident through the interchangeable lens 11 on the light receiving surface of the CCD 33 can be monitored. At this time, the shutter 25 is closed, and the optical path toward the CCD 33 is closed. On the other hand, when photographing is performed, the mirror 21 is rotated upward by the control of the mirror driving circuit 34 and becomes horizontal. With the rotation of the mirror 21, the shutter 25 is opened under the control of the shutter drive circuit 35, and the light taken from the interchangeable lens 11 is irradiated onto the light receiving surface of the CCD 33. That is, an image obtained by the lenses 15 and 16 is formed on the light receiving surface, and the CCD 33 generates an imaging signal corresponding to the image.
[0022]
A pulse signal generation circuit (PPG) 36 is connected to the system controller 31, and the pulse signal generation circuit 36 generates various pulse signals under the control of the system controller 31. Based on these pulse signals, the CCD drive circuit 37, the A / D converter 38, and the image signal processing circuit 39 are driven, and the CCD drive circuit 37 controls the operation of the CCD 33. That is, the image pickup signal read from the CCD 33 is converted into a digital signal by the A / D converter 38 and subjected to predetermined image processing in the image signal processing circuit 39. An image buffer memory 40 having a sufficient capacity for storing digital image data corresponding to one image is connected to the image signal processing circuit 39.
[0023]
A monitor interface 41 and a card interface 42 are connected to the image signal processing circuit 39. These interfaces 41 and 42 are controlled by the system controller 31.
[0024]
A backlight 45 and a liquid crystal panel 46 are connected to the monitor interface 41 via a liquid crystal drive circuit 44. In the liquid crystal panel 46, as described above, the liquid crystal driving circuit 44 is controlled based on the image data read from the image buffer memory 40, and a still image is displayed. A card connector 47 is connected to the card interface 42, and a PC card 43 can be attached to the card connector 47.
[0025]
An AF sensor 51, a photometric sensor 52, and an auto white balance (AWB) sensor 53 are connected to the system controller 31. The focus adjustment state of the lenses 15 and 16 is measured by the AF sensor 51. The photometric value (I ₀ To I _Four ) Is measured. The auto white balance sensor 53 measures the color temperature of the ambient light. The photometric sensor 52 is disposed in the vicinity of the eyepiece lens 24 and receives an optical image on the focus plate 22 via the pentaprism 23.
[0026]
The system controller 31 is connected to a photometric switch 54, a release switch 55, and a status display device 56. The metering switch 54 is turned on by half-pressing the shutter button 93, whereby the metering sensor 52 performs metering. The release switch 55 is turned on when the shutter button 93 is fully pressed, whereby the shutter 25 is driven to open and close. That is, the CCD 33 is exposed, and an imaging signal corresponding to the image is generated on the CCD 33.
[0027]
Further, a mode setting switch 95 is connected to the system controller 31. As described above, the mode setting switch 95 is a jog dial. When the jog dial is set at a predetermined rotational position, a predetermined mode is selected from the setting menu displayed on the liquid crystal panel 46, and when the jog dial is pressed, the mode is changed. Is set.
[0028]
FIG. 3 is a diagram showing the relationship between the observation screen 75 by the user and the photometric area by the photometric sensor 52. As described above, the focus plate 22 is disposed at a position optically substantially equivalent to the light receiving surface of the CCD 33, and the photometric area of the photometric sensor 52 is equal to the field of view of the observation screen 75 and the imaging area of the CCD 33 during the photographing operation. I'm doing it. As shown in FIG. 3, the observation screen 75 is a screen observed from the objective lens 24, and includes a region 0 that is a region at the center of the screen and regions 1 to 4 that divide the remaining region into four. The photometric sensor 52 has a light receiving portion corresponding to each area of the observation screen 75, and a photometric value (I ₀ To I _Four ) Is detected.
[0029]
Image generation of the present embodiment will be described with reference to FIG.
The subject 71 of the subject 72 is backlit, and the luminance of the subject 71 is very small compared to the luminance of the background 70. Conventionally, when the subject 71 is backlit in this way, for example, when shooting in the normal shooting mode of a digital camera, the background 70 is properly shot, whereas the subject 71 is shot as blackened. . On the other hand, when the subject 71 is photographed in the backlight photographing mode of the present embodiment, the resultant composite image 86 is properly photographed for both the subject 71 and the background 70.
