Patent Publication Number: US-2019174053-A1

Title: Lens barrel, replacement lens, imaging device, and control program

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a Continuation of application Ser. No. 15/124,127 filed Dec. 21, 2016, which is based upon and claims the benefit of priority from Japanese Patent Application Nos. 2014-049348 filed Mar. 12, 2014, 2014-048749 filed Mar. 12, 2014, and 2014-048721 filed Mar. 12, 2014, the entire contents of the prior applications being incorporated herein by reference. 
    
    
     BACKGROUND 
     1. Technical Field 
     The present invention relates to a lens barrel, a replacement lens, an imaging device, and a control program. 
     2. Related Art 
     A lens barrel is known that includes a focus limiter for limiting an optical system such that the optical system can only move within a specified range. 
     Furthermore, an imaging device is known that judges whether the current position of a focus lens is at an end of a search range and, when it is judged that the focus lens is at the end of the search range, sets the movement direction to be a direction toward the opposite end of the search range and begins moving the focus lens.
     Patent Document 1: Japanese Patent Application Publication No. 2001-042419   Patent Document 2: Japanese Patent Application Publication No. 2014-038197   

     If the movable range of the optical system is limited by the focus limiter, regardless of the settings of the camera body, the replacement lens drives the focus lens unit within the limited range. At this time, information concerning the focus limit cannot be transferred between the replacement lens and the camera body, and there are cases where control for effectively utilizing the settings of the camera body cannot be realized. (First Problem) 
     Conventionally, the focus lens unit and the focus limiter are mechanically linked. Therefore, it is impossible to establish both a manual focus operation and a focus limit. (Second Problem) 
     When the camera body instructs the replacement lens concerning the movement direction of the focus lens unit according to the current position of the focus lens unit, the replacement lens continues moving the focus lens unit according to the most recent instructions until new instructions are received. When the camera body determines that the focus lens unit has reached the end of the preset range, based on the current position of the focus lens unit, the camera body transmits stop instructions to stop the movement. Therefore, at the timing when the replacement lens stops the movement of the focus lens unit according to the stop instructions, there are cases where the focus lens unit is already beyond the preset range. (Third Problem) 
     SUMMARY 
     To solve the first problem, according to a first aspect of the present invention, provided is a lens barrel attached to an imaging device, comprising a focus lens unit that is movable in an optical axis direction; an actuator that moves the focus lens unit along the optical axis direction; a drive control section that controls drive of the actuator; and a setting section that is capable of setting a movement range of the focus lens unit to be one of a first range and a second range that differ from each other with respect to at least one of one end and another end thereof, each range defining the range in which the focus lens unit is allowed to move. Even when the movement range of the focus lens unit is set by the setting section to be one of the first range and the second range, the drive control section removes the setting of the movement range when instructions are received from the imaging device. 
     According to a second aspect of the present invention, provided is an imaging device to which can be attached a replacement lens capable of setting a movement range of a focus lens unit to be one of a first range and a second range that differ from each other with respect to at least one of one end and another end thereof, each range defining a range in which the focus lens unit is allowed to move, the imaging device comprising a transmitting section that, regardless of the setting of the replacement lens, transmits the range in which the focus lens unit is allowed to move. 
     According to a third aspect of the present invention, provided is a control program used by a replacement lens that is attached to an imaging device and includes a focus lens unit that is movable in an optical axis direction and an actuator that moves the focus lens unit along the optical axis direction. The control program causes a computer to perform a setting step of setting a movement range of the focus lens unit to be one of a first range and a second range that differ from each other with respect to at least one of one end and another end thereof, each range defining the range in which the focus lens unit is allowed to move; and a drive step of, even when the movement range of the focus lens unit is set in the setting step to be one of the first range and the second range, driving the actuator in a manner to remove the setting of the movement range when instructions are received from the imaging device. 
     According to a fourth aspect of the present invention, provided is a control program used by an imaging device that is attachable to a replacement lens capable of setting a movement range of a focus lens unit to be one of a first range and a second range that differ from each other with respect to at least one of one end and another end thereof, each range defining the range in which the focus lens unit is allowed to move. The control program causes a computer to perform a transmission step of, regardless of the setting of the replacement lens, transmitting the range in which the focus lens unit is allowed to move. 
     To solve the second problem, according to a fifth aspect of the present invention, provided is a replacement lens attached to an imaging device, comprising a focus lens unit; an actuator that drives the focus lens unit; and a drive control section that, when an allowable range in which the focus lens unit is allowed to move is switched from a first range to a second range that is narrower than the first range, limits movement instructions for the focus lens unit resulting from a user manipulation and drives the actuator. 
     According to a sixth aspect of the present invention, provided is an imaging device comprising a receiving section that receives first information relating to a first range that is a range in which a focus lens unit is allowed to move, second information relating to a second range that is a narrower range than the first range, and movement instructions for the focus lens unit resulting from a user manipulation; a selecting section that selects the first information or the second information; and a drive control section that controls drive of the focus lens unit. When the range in which the focus lens unit is allowed to move is switched from the first range to the second range, the drive control section limits the movement instructions for the focus lens unit resulting from the user manipulation. 
     According to a seventh aspect of the present invention, provided is a control program of a replacement lens that is attached to an imaging device and includes a focus lens unit and an actuator for driving the focus lens unit. The control program causes a computer to perform a switching step of switching an allowable range in which the focus lens unit is allowed to move from a first range to a second range that is narrower than the first range; a receiving step of receiving movement instructions for the focus lens unit resulting from a user manipulation; and a drive control step of driving the actuator while limiting the movement instructions. 
     According to an eighth aspect of the present invention, provided is a control program performing control from an imaging device having attached thereto a replacement lens that includes a focus lens unit and an actuator for driving the focus lens unit. The control program causes a computer to perform a receiving step of receiving first information relating to a first range that is a range in which the focus lens unit is allowed to move, second information relating to a second range that is a narrower range than the first range, and movement instructions for the focus lens unit resulting from a user manipulation; a selection step of selecting the first information or the second information; and a drive control step of, when the range in which the focus lens unit is allowed to move is switched from the first range to the second range, controlling the drive of the focus lens unit by limiting the movement instructions for the focus lens unit resulting from the user manipulation. 
     To solve the third problem, according to a ninth aspect of the present invention, provided is An imaging device having attached thereto and removed therefrom a replacement lens including a focus lens unit that is driven by an actuator, the imaging device comprising an acquiring section that acquires mobility information relating to a movable range of the focus lens unit; and a transmitting section that transmits response information based on the mobility information to the replacement lens, in association with a drive signal for driving the focus lens unit. 
     According to a tenth aspect of the present invention, provided is a replacement lens attached to an imaging device, comprising a focus lens unit; an actuator that drives the focus lens unit; a receiving section that receives a drive signal for driving the focus lens unit from the imaging device; and a drive control section that, when response information based on mobility information relating to a movable range of the focus lens unit is associated with the drive signal, drives the actuator based on the response information. 
     According to an eleventh aspect of the present invention, provided is a control program used by an imaging device having attached thereto and removed therefrom a replacement lens including a focus lens unit that is driven by an actuator. The control program causes a computer to perform an acquisition step of acquiring mobility information relating to a movable range of the focus lens unit; and a transmission step of transmitting response information based on the mobility information to the replacement lens, in association with a drive signal for driving the focus lens unit. 
     According to a twelfth aspect of the present invention, provided is a control program used by a replacement lens attached to an imaging device. The control program causes a computer to perform a reception step of receiving a drive signal for driving a focus lens unit included in the replacement lens from the imaging device; and a drive control step of, when response information based on mobility information relating to a movable range of the focus lens unit is associated with the drive signal, driving an actuator for moving the focus lens unit based on the response information. 
     The summary clause does not necessarily describe all necessary features of the embodiments of the present invention. The present invention may also be a sub-combination of the features described above. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an external perspective view of a camera system according to a first embodiment. 
         FIG. 2  is a drawing for describing the configuration of the camera system. 
         FIG. 3  is a drawing for describing the first range and the second range. 
         FIG. 4  is a drawing for describing the first information and the second information. 
         FIG. 5  is a drawing for describing the display control of an indicator relating to the focus limit when an MF manipulation is performed. 
         FIG. 6  is a flow chart showing an exemplary process relating to a steady sequence of the replacement lens. 
         FIG. 7  is a flow chart showing an exemplary process for selecting the drive range of the focus lens unit performed by the camera body. 
         FIG. 8  is a drawing for describing the display control of the indicator relating to the focus limit. 
         FIG. 9A  is a drawing for describing the display control of the indicator relating to the focus limit. 
         FIG. 9B  is a drawing for describing the display control of the indicator relating to the focus limit. 
         FIG. 9C  is a drawing for describing the display control of the indicator relating to the focus limit. 
         FIG. 10  is an external perspective view of a camera system according to a second embodiment. 
         FIG. 11  is a drawing for describing the configuration of the camera system. 
         FIG. 12  is a drawing for describing the first range and the second range. 
         FIG. 13  shows an exemplary display of an indicator relating to the focus limit during the manual focus manipulation. 
         FIG. 14  is a schematic view for describing the control performed by the camera body control section when the focus limit setting is switched from the first range to the second range. 
         FIG. 15  is a schematic view for describing control that is different from the control described using  FIG. 5 , performed by the camera body control section when the focus limit setting is switched from the first range to the second range. 
         FIG. 16  is a schematic view for describing control according to another embodiment example performed by the camera body control section when the focus limit setting is set to the second range. 
         FIG. 17A  is a perspective view for describing a difference between control performed when the M/A mode is selected and control performed when the M mode is selected, in a case where the focus limit switching switch is set to LIMIT  1 . 
         FIG. 17B  is a perspective view for describing a difference between control performed when the M/A mode is selected and control performed when the M mode is selected, in a case where the focus limit switching switch is set to LIMIT  1 . 
         FIG. 18  is a drawing for describing a case where the camera system is controlled by a tablet terminal that is an external device. 
         FIG. 19  is a flow chart showing an example of the drive control of the focus lens unit performed by the camera body. 
         FIG. 20  is an external perspective view of a camera system according to a second embodiment. 
         FIG. 21  is a drawing for describing the configuration of the camera system. 
         FIG. 22  is a drawing for describing the first range and the second range. 
         FIG. 23  is a drawing for describing the first information and the second information. 
         FIG. 24A  is a drawing for describing the control command designating the drive of the focus lens unit  3212 . 
         FIG. 24B  is a drawing for describing the control command designating the drive of the focus lens unit  3212 . 
         FIG. 25  is a flow chart showing an exemplary process relating to the manual focus manipulation performed by the replacement lens. 
         FIG. 26  is a flow chart showing an exemplary process for selecting a control command performed by the camera body. 
         FIG. 27  is a flow chart showing an exemplary process for driving the focus lens unit when the autofocus operation is performed by the replacement lens. 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     Hereinafter, some embodiments of the present invention will be described. The embodiments do not limit the invention according to the claims, and all the combinations of the features described in the embodiments are not necessarily essential to means provided by aspects of the invention. 
       FIG. 1  is an external perspective view of a camera system  1100  according to a first embodiment. The camera system  1100  is a single-lens reflex camera with a replacement lens formed by attaching a replacement lens  1200  to a camera body  1300  serving as an imaging device. The replacement lens  1200  includes a lens mount  1221 , and the camera body  1300  includes a camera mount  1321 . When the lens mount  1221  and the camera mount  1321  engage with each other to form the replacement lens  1200  and the camera body  1300  integrally, the replacement lens  1200  and the camera body  1300  function as the camera system  1100 . 
     The lens mount  1221  is brought near the camera mount  1321  along the arrow  1021  parallel to the optical axis  1011 , such that the lens marker  1209  and the body marker  1340  face each other and are in contact with each other. Furthermore, the replacement lens  1200  is rotated in the direction of the arrow  1022  while contact is maintained between the mounting surface of the lens mount  1221  and the mounting surface of the camera mount  1321 . When this happens, the lock mechanism formed by the lock pin  1350  operates to secure the replacement lens  1200  to the camera body  1300 . In this state, a connection terminal on the replacement lens  1200  side is electrically connected to a connection terminal on the camera body  1300  side. As a result, it is possible to transfer power and communication such as control signals between the replacement lens  1200  and the camera body  1300 . 
     The replacement lens  1200  includes a focus limit switching switch  1201  serving as a switching section and a focus ring  1202 . The focus limit switching switch  1201  switches between a first range, which is a range in which movement of the focus lens unit is allowed, and a second range that is different from the first range. By switching the focus limit switching switch  1201 , a user can select a drive range for the focus lens unit. In the present embodiment, the first range is a range in which there is no focus limit, and the second range is a range that is narrower than the first range, i.e. a range in which there is a focus limit. In the present embodiment, two focus limits are set as the second range. As described in detail further below, a focus limit for an infinitely far region and a focus limit for a very close region are set. 
     The user can set the first range by switching the focus limit switching switch  1201  to FULL, set the focus limit for the infinitely far region by switching the focus limit switching switch  1201  to LIMIT  1 , and set the focus limit for the very close region by switching the focus limit switching switch  1201  to LIMIT  2 . In other words, it is possible to select any one of three positions by switching the focus limit switching switch  1201 . By limiting the movement range of the focus lens unit, it is possible to shorten the focusing time. Regardless of which of the three positions the focus limit switching switch  1201  is switched to, the replacement lens  1200  transmits both first information relating to the first range and second information relating to the second range to the camera body  1300 . Furthermore, the replacement lens  1200  transmits switch state information as setting information indicating which of the three positions is switched to. 
     The camera body  1300  receives both the first information and the second information, and also the switch state information. The camera body  1300  moves the focus lens unit in the drive range of the focus lens unit corresponding to the switch state information. However, as described in detail further below, there are cases where it is undesirable for the focus lens unit to be driven in the drive range corresponding to the switch state information, depending on the state of the settings relating to image capturing on the camera body  1300  side. Therefore, the camera body  1300  selects any one of the first range and the second range according to the state of the settings relating to the image capturing, in addition to the switch state information, and moves the focus lens unit according to the selected range. Since the drive range of the focus lens unit is selected according to the state of the settings relating to image capturing, this drive range can be determined with flexibility. 
       FIG. 2  is a drawing for describing the configuration of the camera system  1100 . The replacement lens  1200  includes, in addition to the focus limit switching switch  1201  and the focus ring  1202 , an image capturing lens  1210 , a replacement lens control section  1220 , a zoom lens drive section  1240 , a focus lens drive section  1250 , and a detecting section  1260  serving together as an image capturing optical system. The camera body  1300  includes an AF sensor  1307 , an imaging element  1308 , an A/D converter  1309 , an internal memory  1310 , an image processing section  1311 , a storage medium IF  1312 , a display control section  1313 , a display section  1314 , a manipulation member  1315 , a power supply control section  1316 , a camera body control section  1318 , and a power supply switch  1323 . 
     The replacement lens control section  1220  and the camera body control section  1318  are connected to each other via the lens mount  1221  and the camera mount  1321 . The replacement lens control section  1220  and the camera body control section  1318  work together while communicating with each other to control the replacement lens  1200  and the camera body  1300 . 
     There are a plurality of types of replacement lenses  1200  with different optical characteristics. The user can attach any one of these replacement lenses  1200  to the camera body  1300 . The image capturing lens  1210  included in the replacement lens  1200  is formed by a plurality of optical lens groups. Specifically, the image capturing lens  1210  is formed by a zoom lens unit  1211  and a focus lens unit  1212 . The image capturing lens  1210  guides subject light flux incident thereto along an optical axis  1011  to an imaging element  1308  arranged within the camera body  1300 . 
     A portion of the subject light flux that transparently passes through the optical system to be incident thereto is guided to the AF sensor  1307 . The AF sensor  1307  includes a plurality of photoelectric converting element columns that receive a portion of the subject light flux guided thereto. The AF sensor  1307  outputs signals with matching phases when in the focused state and outputs signals with relatively shifted phases when in a front focus state or rear focus state. The amount of the phase shift corresponds to the amount of shift from the focus state. The AF sensor  1307  detects the phase difference by calculating the correlation of the output of the photoelectric converting element columns, and outputs a phase difference signal indicating the phase difference to the camera body control section  1318 . The camera body control section  1318  outputs a control signal for moving the focus lens unit  1212  to a target position to the replacement lens control section  1220 . The camera body  1300  need not include the AF sensor  1307  as a separate component from the imaging element  1308 , and may include the imaging element  1308  that has pixels with a distance measuring function. 
     The imaging element  1308  is an element that photoelectrically converts an optical image, which is the subject image. A CCD sensor or CMOS sensor can be used as the imaging element  1308 . The subject image resulting from the photoelectric conversion by the imaging element  1308  is converted from an analog signal into a digital signal by the A/D converter  1309 . 
     The subject image that has been converted into a digital signal is sequentially processed as image data. The image data is temporarily stored in the internal memory  1310 . The internal memory  1310  is a random access memory that can perform reading and writing at high speed. A DRAM and an SRAM can be used as the internal memory  1310 . The internal memory  1310  serves as a work memory in which the image processing section  1311  performs image processing and a compression process. The internal memory  1310  has a memory capacity sufficient for fulfilling this role. 
