Abstract:
The effect of a shadow created on the background of a subject by emitted light from a strobe is suppressed. To accomplish this so, a shadow created by strobe light emission is detected and the shadow is eliminated. Alternately, the size of shadow created by strobe light emission is previously evaluated using the distance between the camera lens and strobe X 0 , the distance to the subject L 1 , and the distance to the background L 2  and a warning is given if necessary. This allows the elimination of the shadow created by strobe light emission or allows compositional arrangement change when a large shadow is expected due to strobe light emission. Therefore, undesired shadow due to strobe light emission is suppressed. Shadow suppression is particularly useful for photographs for photo IDs. It can be also applicable to corrections of some features on the picked up image caused by strobe light emission.

Description:
CROSS-REFFERENCE TO RELATED APPLICATION  
         [0001]    This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2001-367604, filed Nov. 30, 2001. The entire contents of the application are incorporated herein by reference.  
         BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    The present invention relates to a camera that can emit strobe light onto a subject and evaluate the effect of a strobe light in a camera.  
           [0004]    2. Description of the Related Art  
           [0005]    It is traditionally well-known to emit strobe light onto a subject as supplementary light during exposure in the dark or under a backlight condition. However, when the main subject has a wall in the background and strobe light is used, a shadow may appear on the wall or the like behind the main subject. Such a shadow may appear, for example, when a regular camera is used to take a photograph for photo IDs such as passports, and may be distracting.  
           [0006]    The present invention is proposed in view of the above circumstances.  
         BRIEF SUMMARY OF THE INVENTION  
         [0007]    The camera according to the present invention detects a shadow created by strobe light emission in the photographic image that is taken with a strobe light emission on the subject, and eliminates the shadow. Otherwise, the size of a shadow to be created by the strobe is calculated before taking a photograph with strobe light emission and a warning is given if necessary.  
           [0008]    Thus, eliminating the shadow created by a strobe light emission from the photographic image, or changing the compositional arrangement to avoid the presence of a large shadow in the photographic image when the shadow is anticipated as a result of the strobe light emission, become possible. Consequently, an undesired shadow caused by a strobe light is suppressed. The present invention is particularly useful for taking a photograph for photo ID.  
           [0009]    One of the methods for detecting a shadow created by a strobe light emission involves comparing an image obtained with a strobe light emission and an image obtained without a strobe light emission to detect a drop in light intensity due to the shadow.  
           [0010]    One of the methods for estimating the size of a shadow created by a strobe light emission involves calculating the shadow area using the distance to the subject L 1 , the distance to the background L 2 , and the distance between the strobe and camera lens X 0 .  
           [0011]    Preferably, the distance to the background L 2  is examined and it is determined whether it is short enough for a strobe light to reach the background and make a shadow. If the distance L 2  is long enough such that the strobe light will not reach the background, the shadow elimination procedure should be omitted.  
           [0012]    Preferably, the width of the shadow is evaluated and only a shadow wider than a predetermined width is eliminated.  
           [0013]    One of the methods for eliminating a shadow involves replacing the shadow with image data surrounding the shadow. In this case, it is desired to display a warning and no replacement is done when image data surrounding the shadow are non-uniform.  
           [0014]    One of the methods for eliminating a shadow involves the emission of another strobe light so that a shadow is not created.  
           [0015]    The present invention can be applied to corrections of characteristic events in the images caused by strobe light emission besides the shadow elimination.  
           [0016]    Preferably, the camera of the invention has a photographic mode in which a shadow created by strobe light emission is eliminated (for example, preferably photo ID mode) and other photographic mode in which the shadow is not eliminated, and switching can be done between them.  
           [0017]    In the present invention, the strobe light includes a flash and other artificial supplementary light. The strobe can be built-in or auxiliary, and can emit light afar from the camera itself.  
           [0018]    The camera according to the present invention is not confined to a digital camera and includes a film camera and a video camera as far as it is applicable to them. Furthermore, the camera can be built in electronic devices. 
