Description Title of Invention DISPLAY CONTROL DEVICE, DISPLAY CONTROL METHOD AND PROGRAM Technical Field [01] The present invention relates to a display control device, a display control method, and a program. Background Art [02] A digital still camera generates digital image data by converting a subject image (optical image) incident on an image sensor into an electric signal and records the digital image data in a recording medium such as a memory card in accordance with a release operation by an imager. The digital still camera is generally mounted with an auto-focus (automatic focus) mechanism to facilitate the focusing and adopts an optical system having a deep depth of field with a large F value. Accordingly, the imager can capture the subject image in which a subject is in focus by the auto- focus mechanism and record the digital image data of the subject image by simply operating a release button with the digital still camera directed toward the subject. [03] Patent Literature 1 discloses a digital still camera that performs multifocus imaging in response to one release operation to provide a digital still camera capable of generating digital image data in which a focused range (focused point) can arbitrarily be changed after imaging. In the multifocus imaging according to Patent Literature 1, a plurality of pieces of image data in which focal positions are different from each other is obtained by performing imaging in a stepwise manner while automatically changing the focal position from the focal position on the shortest distance side to the focal position on the infinity side in response to one release. Citation List Patent Literature [4] Patent Literature 1: JP 2003-143461A Patent Literature 2: JP 2006-54523A Summary of Invention Technical Problem [5] However, how to present a plurality of pieces of image data (a series of images with different focal positions) obtained by multifocus imaging to a user in an easily understood manner has not been proposed at all. For example, Patent Literature 1 does not suggest any display method (presentation method) of the plurality of pieces of image data captured as multifocus images. [6] On the other hand, the slideshow method that successively shows a plurality of pieces of image data one by one is generally used as a conventional image presentation method. However, if the above plurality of pieces of image data captured as multifocus images is displayed without accentuation by the general slideshow method, the user will be forced to view many similar images of the same imaging range (angle of view) for a long time, causing a feeling of ennui. Further, even if the user aimlessly views the plurality of pieces of image data displayed in a slideshow, the intention of the imager is unknown to the user because which object is in focus during imaging is not known, making it difficult to identify the desired image. [07] Patent Literature 2, for example, discloses that when a plurality of pieces of image data is displayed in a slideshow, the motion (a zoom-in operation or panning operation) of individual reproduced images is determined based on AF information when each piece of image data is captured and the reproduced image is displayed with the determined motion. However, the technology in Patent Literature 2 is intended only to control the display mode when individual images are displayed based on AF information and is not intended to control the slideshow display method (such as the display time and display sequence) of the whole group of images captured as multifocus images. Thus, the above issue of how to present a series of images obtained by multifocus imaging and having different focal positions to the user in an easily understood manner has not yet been resolved. [08] The present invention has been made in view of the above situation and it is desirable to provide a novel and improved display control device capable of presenting a series of images obtained by multifocus imaging and having different focal positions in an easily understood manner and effectively in accordance with the focused point while imaging, a display control method, and a program. Solution to Problem [9] According to the first aspect of the present invention in order to achieve the above-mentioned object, there is provided a display control device including: a display mode decision unit that decides a display mode in which an image data group including a plurality of pieces of image data obtained by capturing a subject image in a plurality of mutually different focal positions based on focused image determination information to determine focused image data in which a predetermined subject is in focus from the image data group; and a display control unit that controls a slideshow display of the image data group based on the display mode decided by the display mode decision unit. [10] The display mode decision unit may determine the focused image data from the image data group based on the focused image determination information and decide the display mode in such a way that the focused image data can visually be recognized more easily than other image data, which is the image data group excluding the focused image data. [11] The display mode decision unit may control a display time of each piece of the image data so that the display time of the focused image data becomes longer than the display time of the other image data. [12] The display mode decision unit may decide a display order of the plurality of pieces of image data belonging to the image data group based on focal position information representing a focal position of each piece of the image data belonging to the image data group in favor of a first display order in which the image data the focal position of which is on a close-range side is first displayed or a second display order in which the image data the focal position of which is on a long-range side is first displayed. [13] The display mode decision unit may determine whether the focused image data is on the close-range side or the long-range side based on the focal position information of an (N-l)-th image data group when the plurality of pieces of image data belonging to the (N-l)-th image data group is arranged in order of the focal position, determine whether the focused image data is on the close-range side or the long-range side based on the focal position information of an N-th image data group when the plurality of pieces of image data belonging to the N-th image data group is arranged in order of the focal position, and decide the display order of the N-th image data group in accordance with results of the determination of the (N-l)-th and N-th image data groups and the display order of the (N-l)-th image data group. [14] The display mode decision unit may determine whether the focused image data is on the close-range side or the long-range side based on the focal position information when the plurality of pieces of image data belonging to the image data group is arranged in order of the focal position, and decide the display order of the image data group in accordance with a result of the determination. [15] The display mode decision unit may determine a number of pieces of the other image data present on the close-range side or the long-range side of the focused image data based on the focal position information when the plurality of pieces of image data belonging to the image data group is arranged in order of the focal position, and control the display mode in accordance with the number so that a display time of the whole other image data on the close-range side or the long-range side becomes equal to a predetermined time or less. [16] The display mode decision unit may exclude a portion of the other image data on the close-range side or the long-range side of the focused image data from the image data to be displayed as a slideshow when the number is equal to or greater than a threshold. [17] When first focused image data and second focused image data are present in the one image data group, the display mode decision unit does not have to exclude the other image data present between the first focused image data and the second focused image data from the image data to be displayed as the slideshow. The display mode decision unit may control at least a portion of the display time of the other image data on the close-range side or the long-range side of the focused image data in accordance with the number. [19] The display mode decision unit may determine a difference in arrangement order between the focused image data and the other image data based on the focal position information when the plurality of pieces of image data belonging to the image data group is arranged in order of the focal position and controls a display time of the other image data in accordance with the difference in arrangement order. [20] Further, the display control device may include a storing unit which stores the image data group, focal position information representing a focal position of each piece of image data belonging to the image data group, and focused image determination information for determining focused image data in which a predetermined subject is in focus from the image data group, as corresponding to each other. Further, the display control device may include a reading unit which reads the image data group, the focal position information, and the focused image determination information from the storing unit. Furthermore, a display mode decision unit may display the image data group in order of the focal position represented by the focal position information as a