     The image processing section  1311  converts the image data into image data in compliance with a prescribed image format, according to the set image capturing mode and instructions from the user. For example, when generating a JPEG file as a still image, a compression process is performed by applying a suitable discrete cosine transformation or the like after performing image processing such as a color conversion process, gamma process, or a white balance process. The converted image data is again stored in the internal memory  1310 . 
     The image data processed by the image processing section  1311  is stored in the storage medium  1400  from the internal memory  1310 , via the storage medium IF  1312 . The storage medium  1400  is a non-volatile memory that can be attached to and removed from the camera body  1300  and is formed by a flash memory or the like. The image processing section  1311  generates the image data to be displayed, in parallel with the processed image data to be stored. The generated image data to be displayed is displayed in the display section  1314  under the control of the display control section  1313 . Regardless of whether storage is performed, the camera body control section  1318  can present a live view as an electronic finder function by having the image processing section  1311  generate sequential pieces of image data to be displayed and having the display section  1314  display this image data. Furthermore, it is possible to display an indicator or the like relating to the focus limit, which is described further below, in the display section  1314 . 
     The power supply control section  1316  communicates with the power supply  1410  to detect the remaining power, monitor the power supply, supply power, and the like. The power supply  1410  is formed by a battery, for example. 
     The camera body  1300  includes each element used for the image processing described above, and is directly or indirectly controlled by the camera body control section  1318 . The camera body control section  1318  includes a system memory  1317 . The system memory  1317  is a non-volatile memory that can be electrically erased and recorded on, and is formed by an EEPROM (Registered Trademark) or the like, for example. The system memory  1317  stores constants, variables, programs, and the like that are needed when the camera system  1100  operates, such that this information is not lost when the camera system  1100  is not operating. The camera body control section  1318  suitably extracts these constants, variables, programs, and the like in the internal memory  1310  and uses this information to control the camera system  1100 . The camera body control section  1318  functions as a receiving section that receives the first information and the second information, a selecting section that selects one of the first information and the second information based on the setting information relating to image capturing, and a control section that controls the driving of the focus lens unit  1212  according to the selected first information or second information. The camera body control section  1318  may drive the focus lens unit  1212  such that the subject image in a specified region is in focus on the light receiving surface of the imaging element  1308 , according to contrast AF information using the pieces of image data acquired in series. 
     The camera system  1100  includes a plurality of manipulation members  1315  that receive manipulations from the user. The manipulation members  1315  are used to set the image capturing mode, for example. The image capturing mode includes a full auto mode, a scene mode, and a manual mode. The user can set the image capturing mode by manipulating the manipulation members  1315 . The camera body control section  1318  detects that these manipulation members  1315  have been manipulated and performs operations according to the manipulations. 
     The camera system  1100  includes a release switch serving as one type of manipulation member  1315 . The release switch is formed by a press button that can detect two stages in a pressing direction. The camera body control section  1318  performs AF or the like, which is an image capturing preparation operation, in response to detecting SW 1 , which is a first-stage press, and performs an operation to acquire the subject image with the imaging element  1308  in response to detecting SW 2 , which is a second-stage press. 
     The zoom lens unit  1211  is driven by the zoom lens drive section  1240 , under the overall control of the camera body control section  1318  and the replacement lens control section  1220 . The zoom lens drive section  1240  changes the field angle by driving the zoom lens unit  1211  according to instructions from the user. 
     The focus lens unit  1212  is driven by the focus lens drive section  1250 , under the overall control of the camera body control section  1318  and the replacement lens control section  1220 . The focus lens drive section  1250  drives the focus lens unit  1212  such that the subject image of a specified region is focused on the light receiving surface of the imaging element  1308 , according to the information of the AF sensor  1307 . The focus lens drive section  1250  includes a drive motor  1251  serving as an actuator for driving the focus lens unit  1212  and an encoder  1252  for detecting the position of the focus lens unit  1212 . The information indicating the current position of the focus lens unit  1212  detected by the encoder  1252  is transmitted to the camera body control section  1318  via the replacement lens control section  1220 . 
     The replacement lens control section  1220  includes a system memory  1230 . The system memory  1230  stores information relating to the replacement lens  1200 . Lens function information indicating that the replacement lens includes the focus limit switching switch  1201 , a set including first pulse information indicating the first range and second pulse information indicating the second range, display information relating to the display of the focus limit, and the like are stored as the information relating to the replacement lens  1200 . A plurality of the sets of the first pulse information and the second pulse information are stored, according to the focal distance. The display information relating to the display of the focus limit includes limited position information for the focus lens unit  1212  corresponding to the state of the focus limit switching switch  1201  and the number of divisions of the distance position of the focus lens unit  1212  at the current zoom position. A plurality of pieces of the display information relating to the display of the focus limit are also stored according to the focal distance. 
     When communication is established with the camera body control section  1318 , the replacement lens control section  1220  transmits the information relating to the replacement lens  1200  to the camera body control section  1318 . For example, the replacement lens control section  1220  transmits the lens function information described above. After this, every time polling is received from the camera body  1300 , the set of the first pulse information and the second pulse information and the switch state information are transmitted. Furthermore, the replacement lens control section  1220  transmits the limited position information for the focus lens unit  1212  corresponding to the state of the focus limit switching switch  1201 , the distance position information of the focus lens unit  1212  at the current zoom position, and the number of divisions of the distance position at the current zoom position. 
     The replacement lens control section  1220  functions as a drive control section that drives the drive motor  1251  according to the second range in response to instructions from the camera body even when the allowable movement range of the focus lens unit  1212  is switched to the first range and drives the drive motor  1251  according to the first range in response to instructions from the camera body  1300  even when the allowable movement range of the focus lens unit  1212  is switched to the second range. The replacement lens control section  1220  drives the drive motor  1251  to move the focus lens unit  1212 , and controls the driving of the drive motor  1251  based on the pulse information detected by the encoder  1252 . 
     The detecting section  1260  detects the rotation amount per unit time of the focus ring  1202  due to the manipulation by the user. When the manual focus manipulation is performed by the user, the replacement lens control section  1220  transmits the detected rotation amount per unit time to the camera body control section  1318 . The focus lens unit  1212  is then driven according to the drive instructions from the camera body control section  1318 . 
       FIG. 3  is a drawing for describing the first range and the second range. Portion (a) in  FIG. 3  is used to describe the first range. Portions (b) and (c) in  FIG. 3  are used to describe the second range. Specifically, portion (b) in  FIG. 3  is used to describe the focus limit for an infinitely far region, and portion (c) in  FIG. 3  is used to describe the focus limit for a very close region. In the present embodiment, an infinitely far end design value is set as the reference for the drive range of the focus lens unit  1212 , i.e. a 0 pulse, and the number of pulses for each type of soft limit and each type of design value described further below are determined. 
     As shown in portion (a) of  FIG. 3 , the very close end design value is a value indicating the end point of the focusable range on the very close side. In the first range, the focus lens unit  1212  can achieve focus in the range between the infinitely far end design value and the very close end design value. Furthermore, the infinitely far end soft limit on the infinitely far side is determined from the infinitely far end design value and the very close end soft limit on the very close side is determined from the very close end design value. The infinitely far end soft limit is a value indicating the end point of the drive range of the focus lens unit  1212  determined in advance on the infinitely far side. The very close end soft limit is a value indicating the end point of the drive range of the focus lens unit  1212  determined in advance on the very close side. The range from the infinitely far end design value to the infinitely far end soft limit and the range from the very close end design value to the very close end soft limit are over-stroke ranges that are outside of the focusable range. In a case where the camera body  1300  performs contrast AF, when focus is achieved at the infinitely far end design value, for example, the focal point temporarily moves to the infinitely far side of the infinitely far end design value. Therefore, in the present embodiment, the over-stroke range is established by determining the infinitely far end soft limit. The same is true for the very close end soft limit. 
     At the focus limit for the infinitely far region, the focusable range is limited to be near an infinitely far position, as shown in portion (b) of  FIG. 3 . More specifically, a close end design value is determined to be on the infinitely far side from the very close end design value. The close end design value is a value indicating the end point of the focusable range on the very close side. The focus lens unit  1212  can focus in the range between the infinitely far end design value and the close end design value. Furthermore, the close end soft limit is determined between the close end design value and the very close end design value. The close end soft limit is a value indicating the end point of the drive range of the focus lens unit  1212  on the very close side. The range from the infinitely far end design value to the infinitely far end soft limit and the range from the close end design value to the close end soft limit are over-stroke ranges. 
     At the focus limit for the very close region, the focusable range is limited to be near the very close end, as shown in portion (c) of  FIG. 3 . More specifically, a far end design value is determined to be on the very close side from the infinitely far end design value. The far end design value is a value indicating the end point of the focusable range on the infinitely far side. The focus lens unit  1212  can focus in the range between the far end design value and the very close end design value. Furthermore, a far end soft limit is determined between the far end design value and the infinitely far end design value. The far end soft limit is a value indicating the end point of the drive range of the focus lens unit  1212  on the infinitely far side. The range from the far end design value to the far end soft limit and the range from the very close end design value to the very close end soft limit are over-stroke ranges. 
       FIG. 4  is a drawing for describing the first information and the second information. As described above, the system memory  1230  stores a plurality of sets that each include the first information and the second information, according to the focal distance. If the focal distance of the zoom lens unit  1211  is from 35 mm to 100 mm, the system memory  1230  stores a set of the first information and the second information corresponding to each of three ranges, which are a range from 35 mm to 50 mm, a range from 50 mm to 75 mm, and a range from 75 mm to 100 mm, for example.  FIG. 4  shows the various design values indicating the ends of the drive range of the focus lens unit  1212  and the various soft limits indicating the ends of the focusable range in the case where the focal distance is a range from 35 mm to 100 mm. The various design values and various soft limits surrounded by the parentheses in the drawing need not be transmitted to the camera body  1300 , as described further below. 
     The replacement lens  1200  transmits the infinitely far end soft limit and the very close end soft limit to the camera body  1300  as the first information corresponding to there being no focus limit. In the present embodiment, the replacement lens  1200  also transmits the infinitely far end design value and the very close end design value as information indicating the focusable range. The infinitely far end design value is set to 0, and therefore the replacement lens control section  1220  need not transmit this value to the camera body  1300 . 
     The replacement lens  1200  transmits the close end soft limit as the second information indicating the focus limit for the infinitely far region. In the present embodiment, the replacement lens  1200  also transmits the close end design value as information indicating the focusable range. The infinitely far end soft limit is the same as in the first information, and therefore does not need to be transmitted. Furthermore, the far end soft limit is transmitted as second information indicating the focus limit for a very close region. In the present embodiment, the replacement lens  1200  also transmits the far end design value as information indicating the focusable range. The very close end design value and the very close end soft limit are the same as in the first information, and therefore do not need to be transmitted. 
     As described above, the infinitely far end soft limit and the very close end soft limit are each set as a number of pulses. Accordingly, the first information is expressed as pulse information. Similarly, the close end soft limit and the far end soft limit are also each set as a number of pulses. Accordingly, the second information is also expressed as pulse information. 
     When moving the focus lens unit  1212 , the camera body  1300  transmits control signal drive instructions relating to a target position, such as a lens drive amount expressed as a number of pulses, from the camera body control section  1318  to the replacement lens control section  1220 . After receiving the drive instructions for the focus lens unit  1212  from the camera body control section  1318 , the replacement lens control section  1220  drives the drive motor  1251  to move the focus lens unit  1212 . The replacement lens control section  1220  detects the position of the focus lens unit  1212  using the encoder  1252  and drives the drive motor  1251  until reaching the number of pulses transmitted from the camera body control section  1318 . Here, when moving the focus lens unit  1212  from the infinitely far end to the very close end, for example, the focus lens unit  1212  is driven by a pulse amount indicated by the very close end design value corresponding to the current focal distance. For example, if the focal distance is from 35 mm to 50 mm and the very close end design value for this focal distance is 3000 pulses, the camera body control section  1318  transmits instructions for 3000 pulses of driving to the replacement lens control section  1220 . In the same manner, when the focal distance is from 50 mm to 75 mm and the very close end design value for this focal distance is 2800 pulses, the camera body control section  1318  transmits instructions for 2800 pulses of driving to the replacement lens control section  1220 . As described above, the number of pulses indicated by the very close end design value differs according to the focal distance. By transmitting a number of pulses corresponding to the focal distance to the replacement lens control section  1220 , it is possible to suitably control the driving of the focus lens unit  1212 . 
       FIG. 5  is a drawing for describing the display control of an indicator relating to the focus limit when an MF manipulation is performed. Portion (a) in  FIG. 5  shows an exemplary MF manipulation screen in a state where there is no focus limit. The camera body control section  1318  displays a display bar  1401 , a focus lens unit position  1402  that is information indicating the current position of the focus lens unit  1212 , and an MF manipulation guide  1403  in the MF manipulation screen. Furthermore, the camera body control section  1318  displays a marker  1404  indicating the far end of the display bar  1401  and a marker  1405  indicating the close end of the display bar  1401 . The user can manipulate the focus ring  1202  while checking the position of the focus lens unit  1212  with the display bar  1401 . 
     The camera body control section  1318  displays the focus lens unit position  1402  according to the number of divisions of the distance position at the current zoom position. Here, the number of divisions of the distance position indicates the resolution in the display of the display bar  1401 . For example, if the number of divisions is 100, it is possible to display the focus lens unit position  1402  at 100 stages. In the present embodiment, the number of divisions is determined using the infinitely far end as a reference. In other words, the position value is 0 at the infinitely far end. As the position becomes closer to the very close side, the position value increases and reaches a maximum value at the very close end. Using the example described above, the position value is 99 at the very close end. The camera body control section  1318  displays the focus lens unit position  1402  according to the distance position value indicated in the distance position information. As described above, the camera body control section  1318  displays the focus lens unit position  1402  in the display bar  1401  in a manner to correspond to the position corresponding to the current position of the focus lens unit  1212 . 
     The display of the focus lens unit position  1402  changes according to the manipulation of the focus ring  1202  by the user. When the number of divisions of the distance position at the current zoom position of the focus lens unit  1212  is 100, the variable X indicating the focus lens unit position  1402  is calculated as shown by Expression 1 below. 
         X =(1−(( A−C )/( B−C )))×100  Expression 1:
 
     It should be noted that A indicates the current focus lens unit position  1402 , B indicates the close end position value, and C indicates the far end position value. Furthermore, the focus lens unit position  1402  is set such that the closest position is 0. Here, X is calculated by replacing A with C if A−C≤0, and X is calculated by replacing A with B if B−A≤0. The camera body control section  1318  determines the close end position value and the far end position value according to the state indicated by the switch state information. 
     Portion (b) in  FIG. 5  shows the relationship between the state indicated by the switch state information and the far end position value, and portion (c) in  FIG. 5  shows the relationship between the state indicated by the switch state information and the close end position value. The far end position value and the close end position value can each be one of three values according to the state indicated by the switch state information. 
     As shown in portion (b) of  FIG. 5 , the far end position value is set to 0 when the switch state information indicates FULL. The far end position value is also set to 0 when the switch state information indicates LIMIT  1 . When the switch state information indicates LIMIT  2 , the far end position value is set to the far end focus limit position value. The far end focus limit position value is set according to the focal distance. 
     As shown by portion (c) in  FIG. 5 , the close end position value is set to a value equal to 1 less than the number of divisions of the distance position when the switch state information indicates FULL. When the switch state information indicates LIMIT  1 , the close end position value is set to the close end focus limit position value. The close end focus limit position value is set according to the focal distance. When the switch state information indicates LIMIT  2 , the close end position value is set to a value equal to 1 less than the number of divisions of the distance position. 
       FIG. 6  is a flow chart showing an exemplary process relating to a steady sequence of the replacement lens  1200 . This flow is begun after the end of a series of activation sequences that include a process for transmitting the lens function information to the camera body  1300 , a process for initializing the replacement lens  1200 , and the like. During the initialization process, upon receiving an initialization execution command from the camera body control section  1318 , the replacement lens control section  1220  drives the focus lens unit  1212  into the range corresponding to the switch state information at the time when the initialization process is begun. 
     The replacement lens control section  1220  judges whether polling has been received from the camera body control section  1318  (step S 1101 ). If it is judged that polling has been received (YES at step S 1101 ), the replacement lens control section  1220  acquires the switch state information and the focal distance information indicating the selected focal distance (step S 1102 ). The replacement lens control section  1220  then acquires the various design values and various soft limits corresponding to the focal distance information (step S 1103 ). For example, if the selected focal distance is from 35 mm to 50 mm, the replacement lens control section  1220  acquires the various design values and the various soft limits corresponding to the 35 mm to 50 mm range shown in  FIG. 4 . 
     The replacement lens control section  1220  acquires the display information relating to the display of the focus limit corresponding to the focal distance information (step S 1104 ). The replacement lens control section  1220  uses the acquired display information to calculate the distance position value of the focus lens unit position  1402 , as described in  FIG. 5  (step S 1105 ). The replacement lens control section  1220  then transmits the various acquired design values, the various acquired soft limits, the switch state information, the display information, and the calculated distance position value to the camera body control section  1318  (step S 1106 ). The replacement lens control section  1220  judges whether the power supply has been turned OFF (step S 1107 ), and when it is judged that the power supply has not been turned OFF (NO at step S 1107 ), the process moves to step S 1101 . When it is judged that the power supply has been turned OFF (YES at step S 1107 ), the series of processes is finished. 