[0030]
In the present embodiment, it is first determined whether or not the subject 72 is in a backlight state. That is, I mentioned above ₀ To I _Four First photometric value I having the maximum photometric value _max And the second photometric value I having the smallest photometric value _min Is selected. Selected first and second photometric values I _max , I _min Is larger than a certain value, it is determined that the subject 71 is backlit, and the photographing object 72 is photographed in the backlight photographing mode described below. If the difference is smaller than the certain value, the photographing object 72 is photographed in the normal photographing mode. Taken.
[0031]
When shooting in the backlight mode, the first and second photometric values I _max , I _min Determines the first and second exposure conditions. The photographing object 72 is photographed twice according to the determined exposure condition, and two original images 77 and 80 are obtained. In other words, the shooting target 72 is shot under the first exposure condition to obtain a first original image 77, and the shooting target 72 is shot under the second exposure condition to obtain a second original image 80.
[0032]
In the first exposure condition, the photometric value is the maximum value (I _max The first original image 77 is photographed with the exposure adjusted to the background 70 having a relatively high luminance. Therefore, while the background image 70 ′ is properly photographed, the subject image 71 ′ having a relatively low brightness is photographed as if it was shadowed and blackened because the exposure amount was too small.
[0033]
The second exposure condition is that the photometric value is the minimum value (I _min ), The second original image 80 is photographed in accordance with the subject 71 whose exposure is relatively low in luminance. Therefore, while the subject image 71 ″ is properly photographed, the background image 70 ″ having a relatively large luminance is photographed so that the outline is white because the exposure amount is too large.
[0034]
Next, the second original image 80 is divided into a first image area 81 in which the pixel luminance data is larger than a predetermined value and a second image area 82 in which the pixel luminance data is smaller than a predetermined value. Each pixel data of the divided original image 80 is converted into [1] in the first image area 81 and [0] in the second image area 82 to form a binarized mask image 85. To do.
[0035]
Next, the pixel data of the first original image 77 included in the first image area 81 and the pixel data of the second original image 80 included in the second image area 82 are combined to obtain a combined image 86. It is done. That is, the pixel data of the area [0] in the binarized mask image 85 is extracted from the second original image 80, and the pixel data of the area [1] is extracted from the first original image 77 and extracted. A composite image 86 is obtained by combining the pixel data. In other words, the background image 70 ′ of the first original image 77 with appropriate luminance and the subject image 71 ″ of the second original image 80 with appropriate luminance are combined to obtain a combined image 86. .
[0036]
As described above, in the present embodiment, the composite image 86 is formed by combining the appropriate areas of the exposure conditions of the two original images 77 and 80 obtained by photographing with different exposure conditions. As in the case of the above, the background 70 which is a bright part and the subject 71 which is a dark part are clearly expressed images.
In the present embodiment, the mask image 85 is generated based on the second original image 80. However, the mask image 85 may be generated based on the first original image 77.
[0037]
FIG. 5 is a flowchart of the photographing operation routine in the present embodiment. In step 100, it is determined whether or not the photometric switch 54 is on. If the photometric switch 54 is on, the process proceeds to step 110, and if not, the process returns to step 100. In step 110, as described above, the photometric value (I ₀ To I _Four ) Is detected. Detected I ₀ ~ I _Four To the first photometric value I which is the maximum value in step 111 _max And the minimum second photometric value I _min Is selected.
[0038]
In step 120, the first photometric value I _max And the second photometric value I _min Are compared, and the difference is a predetermined value I _th It is determined whether or not it is larger. The difference is a predetermined value I _th If it is determined that the value is smaller, the process proceeds to step B, and the shooting of the shooting target 72 is performed in the normal shooting mode. On the other hand, the difference is a predetermined value I _th If it is determined that it is larger, the process proceeds to step 130, and the photographing object 72 is photographed in the backlight photographing mode.