slideshow. [21] According to the second aspect of the present invention in order to achieve the above-mentioned object, there is provided a display control method, including: deciding a display mode in which an image data group including a plurality of pieces of image data obtained by capturing a subject image in a plurality of mutually different focal positions based on focused image determination information to determine focused image data in which a predetermined subject is in focus from the image data group; and controlling a slideshow display of the image data group based on the display mode decided by the display mode decision step. [22] According to the third aspect of the present invention in order to achieve the above-mentioned object, there is provided a program causing a computer to execute: deciding a display mode in which an image data group including a plurality of pieces of image data obtained by capturing a subject image in a plurality of mutually different focal positions based on focused image determination information to determine focused image data in which a predetermined subject is in focus from the image data group; and controlling a slideshow display of the image data group based on the display mode decided by the display mode decision step. [23] With the above configuration, the display mode when an image data group including a plurality of pieces of image data obtained by capturing a subject image in a plurality of mutually different focal positions is displayed as a slideshow is decided based on focused image determination information to determine focused image data in which a predetermined subject is in focus from the image data group and the slideshow display of the image data group is controlled based on the decided display mode. Accordingly, the display mode when the plurality of pieces of image data belonging to the image data group is displayed as a slideshow can be controlled in accordance with the focused image data and therefore, the plurality of pieces of image data can effectively be displayed as a slideshow in an easily understood manner. Advantageous Effects of the Invention [24] According to the embodiments of the present invention described above, a series of images obtained by multifocus imaging and having different focal positions can be presented in an easily understood manner and effectively in accordance with the focused point while imaging. Brief Description of Drawings [25] [Fig. 1] Fig. 1 is a block diagram showing a configuration of an imaging apparatus according to a first embodiment of the present invention. [Fig. 2] Fig. 2 is a schematic diagram schematically showing imaging processing by the imaging apparatus according to the embodiment. [Fig. 3] Fig. 3 is a schematic diagram showing a change of a focal position using a deformed mirror device according to the embodiment. [Fig. 4] Fig. 4 is an explanatory diagram showing changes of the focal position according to the embodiment. [Fig. 5] Fig. 5 is a schematic diagram illustrating settings of a change position of the focal position in the imaging apparatus according to the embodiment. [Fig. 6] Fig. 6 is a schematic diagram illustrating a depth of field for each focal position according to the embodiment. [Fig. 7] Fig. 7 is a schematic diagram showing an example of focus control according to the embodiment. [Fig. 8] Fig. 8 is a schematic diagram showing another example of the focus control according to the embodiment. [Fig. 9] Fig. 9 is a schematic diagram showing a first modification of the focus control according to the embodiment. [Fig. 10] Fig. 9 is a schematic diagram showing a second modification of the focus control according to the embodiment. [Fig. 11] Fig. 9 is a schematic diagram showing a third modification of the focus control according to the embodiment. [Fig. 12] Fig. 12 is a block diagram showing a hardware configuration of a display control device according to the embodiment. [Fig. 13] Fig. 13 is a block diagram showing a function configuration of the display control device according to the embodiment. [Fig. 14] Fig. 14 is an explanatory diagram showing a data structure of metadata according to the embodiment. [Fig. 15] Fig. 15 is an explanatory diagram showing a modification of the data structure of the metadata according to the embodiment. [Fig. 16] Fig. 16 is a schematic diagram schematically showing a slideshow display according to the embodiment. [Fig. 17] Fig. 17 is a flow chart showing the slideshow display according to the embodiment. [Fig. 18] Fig. 18 is a schematic diagram showing an image selection window 40 displayed in a display screen of the display control device according to the embodiment. [Fig. 19] Fig. 19 is a schematic diagram schematically showing the slideshow display according to a second embodiment. [Fig. 20] Fig. 20 is a flow chart showing the slideshow display according to the embodiment. [Fig. 21] Fig. 21 is a flow chart showing decision processing of a display order according to the embodiment. [Fig. 22] Fig. 22 is a schematic diagram schematically showing the slideshow display according to a modification of the embodiment. [Fig. 23] Fig. 23 is a flow chart showing the decision processing of the display order according to the modification of the embodiment. [Fig. 24] Fig. 24 is a schematic diagram schematically showing the slideshow display according to a third embodiment. [Fig. 25] Fig. 25 is a schematic diagram showing an array of an image data group according to the embodiment. [Fig. 26] Fig. 26 is a flow chart showing the slideshow display according to the embodiment. [Fig. 27] Fig. 27 is a flow chart showing image selection processing according to the embodiment. [Fig. 28] Fig. 28 is a schematic diagram schematically showing the slideshow display according to a fourth embodiment. [Fig. 29] Fig. 29 is a flow chart showing the slideshow display according to the embodiment. [Fig. 30] Fig. 30 is a flow chart showing calculation processing of a display time according to the embodiment. Reference Signs List [26] 1 Imaging apparatus 2 Deformed mirror device 2a Mirror surface 3 Diaphragm 4 Image sensor 5 Pre-processing unit 6 Signal processing unit 7 AF element 8 Mirror drive circuit 9 Diaphragm controller 10 Imaging controller 11 CPU 12 Memory unit 13 Operation input unit 14 Bus 15 Display unit 16 Compression/decompression processing unit 17 Storage unit 20 Display control device 21 Data acquisition unit 22 Storing unit 23 Data reading unit 24 Display mode decision unit 25 Display controller 26 Display unit 27 Input unit 30,35 Metadata 32 Individual metadata 34 Common metadata 36 Metadata on an image data group 38 Metadata on individual image data 40 Window 42 Thumbnail image N-1, N, N+1 Group of image data Q Display time Description of Embodiments [27] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the appended drawings. Note that, in this specification and the drawings, elements that have substantially the same function and structure are denoted with the same reference signs, and repeated explanation is omitted. The description of the present invention will be provided in the order shown below: First, before starting to describe each embodiment of the present invention, various terms used herein will be described. [30] An "imaging apparatus" is an apparatus to acquire image data by capturing a subject image. The imaging apparatus includes a digital still camera to mainly acquire still image (photo) data and a digital camcorder to mainly acquire video data. The digital still camera may also have a function to acquire video data and the digital camcorder may also have a function to acquire still image data. The digital still camera is mainly taken as an example of an imaging apparatus of the present invention in the embodiments below, but the imaging apparatus of the present invention may be any camera such as a digital camcorder. "Imaging" means converting a subject image received from an image sensor into an image signal in an imaging apparatus. An "imaging range" is a range of an imaging space that can be imaged by an imaging apparatus and corresponds to the angle of view. A "subject image" is an optical image entering an image sensor via an imaging optical system of an imaging apparatus and an optical image representing a subject present within an imaging range of the imaging apparatus. "Image data" is digital data obtained by performing signal processing on an image signal obtained by capturing a subject image through an image sensor. A "focal position" is a position of the focus (focus point) of an imaging optical system of an imaging apparatus. More specifically, a "focal position" is a position on an optical axis of an imaging optical system in which the focus of the imaging optical system is present in an imaging space. The focal position can be changed by driving the imaging optical system of the imaging apparatus or the imaging apparatus. The distance from the lens center of the imaging optical system of the imaging apparatus to the focal position is called a "focal length". "Focusing" is an adjustment of the focus of an imaging optical system of an imaging apparatus to a predetermined subject within an imaging range. A "focused point position" is a focal position in which an imaging optical system of an imaging apparatus focuses on a predetermined subject within an imaging range. A "focused range" is a range of the focal position around the focused point position when the focal position is in some focused point position in which focusing is obtained due to depth of field of an imaging optical system. "Around the focused point position" is a