     As described above, the replacement lens control section  1220  transmits the information relating to the focus limit to the camera body control section  1318  every time the polling is received. Accordingly, the camera body  1300  can perform the lens control and the display control using the newest focus limit range. 
       FIG. 7  is a flow chart showing an exemplary process for selecting the drive range of the focus lens unit  1212  performed by the camera body  1300 . This flow is begun when the camera body control section  1318  receives the switch state information and the information relating to the focus limit from the replacement lens  1200  according to the steady sequence. The received switch state information and information relating to the focus limit are held in the internal memory  1310 . 
     The camera body control section  1318  judges whether the attached replacement lens  1200  includes a focus limit switching switch (step S 1201 ). The camera body control section  1318  can make this judgment by referencing the lens function information transmitted from the replacement lens  1200  according to the activation sequence. When it is judged that the replacement lens  1200  does not include a focus limit switching switch (NO at step S 1201 ), the process is ended without performing the processes described further below. 
     When it is judged that the replacement lens  1200  includes the focus limit switching switch (YES at step S 1201 ), the camera body control section  1318  acquires the switch state information from the internal memory  1310  (step S 1202 ). The drive range of the focus lens unit  1212  is then selected according to the switch state information and the setting information relating to image capturing. Specifically, a judgment is made as to whether the switch state information is set to FULL (step S 1203 ) and, when it is judged that the switch state information is set to FULL (YES at step S 1203 ), a judgement is made as to whether the image capturing mode is set to a macro mode (step S 1204 ). When it is judged that the image capturing mode is set to the macro mode (YES at step S 1204 ), the focus limit for the very close region is selected (step S 1205 ). As described above, even if it is assumed that the switch state information is set to FULL, the focus limit for the very close region is selected by prioritizing the settings on the camera body  1300  side. 
     When the image capturing mode is not set to the macro mode (NO at step S 1204 ), a further judgment is made as to whether a distant view mode is set (step S 1206 ). When a distant view mode is set (YES at step S 1206 ), the focus limit for the infinitely far region is selected (step S 1207 ). As described above, even if the switch state information is set to FULL, the focus limit for the infinitely far region is selected by prioritizing the settings on the camera body  1300  side. When the distant view mode is not set (NO at step S 1206 ), the setting without a focus limit is selected (step S 1208 ). 
     When it is not indicated that the switch state information is set to FULL, i.e. when it is indicated that the switch state information is set to LIMIT  1  or LIMIT  2  (NO at step S 1203 ), a judgment is made as to whether the image capturing mode is set to full auto or to a manual mode (step S 1209 ). When the image capturing mode is set to full auto (YES at step S 1209 ), image capturing is preferably performed in an optimal state corresponding to the scene. Therefore, even when the focus limit switching switch  1201  has been switched to LIMIT  1  or LIMIT  2 , the full auto setting is prioritized. Accordingly, the setting without a focus limit is selected (step S 1210 ). Furthermore, when the manual mode is set (YES at step S 1209 ), since there will be an intentional manipulation by the user, manipulation by the user is preferably prioritized and the focus limit is not applied. Accordingly, the setting without a focus limit is selected (step S 1210 ). 
     When neither full auto nor the manual mode is set (NO at step S 1209 ), the focus limit is selected according to the switch state information. Specifically, when LIMIT  1  is selected (YES at step S 1211 ), the focus limit for the infinitely far region is set, and when LIMIT  1  is not set, i.e. when LIMIT  2  is set (NO at step S 1211 ), the focus limit for the very close region is selected (step S 1213 ). 
     Upon selecting either of the ranges, the camera body control section  1318  ends the series of processes. Upon selecting the drive range in the manner described above, if SW 1  is detected, the camera body control section  1318  moves the focus lens unit  1212  in the selected range. 
       FIG. 8  is a drawing for describing the display control of the indicator relating to the focus limit. Portions (a), (b), and (c) in  FIG. 8  are the same as portions (a), (b), and (c) in  FIG. 3 . Portion (d) in  FIG. 8  shows an exemplary display relating to the focus limit. Portion (d) in  FIG. 8  is the same as the exemplary display relating to the indicator in the MF manipulation screen shown in portion (a) of  FIG. 5 . 
     As shown in portions (a) and (d) in  FIG. 8 , for the first range, the camera body control section  1318  displays the infinitely far end design value in correspondence with the far end  1406  of the display bar  1401  and displays the very close end design value in correspondence with the close end  1407  of the display bar  1401 . The camera body control section  1318  does not change the display of the focus lens unit position  1402  while the focus lens unit  1212  is moving from the infinitely far end design value to the infinitely far end soft limit and while the focus lens unit  1212  is moving from the very close end design value to the very close end soft limit. In other words, the display of the focus lens unit position  1402  is not changed while the focus lens unit  1212  is moving beyond the range set as the focusable range. In this case, although the focus lens unit  1212  is moving, the focus lens unit position  1402  does not move in the display. 
     Therefore, the camera body control section  1318  detects whether the focus lens unit  1212  has reached the infinitely far end soft limit, for example, and upon detecting that the focus lens unit  1212  has reached the infinitely far end soft limit, may change the color in which the display bar  1401  is displayed. In this way, when performing the MF manipulation, the user can judge that the infinitely far end soft limit has been reached, even though the display of the focus lens unit position  1402  does not change. 
     As shown in portions (b) and (d) in  FIG. 8 , for the focus limit for the infinitely far region, the camera body control section  1318  displays the infinitely far end design value in correspondence with the far end  1406  of the display bar  1401  and displays the close end soft limit in correspondence with the close end  1407  of the display bar  1401 . In this case as well, as described above, the camera body control section  1318  detects whether the focus lens unit  1212  has reached the infinitely far end soft limit and, upon detecting that the focus lens unit  1212  has reached the infinitely far end soft limit, may change the color in which the display bar  1401  is displayed. As shown in portions (c) and (d) in  FIG. 8 , for the focus limit for the very close region, the camera body control section  1318  displays the far end soft limit in correspondence with the far end  1406  of the display bar  1401  and displays the very close end design value in correspondence with the close end  1407  of the display bar  1401 . 
       FIGS. 9A to 9C  are drawings for describing the display control of the indicator relating to the focus limit.  FIG. 9A  shows an exemplary display relating to the focus limit in a state where there is no focus limit.  FIG. 9A  shows an exemplary display that is the same as the exemplary display relating to the indicator in the MF manipulation screen shown in portion (a) in  FIG. 5 .  FIGS. 9B and 9C  each show an exemplary display relating to the focus limit in a state where a focus limit for the infinitely far region is used. 
     The replacement lens control section  1220  uses a different display for the indicator relating to the movement range of the focus lens unit between a case where the allowable movement range of the focus lens unit  1212  is set to be the first range and a case where the allowable movement range of the focus lens unit  1212  is set to be the second range. Specifically, as shown in  FIG. 9B , the replacement lens control section  1220  changes the marker  1405  for at least a portion of the display bar  1401  without changing the display range of the focus lens unit position  1402 . Here, the marker  1405  is displayed as “7 m”. 
     Furthermore, as shown in  FIG. 9C , the replacement lens control section  1220  may change the display range of the focus lens unit position  1402  without changing the marker  1405 . In this case, a movement-prohibited region  1408  may be displayed to indicate that the focus lens unit  1212  cannot move beyond the close end soft limit toward the very close side. In this way, the user can easily visually recognize that the focus lens unit  1212  cannot move beyond the close end soft limit toward the very close side. 
     In the above description, the camera body control section  1318  selects the setting without a focus limit if the image capturing mode is set to be full auto or the manual mode, but the setting without a focus limit may also be selected when control is performed by an external apparatus such as a smartphone, tablet terminal, personal computer, or the like. When the camera system  1100  is manipulated by an external apparatus, there are cases where the user performs more precise control by manipulating the external apparatus at a position distanced from the camera system  1100 , i.e. a position where the focus limit switching switch  1201  of the replacement lens  1200  cannot be manipulated. 
     In the above description, the camera body control section  1318  selects the setting without a focus limit if the image capturing mode is set to full auto or the manual mode, but the setting with a focus limit may be selected when the image capturing mode is set to at least one of full auto and the manual mode. In this way, the intent of the user is reflected via the focus limit switching switch  1201  and it is possible to perform the focus driving with more flexibility. 
     In the above description, the focus limiter is set on the replacement lens  1200  side, but the focus limiter may instead be set on the camera body  1300  side. In this case, the camera body control section  1318  may display a menu screen for switching the settings of the focus limiter in the display section  1314  and perform switching according to the manipulations by the user via the manipulation members  1315 . Furthermore, the camera body control section  1318  may transmit the switch state information to the replacement lens  1200  when polling is performed. Upon receiving the polling, the replacement lens control section  1220  transmits the number of divisions corresponding to the state indicated by the switch state information, the limited position information, and the like along with the first information and the second information. 
     In the above description, the replacement lens  1200  is a zoom lens, but the replacement lens  1200  may instead be a single focus lens. In this case, the focal distance does not change, and therefore the first information and the second information have fixed values. Accordingly, the replacement lens control section  1220  need only transmit the first information and the second information once. In other words, this information need not be transmitted every time the polling is received during the steady sequence. The same is true for the display information. 
     In the above description, the replacement lens control section  1220  transmits the first information and the second information as a number of pulses, but the replacement lens control section  1220  may instead transmit distance information. In this case, the camera body  1300  receives the distance information and converts this distance information into a number of pulses. In the above description, the infinitely far end design value is used as the reference value, but another value may be used as the reference value instead. For example, the very close end design value may be used as the reference value. In the above description, the settings on the camera body  1300  side are prioritized when selecting the drive range of the focus lens unit  1212 , but instead, a manipulation by the user may be performed to set which of the settings on the replacement lens  1200  side or the settings on the camera body side are prioritized. In this way, the intent of the user can be reflected to a greater degree. 
     In the above description, the replacement lens control section  1220  transmits the very close end soft limit and the infinitely far end soft limit to the camera body  1300  as the first information corresponding to the setting without a focus limit, but instead, the infinitely far end design value and the very close end design value may be transmitted as the first information. Similarly, the replacement lens control section  1220  may transmit the infinitely far end design value and the very close end design value as the second information, as the focus limit for the infinitely far region, and may transmit the far end design value and the very close end design value as the second information, as the focus limit for the very close region. As described above, in a case where the autofocus is performed using a contrast method, when focus is achieved at the infinitely far end design value, for example, the actual focus point moves beyond the infinitely far end design value toward the infinitely far side. In contrast to this, when the autofocus is performed using a phase difference method, focus can be achieved at the infinitely far end design value without moving beyond the infinitely far end design value toward the infinitely far side. Accordingly, the replacement lens control section  1220  may transmit different second information in a case where the autofocus is performed using a contrast method and a case where the autofocus is performed using a phase difference method. When the autofocus is performed using the phase difference method, the values at the ends of the focusable range may be transmitted without transmitting the values at the ends of the drive range of the focus lens unit  1212 . 
     In the above description, the replacement lens  1200  transmits compression information that is information relating to a range narrower than the first range as the second information, but instead the replacement lens  1200  may transmit expansion information that is information relating to a range wider than the first range. For example, a number of pulses closer to the very close end than the very close end soft limit described in  FIG. 3  is transmitted as the second information. In this case, the replacement lens  1200  may also transmit recommendation information indicating which of the first range and the second range is a recommended drive range that ensures optical performance greater than or equal to a predetermined reference. If one of a mode prioritizing the focus range and a mode prioritizing image quality is set on the camera body  1300  side, the drive range of the focus lens unit  1212  may be selected according to this setting. In this case, the focus limit switching switch  1201  does not function as a switching section and a switch may be provided that switches between the mode prioritizing the focus range and the mode prioritizing the image quality. If the mode prioritizing the image quality is set, information relating to the range indicated by the recommendation information is selected. On the other hand, if the mode prioritizing the focus range is set, information relating to a range differing from the range indicated by the recommendation information is selected. Furthermore, the range may be selected according to the setting information on the camera body  1300  side. For example, when the image capturing mode is set to the full auto mode, the range may be selected to prioritize the focus range even when the mode prioritizing the image quality is set. Furthermore, the switching section may be a switch that switches the AF speed. In particular, when the mode for performing high-speed AF is set for the contrast AF, a narrower range is selected than when a mode for performing low-speed AF is set. 
     In the above description, the second range includes a focus limit for the infinitely far region and a focus limit for a very close region, but the second range may instead include only one of these focus limits. In other words, the focus limit switching switch  1201  may be a switch that switches between two positions instead of three positions. Furthermore, the second range may include three or more ranges. 
     In the above description, as shown in  FIG. 7 , the camera body control section  1318  switches the range of the focus limit according to the switch state information, but instead the camera body control section  1318  may prohibit the switching process for switching the range of the focus limit under a predetermined condition. For example, the predetermined condition may be exemplified by an AF lock being in effect, the focus lens unit  1212  being driven, or the like. When the switching process is prohibited, the switching process is put on hold until the condition is removed, i.e. the operation in the immediately prior focus limit range continues. When the condition is removed, the switching process that was put on hold is performed. The switching process may be performed only when the focus control state is AF. While the switching is being performed and while the switching process is on hold, the camera body control section  1318  need not perform the switching of the focus control state, the MF operation, and the AF operation. When the focus control state is MF, the switching process need not be performed regardless of the position of the focus lens unit  1212 . In this case, only the switch state information, the various design values, and the various soft limits in the internal memory  1310  are updated. 
     In the above description, a number of pulses is given as an example of the control signal for moving the focus lens unit  1212  to the target position, but the present invention is not limited to this and any format can be used as long as at least one of a movement amount and a target position can be transferred. 
       FIG. 10  is an external perspective view of a camera system  2100  according to a second embodiment. The camera system  2100  is a single-lens reflex camera with a replacement lens formed by attaching a replacement lens  2200  serving as an imaging device to a camera body  2300 . The replacement lens  2200  includes a lens mount  2221  and the camera body  2300  includes a camera mount  2321 . When the lens mount  2221  and the camera mount  2321  engage with each other to form the replacement lens  2200  and the camera body  2300  integrally, the replacement lens  2200  and the camera body  2300  function as the camera system  2100 . 
     The lens mount  2221  is brought near the camera mount  2321  along the arrow  2021  parallel to the optical axis  2011 , such that the lens marker  2209  and the body marker  2340  face each other and are in contact with each other. Furthermore, the replacement lens  2200  is rotated in the direction of the arrow  2022  while contact is maintained between the mounting surface of the lens mount  2221  and the mounting surface of the camera mount  2321 . When this happens, the lock mechanism formed by the lock pin  2350  operates to secure the replacement lens  2200  to the camera body  2300 . In this state, a connection terminal on the replacement lens  2200  side is electrically connected to a connection terminal on the camera body  2300  side. As a result, it is possible to transfer power and communication such as control signals between the replacement lens  2200  and the camera body  2300 . 
     The replacement lens  2200  includes a focus limit switching switch  2201  serving as the switching section, a focus ring  2202 , and an AF/MF switching switch  2203 . 
     The AF/MF switching switch  2203  switches the focus control state between an M mode and an M/A mode. The user can set the M mode that enables the manual focus operation by switching the AF/MF switching switch  2203  to M. Furthermore, the user can set the M/A mode that enables both the autofocus operation and the manual focus operation by switching the AF/MF switching switch  2203  to M/A. 
     The release switch  2360  is formed by a press button that can detect two stages in a pressing direction. When the M/A mode is set, the user can perform the autofocus operation by pressing the release switch  2360  to the first stage. Furthermore, after the autofocus operation has ended, the user can perform the manual focus operation by manipulating the focus ring  2202 . By additionally performing the manual focus operation, the focus lens unit that was moved once by the autofocus operation can be driven to correct the focal position. In the manner described above, in the present embodiment, the modes that can be selected by the AF/MF switching switch  2203  are the M mode and the M/A mode. However, instead of the M/A mode, an A mode may be adopted that is an autofocus mode not allowing the manual focus manipulation using the focus ring  2202 . 
     As described in detail further below, in the present embodiment, the focus ring  2202  and the focus lens unit are not mechanically linked. The information concerning the rotation direction and the rotation amount per unit time applied to the focus ring  2202  by the user is temporarily converted into an electrical signal. An actuator drives the focus lens unit in the direction of the optical axis in order to change the focal position, according to this electrical signal. 
     The focus limit switching switch  2201  switches between a first range, which is a range in which movement of the focus lens unit is allowed, and a second range that is different from the first range. By switching the focus limit switching switch  2201 , a user can select a drive range for the focus lens unit. In the present embodiment, the first range is a range in which there are no focus limitations, and the second range is a range that is narrower than the first range, i.e. a range in which there is a focus limitation. In the present embodiment, two focus limits are set as the second range. As described in detail further below, a focus limit for an infinitely far region and a focus limit for a very close region are set. 