[0039]
In steps 130 to 150, the first photometric value I _max In accordance with the first exposure condition for obtaining the first original image 77 is the second photometric value I. _min Accordingly, the second exposure condition for obtaining the second original image 80 is determined. In the present embodiment, first, in step 130, the second photometric value I _min To the CCD sensitivity Sv, the exposure value Ev in the second exposure condition ₂ Is calculated. In step 140, the calculated Ev ₂ Accordingly, the shutter speed Tv used when the second original image 80 is obtained from the combination of the shutter speed and the aperture value stored in the system controller 31 in advance. ₂ The aperture value Av is selected.
[0040]
The aperture value Av selected here is also used when obtaining the first original image 77. Accordingly, in step 150, the first photometric value I _max The exposure value Ev under the first exposure condition in consideration of the CCD sensitivity Sv ₁ Is calculated and its Ev ₁ And the shutter speed Tv used when obtaining the first original image 77 from the aperture value Av. ₁ Is calculated.
[0041]
In step 151, it is confirmed again whether or not the photometric switch 151 is in the ON state. If it is on, the process proceeds to step 160. If it is not on, the process returns to step 100. In step 160, it is determined whether or not the release switch 55 is on. If the release switch 55 is in the ON state, the process proceeds to step 170 and the photographing operation is started. If the switch 55 is not on, the process returns to step 100.
[0042]
In step 170, the quick return mirror 21 is mirrored up. With the mirror up, in step 180, the diaphragm 17 is driven in accordance with the aperture value Av, and in step 190, the shutter speed Tv is driven. ₁ The shutter 25 is opened for a time corresponding to the above. Thereby, the light taken in from the interchangeable lens 11 is irradiated on the light receiving surface of the CCD 33, and the CCD 33 receives Av and Tv. ₁ In step 200, the RGB data of the first original image 77 generated in accordance with the signal is stored in the image buffer memory 40.
[0043]
In step 210, the shutter speed Tv is again reached. ₂ The shutter 25 is opened for a time corresponding to the above. As a result, light is again taken into the CCD 33 by the interchangeable lens 11, and Av and Tv in the CCD 33. ₂ In step 220, the RGB data of the second original image 80 generated in accordance with the signal is stored in the image buffer memory 40. Thereby, different original images 77 and 80 corresponding to different exposure conditions are generated for the same photographing object 72.
[0044]
Next, in step 230, the diaphragm 17 is opened to the initial state, and in step 240, the quick return mirror 21 is mirrored down, the photographing operation is terminated, and the process proceeds to step A to start image processing.
[0045]
FIG. 6 shows an image processing routine performed by the image signal processing circuit 39 of the original images 77 and 80 obtained by the photographing operation. The RGB data of the original images 77 and 80 stored in the memory 40 are converted into luminance / color difference image data (Y ₁ , Cb ₁ , Cr ₁ ), (Y ₂ , Cb ₂ , Cr ₂ ).
[0046]
In step 270, the obtained luminance data Y ₁ , Y ₂ Is obtained as a predetermined threshold value. That is, the luminance data Y which is the average value of all the pixels of the original images 77 and 80, respectively. _1AVE , Y _2AVE (Y _1AVE + Y _2AVE ) / 2 is a predetermined threshold value.
[0047]
In step 280, luminance / color difference image data (Y ₂ , Cb ₂ , Cr ₂ The second original image 80 converted into () is binarized using a predetermined threshold. That is, the luminance data Y of each pixel of the second original image 80 ₂ However, if it is larger than the threshold value calculated in step 270, the pixel is converted to [1] data, and if it is smaller than the threshold value, the pixel is converted to [0] data, and a mask image 85 is obtained.
[0048]
In step 290, pixel image data corresponding to the data [1] of the mask image 85 is extracted from the first original image 77, and the data [0] of the mask image 85 is converted from the second original image 80. Corresponding pixel image data is extracted, and the extracted image data is combined to generate a combined image 86. The generated image data of the composite image 86 is stored in the image buffer memory 40.
[0049]
The composite image 86 is displayed on the liquid crystal panel 46 in step 300. In step 310, the image data of the composite image 86 is JPEG encoded and then recorded in the PC card 43 in step 320, and the image generation routine ends.