       
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING  
       [0019]    These and other features, aspects, and advantages of the apparatus and methods of the present invention will become better understood with regard to the following description appended claims, and accompanying drawings where:  
         [0020]    [0020]FIG. 1 is a block diagram which shows the structure of a camera according to Embodiment 1 of the present invention;  
         [0021]    [0021]FIG. 2 is an illustration which shows an example of taking a photograph of a person with his/her back to a wall;  
         [0022]    [0022]FIG. 3A is an illustration which shows a photographic image with strobe light;  
         [0023]    [0023]FIG. 3B is an illustration which shows a photographic image without strobe light;  
         [0024]    [0024]FIG. 4 is a flowchart to explain the operation of the camera according to Embodiment 1 of the present invention;  
         [0025]    [0025]FIG. 5A is a graphic representation which shows light intensity profiles when strobe light is used (a) and unused (b) in a juxtaposed manner;  
         [0026]    [0026]FIG. 5B is a graphic representation which shows light intensity profiles when strobe light is used (a) and unused (b) in an overlapped manner;  
         [0027]    [0027]FIG. 6A is an illustration to explain how a shadow appears when strobe light is used;  
         [0028]    [0028]FIG. 6B is an illustration which shows how a shadow on a wall appears on an image pick-up element;  
         [0029]    [0029]FIG. 7A is an illustration which shows that ranging measurements are taken for plural spots on a monitor;  
         [0030]    [0030]FIG. 7B is an illustration which shows the structure of Embodiment 2 of the present invention;  
         [0031]    [0031]FIG. 8 is a flowchart to explain the operation of a camera according to Embodiment 2 of the present invention;  
         [0032]    [0032]FIG. 9 is a flowchart to explain the operation of the camera according to Embodiment 3 of the present invention;  
         [0033]    [0033]FIG. 10 is a flowchart to explain the operation of the camera according to Embodiment 4 of the present invention;  
         [0034]    [0034]FIG. 11 is an illustration which shows a modified method for eliminating a shadow. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0035]    A preferred embodiment of the present invention is described hereinafter with reference to the drawings.  
         [0036]    Embodiment 1 of the present invention is described with reference to FIGS.  1  to  5 .  
         [0037]    [0037]FIG. 1 is a block diagram which shows the structure of a camera according to Embodiment 1 of the present invention. It is assumed that the camera is a digital camera and has a function to eliminate a shadow created by strobe light emission onto a subject by digital image processing.  
         [0038]    As shown in FIG. 1, a camera lens  2  is followed by an image pick-up portion  3  that is connected to an image processor IC  4 , and the image processor IC  4  is connected to a CPU  1  that serves as both an operation circuit and a control circuit. A memory  5  and a display  6  are connected to the image processor IC  4 . A ranging portion  9  and a strobe circuit  10   a  are connected to the CPU  1 . A strobe light emission portion  10   b  is connected to the strobe circuit  10   a.  A release switch  7  and a mode change switch  8  are also connected to the CPU  1 .  
         [0039]    The CPU  1  controls the entire camera operation and various sequences for image processing performed in the image processor IC  4 . The CPU  1  also functions as a shadow detecting portion  1   a  that detects the shadow created by a strobe light emission in the input image. The function of the shadow detecting portion  1   a  may be realized by a program that runs on the CPU  1  or a dedicated electronic circuit.  
         [0040]    The camera lens  2  forms an image of the subject on the image pick-up portion  3  that is an image pick-up element such as a CCD. The image pick-up portion  3  transforms the subject image formed by the camera lens  2  into electric signals and integrates the electronic signals to provide them to the image processor IC  4  as subject image signals. The subject image signals are also provided to the shadow detecting portion  1   a  in the CPU  1 .  
         [0041]    The image processor IC  4  performs various image processes such as an image signal compression and a shadow elimination described later. The image processor IC  4  comprises a first image storage part  4   a  for storing an image that is captured without a strobe light emission, a second image storage part  4   b  for storing an image that is captured with a strobe light emission, and a shadow elimination portion  4   c  for eliminating the shadow detected by the shadow detecting portion  1   a  of the CPU  1 .  
         [0042]    The memory  5  is a storage comprising, for example, a nonvolatile semiconductor memory to store captured images.  
         [0043]    The display  6  comprising, for example, a liquid crystal display to display captured images.  
         [0044]    The release switch  7  is a switch to start the photographic operation. The mode change switch  8  is a switch to change a current operation mode of the camera from a normal mode to a photo ID mode for taking a photograph for photo IDs such as for a passport. The CPU  1  detects the states of the switches so as to allow photographic actions or mode changes.  
         [0045]    The ranging portion  9  is used to measure the distance to the subject for focusing the camera lens  2 . The strobe unit is used to emit strobe light onto the subject depending on photographic scenes and comprises a strobe circuit  10   a  and a strobe light emission portion  10   b.    