     The user can set the first range by switching the focus limit switching switch  2201  to FULL, set the focus limit for the infinitely far region by switching the focus limit switching switch  2201  to LIMIT  1 , and set the focus limit for the very close region by switching the focus limit switching switch  2201  to LIMIT  2 . In other words, it is possible to select any one of three positions by switching the focus limit switching switch  2201 . By limiting the movement range of the focus lens unit, it is possible to shorten the focusing time. Regardless of which of the three positions the focus limit switching switch  2201  is switched to, the replacement lens  2200  transmits both first information relating to the first range and second information relating to the second range to the camera body  2300 . Furthermore, the replacement lens  2200  transmits switch state information as setting information indicating which of the three positions is switched to. 
     When the focus limit switching switch  2201  is switched to LIMIT  1  or LIMIT  2 , the drive range of the focus lens unit during the autofocus operation is limited to the second range. Furthermore, when the focus limit switching switch  2201  is switched to LIMIT  1  or LIMIT  2 , the drive range and the drive operation of the focus lens unit during the manual focus operation are limited as described further below. 
     The camera body  2300  receives both the first information and the second information, and also the switch state information. The camera body  2300  moves the focus lens unit in the drive range of the focus lens unit corresponding to the switch state information. However, as described in detail further below, there are cases where it is undesirable for the focus lens unit to be driven in the drive range corresponding to the switch state information, depending on the state of the settings relating to image capturing on the camera body  2300  side. Therefore, the camera body  2300  selects any one of the first range and the second range according to the state of the settings relating to the image capturing, in addition to the switch state information, and moves the focus lens unit according to the selected range. Since the drive range of the focus lens unit is selected according to the state of the settings relating to image capturing, this drive range can be determined with flexibility. 
       FIG. 11  is a drawing for describing the configuration of the camera system  2100 . The replacement lens  2200  includes, in addition to the focus limit switching switch  2201 , the focus ring  2202 , and the AF/MF switching switch  2203 , an image capturing lens  2210 , a replacement lens control section  2220 , a zoom lens drive section  2240 , a focus lens drive section  2250 , and a second encoder  2260  serving as an image capturing optical system. The camera body  2300  includes an AF sensor  2307 , an imaging element  2308 , an A/D converter  2309 , an internal memory  2310 , an image processing section  2311 , a storage medium IF  2312 , a display control section  2313 , a display section  2314 , a manipulation member  2315 , a power supply control section  2316 , a camera body control section  2318 , an external communication section  2319 , and a power supply switch  2323 . 
     The replacement lens control section  2220  and the camera body control section  2318  are connected to each other via the lens mount  2221  and the camera mount  2321 . The replacement lens control section  2220  and the camera body control section  2318  work together while communication with each other to control the camera body  2300  and the replacement lens  2200 . 
     There are a plurality of types of replacement lenses  2200  with different optical characteristics. The user can attach any one of these replacement lenses  2200  to the camera body  2300 . The image capturing lens  2210  included in the replacement lens  2200  is formed by a plurality of optical lens groups. Specifically, the image capturing lens  2210  is formed by a zoom lens unit  2211  and a focus lens unit  2212 . The image capturing lens  2210  guides subject light flux incident thereto along an optical axis  2011  to an imaging element  2308  arranged within the camera body  2300 . 
     A portion of the subject light flux that transparently passes through the optical system to be incident thereto is guided to the AF sensor  2307 . The AF sensor  2307  includes a plurality of photoelectric converting element columns that receive a portion of the subject light flux guided thereto. The AF sensor  2307  outputs signals with matching phases when in the focused state and outputs signals with relatively shifted phases when in a front focus state or rear focus state. The amount of the phase shift corresponds to the amount of shift from the focus state. The AF sensor  2307  detects the phase difference by calculating the correlation of the output of the photoelectric converting element columns, and outputs a phase difference signal indicating the phase difference to the camera body control section  2318 . During the autofocus operation, the camera body control section  2318  outputs a control signal for moving the focus lens unit  2212  to a target position to the replacement lens control section  2220 . The camera body  2300  need not include the AF sensor  2307  as a separate component from the imaging element  2308 , and may include the imaging element  2308  that has pixels with a distance measuring function. 
     The imaging element  2308  is an element that photoelectrically converts an optical image, which is the subject image. A CCD sensor or CMOS sensor can be used as the imaging element  2308 . The subject image resulting from the photoelectric conversion by the imaging element  2308  is converted from an analog signal into a digital signal by the A/D converter  2309 . 
     The subject image that has been converted into a digital signal is sequentially processed as image data. The image data is temporarily stored in the internal memory  2310 . The internal memory  2310  is a random access memory that can perform reading and writing at high speed. A DRAM and an SRAM can be used as the internal memory  2310 . The internal memory  2310  serves as a work memory in which the image processing section  2311  performs image processing and a compression process. The internal memory  2310  has a memory capacity sufficient for fulfilling this role. 
     The image processing section  2311  converts the image data into image data in compliance with a prescribed image format, according to the set image capturing mode and instructions from the user. For example, when generating a JPEG file as a still image, a compression process is performed by applying a suitable discrete cosine transformation or the like after performing image processing such as a color conversion process, gamma process, or a white balance process. The converted image data is again stored in the internal memory  2310 . 
     The image data processed by the image processing section  2311  is stored in the storage medium  2400  from the internal memory  2310 , via the storage medium IF  2312 . The storage medium  2400  is a non-volatile memory that can be attached to and removed from the camera body  2300  and is formed by a flash memory or the like. The image processing section  2311  generates the image data to be displayed, in parallel with the processed image data to be stored. The generated image data to be displayed is displayed in the display section  2314  under the control of the display control section  2313 . Regardless of whether storage is performed, the camera body control section  2318  can present a live view as an electronic finder function by having the image processing section  2311  generate sequential pieces of image data to be displayed and having the display section  2314  display this image data. Furthermore, it is possible to display an indicator or the like relating to the focus limit, which is described further below, in the display section  2314 . 
     The power supply control section  2316  communicates with the power supply  2410  to detect the remaining power, monitor the power supply, supply power, and the like. The power supply  2410  is formed by a battery, for example. 
     The camera body  2300  includes each element used for the image processing described above, and is directly or indirectly controlled by the camera body control section  2318 . The camera body control section  2318  includes a system memory  2317 . The system memory  2317  is a non-volatile memory that can be electrically erased and recorded on, and is formed by an EEPROM (Registered Trademark) or the like, for example. The system memory  2317  stores constants, variables, programs, and the like that are needed when the camera system  2100  operates, such that this information is not lost when the camera system  2100  is not operating. The camera body control section  2318  suitably extracts these constants, variables, programs, and the like in the internal memory  2310  and uses this information to control the camera system  2100 . The camera body control section  2318  functions as a receiving section that receives the first information and the second information, a selecting section that selects one of the first information and the second information based on the setting information relating to image capturing, and a control section that controls the driving of the focus lens unit  2212  according to the selected first information or second information. The camera body control section  2318  may drive the focus lens unit  2212  such that the subject image in a specified region is in focus on the light receiving surface of the imaging element  2308 , according to contrast AF information using the pieces of image data acquired in series. 
     The camera system  2100  includes a plurality of manipulation members  2315  that receive manipulations from the user. The manipulation members  2315  are used to set the image capturing mode, for example. The image capturing mode includes a full auto mode, a scene mode, and a manual mode. The user can set the image capturing mode by manipulating the manipulation members  2315 . The camera body control section  2318  detects that these manipulation members  2315  have been manipulated and performs operations according to the manipulations. 
     The zoom lens unit  2211  is driven by the zoom lens drive section  2240 , under the overall control of the camera body control section  2318  and the replacement lens control section  2220 . The zoom lens drive section  2240  changes the field angle by driving the zoom lens unit  2211  according to instructions from the user. 
     The focus lens unit  2212  is driven by the focus lens drive section  2250 , under the overall control of the camera body control section  2318  and the replacement lens control section  2220 . The focus lens drive section  2250  includes a drive motor  2251  serving as an actuator for driving the focus lens unit  2212  and a first encoder  2252  for detecting the position of the focus lens unit  2212 . The information indicating the current position of the focus lens unit  2212  detected by the first encoder  2252  is transmitted to the camera body control section  2318  via the replacement lens control section  2220 . 
     When the AF/MF switching switch  2203  is switched, an electrical signal corresponding to the selected position of the switch is transmitted to the replacement lens control section  2220 . The replacement lens control section  2220  controls the focus according to the received electrical signal. 
     When performing the autofocus operation, the focus lens drive section  2250  drives the focus lens unit  2212  according to the information of the AF sensor  2307 . Specifically, first, the AF sensor outputs to the camera body control section  2318  a phase difference signal indicating a phase difference corresponding to the shift amount from the focused state. The camera body control section  2318  converts this phase difference signal into a control signal. The control signal is then transmitted to the replacement lens control section  2220 . The replacement lens control section  2220  outputs the received control signal to the focus lens drive section  2250 . The focus lens drive section  2250  drives the drive motor  2251  according to this control signal. The drive motor  2251  moves the focus lens unit  2212  to the position where the subject image of a specified region is focused on the light receiving surface of the imaging element  2308 . 
     When performing the manual focus operation, the focus lens drive section  2250  drives the focus lens unit  2212  according to information of the rotation direction and rotation amount per unit time applied to the focus ring  2202  by the user. Specifically, the second encoder  2260  detects the rotation direction and rotation amount per unit time applied to the focus ring  2202  by the user and converts the detected information into an electrical signal. The second encoder  2260  then transmits this electrical signal to the camera body control section  2318  via the replacement lens control section  2220 . The camera body control section  2318  converts the received electrical signal into a drive control signal expressing the drive direction and drive amount per unit time, and transfers the drive control signal to the replacement lens control section  2220 . The replacement lens control section  2220  outputs this received control signal to the focus lens drive section  2250 . The focus lens drive section  2250  generates a drive pulse corresponding to this control signal and drives the drive motor  2251 . The drive motor  2251  moves the focus lens unit  2212  in the optical axis direction to change the focal position. As described in detail further below, when the allowable movement range of the focus lens unit  2212  is switched to the second range, the autofocus operation and the manual focus operation have respectively different limits. 
     The replacement lens control section  2220  includes a system memory  2230 . The system memory  2230  stores information relating to the replacement lens  2200 . Lens function information indicating that the replacement lens includes the focus limit switching switch  2201 , a set including first pulse information indicating the first range and second pulse information indicating the second range, display information relating to the display of the focus limit, and the like are stored as the information relating to the replacement lens  2200 . A plurality of the sets of the first pulse information and the second pulse information are stored, according to the focal distance. The display information relating to the display of the focus limit includes limited position information for the focus lens unit  2212  corresponding to the state of the focus limit switching switch  2201  and the number of divisions of the distance position of the focus lens unit  2212  at the current zoom position. A plurality of pieces of the display information relating to the display of the focus limit are also stored according to the focal distance. 
     When communication is established with the camera body control section  2318 , the replacement lens control section  2220  transmits the information relating to the replacement lens  2200  to the camera body control section  2318 . For example, the replacement lens control section  2220  transmits the lens function information described above. After this, every time polling is received from the camera body  2300 , the set of the first pulse information and the second pulse information and the switch state information are transmitted. Furthermore, the replacement lens control section  2220  transmits the limited position information for the focus lens unit  2212  corresponding to the state of the focus limit switching switch  2201 , the distance position information of the focus lens unit  2212  at the current zoom position, and the number of divisions of the distance position at the current zoom position. 
     The replacement lens control section  2220  functions as a drive control section that drives the drive motor  2251  according to the second range in response to instructions from the camera body even when the allowable movement range of the focus lens unit  2212  is switched to the first range and drives the drive motor  2251  according to the first range in response to instructions from the camera body  2300  even when the allowable movement range of the focus lens unit  2212  is switched to the second range. The replacement lens control section  2220  drives the drive motor  2251  to move the focus lens unit  2212 , and controls the driving of the drive motor  2251  based on the pulse information detected by the first encoder  2252 . 
       FIG. 12  is a drawing for describing the first range and the second range. Portion (a) in  FIG. 12  is used to describe the first range. Portions (b) and (c) in  FIG. 12  are used to describe the second range. Specifically, portion (b) in  FIG. 12  is used to describe the focus limit for an infinitely far region, and portion (c) in  FIG. 12  is used to describe the focus limit for a very close region. In the present embodiment, portions (a), (b), and (c) in  FIG. 12  respectively correspond to states resulting from the focus limit switching switch  2201  being switched to FULL, LIMIT  1 , and LIMIT  2 . In the present embodiment, an infinitely far end design value is set as the reference for the drive range of the focus lens unit  2212 , i.e. a 0 pulse, and the number of pulses for each type of soft limit and each type of design value described further below are determined. 
     As shown in portion (a) of  FIG. 12 , the very close end design value is a value indicating the end point of the focusable range on the very close side. When performing the autofocus operation, the focus lens unit  2212  can achieve focus in the range between the infinitely far end design value and the very close end design value, which is the focusable range of the first range. Furthermore, the infinitely far end soft limit on the infinitely far side is determined from the infinitely far end design value, and the very close end soft limit on the very close side is determined from the very close end design value. The infinitely far end soft limit is a value indicating the end point of the drive range of the focus lens unit  2212  determined in advance on the infinitely far side. The very close end soft limit is a value indicating the end point of the drive range of the focus lens unit  2212  determined in advance on the very close side. The range from the infinitely far end design value to the infinitely far end soft limit and the range from the very close end design value to the very close end soft limit are over-stroke ranges that are outside of the focusable range. In a case where the camera body  2300  performs contrast AF, when focus is achieved at the infinitely far end design value, for example, the focal point temporarily moves to the infinitely far side of the infinitely far end design value. Therefore, in the present embodiment, the over-stroke range is established by determining the infinitely far end soft limit. The same is true for the very close end soft limit. 
     At the focus limit for the infinitely far region, the focusable range is limited to be near an infinitely far position, as shown in portion (b) of  FIG. 12 . More specifically, a close end design value is determined to be on the infinitely far side from the very close end design value. The close end design value is a value indicating the end point of the focusable range on the very close side. When performing the autofocus operation, the focus lens unit  2212  can focus in the range between the infinitely far end design value and the close end design value, which is the focusable range. Furthermore, the close end soft limit is determined between the close end design value and the very close end design value. The close end soft limit is a value indicating the end point of the drive range of the focus lens unit  2212  on the very close side. The range from the infinitely far end design value to the infinitely far end soft limit and the range from the close end design value to the close end soft limit are over-stroke ranges. 
     At the focus limit for the very close region, the focusable range is limited to be near the very close end, as shown in portion (c) of  FIG. 12 . More specifically, a far end design value is determined to be on the very close side from the infinitely far end design value. The far end design value is a value indicating the end point of the focusable range on the infinitely far side. When performing the autofocus operation, the focus lens unit  2212  can focus in the range between the far end design value and the very close end design value, which is the focusable range. Furthermore, a far end soft limit is determined between the far end design value and the infinitely far end design value. The far end soft limit is a value indicating the end point of the drive range of the focus lens unit  2212  on the infinitely far side. The range from the far end design value to the far end soft limit and the range from the very close end design value to the very close end soft limit are over-stroke ranges. 
     When performing the manual focus operation, in a case where the second range is selected, the focus lens unit  2212  can move in the second range according to the manipulation by the user. On the other hand, as described in detail further below, the movement of the focus lens unit  2212  by the user is limited outside of the focusable range. In order to simplify the following description, a case is described in which the user switches to LIMIT  1  as the second range to limit the movement of the focus limit switching switch  2201  on the very close region side. When LIMIT  2  has been switched to in order to limit the movement on the infinitely far region side, the only difference is that the same limitation is performed on the infinitely far region side instead of on the very close region side, and therefore a description thereof is omitted. 
       FIG. 13  shows an exemplary display of an indicator relating to the focus limit during the manual focus manipulation. A state is shown in which the indicator image  2420  relating to the focus limit is displayed by being superimposed on the live view image  2430  displayed by the display section  2314  of the camera body  2300 . 
     More specifically, the subject image that is imaged on the imaging element  2308  through the replacement lens  2200  is sequentially converted into image data for the live view display by the imaging element  2308 , the A/D converter  2309 , and the image processing section  2311 . The camera body control section  2318  displays the image data for the live view display in the display section  2314  as the live view image  2430 , via the display control section  2313 . Furthermore, the camera body control section  2318  generates an indicator image  2420  relating to the focus limit from the position information of the focus lens unit  2212  received from the replacement lens control section  2220 , the switch state information of the focus limit switching switch  2201 , and the like. The camera body control section  2318  displays the generated indicator image  2420  superimposed on the live view image  2430  of the display section  2314 , via the display control section  2313 . 
     The indicator image  2420  includes a display bar  2401 , a lens icon  2411  indicating the focal position corresponding to the current position of the focus lens unit  2212 , and an MF icon  2405 . The indicator image  2420  also includes a close side marker  2402  indicating the close end of the display bar  2401 , a far side marker  2403  indicating the far end, and a limit marker  2404  indicating the close side limit. Furthermore, the indicator image  2420  includes a movement-prohibited region  2406  indicating the region outside the focus limit range. 