[0050]
FIG. 7 shows a shooting and image processing routine in the normal shooting mode. First, in step 410, the metering mode is confirmed. If the metering mode is the center-weighted metering mode, the process proceeds to step 420. If the metering mode is the average metering mode, the process proceeds to step 430. In step 420, the photometric value I of region 0 ₀ The exposure condition corresponding to is calculated, and the process proceeds to step 440. On the other hand, in step 430, the photometric values I in regions 0 to 4 are displayed. ₀ To I _Four Average value up to _ave In step 431, I _ave The exposure condition corresponding to is calculated, and the process proceeds to step 440.
[0051]
In step 440, it is determined again whether or not the photometric switch 54 is in the on state. If it is in the on state, the process proceeds to step 450, and if it is not in the on state, the process returns to step 100. Next, at step 450, it is determined whether or not the release switch 56 is on. If it is not on, the process returns to step 440, and if it is on, the process proceeds to step 460.
[0052]
In step 460, the mirror 21 is mirrored up, and in accordance with the mirror up, in step 470, the aperture 17 is driven by the aperture value based on the exposure condition calculated in step 420 or 431. In step 490, the shutter 25 is opened for a time corresponding to the shutter speed based on the exposure condition. Thereby, the light taken in from the interchangeable lens 11 is irradiated on the light receiving surface of the CCD 33, and the CCD 33 generates an image pickup signal of the shooting target 72 according to the aperture value and the shutter speed. The generated RGB data of the original image is stored in the image buffer memory 40.
[0053]
After the image data is stored, in step 500, the diaphragm 17 is opened to the initial state, and in step 510, the mirror 21 is mirrored down, and the photographing operation ends.
[0054]
Next, at step 520, the captured image data is subjected to image processing by the image signal processing circuit 39. That is, Y, Cb, and Cr data are generated from the RGB data, and the generated data is stored in the image buffer memory 40.
[0055]
The stored data is displayed on the liquid crystal panel 46 at step 530 and the image corresponding to the data is displayed on the PC card 43 at step 550 after being JPEG-encoded at step 540. Ends.
[0056]
As described above, in the present embodiment, when the luminance difference for each region in the observation image is large, for example, when the subject is backlit, the mode is automatically set to the backlit mode. As a result, two shootings are performed on the same shooting target, and two original image data are obtained. By combining the image data of the appropriate areas of the exposure conditions in each data, it can be seen with the naked eye. It is possible to obtain a natural image close to the captured image.
[0057]
In steps 130 to 150 of the present embodiment, the aperture value Av is the same (fixed) and the shutter speed Tv is set so that the exposure conditions are different in the two shootings. ₁ , Tv ₂ The only difference is that This is to eliminate the time lag between the first shooting and the second shooting so that the shooting targets of the first shooting and the second shooting are not shifted as much as possible.
Controlling the aperture 17 to the aperture corresponding to the aperture value Av requires a relatively long time, and for the pixel signal transfer at the time of the first shooting, the shutter must be once closed and then opened again. The control becomes complicated. That is, when the aperture value Av is changed, a long time lag occurs between the first shooting and the second shooting, and when the shooting target 72 moves, the original image 77 for the same shooting target 72 is generated. , 80 is not obtained. Therefore, in this embodiment, the aperture value Av is fixed.
[0058]
In Steps 190 to 220, the shooting under the first exposure condition is performed prior to the shooting under the second shooting condition. ₁ Is Tv ₂ This is because the time lag between the first shooting and the second shooting can be eliminated if the shooting under the first exposure condition is performed prior to the second exposure condition.
[0059]
Further, in step 111, the detected I ₀ ~ I _Four The first photometric value I which is the maximum value from _max And the minimum second photometric value I _min Is selected because it is effective as the gradation control of the finally obtained image, and the photometric value I to be selected is selected. _max , I _min I _max Is I _min For example, the second value from the maximum value and the second value from the minimum value may be used.
In the present embodiment, since the photometric operation is performed using the photometric sensor 52 without using the imaging signal from the CCD 33 as the photometric means, complicated image signal processing is performed for photometry and exposure calculation. Since it is not necessary to perform this, the photometry operation can be quickly shifted to the photographing operation.