         [0046]    The operation of the camera having the structure above is described hereafter with reference to FIG. 2.  
         [0047]    When a camera  11  is used to take a photograph of a person  12  as a main subject with his/her back to a wall  13 , the person  12  has a shadow  14  on the wall  13  created by strobe light from the strobe emission portion  10   b.  Consequently, the shadow  14  appears in a photograph image  15  that is taken through the camera lens  2 , as shown in FIG. 3A. Strobe light emission occurs in an instant. Therefore, the user cannot recognize the shadow  14  being created before he/she views the image displayed on the display  6  following the photography.  
         [0048]    In Embodiment 1 of the present invention, the shadow created by the strobe light emission is automatically eliminated by executing the operation of the flowchart shown in FIG. 4. Here, the shadow elimination function of the camera according to this embodiment is utilized on the assumption that the background wall essentially has no pattern and is uniform. This assumption can be applied to photographs for photo IDs. In general, plain backgrounds (for example walls) are intentionally selected for photo IDs. The case for taking a photograph for photo IDs is explained next.  
         [0049]    In the flowchart of FIG. 4, after the release switch  7  is turned on by the user to start the photography, the CPU  1  detects the state of the mode change switch  8  and determines whether the current operation mode is a photo ID mode for taking a photograph for photo IDs (Step S 1 ). If it is not the photo ID mode, regular strobe photography is performed in which the CPU  1  allows strobe light emission onto the photographic subject and the captured digital image is stored in the second image storage part  4   b  (Step S 20 ), then the CPU  1  proceeds to Step S 8 . As described, the mode change switch  8  is used to select a desired mode among the plural photographic operation modes and therefore it can be termed as a mode setting portion. The CPU  1 , which detects the state of the mode change switch  8  and determines the current operation mode, can be termed as a mode determination portion. The mode determination portion can be realized by a program that runs on the CPU  1  or a specific electronic circuit for determining an operation mode.  
         [0050]    On the other hand, if the CPU  1  determines that the operation mode is the photo ID mode in step S 1 , a digital image data captured without a strobe light emission (first image) is stored in the first image storage part  4   a  of the image processor IC  4  (Step S 2 ). The first image may be an underexposed image, as shown in FIG. 3B. This first image shows the pre-strobe light emission state and is used to evaluate a shadow, as described later. FIG. 5A (b) shows an image signal on the line Y 0  in the first image shown in FIG. 3B that is obtained by the image pick-up portion  3 . In FIG. 5A, light intensity is plotted on the ordinate and horizontal position on the abscissa. In the case of (b), an image signal has relatively low light intensities throughout the horizontal positions and has more or less fluctuations in intensity at the position corresponding to a person  12 .  
         [0051]    Then, a photograph is taken using a strobe light emitted from the strobe light emission portion  10   b  and the captured digital image (second image) is stored in the second image storage part  4   b  of the image processor IC  4  (Step S 3 ). With strobe light emission onto the subject, the second image may be a well-exposed image, as shown in FIG. 3A. However, the second image has a shadow  14  created by strobe light, as described above. FIG. 5A (a) shows image signals corresponding to the line Y 0  in FIG. 3A. As a whole, light intensities in the image increases in FIG. 5A (a) compared with FIG. 5A (b) because of the influence of the strobe light emission. Local low light intensities (a drop of intensity) are observed to the left of the person  12 . This corresponds to the shadow created by the strobe light.  
         [0052]    Next, the CPU  1  performs shadow evaluation at the shadow detecting portion  1   a  in which the first image in the first image storage part  4   a  of the image processor IC  4  is compared with the second image in the second image storage part  4   b  to detect the shadow position created by the strobe light emission (Step S 4 ).  
         [0053]    Shadow evaluation is described next. The first and second images are compared using respective image signals that are provided to the shadow detecting portion  1   a  from the image pick-up portion  3 . The image signals of the second image shown in (a) of FIG. 5A have increased light intensities due to the strobe light emission compared to the image signals of the first image shown in (b) of FIG. 5A. Therefore, to compare the both signals, the influence of the strobe light emission is compensated and the amplitudes of the both signals are simply compared. FIG. 5B shows signal levels adjusted to have the same background light intensity for the comparison of waveforms of FIG. 5A (a) and (b). The comparison of the waveforms of (a) and (b) in FIG. 5B shows a drop in light intensity in the waveform of (a), which is not seen in the waveform of (b). The light intensity drop range X 2  corresponds to the shadow with high contrast created by the strobe light. Thus, detecting the range X 2  in FIG. 5B leads to the detection of the shadow position.  