     The camera body control section  2318  displays the lens icon  2411  in the display bar  2401  in correspondence with the current position of the focus lens unit  2212 . The display position of the lens icon  2411  changes according to the manipulation of the focus ring  2202  by the user. The user can manipulate the focus ring  2202  while checking the current position of the focus lens unit  2212  based on the position of the lens icon  2411  on the display bar  2401 . Furthermore, when the lens icon  2411  is in the movement-prohibited region  2406 , i.e. when the focus lens unit  2212  is outside of the second range, the outline of the icon may be displayed as a dashed line or the like, as shown by the lens icon  2412 . 
       FIG. 14  is a schematic view for describing the control performed by the camera body control section  2318  when the focus limit setting is switched from the first range to the second range. Here, as an example of a case in which the focus limit setting is switched from the first range to the second range, the control performed when the AF/MF switching switch  2203  is set to the M mode and the focus limit switching switch  2201  is switched from FULL to LIMIT  1  is described. 
     When the focus limit switching switch  2201  is switched from FULL to LIMIT  1  by the user, the camera body control section  2318  judges whether the focus lens unit  2212  is positioned outside the second range. When it is judged that the focus lens unit  2212  is positioned outside the second range, the focus lens unit  2212  is forcefully moved to a boundary region of the second range. 
     Specifically, when switching of the focus limit switching switch  2201  is detected, the camera body control section  2318  acquires the position information of the focus lens unit  2212  detected by the first encoder  2252  from the replacement lens control section  2220 . The camera body control section  2318  then judges whether the current position of the focus lens unit  2212  is within the second range. When it is judged that the focus lens unit  2212  is outside of the second range, the camera body control section  2318  calculates the movement amount, such as the number of pulses, needed to move the focus lens unit  2212  from the current position to the boundary position of the second range. The camera body control section  2318  transmits a control signal including the calculated number of pulses and the movement direction to the replacement lens control section  2220 . The replacement lens control section  2220  outputs the received control signal to the focus lens drive section  2250 . The focus lens drive section  2250  drives the drive motor  2251  according to the control signal and forcefully moves the focus lens unit  2212  to the boundary position of the second range. The movement of the focus lens unit  2212  is performed such that the focus lens unit  2212  is moved to a position included in the second range that is the shortest distance from the current position. In other words, among the two boundary positions of the second range, the one boundary position closer to the current position is set as the target position. By setting the target position in this manner, the time needed to forcefully move the focus lens unit  2212  can be minimized. If the time needed to forcefully move the focus lens unit  2212  is minimized, the user can perform the manual focus operation that much faster. The target position is not limited to being this boundary position, and can instead be set to a different predetermined position, such as a position designated by the user or the position in the center of the second range, for example. 
     When the movement of the focus lens unit  2212  is finished, the user can manipulate the focus ring  2202  to perform the manual focus manipulation. The camera body control section  2318  limits the drive range of the focus lens unit  2212  to be within the second range. The user can move the focus lens unit  2212  freely in the second range. On the other hand, the user cannot move the focus lens unit  2212  to the outside of the second range. 
     Specifically, the second encoder  2260  detects the rotation direction and rotation amount per unit time of the focus ring  2202  resulting from the manipulation by the user, and converts this information into an electrical signal. The second encoder  2260  then transmits the electrical signal to the camera body control section  2318  via the replacement lens control section  2220 . 
     The camera body control section  2318  calculates the number of pulses corresponding to the target position of the focus lens unit  2212 , according to the received electrical signal. When the focus lens unit  2212  is driven according to the manual focus manipulation by the user, the camera body control section  2318  judges whether the focus lens unit  2212  has moved outside the second range based on the calculated number of pulses and the position information of the focus lens unit  2212  and the second pulse information received from the replacement lens control section  2220 . 
     When it is judged that the focus lens unit  2212  is not outside the second range, the camera body control section  2318  transmits the number of pulses calculated according to the manual focus manipulation by the user to the replacement lens control section  2220 . The replacement lens control section  2220  drives the focus lens unit  2212  according to the received number of pulses. When it is judged that the focus lens unit  2212  is outside the second range, the camera body control section  2318  transmits the number of pulses for moving the focus lens unit  2212  to the boundary of the second range to the replacement lens control section  2220 . The replacement lens control section  2220  moves the focus lens unit  2212  to the boundary of the second range according to the received number of pulses. 
     After the focus lens unit  2212  has reached the second range, when the a manual focus manipulation is performed to further move the focus lens unit  2212  outside of the second range, the camera body control section  2318  ignores the control signal transmitted from the replacement lens control section  2220 . Furthermore, the replacement lens control section  2220  may ignore the electrical signal from the second encoder  2260  corresponding to such a manual focus manipulation. 
     When it is judged that the manual focus manipulation performed by the user causes the focus lens unit  2212  to be outside the second range, the camera body control section  2318  may display in the display section  2314  a display notifying the user that the manipulation would result in the focus lens unit  2212  being outside the focus limit range. For example, the camera body control section  2318  may display the MF icon  2405  with a changed color in a blinking manner. 
       FIG. 15  is a schematic view for describing control that is different from the control described using  FIG. 14 , performed by the camera body control section  2318  when the focus limit setting is switched from the first range to the second range. Here, as an example of a case in which the focus limit setting is switched from the first range to the second range, the control performed when the AF/MF switching switch  2203  is set to the M mode and the focus limit switching switch  2201  is switched from FULL to LIMIT  1  is described, in the same manner as the example shown in  FIG. 14 . 
     When the focus limit switching switch  2201  is switched from FULL to LIMIT  1  by the user, the camera body control section  2318  judges whether the focus lens unit  2212  is positioned outside the second range. In the present embodiment, even when it is judged that the focus lens unit  2212  is positioned outside the second range, the focus lens unit  2212  is not moved to a boundary position of the second range. In this case, the user can more quickly perform the manual focus manipulation without waiting while the focus lens unit  2212  is moved. 
     When the focus lens unit  2212  is outside of the second range, the camera body control section  2318  performs drive control according to the drive direction of the focus lens unit  2212 . When the manual focus manipulation is performed in a manner to move the focus lens unit  2212  in a direction toward the second range, the camera body control section  2318  does not limit the driving. However, when the manual focus manipulation is performed in a manner to move the focus lens unit  2212  in a direction away from the second range, the camera body control section  2318  does not drive the focus lens unit  2212 . 
     Specifically, the camera body control section  2318  calculates the number of pulses corresponding to the target position of the focus lens unit  2212  according to the manual focus manipulation performed by the user via the focus ring  2202 . In a case where the focus lens unit  2212  is outside the second range, when the manual focus manipulation performed by the user is judged to be a manipulation that would cause the focus lens unit  2212  to move in a direction away from the second range, the camera body control section  2318  does not transmit the control signal to the replacement lens control section  2220 . On the other hand, when the manual focus manipulation performed by the user is judged to be a manipulation that would cause the focus lens unit  2212  to move in a direction toward from the second range, the camera body control section  2318  transmits the control signal to the replacement lens control section  2220 . The replacement lens control section  2220  drives the drive motor  2251  according to the received control signal to move the focus lens unit  2212 . In a case where the focus lens unit  2212  does not reach the second range as a result of the one manual focus operation as well, the camera body control section  2318  continues to prohibit the focus lens unit  2212  from moving in a direction away from the second range. After the focus lens unit  2212  has reached the second range, the camera body control section  2318  performs control in the same manner as in the example of  FIG. 14 . 
       FIG. 16  is a schematic view for describing control according to another embodiment example performed by the camera body control section  2318  when the focus limit setting is set to the second range. In this embodiment example as well, the user can freely move the focus lens unit  2212  within the second range, in the same manner as in the examples of  FIG. 14  and  FIG. 15 . On the other hand, in the present embodiment example, the user can move the focus lens unit  2212  even outside of the second range under a predetermined limit condition. A variety of conditions can be set as the limit condition, but here, a condition is set that there is a greater feeling of resistance when performing the manual focus manipulation in a case where the focus lens unit  2212  is being moved outside of the second range in a direction away from the second range than in a case where the focus lens unit  2212  is being moved in a direction toward the second range. 
     Specifically, the camera body control section  2318  sets the drive amount of the focus lens unit  2212  relative to a rotation amount of the focus ring  2202  causing the focus lens unit  2212  to move in a direction away from the second range to be less than the drive amount of the focus lens unit  2212  relative to a rotation amount of the focus ring  2202  causing the focus lens unit  2212  to move in a direction toward the second range. For example, assuming that the focus lens unit  2212  is moved by d (mm) when the user rotates the focus ring  2202  by r (°) in a direction causing the focus lens unit  2212  to move toward the second range, control is performed such that the focus lens unit  2212  is moved by d/2 (mm) when the user rotates the focus ring  2202  by r (°) in a direction causing the focus lens unit  2212  to move away from the second range. 
     By performing such control, the user can sense that the focus lens unit  2212  is being moved farther beyond the second range. In a case where the focus lens unit  2212  is moved by d (mm) when the user rotates the focus ring  2202  by r (°) while the focus lens unit  2212  is within the second range, control may be performed such that the focus lens unit  2212  is moved by 2d (mm) when the user rotates the focus ring  2202  by r (°) in a direction causing the focus lens unit  2212  to move from outside the second range toward the second range. In other words, control may be performed such that the focus lens unit  2212  is moved more quickly to be inside the second range. With this control, when the user senses that the focus lens unit  2212  is outside the second range, the user can move the focus lens unit  2212  more quickly back into the second range. 
     In the present embodiment, when movement instructions are received that cause the focus lens unit  2212  to move outside the second range, the camera body control section  2318  drives the drive motor  2251  via the replacement lens control section  2220  such that the movement amount of the focus lens unit  2212  relative to the manipulation amount is reduced. In other words, during autofocus, when the focus limit switching switch  2201  is switched to LIMIT  1 , the focus lens unit  2212  can only move within the second range, but during the manual focus, even when the focus limit switching switch  2201  is switched to LIMIT  1 , the focus lens unit  2212  can move even outside the second range under the limit condition. By providing such a difference, the operations on the camera side can be reliably limited during the autofocus, and the intent of the user can be prioritized during the manual focus. 
     As another variation, in a case where a manipulation of the focus ring  2202  continues being received from the user as well, the camera body control section  2318  can perform control to temporarily stop the movement of the focus lens unit  2212  at a boundary position of the second range. For example, when the focus lens unit  2212  has reached a boundary position of the second range, the camera body control section  2318  ignores the manipulation until the user has rotated the focus ring  2202  by at least 180°, thereby stopping the focus lens unit  2212  at the boundary position. When the user further rotates the focus ring  2202 , the focus lens unit  2212  is driven according to this rotation amount away from the second range. The movement amount relative to the rotation amount may be limited as described above. By performing such control, the user can sense that the focus lens unit  2212  is moving outside of the second range. 
       FIGS. 17A and 17B  are each a perspective view for describing a difference between control performed when the M/A mode is selected and control performed when the M mode is selected, in a case where the focus limit switching switch  2201  is set to LIMIT  1 .  FIG. 17A  shows an example of the drive limit of the focus lens unit  2212  when the M/A mode is selected. When the autofocus operation is performed, the movement of the focus lens unit  2212  is limited to be within the second range. In other words, when the autofocus operation is performed, the camera body control section  2318  limits the drive range of the focus lens drive section  2250  such that the focus lens unit  2212  is stopped in the second range. On the other hand, when the manual focus operation is performed, the user can freely move the focus lens unit  2212  in the first range without being limited to the second range. Specifically, the camera body control section  2318  drives the focus lens unit  2212  according to the manipulation amount, without adding any limit to the manual focus manipulation by the user. With such control, when the M/A mode is selected, the user can correct the focal position resulting from the autofocus by performing the manual focus manipulation, without being limited to the second range. 
       FIG. 17B  shows an exemplary drive limit of the focus lens unit  2212  when the M mode is selected. When the M mode is selected, the movement of the focus lens unit  2212  is limited to be within the second range. In other words, the user can freely move the focus lens unit  2212  within the second range, but cannot move the focus lens unit  2212  outside the second range. With such control, when the M mode is selected, the user is prevented from moving the focus lens unit  2212  outside of the focus limit set intentionally by the user. The camera body control section  2318  need not completely prohibit movement of the focus lens unit  2212  in the second range, and may limit the movement as described using  FIG. 16 . 
       FIG. 18  is a drawing for describing a case where the camera system  2100  is controlled by a tablet terminal  2500  that is an external device. In particular, a case is described in which the drive of the focus lens unit  2212  of the camera system  2100  is controlled by the tablet terminal  2500 . The camera system  2100  and the tablet terminal  2500  communicate wirelessly with each other. Various wireless communication standards such as Wi-Fi (Registered Trademark) and Bluetooth (registered trademark) can be adopted for the wireless communication. Furthermore, a tablet terminal is given as an example of the external device, but instead a smartphone, personal computer, mobile telephone, wearable terminal, or the like can be used as the external device. 
     When the camera system  2100  is controlled by the tablet terminal  2500 , the camera system  2100  is set in advance to a remote manipulation mode in which the camera system  2100  is manipulated remotely by the user using the external device. When the camera system  2100  is set to the remote manipulation mode, the user can perform the manual focus manipulation of the focus lens unit  2212  of the camera system  2100 , for example, via the tablet terminal  2500 . The camera system  2100  is arranged in front of a subject that is the image capturing target. In  FIG. 18 , the camera system  2100  is secured to a tripod. The camera system  2100  captures an image of scenery  2700  expanding in front of the camera system  2100  to sequentially generate a live view image. Furthermore, as described in  FIG. 13 , the camera system  2100  generates an indicator image relating to the focus limit. The camera system  2100  transmits the generated live view image and indicator image to the tablet terminal  2500 . 
     The tablet terminal  2500  includes a display section  2501 . The tablet terminal  2500  receives the transmitted live view image and indicator image, and displays these images in the display section  2501  in a superimposed manner. The indicator image includes a display bar  2502  and a lens icon  2503  indicating the focal position corresponding to the current position of the focus lens unit  2212 . The display bar  2502  also includes a close side marker  2504  indicating the close end of the display bar  2502  and a far side marker  2505  indicating the far end of the display bar  2502 . 
     The user can perform the manual focus manipulation of the focus lens unit  2212  of the camera system  2100  by manipulating the lens icon  2503  displayed in the display section  2501 . Specifically, the user uses a finger  2600  to press the lens icon  2503  displayed in the display section  2501 . Then, while maintaining the pressing state, the user slides the finger up or down on the display bar  2502 . The tablet terminal  2500  calculates the movement amount of the focus lens unit  2212  according to this slide manipulation. Specifically, the tablet terminal  2500  first calculates the movement amount of the lens icon  2503  caused by the slide manipulation. The tablet terminal  2500  then calculates the movement amount of the focus lens unit  2212  corresponding to the movement amount of the lens icon  2503 , by using a preset conversion formula between the movement amount of the lens icon  2503  and the movement amount of the focus lens unit  2212 . The tablet terminal  2500  preferably calculates the movement amount of the lens icon  2503  as a number of pulses. The tablet terminal  2500  transmits the calculated movement amount of the focus lens unit  2212  to the camera system  2100 . 
     Upon receiving the movement amount of the focus lens unit  2212 , the camera system  2100  drives the focus lens unit  2212  via the replacement lens control section  2220  according to the movement amount. Here, when the user remotely manipulates the camera system  2100  using the tablet terminal  2500 , it is assumed that the user is at a position distanced from the camera system  2100 . When the user is at a position distanced from the camera system  2100 , the user cannot perform switching by manipulating the focus limit switching switch  2201  provided on the replacement lens  2200 . Therefore, in the present embodiment, when the user performs the manual focus manipulation of the focus lens unit  2212  of the camera system  2100  remotely using the tablet terminal  2500 , even if the focus limit switching switch  2201  is switched to the second range, for example, the camera body control section  2318  drives the focus lens unit  2212  in the first range. In this way, the user can perform the manual focus manipulation in the first range via the tablet terminal  2500 , without directly manipulating the focus limit switching switch  2201 . 
     After this, when the image capturing instructions are received from the user, the tablet terminal  2500  instructs the camera system  2100  to perform image capturing. As described above, by remotely operating the camera system using the tablet terminal  2500 , the user can capture an image of the scenery  2700  with the desired focus achieved through the manual focus manipulation. 
     In the above description, the allowable movement range of the focus lens unit is switched by the focus limit switching switch  2201 , but this range may instead be switched by the tablet terminal  2500 . In this case, the tablet terminal  2500  may display a menu screen for switching the focus limiter setting in the display section  2501  and perform switching according to the manipulation by the user. When the allowable movement range of the focus lens unit is switched to the second range by the tablet terminal  2500 , the tablet terminal  2500  may display the indicator image corresponding to the second range. For example, as shown in  FIG. 13 , the limit marker may be displayed. Furthermore, when the allowable movement range is switched to the second range, the tablet terminal  2500  may limit the manipulation range of the lens icon  2503  by the user to correspond to the second range. 