[0060]
In the present embodiment, the photometric value I _max And I _min In the above-described configuration, the photographing and the image generation are performed in the backlight photographing mode when the difference is larger than the predetermined value. However, the mode setting switch 95 is used to manually determine whether the backlight photographing mode is selected. good.
[0061]
In this specification, for example, “greater than a predetermined value” and “smaller than a predetermined value” are not mathematically strict meanings, and include cases of “greater than a predetermined value” and “below a predetermined value”.
[0062]
【The invention's effect】
As described above, according to the present invention, it is possible to appropriately capture both a bright part and a dark part on one image even when there is a large difference in brightness of a subject to be photographed, for example, in a backlight state.
[Brief description of the drawings]
FIG. 1 is a perspective view of a digital camera according to an embodiment of the present invention as viewed from the rear.
FIG. 2 is a block diagram mainly showing an electrical configuration of the digital camera.
FIG. 3 shows a photometric area in an embodiment of the present invention.
FIG. 4 is a diagram for explaining image generation in the embodiment of the present invention.
FIG. 5 is a flowchart of a shooting operation routine of the digital camera.
FIG. 6 is a flowchart of an image processing routine of the digital camera.
FIG. 7 is a flowchart of a shooting and image processing routine in a normal shooting mode.
[Explanation of symbols]
77 The first original image
80 Second original image
81 First image area
82 Second image area
86 Composite Image

Claims (8)

A photometric means for dividing the observation screen into a plurality of areas and detecting a photometric value of an imaging target for each area;
Photometric value selection means for selecting a first photometric value having a relatively large value from the photometric values for each region, and a second photometric value having a relatively small value;
Exposure condition determining means for determining a first exposure condition according to the first photometric value and determining a second exposure condition according to the second photometric value;
First photographing means for photographing the photographing object according to the first exposure condition and obtaining a first original image;
A second photographing means for photographing the photographing object according to the second exposure condition and obtaining a second original image;
Image area dividing means for dividing the first or second original image into a first image area having a pixel luminance greater than a predetermined value and a second image area having a luminance smaller than a predetermined value;
A digital camera comprising: the first original image included in the first image region; and an image combining unit that combines the second original image included in the second image region. 2. The digital camera according to claim 1, wherein the first photometric value is a maximum photometric value for each region, and the second photometric value is a minimum photometric value for each region. . Determining an aperture value in the first and second imaging means according to the second photometric value;
2. The digital camera according to claim 1, wherein exposure times in the first and second photographing means are determined according to the first and second exposure conditions and the aperture value. 4. The digital camera according to claim 3, wherein photographing by the first photographing unit is performed prior to photographing by the second photographing unit. 2. The digital camera according to claim 1, wherein the exposure condition determining unit compares the first and second photometric values, and is executed only when the difference is larger than a second predetermined value. The digital camera according to claim 1, wherein an average value of the luminance of the first original image and the luminance of the second original image is set as the predetermined value. The first and second imaging means have the same imaging device and the same imaging optical system that forms an optical image of the imaging target on the light receiving surface of the imaging device,
The photometric means comprises a light receiving sensor having a plurality of light receiving surfaces and capable of outputting the amount of light received for each light receiving surface, while the observation screen is located at a position different from the light receiving surface of the image sensor. The digital camera according to claim 1, wherein the digital camera is a surface optically equivalent to a light receiving surface of the image sensor. A photometric value detection step for dividing the observation screen into a plurality of areas and detecting a photometric value of a photographing target for each area;
A photometric value selection step of selecting a first photometric value having a relatively large value from the photometric values for each region and a second photometric value having a relatively small value;
An exposure condition determining step of determining a first exposure condition in accordance with the first photometric value and determining a second exposure condition in accordance with the second photometric value;
A first photographing step of photographing the photographing object according to the first exposure condition to obtain a first original image;
A second photographing step of photographing the photographing object according to the second exposure condition to obtain a second original image;
An image area dividing step of dividing the first or second original image into a first image area having a pixel luminance greater than a predetermined value and a second image area having a luminance smaller than a predetermined value;
An image generation method comprising: the first original image included in the first image region; and an image combining step of combining the second original image included in the second image region.

Images