         [0054]    Shadow evaluation can be preformed for all the lines in the photographic image  15  or can be discontinued when the shadow-indicating features in the signal amplitude is no longer observed.  
         [0055]    In Embodiment 1, the shadow area that is detected through the shadow evaluation above is covered over (has its data overwritten) with image data surrounding the shadow to eliminate it. In this case, when the background wall has patterns or uneven contrasts, it is required to determine which image data should be used to replace the shadow area among the image data outside the shadow area. This will complicate the apparatus structure. Therefore, Embodiment 1 omits shadow elimination when the background wall has a complex pattern, which corresponds to Steps S 5  and S 6 . Thus, after the shadow position is found at Step S 4 , the CPU  1  detects the image data pattern outside the shadow area (Step S 5 ). Such pattern detection is performed for a certain range that surrounds the shadow (outside the shadow in FIG. 5B). This pattern detection outside the shadow should be performed for all the lines along the X axis in the photograph image  15  of FIG. 3A to form the area consisting of image data outside the shadow.  
         [0056]    An example of pattern evaluation is given hereafter. In FIG. 3A, the CPU  1  assumes that the area that has less fluctuation in brightness is background among the adjacent areas to the shadow and extracts it with the same width as the shadow along the X axis. As is apparent from FIG. 5A, this is based on the feature that the subject area has more fluctuation in brightness and the background has less fluctuation in brightness. Then, the CPU  1  determines whether the selected area is uniform pattern based on brightness. If the fluctuation in brightness of the area is within a predetermined range, it is assumed that the area essentially consists of a uniform pattern. If the fluctuation in brightness of the area is larger than the predetermined range, it is assumed that the area consists of a non-uniform pattern.  
         [0057]    According to the pattern detection results, image data surrounding the shadows are found to be uniform or not (Step S 6 ). For example, when image data in the selected area are all equal, the wall is assumed to be uniform. Instead of such a strict condition, the condition for a uniform pattern wall can be that 90% of the image data is equal. In this way, for example, if there is a stain on the wall, the background (outside image) can nonetheless be within an error range for shadow elimination. Pattern evaluation can be done on a line-by-line basis along the X axis, rather than on an area basis. The CPU  1  can be termed as a pattern evaluation portion, and determines whether image data surrounding the shadow in the photograph image consist of a nearly uniform pattern over a certain range. The CPU  1  can also be termed as a background image evaluation portion that evaluates image data in the background of the subject and determines whether the background image data are uniform. The pattern evaluation (background image evaluation) portion can be realized by a program that runs on the CPU  1 , or a dedicated electronic circuit.  
         [0058]    According to the evaluation results at Step S 6 , if the image data are uniform, the CPU  1  sends a command to the image processor IC  4  to replace the shadow area detected at Step S 4  with the image data within the area described above (in other words, the shadow component is covered over (its data is overwritten) with the image data in the area described above) so as to eliminate the shadow by the shadow elimination component  4   c  (Step S 7 ). Then, the image stored in the second image storage part  4   b,  after the shadow is eliminated, is displayed on the display  6  as a captured image (Step S 8 ). Then, the displayed image may be compressed and stored in the memory  5  (Step S 9 ) before the procedure ends.  
         [0059]    If the background (outside) image data are determined to be non-uniform in Step S 6 , the CPU  1  displays a warning that the shadow elimination is not performed on the display  6  (Step S 10 ) and does not perform a shadow elimination. Then CPU  1  proceeds to Step S 8  where the captured image is displayed. Then, the displayed image may be compressed and stored in the memory  5  at Step S 9  before the procedure ends.  
         [0060]    In Embodiment 1, the shadow is covered over with the image data surrounding it to eliminate the shadow. However, the shadow elimination is not limited to this way. For example, the corresponding area of the shadow in an image data captured without strobe light emission may be cut out and pasted on the shadow area after the brightness is adjusted. Alternatively, plain image data having the same color and brightness as the area surrounding the shadow is created and pasted on the shadow. Alternatively, only the subject component in the image is slightly expanded in the horizontal direction to cover the shadow.  