       FIG. 19  is a flow chart showing an example of the drive control of the focus lens unit  2212  performed by the camera body  2300 . This flow is begun by the camera body control section  2318  detecting SW 1 , if the focus control state is the M/A mode, or by the camera body control section  2318  receiving the rotation amount of the focus lens unit  2212  caused by the user from the replacement lens control section  2220 , if the focus control state is the M mode. In the above description, the focus limit switching switch  2201  is switched to one of three positions that include FULL, LIMIT  1 , and LIMIT  2 , but in this flow, in order to simplify the description, a case is described in which the focus limit switching switch  2201  is switched to one of FULL and LIMIT  1 . Switching to LIMIT  2  uses the same process as switching to LIMIT  1 . The camera body control section  2318  receives the switch state information from the replacement lens  2200  according to the steady sequence performed periodically with the replacement lens control section  2220 . The received switch state information is held in the internal memory  2310 . 
     The camera body control section  2318  references the switch state information and judges whether the focus limit switching switch  2201  is switched to LIMIT  1  (step S 2101 ). When it is judged that the focus limit switching switch  2201  is not switched to LIMIT  1 , i.e. when it is judged that the focus limit switching switch  2201  is switched to FULL (NO at step S 2101 ), the camera body control section  2318  controls the replacement lens control section  2220  to drive the focus lens unit  2212  in the first range, i.e. the entire range (step S 2105 ). 
     When it is judged that the focus limit switching switch  2201  is switched to LIMIT  1  (YES at step S 2101 ), the camera body control section  2318  judges whether an image capturing manipulation has been performed by an external device (step S 2102 ). By judging whether the external communication section  2319  has received a signal relating to an image capturing manipulation from an external device, the camera body control section  2318  can judge whether an image capturing manipulation has been performed by the external device. The signal relating to the image capturing manipulation includes a signal indicating image capturing instructions and a signal indicating the movement amount of the focus lens unit  2212 , as described in  FIG. 18 . When it is judged that an image capturing manipulation has been performed by the external device (YES at step S 2102 ), even if the focus limit switching switch  2201  is switched to LIMIT  1 , the camera body control section  2318  controls the replacement lens control section  2220  to drive the focus lens unit  2212  in the entire range, as described in  FIG. 18  (step S 2105 ). 
     When it is judged that an image capturing manipulation has not been performed by the external device (NO at step S 2102 ), a judgment is made as to whether the focus control state is switched to the M/A mode (step S 2103 ). When it is judged that the focus control state is not switched to the M/A mode, i.e. when it is judged that the focus control state is switched to the M mode (NO at step S 2103 ), as shown in  FIG. 17B , the camera body control section  2318  selects the focus limit for the infinitely far region and controls the replacement lens control section  2220  to drive the focus lens unit  2212  within this focus limit, i.e. to perform limited driving of the focus lens unit  2212  (step S 2106 ). When it is judged that the focus control state is switched to the M/A mode (YES at step S 2103 ), the camera body control section  2318  judges whether the AF operation is currently being performed (step S 2104 ). 
     When it is judged that the AF operation is currently being performed (YES at step S 2104 ), the camera body control section  2318  selects the focus limit for the infinitely far region and controls the replacement lens control section  2220  to drive the focus lens unit  2212  within this focus limit, i.e. to perform limited driving of the focus lens unit  2212  (step S 2106 ). When it is judged that the AF operation is not currently being performed (NO at step S 2104 ), the camera body control section  2318  controls the replacement lens control section  2220  to drive the focus lens unit  2212  within the first range, i.e. to drive the focus lens unit  2212  in the entire range, without limiting the focus, as shown in  FIG. 17A  (step S 2105 ). 
     After the focus lens unit  2212  has been driven according to step S 105  or step S 106 , the camera body control section  2318  judges whether image capturing instructions have been received from the user (step S 2107 ). When it is judged that the image capturing instructions have not been received from the user (NO at step S 2107 ), the process moves to step S 2101 . When it is judged that the image capturing instructions have been received from the user (YES at step S 2017 ), this series of processes is ended and the processing returns to the image capturing sequence. 
     In the above description, when the focus ring  2202  is rotationally manipulated by the user, the replacement lens control section  2220  transmits to the camera body control section  2318  the information concerning the rotation direction and the rotation amount of the focus ring  2202 . Then, when the allowable movement range of the focus lens unit  2212  is switched from the first range to the second range, the focus lens drive section  2250  limits the movement instructions of the focus lens unit  2212  by the user manipulation according to the drive instructions from the camera body control section  2318 . However, when communication cannot be performed with the camera body control section  2318  and the replacement lens control section  2220 , the focus lens drive section  2250  may limit the movement instructions of the focus lens unit  2212  by the user manipulation according to the drive instructions from the replacement lens control section  2220 . In this case, the replacement lens control section  2220  need not transmit the information concerning the rotation direction and rotation amount of the focus ring  2202  to the camera body control section  2318 . 
     In the above description, the focus limiter is set on the replacement lens  2200  side, but the focus limiter may instead be set on the camera body  2300  side. In this case, the camera body control section  2318  may display a menu screen for switching the setting of the focus limiter in the display section  2314  and may perform switching according to the manipulation by the user made via the manipulation member  2315 . Furthermore, the camera body control section  2318  may transmit the switch state information to the replacement lens  2200  when polling occurs. Upon receiving the polling, the replacement lens control section  2220  transmits the number of divisions corresponding to the state indicated by the switch information, the limited position information, and the like along with the first information and the second information. 
     In the above description, the replacement lens  2200  is a zoom lens, but the replacement lens  2200  may instead be a single focus lens. In this case, the focal distance does not change, and therefore the first information and the second information have fixed values. Accordingly, the replacement lens control section  2220  need only transmit the first information and the second information once. In other words, this information need not be transmitted every time the polling is received during the steady sequence. The same is true for the display information. 
     In the above description, the replacement lens control section  2220  transmits the first information and the second information as a number of pulses, but the replacement lens control section  2220  may instead transmit distance information. In this case, the camera body  2300  receives the distance information and converts this distance information into a number of pulses. In the above description, the infinitely far end design value is used as the reference value, but another value may be used as the reference value instead. For example, the very close end design value may be used as the reference value. In the above description, the settings on the camera body  2300  side are prioritized when selecting the drive range of the focus lens unit  2212 , but instead, a manipulation by the user may be performed to set which of the settings on the replacement lens  2200  side or the settings on the camera body side are prioritized. In this way, the intent of the user can be reflected to a greater degree. 
     In the above description, a number of pulses is given as an example of the control signal for moving the focus lens unit  2212  to the target position, but the present invention is not limited to this and any format can be used as long as at least one of a movement amount and a target position can be transferred. 
     In the above description, the replacement lens control section  2220  transmits the very close end soft limit and the infinitely far end soft limit to the camera body  2300  as the first information corresponding to the setting without a focus limit, but instead, the infinitely far end design value and the very close end design value may be transmitted as the first information. Similarly, the replacement lens control section  2220  may transmit the infinitely far end design value and the very close end design value as the second information, as the focus limit for the infinitely far region, and may transmit the far end design value and the very close end design value as the second information, as the focus limit for the very close region. As described above, in a case where the autofocus is performed using a contrast method, when focus is achieved at the infinitely far end design value, for example, the actual focus point moves beyond the infinitely far end design value toward the infinitely far side. In contrast to this, when the autofocus is performed using a phase difference method, focus can be achieved at the infinitely far end design value without moving beyond the infinitely far end design value toward the infinitely far side. Accordingly, the replacement lens control section  2220  may transmit different second information in a case where the autofocus is performed using a contrast method and a case where the autofocus is performed using a phase difference method. When the autofocus is performed using the phase difference method, the values at the ends of the focusable range may be transmitted without transmitting the values at the ends of the drive range of the focus lens unit  2212 . 
     In the above description, the replacement lens  2200  transmits compression information that is information relating to a range narrower than the first range as the second information, but instead the replacement lens  2200  may transmit expansion information that is information relating to a range wider than the first range. For example, a number of pulses closer to the very close end than the very close end soft limit described in  FIG. 12  is transmitted as the second information. In this case, the replacement lens  2200  may also transmit recommendation information indicating which of the first range and the second range is a recommended drive range that ensures optical performance greater than or equal to a predetermined reference. If one of a mode prioritizing the focus range and a mode prioritizing image quality is set on the camera body  2300  side, the drive range of the focus lens unit  2212  may be selected according to this setting. In this case, the focus limit switching switch  2201  does not function as a switching section and a switch may be provided that switches between the mode prioritizing the focus range and the mode prioritizing the image quality. If the mode prioritizing the image quality is set, information relating to the range indicated by the recommendation information is selected. On the other hand, if the mode prioritizing the focus range is set, information relating to a range differing from the range indicated by the recommendation information is selected. Furthermore, the range may be selected according to the setting information on the camera body  2300  side. For example, when the image capturing mode is set to the full auto mode, the range may be selected to prioritize the focus range even when the mode prioritizing the image quality is set. Furthermore, the switching section may be a switch that switches the AF speed. In particular, when the mode for performing high-speed AF is set for the contrast AF, a narrower range is selected than when a mode for performing low-speed AF is set. 
     In the above description, the second range includes a focus limit for the infinitely far region and a focus limit for a very close region, but the second range may instead include only one of these focus limits. In other words, the focus limit switching switch  2201  may be a switch that switches between two positions instead of three positions. Furthermore, the second range may include three or more ranges. 
     In the above description, as shown in  FIG. 16 , the camera body control section  2318  switches the range of the focus limit according to the switch state information, but instead the camera body control section  2318  may prohibit the switching process for switching the range of the focus limit under a predetermined condition. For example, the predetermined condition may be exemplified by an AF lock being in effect, the focus lens unit  2212  being driven, or the like. When the switching process is prohibited, the switching process is put on hold until the condition is removed, i.e. the operation in the immediately prior focus limit range continues. When the condition is removed, the switching process that was put on hold is performed. The switching process may be performed only when the focus control state is AF. While the switching is being performed and while the switching process is on hold, the camera body control section  2318  need not perform the switching of the focus control state, the MF operation, and the AF operation. When the focus control state is MF, the switching process need not be performed regardless of the position of the focus lens unit  2212 . In this case, only the switch state information, the various design values, and the various soft limits in the internal memory  2310  are updated. 
       FIG. 20  is an external perspective view of a camera system  3100  according to a third embodiment. The camera system  3100  is a single-lens reflex camera with a replacement lens formed by attaching a replacement lens  3200  serving as an imaging device to a camera body  3300 . The replacement lens  3200  includes a lens mount  3221  and the camera body  3300  includes a camera mount  3321 . When the lens mount  3221  and the camera mount  3321  engage with each other to form the replacement lens  3200  and the camera body  3300  integrally, the replacement lens  3200  and the camera body  3300  function as the camera system  3100 . 
     The lens mount  3221  is brought near the camera mount  3321  along the arrow  3021  parallel to the optical axis  3011 , such that the lens marker  3209  and the body marker  3340  are opposite each other and in contact with each other. Furthermore, the replacement lens  3200  is rotated in the direction of the arrow  3022  while contact is maintained between the mounting surface of the lens mount  3221  and the mounting surface of the camera mount  3321 . When this happens, the lock mechanism formed by the lock pin  3350  operates to secure the replacement lens  3200  to the camera body  3300 . In this state, a connection terminal on the replacement lens  3200  side is electrically connected to a connection terminal on the camera body  3300  side. As a result, it is possible to transfer power and communication such as control signals between the replacement lens  3200  and the camera body  3300 . 
     The replacement lens  3200  includes a focus limit switching switch  3201  serving as the switching section, a focus ring  3202 , and an AF/MF switching switch  3203 . The AF/MF switching switch  3203  switches the focus control state between an M mode and an M/A mode. The user can set the M mode that enables the manual focus operation by switching the AF/MF switching switch  3203  to M. Furthermore, it is possible to set the M/A mode that enables both the autofocus operation and the manual focus operation by switching the AF/MF switching switch  3203  to M/A. 
     The camera body  3300  includes a release switch  3360 . The release switch  3360  is formed by a press button that can detect two stages in a pressing direction. When the M/A mode is set, the user can perform the autofocus operation by pressing the release switch  3360  to the first stage. Furthermore, after the autofocus operation has ended, the user can perform the manual focus operation by manipulating the focus ring  3202 . By additionally performing the manual focus operation, the focus lens unit that was moved once by the autofocus operation can be further driven to correct the focal position. In the manner described above, in the present embodiment, the modes that can be selected by the AF/MF switching switch  3203  are the M mode and the M/A mode. However, instead of the M/A mode, an A mode may be adopted that is an autofocus mode not allowing the manual focus manipulation using the focus ring  3202 . 
     As described in detail further below, in the present embodiment, the focus ring  3202  and the focus lens unit are not mechanically linked. The information concerning the rotation direction and the rotation amount per unit time applied to the focus ring  3202  by the user is temporarily converted into an electrical signal. An actuator drives the focus lens unit in the direction of the optical axis in order to change the focal position, according to this electrical signal. 
     The focus limit switching switch  3201  switches between a first range, which is a range in which movement of the focus lens unit is allowed, and a second range that is different from the first range. By switching the focus limit switching switch  3201 , a user can select a drive range for the focus lens unit. In the present embodiment, the first range is a range in which there are no focus limitations, and the second range is a range that is narrower than the first range, i.e. a range in which there is a focus limitation. In the present embodiment, two focus limits are set as the second range. As described in detail further below, a focus limit for an infinitely far region and a focus limit for a very close region are set. 
     The user can set the first range by switching the focus limit switching switch  3201  to FULL, set the focus limit for the infinitely far region by switching the focus limit switching switch  3201  to LIMIT  1 , and set the focus limit for the very close region by switching the focus limit switching switch  3201  to LIMIT  2 . In other words, it is possible to select any one of three positions by switching the focus limit switching switch  3201 . By limiting the movement range of the focus lens unit, it is possible to shorten the focusing time. Regardless of which of the three positions the focus limit switching switch  3201  is switched to, the replacement lens  3200  transmits both first information relating to the first range and second information relating to the second range to the camera body  3300 , as mobility information relating to the movable range of the focus lens unit. Furthermore, the replacement lens  3200  transmits switch state information as setting information indicating which of the three positions is switched to. Yet further, the replacement lens  3200  transmits focus control state information indicating whether the focus control state is switched to the M mode or to the M/A mode. 
     The camera body  3300  receives both the first information and the second information, and also the switch state information. The camera body  3300  moves the focus lens unit in the drive range of the focus lens unit corresponding to the switch state information. However, there are cases where it is undesirable for the focus lens unit to be driven in the drive range corresponding to the switch state information, depending on the state of the settings relating to image capturing on the camera body  3300  side. Therefore, the camera body  3300  selects any one of the first range and the second range according to the state of the settings relating to the image capturing, in addition to the switch state information, and may move the focus lens unit according to the selected range. If the drive range of the focus lens unit is selected according to the state of the settings relating to image capturing, this drive range can be determined with flexibility. 
       FIG. 21  is a drawing for describing the configuration of the camera system  3100 . The replacement lens  3200  includes, in addition to the focus limit switching switch  3201 , the focus ring  3202 , and the AF/MF switching switch  3203 , an image capturing lens  3210 , a replacement lens control section  3220 , a zoom lens drive section  3240 , a focus lens drive section  3250 , and a second encoder  3260  serving as an image capturing optical system. The camera body  3300  includes, in addition to the release switch  3360 , an AF sensor  3307 , an imaging element  3308 , an A/D converter  3309 , an internal memory  3310 , an image processing section  3311 , a storage medium IF  3312 , a display control section  3313 , a display section  3314 , a manipulation member  3315 , a power supply control section  3316 , a camera body control section  3318 , and a power supply switch  3323 . 
     The replacement lens control section  3220  and the camera body control section  3318  are connected to each other via the lens mount  3221  and the camera mount  3321 . The replacement lens control section  3220  and the camera body control section  3318  work together while communication with each other to control the camera body  3300  and the replacement lens  3200 . 
     There are a plurality of types of replacement lenses  3200  with different optical characteristics. The user can attach any one of these replacement lenses  3200  to the camera body  3300 . The image capturing lens  3210  included in the replacement lens  3200  is formed by a plurality of optical lens groups. Specifically, the image capturing lens  3210  is formed by a zoom lens unit  3211  and a focus lens unit  3212 . The image capturing lens  3210  guides subject light flux incident thereto along an optical axis  3011  to an imaging element  3308  arranged within the camera body  3300 . 
     A portion of the subject light flux that transparently passes through the optical system to be incident thereto is guided to the AF sensor  3307 . The AF sensor  3307  includes a plurality of photoelectric converting element columns that receive a portion of the subject light flux guided thereto. The AF sensor  3307  outputs signals with matching phases when in the focused state and outputs signals with relatively shifted phases when in a front focus state or rear focus state. The amount of the phase shift corresponds to the amount of shift from the focus state. The AF sensor  3307  detects the phase difference by calculating the correlation of the output of the photoelectric converting element columns, and outputs a phase difference signal indicating the phase difference to the camera body control section  3318 . During the autofocus operation, the camera body control section  3318  outputs a control signal for moving the focus lens unit  3212  to a target position to the replacement lens control section  3220 . The camera body  3300  need not include the AF sensor  3307  as a separate component from the imaging element  3308 , and may include the imaging element  3308  that has pixels with a distance measuring function. 
     The imaging element  3308  is an element that photoelectrically converts an optical image, which is the subject image. A CCD sensor or CMOS sensor can be used as the imaging element  3308 . The subject image resulting from the photoelectric conversion by the imaging element  3308  is converted from an analog signal into a digital signal by the A/D converter  3309 . 