close-range side (near side) and a long-range side (far side) of the focused point position on an optical axis (Z axis) of the imaging optical system. As is evident from the description of the focused range, there is a width in focal position when some subject is in focus. Thus, "detection of the focused point position focusing on a predetermined subject" in the present invention means detection of any focal position within the focused range in which the subject is in focus. A "focusing enabled range" is a range of the focal position in which focusing of an imaging optical system of an imaging apparatus can physically be achieved, ranging the focal position on the shortest distance side (macro) to the focal position on the infinity side. An "X axis direction" is the horizontal direction of an imaging space, a "Y axis direction" is the vertical direction of the imaging space, and a "Z axis direction" is a depth direction of the imaging space (an optical axis direction of an imaging optical system). The X axis direction and the Y axis direction determine an imaging plane of an image obtained by an imaging apparatus and the Z axis direction is a direction in which the focus of the imaging optical system is changed. [32] A "detection instruction" is an instruction serving as a trigger to detect the focused point position. A typical detection instruction is, for example, an operation to press a release button (shutter button) halfway down by a user. In addition, however, for example, an operation to turn on an imaging apparatus, an operation to switch the operation mode of the imaging apparatus to an imaging mode, other user operations, or face detection by face detection processing on image data obtained by imaging can also serve as a trigger to issue a detection instruction. A "release instruction" is an instruction serving as a trigger to acquire image data obtained by capturing a subject image as a save image data. In a common digital still camera, "release" means recording image data obtained by capturing a subject image in a recording medium and a typical operation thereof is to press the release button all the way down. However, the "release instruction" herein is not limited to the operation to press the release button all the way down and, for example, other user operations on the imaging apparatus or detection of a smiling face of a subject person by smile detection processing on image data obtained by imaging can also serve as a trigger to issue a release instruction. "Save image data" is, among image data obtained by performing signal processing on an image signal of a subject image captured by an image sensor, image data saved in a recording medium by an imaging apparatus or an external device. In a digital still camera, for example, image data is generated by constantly capturing a subject image by an image sensor in imaging mode and the image data is displayed in a monitor of the imaging apparatus as a live view image. Instead of saving all image data obtained chronologically in this manner in a recording medium, image data in the timing in which the above release instruction is generated is saved in the recording medium. In a digital camcorder, on the other hand, all image data obtained chronologically is saved in a recording medium as save image data. [33] "Auto-focus processing" is processing to automatically detect the focal position in which an imaging apparatus focuses on any subject inside an imaging range. The auto-focus (hereinafter, referred to as "AF") processing may contain detection processing to detect the focal position in which a predetermined subject is brought into focus and tracking processing to change the focal position so that the focus is caused to track the subject. The subject for AF may be a subject present, for example, in a predetermined AF area (for example, an image center area) provided in an imaging range or at a reference point or the user may be enabled to freely select the subject for AF in the imaging range by using an AF position specifying means such as a touch panel. "Subject detection processing" is processing to detect one or two or more subjects present inside the imaging range by analyzing image data obtained by capturing subject images in a plurality of changed and mutually different focal positions while changing the focal position. Subjects present within the imaging range and the range of the focused point position in which the subjects are brought into focus can be detected by the subject detection processing. [34], "Bracket imaging processing" is processing to acquire image data obtained by capturing subject images in a plurality of changed focal positions while periodically changing the focal position within a predetermined range containing the detected focused point position as save image data. Bracket imaging is referred to also as focus bracket imaging. In the bracket imaging processing, for example, the focal position may be changed within a predetermined range centered on the focused point position detected by the AF processing or the focal position may be changed within the range of the focused point position in which the subject detected by the subject detection processing is brought into focus. Images can be captured by changing the focal position to positions near the focused point position by the Bracket imaging processing and therefore, position shifts of the focused point position can be compensated for. "Multifocus imaging processing" is processing to acquire image data obtained by capturing subject images in a plurality of changed and mutually different focal positions while changing the focal position within a predetermined range in a stepwise manner or continuously as save image data. Examples of the multifocus processing include "all-range focus imaging processing" that sets the entire range of the focusing enabled range as a range in which the focal position can be changed and "subject imaging processing" that sets the range of the focused point position in which the subject detected by the subject detection processing is brought into focus as a range in which the focal position can be changed. "All-range focus imaging processing" is processing to acquire image data obtained by capturing subject images in a plurality of changed and mutually different focal positions while changing the focal position in the focusing enabled range in a stepwise manner or continuously as save image data. The all-range focus imaging processing is an example of the multifocus processing. "Subject imaging processing" is processing to acquire image data obtained by capturing subject images in a plurality of changed and mutually different focal positions while changing the focal position within a range of the focused point position in which at least one subject of one or two or more subjects detected by the subject detection processing is brought into focus as save image data. The subject imaging processing is an example of the multifocus processing. [35] A "slideshow" is a function to cause a display unit to successively display a plurality of pieces of image data. The slideshow function is implemented in, for example, presentation software and image display software (a so-called viewer). The slideshow function is roughly divided into two types of mode, a mode in which the slide (one piece of image data) is switched each time the user presses an operation key and a mode in which the slide is automatically switched to the next slide (the next image data) in accordance with the passage of a preset elapsed time. A "slideshow display" means displaying a plurality of pieces of image data successively by the slideshow. A "display mode" is a mode in which a plurality of pieces image data is displayed by the slideshow and includes, for example, the display time of the plurality of pieces of image data displayed as the slideshow, the display order, and the selection of image data to be displayed. [36] Next, the second embodiment of the present invention will be described. The slideshow display according to the second embodiment is different from the slideshow display according to the first embodiment in that the display order of image data belonging to an image data group is controlled and the other function configuration is the same as in the first embodiment and thus, a detailed description thereof is omitted. [0226] [2.1. Overview of Slideshow Display] First, an overview of the slideshow display according to the second embodiment will be provided with reference to Fig. 19. Fig. 19 is a schematic diagram schematically showing the slideshow display according to the second embodiment. [227] In the first embodiment described above, the display order when a plurality of pieces of image data belonging to an image data group is displayed as a slideshow typically is, as shown by Route 2 in Fig. 19, from the close-range side to the long- range side. That is, regardless of the arrangement of focused image data in the image data group, image data is typically displayed in the order starting with the image data whose focal position is closest to the close-range side (N (1) N (2) —> ... N (12)). The display order in which a plurality of pieces of image data is successively displayed in the order from the close-range side toward the long-range side (ascending order of focal position) is called a "forward display order". The forward display order corresponds to the display order in the first embodiment of the present invention. [228] However, if the display order is fixed to the forward display order (from the close-range side to the long-range side), the following problem