         [0061]    Besides shadow elimination, other image correction processes, such as lightening the shadow darkness, can be done. Procedures other than shadow processing can be done as well. For example, when a strobe light is emitted, the light intensity of a near subject increases and that of a distant subject does not. This makes the color of the near subject become whiter while that of the distant subject does not change. Such color tone change under the influence of strobe light emission can be corrected. In this way, the shadow elimination component  4   c  can be termed more broadly as an image correction portion when it performs image corrections not limited to the shadow elimination. The memory  5  in which a corrected image is stored can be termed as a corrected image storage portion.  
         [0062]    As described above, Embodiment 1 enables, in the photo ID mode for taking photographs used for photo IDs such as passports, eliminating the shadow created by strobe light emission in the photograph picture. Furthermore, defects in the image caused by a strobe light emission can be corrected by comparing the images with and without the strobe light emission. Of course, the application of Embodiment 1 is not limited to photo IDs.  
         [0063]    Embodiment 2 of the present invention is described hereafter with reference to FIGS.  6  to  8 . Embodiment 2 is a modified version of the shadow evaluation of Embodiment 1. Therefore, the explanation is essentially directed to different portions.  
         [0064]    [0064]FIG. 6A is an illustration which shows how a shadow appears in an image when a strobe light emission is used. A person  12 , a subject, with his/her back to a wall  13  stands in front of the camera  11 . A shadow  14  of the person  12  is created on the wall  13  by the light from the strobe light emission portion  10   b.  It is assumed that the distance between the camera  11  and person  12  is L 1  and the distance between the camera  11  and wall  13  is L 2 .  
         [0065]    If the camera lens  2  of the camera  11  is located apart from the strobe light emission portion  10   b  horizontally by X 0 , the shadow  14  is created on the wall  13  by strobe light emitted on the person  12  that will be captured by the lens  2  will depend on the distance X 0 . The shadow having a width of approximately X 1  defined by the expression 1 is photographed through the camera lens  2 . The width X 1  leads to a width X 2  defined by the expression 2 which is the width of the shadow on the image plane  3   a  of the camera  12 . The positional relationship between X 1  and X 2  is shown in FIG. 6B.  
           X   1   =X   0  ( L   1   −L   2 )/ L   1    (Expression 1)  
           X   2  =( f/L   2 ) X   1    (Expression 2)  
         [0066]    There are at least two possible ways for evaluating the effect of the shadow  14 : using the measurement X 1  of Expression 1 and using the measurement X 2  of Expression 2. In the case X 1  is used for evaluating the effect of the shadow  14 , when L 1  is substantially large so that L1 is almost equal to L 2  (that is to say the person  12  is in a distance), X 1  may be small enough to ignore effects of the shadow. However, if the camera  11  currently in use has a zoom function, the focal length f of the camera lens  2  can be changed according to the zoom operation. In this case, the influence of the focal length to the shadow captured on the image plane  3   a  becomes larger when the focal length becomes longer (independently of X 1 ). Accordingly, it is likely better to use X 2  for evaluating the effect of the shadow  14 .  
         [0067]    The effect of the shadow is further discussed in relation to Expression 2 in this embodiment, which can be applied to a camera having a zoom function. If a camera is without a zoom function, one expression selected from Expression 1 and Expression 2 can be applied.  
         [0068]    The ranging portion  9  used in a camera according to Embodiment 2 is described next. The ranging portion  9  used in Embodiment 2 is supposed to be a multi-point ranging apparatus capable of taking measurements for plural points on the photograph area  15  (indicated by circles) as shown in FIG. 7A. The multi-points ranging apparatus has the structure shown in FIG. 7B.  
         [0069]    Two sensor arrays  21   a  and  21   b  are provided at the focal points of the corresponding light receiving lens  20   a  and  20   b  that receive light from the subject. The sensor arrays  21   a  and  21   b  are connected to an X detection portion  22  which may be an electrical circuit for detecting the horizontal positional difference of the same subject between sensor array  21   a  and  21   b  and the X detection portion  22  is connected to the CPU  1 . The CPU  1  is connected to a light emission circuit  23  having an LED  24 . A light projection lens  25  is provided in front of the LED  24 . In FIG. 7B, a person  12  with his/her back to a wall  13  stands in front of the multi-point ranging apparatus having the above structure.  