     The subject image that has been converted into a digital signal is sequentially processed as image data. The image data is temporarily stored in the internal memory  3310 . The internal memory  3310  is a random access memory that can perform reading and writing at high speed. A DRAM and an SRAM can be used as the internal memory  3310 . The internal memory  3310  serves as a work memory in which the image processing section  3311  performs image processing and a compression process. The internal memory  3310  has a memory capacity sufficient for fulfilling this role. 
     The image processing section  3311  converts the image data into image data in compliance with a prescribed image format, according to the set image capturing mode and instructions from the user. For example, when generating a JPEG file as a still image, a compression process is performed by applying a suitable discrete cosine transformation or the like after performing image processing such as a color conversion process, gamma process, or a white balance process. The converted image data is again stored in the internal memory  3310 . 
     The image data processed by the image processing section  3311  is stored in the storage medium  3400  from the internal memory  3310 , via the storage medium IF  3312 . The storage medium  3400  is a non-volatile memory that can be attached to and removed from the camera body  3300  and is formed by a flash memory or the like. The image processing section  3311  generates the image data to be displayed, in parallel with the processed image data to be stored. The generated image data to be displayed is displayed in the display section  3314  under the control of the display control section  3313 . Regardless of whether storage is performed, the camera body control section  3318  can present a live view as an electronic finder function by having the image processing section  3311  generate sequential pieces of image data to be displayed and having the display section  3314  display this image data. 
     The power supply control section  3316  communicates with the power supply  3410  to detect the remaining power, monitor the power supply, supply power, and the like. The power supply  3410  is formed by a battery, for example. 
     The camera body  3300  includes each element used for the image processing described above, and is directly or indirectly controlled by the camera body control section  3318 . The camera body control section  3318  includes a system memory  3317 . The system memory  3317  is a non-volatile memory that can be electrically erased and recorded on, and is formed by an EEPROM (Registered Trademark) or the like, for example. The system memory  3317  stores constants, variables, programs, and the like that are needed when the camera system  3100  operates, such that this information is not lost when the camera system  3100  is not operating. The camera body control section  3318  suitably extracts these constants, variables, programs, and the like in the internal memory  3310  and uses this information to control the camera system  3100 . The camera body control section  3318  functions as an acquiring section that acquires the mobility information relating to the moveable range of the focus lens unit  3212  and as a transmitting section that transmits response information based on the mobility information in association with a drive signal for driving the focus lens unit  3212  to the replacement lens  3200 . In the present embodiment, a number of supply pulses corresponding to the drive range of the focus lens unit  3212  is associated with the drive signal as the response information. As described in detail further below, when the autofocus operation is performed, the camera body control section  3318  transmits a control command designating a movement direction of the focus lens unit  3212  and a control command designating a drive position of the focus lens unit  3212  to the replacement lens control section  3220 . When the manual focus operation is performed, the camera body control section  3318  converts the electrical signal described further below into a drive control signal expressing the drive direction and drive amount per unit time, and transmits this drive control signal to the replacement lens control section  3220 . 
     The camera body control section  3318  may drive the focus lens unit  3212  such that the subject image in a specified region is in focus on the light receiving surface of the imaging element  3308 , according to contrast AF information using the pieces of image data acquired in series. Furthermore, the camera body control section  3318  performs AF or the like, which is an image capturing preparation operation, in response to detecting SW 1 , which is a first-stage press of the release switch  3360 , and performs an operation to acquire the subject image with the imaging element  3308  in response to detecting SW 2 , which is a second-stage press of the release switch  3360 . 
     The camera system  3100  includes a plurality of manipulation members  3315  that receive manipulations from the user. The manipulation members  3315  are used to set the image capturing mode, for example. The image capturing mode includes a full auto mode, a scene mode, and a manual mode. The user can set the image capturing mode by manipulating the manipulation members  3315 . The camera body control section  3318  detects that these manipulation members  3315  have been manipulated and performs operations according to the manipulations. 
     The second encoder  3260  detects the rotation direction and rotation amount per unit time applied to the focus ring  3202  by the user, and converts this information into an electrical signal. This electrical signal is then transmitted to the camera body control section  3318  via the replacement lens control section  3220 . 
     The zoom lens unit  3211  is driven by the zoom lens drive section  3240 , under the overall control of the camera body control section  3318  and the replacement lens control section  3220 . The zoom lens drive section  3240  changes the field angle by driving the zoom lens unit  3211  according to instructions from the user. 
     The focus lens unit  3212  is driven by the focus lens drive section  3250 , under the overall control of the camera body control section  3318  and the replacement lens control section  3220 . The focus lens drive section  3250  includes a drive motor  3251  serving as an actuator for driving the focus lens unit  3212  and a first encoder  3252  for detecting the position of the focus lens unit  3212 . The information indicating the current position of the focus lens unit  3212  detected by the first encoder  3252  is transmitted to the camera body control section  3318  via the replacement lens control section  3220 . 
     When performing the autofocus operation, the focus lens drive section  3250  drives the focus lens unit  3212  according to the information of the AF sensor  3307 . Specifically, the focus lens drive section  3250  moves the focus lens unit  3212  to the position where the subject image of a specified region is focused on the light receiving surface of the imaging element  3308 , by driving the drive motor  3251  according to the control signal transmitted from the replacement lens control section  3220 . 
     When performing the manual focus operation, the focus lens drive section  3250  drives the focus lens unit  3212  according to information of the rotation direction and rotation amount per unit time applied to the focus ring  3202  by the user. Specifically, the replacement lens control section  3220  drives the focus lens unit  3212  in the optical axis direction to change the focal position, by generating a drive pulse according to the drive control signal transmitted from the replacement lens control section  3220  to drive the drive motor  3251 . 
     When the focus limit switching switch  3201  is switched, an electrical signal corresponding to the selected position of the switch is transmitted to the replacement lens control section  3220 . The replacement lens control section  3220  performs focus control corresponding to the received electrical signal. When the AF/MF switching switch  3203  is switched, an electrical signal corresponding to the selected position of the switch is transmitted to the replacement lens control section  3220 . The replacement lens control section  3220  performs focus control corresponding to the received electrical signal. 
     The replacement lens control section  3220  includes a system memory  3230 . The system memory  3230  stores information relating to the replacement lens  3200 . Lens function information indicating that the replacement lens includes the focus limit switching switch  3201 , a set including first pulse information indicating the first range and second pulse information indicating the second range, and the like are stored as the information relating to the replacement lens  3200 . A plurality of sets that each include first pulse information and second pulse information are stored according to the focal distance. 
     When communication is established with the camera body control section  3318 , the replacement lens control section  3220  transmits the information relating to the replacement lens  3200  to the camera body control section  3318 . For example, the replacement lens control section  3220  transmits the lens function information described above. After this, every time polling is received from the camera body  3300 , the set of the first pulse information and the second pulse information, the switch state information, and the focus control state information are transmitted as the steady sequence. Furthermore, if the user performs a manipulation of the focus ring  3202 , the information concerning the rotation direction and the rotation amount per unit time is transmitted. 
     The replacement lens control section  3220  drives the drive motor  3251  to move the focus lens unit  3212 , and controls the driving of the drive motor  3251  based on the pulse information detected by the first encoder  3252 . Furthermore, the focus lens unit  3212  functions as a receiving section that receives the drive signal for driving the focus lens unit  3212  from the camera body  330  and as a drive control section that drives the drive motor  3251  based on the response information when the response information based on the mobility information relating to the movable range of the focus lens unit  3212  is associated with the drive signal. 
       FIG. 22  is a drawing for describing the first range and the second range. Portion (a) in  FIG. 22  is used to describe the first range. Portions (b) and (c) in  FIG. 22  are used to describe the second range. Specifically, portion (b) in  FIG. 22  is used to describe the focus limit for an infinitely far region, and portion (c) in  FIG. 22  is used to describe the focus limit for a very close region. In the present embodiment, portions (a), (b), and (c) in  FIG. 22  respectively correspond to states resulting from the focus limit switching switch  3201  being switched to FULL, LIMIT  1 , and LIMIT  2 . In the present embodiment, an infinitely far end design value is set as the reference for the drive range of the focus lens unit  3212 , i.e. a 0 pulse, and the number of pulses for each type of soft limit and each type of design value described further below are determined. 
     As shown in portion (a) of  FIG. 22 , the very close end design value is a value indicating the end point of the focusable range on the very close side. When performing the autofocus operation, the focus lens unit  3212  can achieve focus in the range between the infinitely far end design value and the very close end design value, which is the focusable range of the first range. Furthermore, the infinitely far end soft limit on the infinitely far side is determined from the infinitely far end design value, and the very close end soft limit on the very close side is determined from the very close end design value. The infinitely far end soft limit is a value indicating the end point of the drive range of the focus lens unit  3212  determined in advance on the infinitely far side. The very close end soft limit is a value indicating the end point of the drive range of the focus lens unit  3212  determined in advance on the very close side. The range from the infinitely far end design value to the infinitely far end soft limit and the range from the very close end design value to the very close end soft limit are over-stroke ranges that are outside of the focusable range. In a case where the camera body  3300  performs contrast AF, when focus is achieved at the infinitely far end design value, for example, the focal point temporarily moves to the infinitely far side of the infinitely far end design value. Therefore, in the present embodiment, the over-stroke range is established by determining the infinitely far end soft limit. The same is true for the very close end soft limit. 
     At the focus limit for the infinitely far region, the focusable range is limited to be near an infinitely far position, as shown in portion (b) of  FIG. 22 . More specifically, a close end design value is determined to be on the infinitely far side from the very close end design value. The close end design value is a value indicating the end point of the focusable range on the very close side. When performing the autofocus operation, the focus lens unit  3212  can focus in the range between the infinitely far end design value and the close end design value, which is the focusable range. Furthermore, the close end soft limit is determined between the close end design value and the very close end design value. The close end soft limit is a value indicating the end point of the drive range of the focus lens unit  3212  on the very close side. The range from the infinitely far end design value to the infinitely far end soft limit and the range from the close end design value to the close end soft limit are over-stroke ranges. 
     At the focus limit for the very close region, the focusable range is limited to be near the very close end, as shown in portion (c) of  FIG. 22 . More specifically, a far end design value is determined to be on the very close side from the infinitely far end design value. The far end design value is a value indicating the end point of the focusable range on the infinitely far side. When performing the autofocus operation, the focus lens unit  3212  can focus in the range between the far end design value and the very close end design value, which is the focusable range. Furthermore, a far end soft limit is determined between the far end design value and the very close end design value. The far end soft limit is a value indicating the end point of the drive range of the focus lens unit  3212  on the infinitely far side. The range from the far end design value to the far end soft limit and the range from the very close end design value to the very close end soft limit are over-stroke ranges. 
     When performing the manual focus operation, in a case where the second range is selected, the focus lens unit  3212  can move in the second range according to the manipulation by the user. On the other hand, when performing the manual focus operation, the movement of the focus lens unit  3212  may be limited outside of the second range, or movement outside of the second range may be allowed according to the signal from the camera body control section  3318 . 
       FIG. 23  is a drawing for describing the first information and the second information. As described above, the system memory  3230  stores a plurality of sets that each include the first information and the second information, according to the focal distance. If the focal distance of the zoom lens unit  3211  is from 35 mm to 100 mm, the system memory  3230  stores a set of the first information and the second information corresponding to each of three ranges, which are a range from 35 mm to 50 mm, a range from 50 mm to 75 mm, and a range from 75 mm to 100 mm, for example.  FIG. 23  shows the various design values indicating the ends of the drive range of the focus lens unit  3212  and the various soft limits indicating the ends of the focusable range in the case where the focal distance is a range from 35 mm to 100 mm. The various design values and various soft limits surrounded by the parentheses in the drawing need not be transmitted to the camera body  3300 , as described further below. 
     The replacement lens  3200  transmits the infinitely far end soft limit and the very close end soft limit to the camera body  3300  as the first information corresponding to there being no focus limit. In the present embodiment, the replacement lens  3200  also transmits the infinitely far end design value and the very close end design value as information indicating the focusable range. The infinitely far end design value is set to 0, and therefore the replacement lens control section  3220  need not transmit this value to the camera body  3300 . 
     The replacement lens  3200  transmits the close end soft limit as the second information indicating the focus limit for the infinitely far region. In the present embodiment, the replacement lens  3200  also transmits the close end design value as information indicating the focusable range. The infinitely far end soft limit is the same as in the first information, and therefore does not need to be transmitted. Furthermore, the far end soft limit is transmitted as second information indicating the focus limit for a very close region. In the present embodiment, the replacement lens  3200  also transmits the far end design value as information indicating the focusable range. The very close end design value and the very close end soft limit are the same as in the first information, and therefore do not need to be transmitted. 
     As described above, the infinitely far end soft limit and the very close end soft limit are each set as a number of pulses. Accordingly, the first information is expressed as pulse information. Similarly, the close end soft limit and the far end soft limit are also each set as a number of pulses. Accordingly, the second information is also expressed as pulse information. 
     When moving the focus lens unit  3212 , the camera body  3300  transmits control signal drive instructions relating to a target position, such as a lens drive amount expressed as a number of pulses, from the camera body control section  3318  to the replacement lens control section  3220 . After receiving the drive instructions for the focus lens unit  3212  from the camera body control section  3318 , the replacement lens control section  3220  drives the drive motor  3251  to move the focus lens unit  3212 . The replacement lens control section  3220  detects the position of the focus lens unit  3212  using the first encoder  3252  and drives the drive motor  3251  until reaching the number of pulses transmitted from the camera body control section  3318 . Here, when moving the focus lens unit  3212  from the infinitely far end to the very close end, for example, the focus lens unit  3212  is driven by a pulse amount indicated by the very close end design value corresponding to the current focal distance. For example, if the focal distance is from 35 mm to 50 mm and the very close end design value for this focal distance is 3000 pulses, the camera body control section  3318  transmits instructions for 3000 pulses of driving to the replacement lens control section  3220 . In the same manner, when the focal distance is from 50 mm to 75 mm and the very close end design value for this focal distance is 2800 pulses, the camera body control section  3318  transmits instructions for 2800 pulses of driving to the replacement lens control section  3220 . As described above, the number of pulses indicated by the very close end design value differs according to the focal distance. By transmitting a number of pulses corresponding to the focal distance to the replacement lens control section  3220 , it is possible to suitably control the driving of the focus lens unit  3212 . 
       FIG. 24A  is a drawing for describing the control command designating the drive of the focus lens unit  3212 .  FIG. 24A  shows a control command used when the autofocus operation is performed, specifically a control command (referred to hereinafter as a search command) designating a search for a focal position.  FIG. 24B  shows a control command (referred to hereinafter as a PF command) performed during the manual focus operation. 
     The control command shown in  FIG. 24A  includes the search command and a final end position of the search range for the focal position, as response information. The search command is a drive signal for driving the focus lens unit  3212  and, more specifically, indicates a movement speed and a movement direction of the focus lens unit  3212 . The replacement lens control section  3220  can judge whether the focus lens unit  3212  is moving toward the very close side or moving toward the infinitely far side and can determined the movement speed of the focus lens unit  3212 , by referencing the search command. 
     The final end position of the search range for the focal position is determined according to the allowable movement range of the focus lens unit  3212 . In a case where the first range is selected as the allowable range, when the final end position is expressed by four bytes, if the final end position is expressed as 7fffffff, which is the maximum value in hexadecimal notation, the replacement lens control section  3220  drives the focus lens unit  3212  to the position of the very close end soft limit. On the other hand, if the final end position is expressed as 80000000, which is the maximum value in hexadecimal notation, the replacement lens control section  3220  drives the focus lens unit  3212  to the position of the infinitely far end soft limit. 
     In a case where the second range is selected as the allowable range, when the second range is the focus limit for the infinitely far region, the final end position is the position of the infinitely far end soft limit or the close end soft limit. When the second range is the focus limit for the very close region, the final end position is the far end soft limit or the very close end soft limit. By referencing the final end position, the replacement lens control section  3220  can control the movement of the focus lens unit  3212  such that the focus lens unit  3212  does not move beyond the search range for the focal position. 
     When performing the autofocus operation, the camera body control section  3318  transmits the final end position in association with the search command to the replacement lens control section  3220 . The number of pulses associated as the final end point is the same as the number of pulses transmitted from the replacement lens control section  3220 . Accordingly, the replacement lens control section  3220  can be made aware that the camera body control section  3318  understands the focus limiter. 
     The control command shown in  FIG. 24B  includes the PF (Power Focus) command and the drive range of the focus lens unit  3212 , as response information. Furthermore, the PF command includes pulse number information and sampling count information, which are described further below. 
     The drive range of the focus lens unit  3212  is determined according to the allowable movement range of the focus lens unit  3212 . In a case where the first range is selected as the allowable range, the drive range is the infinitely far end soft limit and the very close end soft limit. In a case where the second range is selected as the allowable range, when the second range is the focus limit for the infinitely far region, the drive range is the infinitely far end soft limit and the close end soft limit. In a case where the second range is selected as the allowable range, when the second range is the focus limit for the very close region, the drive range is the far end soft limit and the very close end soft limit. 