arises when a plurality of image data groups is consecutively displayed. For example, a case when, as shown in Fig. 19, focused image data is on the close-range side in an image data group N-l to be displayed first and focused image data is on the long-range side in an image data group N to be displayed second will be considered. In this case, if both the image data group N-l and the image data group N are displayed in the forward display order, after focused image data N-l (2) of the image data group N-l is displayed, 10 pieces of image data N-l (3) to (12) belonging to the image data group N-l are successively displayed. Next, 10 pieces of image data N (3) to (10) belonging to the image data group N are successively displayed. Then, focused image data N (11) of the image data group N is displayed. That is, a total of 20 pieces of out-of-focus image data is displayed between the time when the focused image data N-l (2) is displayed and the time when the focused image data N (11), which could cause the user to have a feeling of ennui. [229] Thus, in the second embodiment, not only the above "forward display order (first display order)", but also "backward display order (second display order)" is used as the display order of image data groups. The "backward display order" is a display order in which image data is displayed starting with the image data whose focal position is closest to the long-range side. In the backward display order, as shown by Route 2 in Fig. 19, a plurality of pieces of image data N (1) to (12) belonging to the image data group N is displayed in the order from the long-range side toward the close-range side (descending order of focal position) (N (12) → N (11) →... N (1)). [230] Then, the display mode decision unit 24 determines whether focused image data is on the close-range side or the long-range side when a plurality of pieces of image data belonging to each of the image data groups N-l, N is arranged in order of focal position. Further, the display mode decision unit 24 decides which of the forward direction and backward direction to adopt as the display order of the next image data group N in accordance with the above determination result and the display order of the previous image data group N-l. [231] [2.2. Decision Technique of Display Order] Next, the decision technique of the display order of each piece of image data according to the present embodiment will be described in detail. As shown in Fig. 19, the display mode decision unit 24 compares a number AN-1 of pieces of image data on the close-range side of the focused image data N-l (2) and a number BN-1 of pieces of image data on the long-range side of the focused image data N-l (2) in the image data group N-l to be displayed first. In the example in Fig. 19, AN-1 = 1 and BN-1 = 10 and thus, BN-1 > AN-1 . Therefore, the focused image data N-l (2) can be determined to be on the close-range side among all image data N-l (1) to (12) in the image data group N-l. [232] Further, the display mode decision unit 24 compares a number AN of pieces of image data on the close-range side of the focused image data N (11) and a number Bn of pieces of image data on the long-range side of the focused image data N (11) in the image data group N to be displayed next. In the example in Fig. 19, AN = 10 and Bn = 1 and thus, AN > BN- Therefore, the focused image data N (11) can be determined to be on the long-range side among all image data N (1) to (12) in the image data group N. [233] Then, the display mode decision unit 24 decides the display order of the image data group N to be displayed next in favor of the forward direction (close- range → long-range) or the backward direction (long-range → close-range) in accordance with the display order of the image data group N-l to be displayed first and the above two determination results (BN-1 > AN-1, AN > BN). In the example in Fig. 19, the display order of the image data group N-l is the forward direction and BN-1 > AN-1, AN > Bn hold and thus, the display order of the image data group N is decided in favor of the backward direction (see Route 2 in Fig. 19). [234] According to the above technique, whether the focused image data N-l (2) is on the close-range side or the long-range side is determined in the image data group N-l based on a comparison result of AN-1 and BN-1- Then, based on a comparison result of AN and BN, whether the focused image data N (11) is on the close-range side or the long-range side from the center of the image data group N is determined. However, the technique to determine the arrangement of focused image data in the image data group N-l is not limited to such an example and, for example, the following determination technique can be also used. That is, first, a half value "ITIN-1/2" of a total number mN-1 (for example, mN = 12) of pieces of focused image data of the image data group N-l is determined as a threshold. Then, based on a comparison result of the threshold "mN-1/2" and AN-1 shown above (or BN- i), whether the focused image data is on the close-range side or the long-range side from the center of the image data group N-l may be determined. Similarly for the image data group N, based on a comparison result of the threshold "mN/2" and AN shown above (or B»), whether the focused image data is on the close-range side or the long-range side from the center of the image data group N can be determined. [235] The technique to decide the display order of the next image data group N in accordance with a determination result using the threshold "m/2" as described above and the display order of the previous image data group N-l will be described in more detail. The total number of pieces of image data in the image data group N-l and the total number of pieces of image data in the image data group N may be the same (mN = mN-1) or different (mN= mN-1). [236] (1) If AN-1 > (mN_1/2) and AN > (mN/2) In this case, focused image data is on the long-range side from the center in both the image data groups N-l, N and thus, the display order of the image data group N is set in the same direction as the display order of the image data group N-l. That is, if the display order of the image data group N-l is the forward direction, the display order of the image data group N is set in the forward direction, and if the display order of the image data group N-l is the backward direction, the display order of the image data group N is set in the backward direction. [237] (2) If AN-1 < (mN.]/2) and AN < (mN/2) In this case, focused image data is on the close-range side from the center in both the image data groups N-l, N and thus, the display order of the image data group N is set in the same direction as the display order of the image data group N-l. [238] (3) If AN-1 > (mN-1/2) and AN < (mN/2) In this case, focused image data is on the long-range side from the center in the image data group N-l and focused image data is on the close-range side from the center in the image data group N and thus, the display order of the image data group N set in the direction opposite to the display order of the image data group N-l. That is, if the display order of the image data group N-l is the forward direction, the display order of the image data group N is set in the backward direction, and if the display order of the image data group N-l is the backward direction, the display order of the image data group N is set in the forward direction. [239] (4) If An_, < (mN-1/2) and AN > (mN/2) In this case, focused image data is on the close-range side from the center in the image data group N-l and focused image data is on the long-range side from the center in the image data group N and thus, the display order of the image data group N set in the direction opposite to the display order of the image data group N-l. [240] [2.3. Slideshow Display Flow] Next, the slideshow display flow according to the present embodiment will be described with reference to Fig. 20. Fig. 20 is a flow chart showing the slideshow display according to the present embodiment. [241] As shown in Fig. 20, the display control device 20 first activates application software for slideshow (S200) and selects image data to be displayed as a slideshow (S202). Next, the data reading unit 23 of the display control device 20 reads the first image data group and metadata thereof among image data groups selected in S202 from the storing unit 22 (S204). Steps S200 to S204 heretofore are substantially the same as steps S100 to S104 in Fig. 17 according to the first embodiment and thus, a detailed description thereof is omitted. [242] Next, the display mode decision unit 24 of the display control device 20 decides the display order of a plurality of pieces of image data belonging to the image data group based on the metadata of the image data group read in S204 (S205). Decision processing of the display order in S205 is a feature of the present embodiment and so will be described in detail with reference to Fig. 21. Fig. 21 is a flow chart showing the decision processing of the display order according to the present embodiment. As shown in Fig. 21, the display mode decision unit 24 first determines whether the image data group N to be displayed is the first image data group (N = 1) of a plurality of image data groups to be displayed as a slideshow (S230). If, as a result of the determination, the image data group N is the first image data group, the display mode decision unit 24 decides the display direction of the plurality of pieces of image data belonging to the image data group N in favor of the preset default display order (S232). The default