         [0070]    The two light receiving lens  20   a  and  20   b  of the ranging apparatus are provided with a horizontal parallax B. The light receiving lens  20   a  and  20   b  monitor the person  12 , a main subject, and form images from the subject on a pair of the sensor arrays  21   a  and  21   b.  The subject images that are formed on the two sensor arrays  21   a  and  21   b  are transformed into electric signals. The relative positional difference X between the two subject images that is caused by the parallax B is detected by the X detection portion  22  which is an electrical circuit f-or receiving outputs of the sensor arrays  21   a  and  21   b  and detecting the relative positional difference X between both images by comparing them. Here, the focal length of the light receiving lenses f, parallax B, relative positional difference X, and distance to the person  12  L 1  have the following relationship:  
           L   1   =Bf/X    (Expression 3)  
         [0071]    and L 1  is calculated by the CPU  1 .  
         [0072]    The distance to the wall  13  L 2  can be obtained by replacing the person  12  with the wall  13 , as shown in the broken line in FIG. 7B. In this embodiment, the wall  13  has uniform contrast. Therefore, the light emission circuit  23  is controlled to emit light from the LED  24  so that supplementary light is projected through the light projection lens  25  to provide contrast. The ranging process described above is performed on each of the multi-points of the photograph area as shown in FIG. 7A. The outputs from the parts of the sensor arrays corresponding to the multi-points are evaluated. The multi-point ranging apparatus described above is a well-known technique and therefore is not explained in detail.  
         [0073]    [0073]FIG. 8 is a flowchart to explain the shadow evaluation of the camera according to Embodiment 2.  
         [0074]    First, the ranging portion  9  performs the multi-point ranging (Step S 31 ) to obtain the distance to the main subject L 1  and the distance to the background of the main subject L 2  (Step S 32 ). Then, it is determined whether L 2  is larger than a certain distance L 20  or not (Step S 33 ). L 20  is a threshold to determine whether the distance L 2  is within a range over which strobe light can reach. If L 2  is larger than L 20 , the background is found to be too far and no shadow can be created for the main subject, and the shadow evaluation ends (step S 35 ) and returns.  
         [0075]    In Step S 33 , if L 2  is not larger than L 20 , it is determined whether X 2  of Expression 2 is less than a certain value X 100  (Step S 34 ). X 100  is a threshold to evaluate the width X 2  of the shadow on the sensor arrays. If the width X 2  of the shadow is smaller than X 100 , the shadow does not have a width that requires the shadow processing. Thus, the shadow evaluation ends and returns (Step  35 ).  
         [0076]    If L 2  is not larger than L 20  at Step S 33  and X 2  is larger than a certain value X 100  in Step S 34 , it is determined that the shadow is present and has a substantial width: therefore, the shadow position is detected (Step S 36 ). In the shadow position detection, a low brightness area is found in image signals captured by the image pick-up portion  3  as described in Embodiment 1. Here, it is known that a shadow is present and has a substantial width X 2  on the image plane  3   a  from the results of Steps S 33  and S 34  as described above. Thus, the low brightness area over the range of X 2  in obtained from the image signals can be assumed as the shadow.  
         [0077]    In this way, Embodiment 2 calculates the range X 2  of the shadow on the sensor arrays. This eliminates comparison between images obtained with and without a strobe light emission. Only images obtained with a strobe light emission must be used to find low brightness areas having a width of the range X 2 , facilitating the detection of the shadow area. Thus, there is no need to store an image prior to strobe light emission and, therefore, no need of storage for it. Processes other than shadow evaluation can be the same as in Embodiment 1.  
         [0078]    As is described above, Embodiment 2 performs the shadow evaluation by measuring the distance to the subject. Shadow evaluation can be done without providing storage for storing image signals in the image processor IC. The shadow evaluation of Embodiment 2 can be combined with the shadow evaluation of Embodiment 1. This allows a double shadow evaluation, improving the precision of the shadow evaluation.  
         [0079]    Embodiment 3 of the present invention is described hereafter with reference to FIG. 9. In Embodiment 1, when the background image data surrounding the shadow are non-uniform, a warning that the shadow elimination procedure is not performed is displayed and then an image with the strobe emission without the shadow elimination is stored in the memory  5  and displayed on the display  6 . In Embodiment 3 , even when the background image data surrounding the shadow are non-uniform, the shadow elimination is performed and a preferred image is selected by the user between the images with and without the shadow. In addition to the structure of Embodiment 1, Embodiment 3 further comprises a display change switch (not shown) for switching the displayed image between the images with and without shadows on the display  6  and a storage switch (not shown) that is operated by the user to determine whether the displayed image is stored in the memory  5 .  