display order may be set to the forward display order (close-range —> long-range) or the backward display order (long-range close-range). [244] On the other hand, if, as a result of the determination in S230, the image data group N is not the first image data group, the display mode decision unit 24 determines whether focused image data in the image data group N-l displayed before the image data group N is on the close-range side or the long-range side (S234). More specifically, the display mode decision unit 24 determines whether focused image data is on the close-range side or the long-range side when a plurality of pieces of image data belonging to the image data group N-l is arranged in order of focal position based on focal position information of the image data group N-l. For this determination, the display mode decision unit 24 compares, for example, a number AN-1 of pieces of image data on the close-range side of focused image data of image data belonging to the image data group N-l with a half value "mN-1/2" of a total number mN-1 of pieces of image data belonging to the image data group N-l. If, as a result, AN-1 > (mN-1/2) holds, the display mode decision unit 24 determines that the focused image data is on the long-range side in the image data group N-l and proceeds to S236. If, on the other hand, AN-1 (mN-1/2) holds, the display mode decision unit 24 determines that the focused image data is on the close-range side in the image data group N-l and proceeds to S238. [245] In both S236 and S238, the display mode decision unit 24 determines whether focused image data in the image data group N is on the close-range side or the long-range side (S236, S238). More specifically, the display mode decision unit 24 determines whether the focused image data is on the close-range side or the long- range side when a plurality of pieces of image data belonging to the image data group N is arranged in order of focal position based on focal position information of the image data group N. For this determination, the display mode decision unit 24 compares, for example, a number AN of pieces of image data on the close-range side of the focused image data of image data belonging to the image data group N with a half value "ITIN/2" of a total number MN of pieces of image data belonging to the image data group N. [246] If, as a result, AN > (ITIN/2) holds in S236 (YES in S236), the display mode decision unit 24 determines that the focused image data is on the long-range side in the image data group N and proceeds to S240. If AN < (ITIN/2) holds in S238 (NO in S238), the display mode decision unit 24 determines that the focused image data is on the close-range side in the image data group N-l and proceeds to S240. Thus, as described above, the processing proceeds to S240 when focused image data is on the long-range side or the close-range side in both the image data group N-l and the image data group N. Then, in S240, the display mode decision unit 24 decides the display order of the image data group N in the same direction as the display order of the image data group N (S240). [247] If, on the other hand, AN < (mN/2) holds in S236 (NO in S236), the display mode decision unit 24 determines that the focused image data is on the close-range side in the image data group N and proceeds to S242. If AN-1 > (ITIN-1/2) holds in S238 (YES in S238), the display mode decision unit 24 determines that the focused image data is on the long-range side in the image data group N and proceeds to S242. Thus, as described above, the processing proceeds to S242 when focused image data is on the opposite sides in the image data group N-l and the image data group N. Then, in S242, the display mode decision unit 24 decides the display order of the image data group N in the opposite direction of the display order of the image data group N (S242). [248] In the foregoing, the decision processing of the display order of the image data group N according to the present embodiment has been described with reference to Fig. 21. The description will continue by returning to Fig. 20. [249] The display order of the image data group N is decided as shown in Fig. 21. Then, the display control unit 25 successively displays a plurality of pieces of image data belonging to the image data group N in the forward direction (close-range —» long-range) or backward direction (long-range -» close-range) according to the display order decided above as a slideshow (S206 to S216). At this point, if image data to be displayed is focused image data (S208), the display control unit 25 displays only the image data for the long display time P (S210) and if image data is not focused image data (S208), the display control unit 25 displays only the image data for the short display time Q (S212). The display processing is repeated sequentially for all image data in the image data group N (S214, S216). Steps S206 to S216 are substantially the same as steps S106 to S116 in Fig. 17 according to the first embodiment and thus, a detailed description thereof is omitted. [250] Then, when the slideshow display of the image data group N ends (S214), the display mode decision unit 24 determines whether the next image data group N+l is present (S218). If the next image data group N+l is present, the display mode decision unit 24 reads the next image data group N+l from the storing unit 22 (S220). When the next image data group N+l is displayed as a slideshow, the display order of the image data group N+l is decided in accordance with the display order of the image data group N according to the flow in Fig. 21 (S205) before starting the slideshow (S206 to S216). By repeating the above processing for all image data groups selected in S202, the slideshow display advances. [251] In the foregoing, the decision processing of the display order of the image data group N according to the present embodiment and the slideshow display processing using the display order have been described. As described above, there is a case when focused image data is on the close-range side in the image data group N-l and focused image data is on the long-range side in the image data group N (see Fig. 19) and also a reversed case thereof. If the display order of all image data groups is the same in such cases, there is a problem that many pieces of out-of-focus image data are displayed for a long time between the time when focused image data of the image data group N-l is displayed and the time when focused image data of the image data group N is displayed. [252] According to the decision technique of the display order according to the present embodiment (see Fig. 21), by contrast, if focused image data of the image data group N-l and focused image data of the image data group N are on opposite sides, the display order of the image data group N is set in the opposite direction of the display order of the image data group N-l displayed previously. Accordingly, the time in which many pieces of out-of-focus image data are displayed consecutively between focused image data of a plurality of image data groups can be reduced and made uniform so that the user can be prevented from becoming tired of viewing the slideshow display. [253] In the flow in Fig. 20, the display order of the image data group N displayed currently is controlled by using information of the image data group N-l displayed previously, but the display order of the image data group N displayed currently can be controlled by using information of the image data group N+l displayed later. In this case, metadata on all image data groups to be displayed as a slideshow may be read in S204 to control the display order of each image data group based on metadata of all the image data groups. Accordingly, the display mode when a plurality of image data groups is displayed as a slideshow can further be optimized. [254] [2.4. Modification of Slideshow Display] Next, a modification of the slideshow display according to the second embodiment will be described with reference to Fig. 22. Fig. 22 is a schematic diagram schematically showing the slideshow display according to a modification of the second embodiment. [255] As shown in Fig. 22, focused image data N (2) may be present lopsidedly on the close-range side or the long-range side in the image data group N to be displayed as a slideshow. In such a case, the display control device 20 according to the present modification decides the display order in such a way that the time before the intended focused image data N (2) is made longer to inflame the feeling of user's anticipation. In the illustrated example, the focused image data N (2) is on the close-range side and thus, a plurality of pieces of image data belonging to the focused image data N is displayed successively from the long-range side in the backward display order to inflame the feeling of user's anticipation (N (mN) → N (mN-l) ... N (2) → N (1)). Conversely, if the focused image data is on the long- range side, a plurality of pieces of image data belonging to the focused image data N is displayed successively from the close-range side in the forward display order to inflame the feeling of user's anticipation (N (1) → N (2) ... N (mN-l) N (mN))- [256] The decision processing of the display order according to the modification of the present embodiment will be described with reference to Fig. 23. Fig. 23 is a flow chart showing the decision processing of the display order according to the modification of the present embodiment. The processing in Fig. 23 corresponds to a subroutine of step S205 in Fig. 21. [257] As shown in Fig. 23, the display mode decision unit 24 first determines whether focused image data is on the close-range side or long-range side in the image data N (S250). More specifically, the display mode decision unit 24 first determines whether the focused image data is on the close-range side or the long- range side when a plurality of pieces of image data belonging to the image data group N is arranged in order of focal position based on focal position information of the image data group N. For this determination, the display mode decision unit 24 compares, for example, a number AN of pieces of image data on the close-range side of the focused image data of image data belonging to the image data group N with a half value "ITIN/2" of a total number IHN of pieces of image data belonging to the image data group N. [0258] If, as a result, AN > (mN/2) holds, the display mode decision unit 24 determines that the focused image data is on the long-range side in the image data group N and proceeds to S252. In S252, the display mode decision unit 24 decides the display order of the plurality of pieces of image data belonging to the image data group N in favor of the forward direction (from the close-range side to the long- range side) (S252). If An < (mN/2) holds, on the other hand, the display mode decision unit 24 determines that the focused image data is on the close-range side in the image data group N and proceeds to S254. In S254, the display mode decision unit 24 decides the display order of the plurality of pieces of image data belonging to the image data group N in favor of the backward direction (from the long-range side to the close-range side) (S252). [0259] The display order is decided based on a comparison result of AN and (ITIN/2) in the above example, but the present embodiment is not limited to such an example and the display order may be decided based on, for example, AN and BN- BN is the number of pieces of image data on the long-range side of the focused image data of the image data group N. If AN > BN holds, the focused image data can be determined to be on the long-range side in the image data group N and if AN < BN holds, the focused image data can be determined to be on the close-range side in the image data group N. [0260] In the foregoing, the decision processing of the display order according to the modification of the present embodiment has been described. According to the present modification, when the image data group N is displayed as a slideshow, whether the focused image data is on the long-range side or the close-range side in the image data group N is determined and the display order of the plurality of pieces of image data belonging to the image data group N is decided in favor of the forward direction or backward direction based on the determination result. Accordingly, the time between the display start of the first image data of the image data group N and the display of the user-desired focused image data can be made longer. Therefore, the feeling of anticipation to want to view an intended representative image can be enhanced so that an effective slideshow display can be made. [0261] D holds (S350). The threshold D is the upper limit of the number of pieces of image data to be displayed as a slideshow and, for example, D=5. If AN > D holds, the number AN of pieces of image data on the close-range side of the first focused image data exceeds the upper limit D and thus, the display mode decision unit 24 sets image data exceeding D of the image data to be excluded before proceeding to S352. If, on the other hand, AN < D holds, the number AN of pieces of image data on the close-range side of the first focused image data is equal to the threshold D or less and thus, the display mode decision unit 24 proceeds to S356 without setting the applicable image data to be excluded. [282] In S352, the display mode decision unit 24 determines whether any image in which a predetermined subject is in focus is present in image data determined to be excluded in S350 (S352). If such an image in which a predetermined subject is in focus is present, the display mode decision unit 24 proceeds to S356 to include the image data, which is determined to be excluded in S350, as image data to be displayed in a slideshow, instead of excluding the image data from the slideshow. [283] If, on the other hand, an image in which a predetermined subject is in focus is not present in S352, the display mode decision unit 24 proceeds to S354 to exclude image data determined to be excluded in S350 from image data to be displayed as a slideshow (S354). As a result, image data on the close-range side of the first focused image data excluding D pieces of focused image data closer to the first focused image data is excluded from image data to be displayed as a slideshow. [284] Next, in S3 5 6, the display mode decision unit 24 determines a number BN of pieces of image data on the long-range side of the second focused image data closest to the long-range side in the image data group and compares the number BN and the threshold D to determine whether Bn > D holds (S356). If BN > D holds, the number BN of pieces of image data on the close-range side of the second focused image data exceeds the upper limit D and thus, the display mode decision unit 24 sets image data exceeding D of the image data to be excluded before proceeding to S358. If, on the other hand, BN < D holds, the number BN of pieces of image data on the close-range side of the second focused image data is equal to the threshold D or less and thus, the display mode decision unit 24 proceeds to S3 62 without setting the applicable image data to be excluded. [285] In S358, the display mode decision unit 24 determines whether any image in which a predetermined subject is in focus is present in image data determined to be excluded in S356 (S358). If such an image in which a predetermined subject is in focus is present, the display mode decision unit 24 proceeds to S362 to include the image data, which is determined to be excluded in S356, as image data to be displayed in a slideshow, instead of excluding the image data from the slideshow. [286] If, on the other hand, an image in which a predetermined subject is in focus is not present in S358, the display mode decision unit 24 proceeds to S360 to exclude image data determined to be excluded in S356 from image data to be displayed as a slideshow (S3 60). As a result, image data on the long-range side of the second focused image data excluding D pieces of focused image data closer to the second focused image data is excluded from image data to be displayed as a slideshow. [287] With the above steps S3 50 to S3 60, image data separated from the first and second focused image data by (D+l) pieces or more on the close-range side and the long-range side respectively when a plurality of pieces of image data of the image data group N is arranged in order of focal position is excluded from image data to be displayed as a slideshow. Incidentally, as shown in Fig. 25, CN pieces of image data between the first focused image data N (3) and the second focused image data N (10) are not excluded from image data to be displayed as a slideshow. Accordingly, continuity of images (continuous transition of the focal position) when CN pieces of image data are displayed as a slideshow can be maintained. [288] Next, in S362, the display mode decision unit 24 calculates the display time Q of each piece of image data to be displayed as a slideshow by using a predetermined formula so that the display time of other image data as a whole on the close-range side or the long-range side of focused image data becomes equal to predetermined time T or less (S362). As described above, the display time P (for example, 2 sec) of focused image data is longer than the display time Q (for example, 0.1 sec) of other image data. Image data to be displayed as a slideshow selected by the selection processing up to S360 described above includes the first focused image data N (3) and the second focused image data N (10), CN pieces of image data N (4) to (9) therebetween, the image data N (1), (2) within D pieces on the close-range side of the first focused image data N (3), and the image data N (11) to (15) within D pieces on the long-range side of the second focused image data N (3). The display time Q of the other image data N (1), (2), (4) to (9), (11) to (15) other than the focused image data is decided so that the image data N (1), (2), (11) to (15) can all be displayed within the preset predetermined time T. [0289] In the foregoing, the decision processing of the display order of the image data group N according to the present embodiment will be described with reference to Fig. 27. The description will continue by returning to Fig. 26. [0290] The image data in the image data N is sorted as shown in Fig. 27 and the display time Q thereof is decided. Then, the display control unit 25 successively displays image data selected in S305 as image data to be displayed as a slideshow from a plurality of pieces of image data belonging to the image data group N in the forward direction (close-range -» long-range) or backward direction (long-range -» close-range) as a slideshow (S306 to S316). Then, if image data to be displayed is focused image data (S308), the display control unit 25 displays only the image data for the long display time P (S310) and if image data to be displayed is not focused image data (S308), the display control unit 25 displays only the image data for the short display time Q decided in S362 (S312). The display processing is repeated for all image data in the image data group N (S314, S316). Steps S306 to S316 are substantially the same as steps SI06 to SI 16 in Fig. 17 according to the first embodiment and thus, a detailed description thereof is omitted. [291] Then, when the slideshow display of the image data group N ends (S314), the display mode decision unit 24 determines whether the next image data group N+l is present (S318). If the next image data group N+l is present, the display mode decision unit 24 reads the next image data group N+l from the storing unit 22 (S320). When the next image data group N+l is displayed as a slideshow, image data to be displayed as a slideshow is selected and the display time Q of the image data are decided according to the flow in Fig. 27 (S305) before starting the slideshow (S306 to S316). By repeating the above processing for all image data groups selected in S302, the slideshow display advances. [292] In the foregoing, the selection processing of image data to be displayed as a slideshow according to the present embodiment and the slideshow display processing using the image data have been described. As described above, if focused image data is on the close-range side or the long-range side in an image data group, there is a problem that many pieces of out-of-focus image data are displayed for a long time after the focused image data on the close-range side is displayed or before the focused image data on the long-range side is displayed. If, for example, flowers are imaged on the macro side using the imaging apparatus 1, an image in which the background is in focus is an out-of-focus image whose utility value is low for the user. Thus, if such out-of-focus images are displayed for a long time in a slideshow display, the user becomes boring. [293] According to the decision technique of the display order according to the present embodiment (see Fig. 27), by contrast, other image data whose focal position is significantly different from the focal position of focused image data in an image data group is excluded from image data to be displayed as a slideshow to reduce the number of pieces of image data displayed as a slideshow. Further, the display speed is made faster by adjusting the display time Q for each piece of image data so that all image data to be displayed as a slideshow can be displayed within a predetermined time. Accordingly, images of the image data group can be displayed as a slideshow within the predetermined time and the time in which out-of-focus image data is continuously displayed can be reduced so that the user can be prevented from becoming tired of viewing the slideshow display. [294] Q2). On the other hand, the image data (1) is apart from the focused image data N (p) and thus, a display time Q1 of the image data (1) is set to a relatively short time (P > Q2 > Ql). Accordingly, when the image data group N is displayed as a slideshow, the display time Q of the image data N (x) gradually becomes longer as the focused image data comes closer and the display time Q of the image data N (x) gradually i becomes shorter as the focused image data moves away. By making the display time Q variable in this manner, accentuation can be provided to the display time Q of each piece of image data in accordance with the focused point position so that the focused image data can be staged effectively to display as a slideshow. [300] i [4.2. Slideshow Display Flow] Next, the slideshow display flow according to the present embodiment will be described with reference to Fig. 29. Fig. 29 is a flow chart showing the slideshow display according to the present embodiment. As shown in Fig. 29, the display control device 20 first activates application software for slideshow (S400) and selects image data to be displayed as a slideshow (S402). Next, the data reading unit 23 of the display control device 20 reads the first image data group and metadata thereof among image data groups selected in S402 from the storing unit 22 (S404). Steps S400 to S404 heretofore are substantially the same as steps S100 to SI04 in Fig. 17 according to the first embodiment and thus, a detailed description thereof is omitted. [302] Next, the display mode decision unit 24 decides the display time Q (x) of other image data N (x) in accordance with differences in arrangement order between the focused image data N (p), N (q) and the other focused image data N (x) based on metadata of the image data groups read in S404 (S405). The arrangement order (for example, the number of pieces from the head) of image data is an arrangement order when a plurality of pieces of image data belonging to the image data group N is arranged in order of focal position. Display time setting processing in S405 is a feature of the present embodiment and so will be described in detail with reference to Fig. 30. Fig. 30 is a flow chart showing calculation processing of the display time Q according to the present embodiment. [303] As shown in Fig. 30, the display mode decision unit 24 first determines differences in arrangement order ABS (x-p), ABS (x-q) between each piece of image data N (x) other than focused image data and the focused image data N (p), N (q) (S450). The differences in arrangement order ABS (x-p), ABS (x-q) correspond to numbers of pieces image data from N (x) to N (p), N (q). In the example in Fig. 28, for example, the difference in arrangement order ABS (1-p) between the image data N (1) and the focused image data N (p) is "2" and the difference in arrangement order ABS (2-p) between the image data N (2) and the focused image data N (p) is "1". [304] Next, the display mode decision unit 24 compares the differences in arrangement order ABS (x-p) with ABS (x-q) and decides the smaller difference as the difference in arrangement order between N (x) and the focused image data closest to N (x) (S452). If, for example, ABS (x-p) > ABS (x-q) holds, the difference in arrangement order between the image data N (x) and the focused image data closest to N (x) is ABS (x-q) and the display mode decision unit 24 proceeds to S454. If, on the other hand, ABS (x-p) < ABS (x-q) holds, the difference in arrangement order between the image data N (x) and the closest focused image data closest is ABS (x-p) and the display mode decision unit 24 proceeds to S456. [305] In S454, the display mode decision unit 24 calculates the display time Q (x) of the image data N (x) by using a predetermined function f (X) by setting the difference in arrangement order ABS (x-p) between the image data N (x) and the closest focused image data as a variable X. That is, Q (x) = f (ABS (x-p)). The function f (X) is a function whose value decreases with an increasing variable Z and, for example, f (X) = 1/X. [306] In S456, on the other hand, the display mode decision unit 24 calculates the display time Q (x) of the image data N (x) by using the predetermined function f (X) by setting the difference in arrangement order ABS (x-q) between the image data N (x) and the closest focused image data as a variable X. That is, Q (x) = f (ABS (x- q)). [307] With the above S454, S456, the display time Q (x) of the image data N (x) is calculated in accordance with the difference in arrangement order ABS (x-p) between the image data N (x) and the closest focused image data. By repeating the calculation of Q (x) for all image data N (x) in the image data group N, Q (1) to Q (mN) are determined. The technique to calculate the display time Q (x) by using the difference in arrangement order and the function f (x) is described above, but the technique to determine the display time Q (x) is not limited to such an example. For example, the display control device 20 may hold a table in which the display time Q (x) in accordance with the difference in arrangement order is preset so that the display time Q (x) of each piece of image data N (x) is decided based on the table. [308] By determining Q (x) as described above, the display time Q (x) of the image data N (x) can be increased/decreased in accordance with the distance (the difference in arrangement order) from the focused image data to the image data N (x). Therefore, when a slideshow is displayed, the display time Q (x) can be made longer for the image data N (x) close to the focused image data and the display time Q can be made shorter for the image data N (x) apart from the focused image data. [309] In the foregoing, the calculation processing of the display time Q (x) of the image data N (x) according to the present embodiment is described with reference to Fig. 30. The description will continue by returning to Fig. 29. Next, the display control unit 25 successively displays image data selected as image data to be displayed as an S slideshow of a plurality of pieces of image data belonging to the image data group N in the forward direction (close-range → long- range) or backward direction (long-range -» close-range) as a slideshow (S406 to S416). If image data to be displayed is focused image data (S408), the display control unit 25 displays only the image data for the long display time P (S410) and if image data to be displayed is not focused image data (S408), the display control unit 25 displays only the image data for the display time Q (x) calculated in S454, S456 described above (S412). The display processing is successively repeated for all image data in the image data group N (S414, S416). Steps S406 to S416 are substantially the same as steps S106 to SI 16 in Fig. 17 according to the first embodiment and thus, a detailed description thereof is omitted. [310] Then, when the slideshow display of the image data group N ends (S414), the display mode decision unit 24 determines