         [0080]    [0080]FIG. 9 is a flowchart to explain the display and storage of the image when the shadow evaluation is unreliable (such as in the case of non-uniform background data) in Embodiment 3.  
         [0081]    The shadow is evaluated according to the procedure in Embodiment 1 or 2. Then, the background image (wall) pattern is evaluated. When the background image pattern is determined to be non-uniform, a warning is displayed and then the shadow is eliminated. The shadow-eliminated image is displayed on the display  6  (Step  51 ). The user views the shadow-eliminated image and determines whether the shadow-eliminated image is stored in the memory  5 . The display change switch, which is to select a displayed image from the shadow eliminated image and the shadow not-eliminated image, it is operated to change the image to another one (the image in which the shadow in not eliminated). The CPU  1  detects the state of the display change switch and determines whether the shadow-eliminated image remains displayed or not (Step  52 ). If the display change switch remains in the shadow-eliminated state, and the process proceeds to Step S 54 . If the display change switch is switched to the shadow not-eliminated state, the image with a shadow is displayed on the display  6  (Step S 53 ) and the process proceeds to Step S 54 . In Step S 54 , the state of the storage switch is detected. If the storage switch is turned on, the currently displayed image may be compressed and stored in the memory  5  (Step S 55 ) and the procedure ends. On the other hand, if the storage switch remains off, a determination is made as to whether the display change switch is re-operated (Step S 56 ). If the display change switch is re-operated, the process returns to Step S 51 . If the display change switch is not re-operated, it returns to Step S 53 .  
         [0082]    As described above, Embodiment 3 allows the user to view and compare the images before and after the shadow elimination so as to select and store a preferred image in the memory.  
         [0083]    Embodiment 4 of the present invention is described hereafter, with reference to FIG. 10. The camera of Embodiment 4 is a modified version of Embodiment 2 and not necessarily a digital camera.  
         [0084]    [0084]FIG. 10 is a flowchart to explain the operation of the camera according to Embodiment 4 of the present invention.  
         [0085]    This embodiment performs the shadow evaluation based on the distance to a subject as in Embodiment 2. However, a possible shadow appearance is evaluated before photography and a warning is displayed when the shadow appearance is anticipated. First, for example, when the release switch  7  is pushed half way (first release ON), the CPU detects the state of the mode change switch  8  to determine whether the current operation mode is the photo ID mode for taking a photograph for photo IDs (Step S 61 ). If it is not the photo ID mode, the process leaves the flowchart to perform regular strobe photography. If it is in the photo ID mode, the distance between the camera  11  and person  12  (L 1 ) and the distance between the camera  11  and wall  13  (L 2 ) are obtained (Step S 62 ). After the distances L 1  and L 2  are obtained, X 2  described above is calculated using Expressions 1 and 2 above (Step S 63 ). Then, a determination is made as to whether the obtained X 2 is larger than a predetermined value X 100  or not (Step S 64 ). If it is not larger than the predetermined value X 100 , the procedure ends. If it is larger than the predetermined value X 100 , a message that a shadow may appear in the photograph monitor is displayed on the display  6  (Step S 65 ) and the procedure ends. When the release switch  7  is further operated and fully pushed after this procedure (second release ON), an image without shadow elimination is captured.  
         [0086]    As described above, Embodiment 4 omits the function to eliminate shadows created by strobe light emission and displays a warning when a possible shadow appearance is detected.  
         [0087]    Therefore, Embodiment 4 can be applied to non-digital cameras. The displayed warning urges the user to change compositional arrangement or distance so that shadows can be avoided. Furthermore, a second strobe  110  connected to the camera  11  as shown in FIG. 11 can be used to avoid the shadow  14 .  
         [0088]    The present invention is described above with reference to embodiments. However, the present invention is not confined to the embodiments described above and various modifications and applications are available within the scope of the present invention.  
         [0089]    As described above in detail, the present invention prevents the shadow from being created when strobe light is emitted onto the subject so that more natural and beautiful images can be obtained through a simple operation.  
         [0090]    Photographs obtained this way are suitable for photo IDs such as passports.  
         [0091]    While there has been shown and described what is considered to be preferred embodiments of the present invention, it is, of course, understood that various modifications and changes in form or detail could readily be made without departing from the spirit of the invention. It is therefore intended that the invention be not limited to the exact forms described and illustrated, but should be constructed to cover all modifications that may fall within the scope of the appended claims.