whether the next image data group N+l is present (S418). If the next image data group N+l is present, the display mode decision unit 24 reads the next image data group N+l from the storing unit 22 (S420). When the next image data group N+l is displayed as a slideshow, the display time Q (x) of each piece of the image data N (x) other than focused image data is calculated according to the flow in Fig. 30 (S405) before starting the slideshow (S406 to S416). By repeating the above processing for all image data groups selected in S402, the slideshow display advances. In the foregoing, the calculation processing of the display time Q of image data according to the present embodiment and the slideshow display processing using the display time Q have been described. If, as described above, when an image data group is displayed as a slideshow, image data other than focused image data is displayed at equal intervals regardless of whether being close to or apart from a focused image, the display may be staged without accentuation. Thus, if images without accentuation are displayed for a long time in a slideshow display, the user may become boring. [312] According to the present embodiment, by contrast, the display time Q of image data close to focused image data is made longer and the display time Q is gradually reduced with an increasing distance from the focused image data. By making the display time Q variable in this manner, the display time Q of each piece of image data is accentuated in accordance with the focused point position so that a slideshow display that effectively stages focused image data can be realized. While images (photos) to which the user pays attention in a slideshow display are focused images, the present embodiment enhances a slideshow effect by using multifocus images around the focused image. Images other than focused images are presented to the user strictly as auxiliary images to enhance stage effects of focused images and thus, the display time thereof may be short. With a slideshow display and presentation using such focused images and auxiliary images, the user can view focused images more impressively. [313] In the foregoing, the display control device 20 and the slideshow display control method according to the first to fourth embodiments of the present invention have been described. According to the above embodiments, when a plurality of image data belonging to an image data group is displayed as a slideshow, the slideshow display mode (for example, the display order, display time, and selection of display images) is controlled based on metadata of the image data group. In this case, the display control device 20 determines focused image data (representative image data) from the plurality of pieces of image data based on focused image determination information contained in the metadata and displays the focused image data in a display mode that enables the user to recognize the focused image data more easily than other image data as a slideshow. Accordingly, focused image data is more highlighted than other image data. Therefore, a plurality of similar images with different focal positions can be displayed effectively as a slideshow and also the user can grasp the intention (which subject is in focus when imaged) of the imager while browsing the plurality of images displayed as a slideshow. [314] The preferred embodiments of the present invention have been described above with reference to the accompanying drawings, whilst the present invention is not limited to the above examples, of course. A person skilled in the art may find various alternations and modifications within the scope of the appended claims, and it should be understood that they will naturally come under the technical scope of the present invention. In the above embodiments, for example, examples of a personal computer (PC) as a display control device have been shown and examples of displaying image data groups acquired from the imaging apparatus 1 as a slideshow have been described. However, in addition to the PC, the display control device in the present invention can be applied to any electronic device, for example, the imaging apparatus 1 such as a digital still camera and digital camcorder, mobile video player, TV set, and mobile phone. For example, also in the imaging apparatus 1 that performs the multifocus imaging, an imaged and recorded image data group can be displayed in the display screen as a slideshow. [0316] The display control device 20 according to the above embodiments includes the display device 209 (corresponding to the display unit 26) that displays image data as a slideshow, but the display control device according to an embodiment of the present invention is not limited to such an example. For example, the display control device may exercise control to cause a display device included in another device connected to the display control device to display image data as a slideshow without including a display device. CLAIMS Claim 1 A display control device, comprising: a display mode decision unit that decides a display mode in which an image data group including a plurality of pieces of image data obtained by capturing a subject image in a plurality of mutually different focal positions based on focused image determination information to determine focused image data in which a predetermined subject is in focus from the image data group; and a display control unit that controls a slideshow display of the image data group based on the display mode decided by the display mode decision unit. Claim 2 The display control device according to claim 1, wherein the display mode decision unit determines the focused image data from the image data group based on the focused image determination information and decides the display mode in such a way that the focused image data can visually be recognized more easily than other image data, which is the image data group excluding the focused image data. Claim 3 The display control device according to claim 2, wherein the display mode decision unit controls a display time of each piece of the image data so that the display time of the focused image data becomes longer than the display time of the other image data. Claim 4 The display control device according to claim 2, wherein the display mode decision unit decides a display order of the plurality of pieces of image data belonging to the image data group based on focal position information representing a focal position of each piece of the image data belonging to the image data group in favor of a first display order in which the image data the focal position of which is on a close-range side is first displayed or a second display order in which the image data the focal position of which is on a long-range side is first displayed. Claim 5 The display control device according to claim 4, wherein the display mode decision unit determines whether the focused image data is on the close-range side or the long-range side based on the focal position information of an (N-l)-th image data group when the plurality of pieces of image data belonging to the (N-l)-th image data group is arranged in order of the focal position, determines whether the focused image data is on the close-range side or the long-range side based on the focal position information of an N-th image data group when the plurality of pieces of image data belonging to the N-th image data group is arranged in order of the focal position, and decides the display order of the N-th image data group in accordance with results of the determination of the (N-l)-th and N-th image data groups and the display order of the (N-l)-th image data group. Claim 6 The display control device according to claim 4, wherein the display mode decision unit determines whether the focused image data is on the close-range side or the long-range side based on the focal position information when the plurality of pieces of image data belonging to the image data group is arranged in order of the focal position, and decides the display order of the image data group in accordance with a result of the determination. Claim 7 The display control device according to claim 4, wherein the display mode decision unit determines a difference in arrangement order between the focused image data and the other image data based on the focal position information when the plurality of pieces of image data belonging to the image data group is arranged in order of the focal position and controls a display time of the other image data in accordance with the difference in arrangement order. Claim 12 A display control method, comprising: deciding a display mode in which an image data group including a plurality of pieces of image data obtained by capturing a subject image in a plurality of mutually different focal positions based on focused image determination information to determine focused image data in which a predetermined subject is in focus from the image data group; and controlling a slideshow display of the image data group based on the display mode decided by the display mode decision step. Claim 13 A program causing a computer to execute: deciding a display mode in which an image data group including a plurality of pieces of image data obtained by capturing a subject image in a plurality of mutually different focal positions based on focused image determination information to determine focused image data in which a predetermined subject is in focus from the image data group; and controlling a slideshow display of the image data group based on the display mode decided by the display mode decision step.