     When performing the manual focus operation, the camera body control section  3318  transmits the drive range in association with the PF command to the replacement lens control section  3220 . The number of pulses associated as the final end position is the same as the number of pulses transmitted from the replacement lens control section  3220 . Accordingly, in the same manner as when performing the autofocus operation, the replacement lens control section  3220  can be made aware that the camera body control section  3318  understands the focus limiter. 
       FIG. 25  is a flow chart showing an exemplary process relating to the manual focus manipulation performed by the replacement lens  3200 . This flow is begun upon detecting that the replacement lens  3200  has received power from the camera body  3300 . When this flow is begun, an initial value is set for the sampling count information described further below. The initial value of the sampling count information may be set after the first pulse number is calculated at step S 3103  described further below. 
     The replacement lens control section  3220  judges whether the user has manipulated the focus ring  3202  (step S 3101 ). The replacement lens control section  3220  can judge whether the focus ring  3202  has been manipulated by judging whether the output of the second encoder  3260  has been received. 
     When it is judged that the focus ring  3202  has been manipulated (YES at step S 3101 ), a judgment is made as to whether a preset time has passed (step S 3102 ). The preset time is 100 [msec], for example. 
     When it is judged that the preset time has not yet passed (NO at step S 3102 ), the process is put on standby and does not proceed. When it is judged that the preset time has passed (YES at step S 3102 ), the number of pulses is calculated from the rotation amount of the focus ring  3202  resulting from the manipulation during this period (step S 3103 ). The replacement lens control section  3220  can calculate the number of pulses using a preset conversion formula between the rotation amount and the number of pulses. The calculated number of pulses is stored in the system memory  3230 . The information concerning the rotation direction of the focus ring  3202  is expressed by a positive or negative sign attached to the number of pulses. When calculating the number of pulses, the sampling count information is incremented (step S 3104 ). The sampling count information is also stored in the system memory  3230 . 
     As described above, every time polling is received from the camera body control section  3318 , the replacement lens control section  3220  transmits the number of pulses calculated at step S 3103  and the sampling count information incremented at step S 3104 . The polling is performed every 16 [msec], for example. In this case, the replacement lens control section  3220  transmits the number of pulses every 6 periods. 
     After the incrementing of the sampling count information at step S 3104 , or when it is judged that the focus ring  3202  has not been manipulated (NO at step S 3101 ), the replacement lens control section  3220  judges whether the power supply has been turned OFF (step S 3105 ). When it is judged that the power supply has not been turned OFF (NO at step S 3105 ), the process moves to step S 3101 . When it is judged that the power supply has been turned OFF (YES at step S 3105 ), the series of processes is ended. 
       FIG. 26  is a flow chart showing an exemplary process for selecting a control command performed by the camera body  3300 . This flow is begun when the information relating to the focus limit, the switch state information, and the focus control state information are received from the replacement lens  3200  by the camera body control section  3318  according to the first instance of the steady sequence. The received information relating to the focus limit, the switch state information, and the focus control state information are held in the internal memory  3310 . 
     The camera body control section  3318  references the focus control state information and judges whether the focus control state is switched to the M/A mode (step S 3201 ). When it is judged that the focus control state is switched to the M/A mode (YES at step S 3201 ), the camera body control section  3318  judges that the AF operation is currently being performed (step S 3202 ). 
     When it is judged that the AF operation is currently being performed (YES at step S 3202 ), even when the number of pulses and the sampling count information described in  FIG. 25  are received, the camera body control section  3318  ignores the received number of pulses and sampling count information. The camera body control section  3318  then judges whether a search for the focal position has been designated (step S 3203 ). When it is judged that a search for the focal position has been designated (YES at step S 3203 ), the camera body control section  3318  attaches the final end position corresponding to the selected allowable range of the focus lens unit  3212  to the search command (step S 3204 ). When it is judged that a search for the focal position has not been designated (NO at step S 3203 ), it is judged that the search for the focal position has ended. In this case, the position designation command, which is the control command designating the drive position of the focus lens unit  3212 , is selected (step S 3205 ). The number of pulses indicating the focal position is designated by the position designation command. 
     When it is judged that the focus control state is not switched to the M/A mode, i.e. when it is judged that the focus control state is switched to the M mode (NO at step S 3201 ), or when it is judged that the AF operation is not currently being performed, i.e. when it is judged that the MF operation is currently being performed (NO at step S 3202 ), a judgment is made as to whether the sampling count information has been updated (step S 3206 ). When it is judged that the sampling count information has been updated (YES at step S 3206 ), a judgment is made as to whether the user has made a new manipulation of the focus ring  3202 . In this case, the drive range corresponding to the selected allowable range of the focus lens unit  3212  is attached to the PF command (step S 3207 ). 
     When the command to be transmitted is selected at step S 3204 , step S 3205 , or step S 3207 , the camera body control section  3318  transmits the selected command to the replacement lens control section  3220  (step S 3208 ). When the AF drive is being performed, the optimal speed for moving the focus lens unit  3212  is also transmitted to the replacement lens control section  3220 . When the MF drive is being performed, the number of pulses corresponding to the manipulation of the focus ring  3202  is also transmitted to the replacement lens control section  3220 . 
     When the selected command has been transmitted to the replacement lens control section  3220 , or when it is judged that the sampling count information has not been updated (NO at step S 3206 ), this series of processes is ended. 
     As described above, the camera body control section  3318  transmits the search command having the final end position attached thereto at step S 3204  to the replacement lens control section  3220  and transmits the PF command having the drive range attached thereto at step S 3207  to the replacement lens control section  3220 . Accordingly, as described further below, when the focus lens unit  3212  reaches the final end position, the replacement lens control section  3220  can control the focus lens unit  3212  to stop at the final end position and not move beyond the final end position. In the same manner, when the focus lens unit  3212  reaches an end of the drive range, the replacement lens control section  3220  can control the focus lens unit  3212  to stop in this drive range and not move beyond the drive range. 
       FIG. 27  is a flow chart showing an exemplary process for driving the focus lens unit  3212  when the autofocus operation is performed by the replacement lens  3200 . This flow is begun when the series of processes in the activation sequence including the process for transmitting the lens function information to the camera body  3300 , the process for initializing the replacement lens  3200 , and the like has ended. During the initialization process, when the initialization execution command is received from the camera body control section  3318 , the replacement lens control section  3220  drives the focus lens unit  3212  in the range corresponding to the switch state information at the time when the initialization is begun. 
     The replacement lens control section  3220  judges whether the control command has been received from the camera body control section  3318  (step S 3301 ). When it is judged that the control command has been received (YES at step S 3301 ), a judgment is made as to whether the received control command is the search command designating a search for the focal position (step S 3302 ). When it is judged that the control command is the search command (YES at step S 3302 ), a judgment may be made as to whether the camera body  330  has a response function to transmit response information associated with the search command (step S 3303 ). Since a camera body  3300  that does not have a response function does not attach the response information to the search command, it is possible to judge whether the camera body  3300  has a response function by judging whether the data length of the control command is a preset length. Different drive control is set for the focus lens unit  3212  according to the judgment result. 
     When the data length of the control command is greater than the preset length, i.e. when the response information is attached, it is judged that the camera body  3300  has a response function (YES at step S 3303 ). In the present embodiment, it is judged that the camera body  3300  has a response function. In this case, the number of pulses indicated by the response information is selected as the final end position of the movement of the focus lens unit  3212  (step S 3304 ). 
     When the data length of the control command is the preset length, i.e. when the response information is not attached, it is judged that the camera body  3300  does not have a response function (NO at step S 3303 ). In this case, a preset range, e.g. the number of pulses mechanically allowed by the specifications of the replacement lens  3200 , is selected as the final end point of the movement of the focus lens unit  3212  (step S 3305 ). 
     When the number of pulses is selected at step S 3304  or step S 3305 , the replacement lens control section  3220  drives the focus lens unit  3212  using the selected number of pulses as the final end position (step S 3306 ). 
     On the other hand, when it is judged that the control command is not the search command, i.e. when it is judged that the control command is a position designation command designating the drive position of the focus lens unit  3212  (NO at step S 3302 ), the replacement lens control section  3220  drives the focus lens unit  3212  according to the number of pulses indicated in the position designation command (step S 3306 ). 
     The replacement lens control section  3220  judges whether the power supply has been turned OFF (step S 3307 ), and when it is judged that the power supply has not been turned OFF (NO at step S 3307 ), the process moves to step S 3301 . When it is judged that the power supply has been turned OFF (YES at step S 3307 ), this series of processes is ended. 
     In a case where the camera body  3300  designates only the movement direction of the focus lens unit  3212 , at the time when the camera body  3300  recognizes that the focus lens unit  3212  has reached an end of the preset range, there are cases where the focus lens unit  3212  has already moved beyond this range. In such a case, if the focal position is located outside of the preset range, the camera body  330  mistakenly recognizes that focus is realized even outside this range. When this happens, the camera body  3300  judges there to be an out-of-focus state regardless of an in-focus state being temporarily achieved. Accordingly, such operation of the camera body  3300  is undesirable. Furthermore, if the search is performed in the very close direction and no focal position is found, there are cases where the search direction is inverted and a search is performed in the infinitely far direction, but at this time, when the search goes beyond the preset range, the search time is increased. 
     With the present embodiment, the camera body  3300  transmits the search command and the associated final end position to the replacement lens  3200  and the replacement lens  3200  drives the focus lens unit  3212  according to this final end position. In other words, the replacement lens  3200  does not stop the movement of the focus lens unit  3212  according to stop instructions from the camera body  330 , but instead, the replacement lens  3200  itself places a limit on the movement of the focus lens unit  3212 . Accordingly, it is possible to stop the focus lens unit  3212  and prevent the focus lens unit  3212  from moving beyond the final end position. 
     In the above description, the process for driving the focus lens unit  3212  performed by the replacement lens  3200  when the autofocus operation is performed is used as an example, but basically the same process is performed when the manual focus operation is performed. In other words, if the camera body  3300  has a response function, the replacement lens control section  3220  drives the focus lens unit  3212  in a range corresponding to the number of pulses indicated in the response information, and if the camera body  3300  does not have a response function, the replacement lens control section  3220  drives the focus lens unit  3212  in a range corresponding to the number of pulses that are mechanically allowed. 
     In the above description, the camera body control section  3318  associates the number of pulses received from the replacement lens control section  3220  as the response information, but instead the camera body control section  3318  may associate a different number of pulses as the response information. Furthermore, in the above description, the camera body control section  3318  associates the final end position or the drive range as the response information with the search command and the PF command, but may instead associate a flag indicating whether the camera body  3300  has a response function with the search command and PF command. By judging whether this flag is attached, the replacement lens control section  3220  can judge whether the camera body  3300  has a response function. Accordingly, the replacement lens  3200  can recognize that the camera body  3300  has acquired the mobility information. 
     In the above description, the final end position or the drive range is attached to the search command and the PF command regardless of the type of replacement lens attached, but instead, when a replacement lens that does not include a focus limit switching switch  3201  is attached, the camera body control section  3318  need not attach the final end position or the drive range to the command. 
     The replacement lens control section  3220  may select the setting without a focus limit if the image capturing mode is set to be full auto or the manual mode, and when control is performed by an external apparatus such as a smartphone, tablet terminal, personal computer, or the like, may select the setting without a focus limit. This is because, when the camera system  3100  is manipulated by an external apparatus, there are cases where more precise control is performed by the external apparatus. This is also because there are cases where the user is at a position distanced from the camera system  3100 . 
     In the above description, the focus limiter is set on the replacement lens  3200  side, but the focus limiter may instead be set on the camera body  3300  side. In this case, the camera body control section  3318  may display a menu screen for switching the settings of the focus limiter in the display section  3314  and perform switching according to the manipulations by the user via the manipulation members  3315 . Furthermore, the camera body control section  3318  may transmit the switch state information to the replacement lens  3200  when polling is performed. In the above description, the camera body control section  3318  receives the mobility information from the replacement lens control section  3220 , but if the mobility information is stored in advance in the system memory  3317 , the camera body control section  3318  may acquire the mobility information from the system memory  3317 . When the camera system  3100  is a lens-integrated camera system, for example, the mobility information may be stored in advance in the system memory  3317 . 
     In the above description, the replacement lens  3200  is a zoom lens, but the replacement lens  3200  may instead be a single focus lens. In this case, the focal distance does not change, and therefore the first information and the second information have fixed values. Accordingly, the replacement lens control section  3220  need only transmit the first information and the second information once. In other words, this information need not be transmitted every time the polling is received during the steady sequence. The same is true for the display information. 
     In the above description, the replacement lens control section  3220  transmits the first information and the second information as a number of pulses, but the replacement lens control section  3220  may instead transmit distance information. In this case, the camera body  3300  receives the distance information and converts this distance information into a number of pulses. In the above description, the infinitely far end design value is used as the reference value, but another value may be used as the reference value instead. For example, the very close end design value may be used as the reference value. In the above description, the settings on the camera body  3300  side are prioritized when selecting the drive range of the focus lens unit  3212 , but instead, a manipulation by the user may be performed to set which of the settings on the replacement lens  3200  side or the settings on the camera body side are prioritized. In this way, the intent of the user can be reflected to a greater degree. 
     In the above description, a number of pulses is given as an example of the control signal for moving the focus lens unit  3212  to the target position, but the present invention is not limited to this and any format can be used as long as at least one of a movement amount and a target position can be transferred. 
     In the above description, the replacement lens control section  3220  transmits the very close end soft limit and the infinitely far end soft limit to the camera body  3300  as the first information corresponding to the setting without a focus limit, but instead, the infinitely far end design value and the very close end design value may be transmitted as the first information. Similarly, the replacement lens control section  3220  may transmit the infinitely far end design value and the very close end design value as the second information, as the focus limit for the infinitely far region, and may transmit the far end design value and the very close end design value as the second information, as the focus limit for the very close region. As described above, in a case where the autofocus is performed using a contrast method, when focus is achieved at the infinitely far end design value, for example, the actual focus point moves beyond the infinitely far end design value toward the infinitely far side. In contrast to this, when the autofocus is performed using a phase difference method, focus can be achieved at the infinitely far end design value without moving beyond the infinitely far end design value toward the infinitely far side. Accordingly, the replacement lens control section  3220  may transmit different second information in a case where the autofocus is performed using a contrast method and a case where the autofocus is performed using a phase difference method. When the autofocus is performed using the phase difference method, the values at the ends of the focusable range may be transmitted without transmitting the values at the ends of the drive range of the focus lens unit  3212 . 
     In the above description, the replacement lens  3200  transmits compression information that is information relating to a range narrower than the first range as the second information, but instead the replacement lens  3200  may transmit expansion information that is information relating to a range wider than the first range. For example, a number of pulses closer to the very close end than the very close end soft limit described in  FIG. 22  is transmitted as the second information. In this case, the replacement lens  3200  may also transmit recommendation information indicating which of the first range and the second range is a recommended drive range that ensures optical performance greater than or equal to a predetermined reference. If one of a mode prioritizing the focus range and a mode prioritizing image quality is set on the camera body  3300  side, the drive range of the focus lens unit  3212  may be selected according to this setting. In this case, instead of the focus limit switching switch  3201 , a switch may be provided that switches between the mode prioritizing the focus range and the mode prioritizing the image quality. If the mode prioritizing the image quality is set, information relating to the range indicated by the recommendation information is selected. On the other hand, if the mode prioritizing the focus range is set, information relating to a range differing from the range indicated by the recommendation information is selected. Furthermore, the range may be selected according to the setting information on the camera body  3300  side. For example, when the image capturing mode is set to the full auto mode, the range may be selected to prioritize the focus range even when the mode prioritizing the image quality is set. 
     In the above description, the second range includes a focus limit for the infinitely far region and a focus limit for a very close region, but the second range may instead include only one of these focus limits. In other words, the focus limit switching switch  3201  may be a switch that switches between two positions instead of three positions. Furthermore, the second range may include three or more ranges. 
     In the above description, the camera body control section  3318  may prohibit the switching process for switching the range of the focus limit under a predetermined condition. For example, the predetermined condition may be exemplified by an AF lock being in effect, the focus lens unit  3212  being driven, or the like. When the switching process is prohibited, the switching process is put on hold until the condition is removed, i.e. the operation in the immediately prior focus limit range continues. When the condition is removed, the switching process that was put on hold is performed. The switching process may be performed only when the focus control state is AF. While the switching is being performed and while the switching process is on hold, the camera body control section  3318  need not perform the switching of the focus control state, the MF operation, and the AF operation. When the focus control state is MF, the switching process need not be performed regardless of the position of the focus lens unit  3212 . In this case, only the switch state information, the various design values, and the various soft limits in the internal memory  3310  are updated. 
     When the camera system  3100  captures a moving image, the contrast AF includes a step of performing a search by moving the focus lens unit  3212  from the very close end to the infinitely far end and/or from the infinitely far end to the very close end, in the same manner as when capturing a still image, and a step of searching for the focal position by moving the focus lens unit  3212  in small intervals. During the latter step, the camera body control section  3318  displays the designated position as a relative number of pulses from the number of pulses at the current position of the focus lens unit  3212 . In this case, the camera body control section  3318  knows the allowable movement range of the focus lens unit  3212 , and can therefore apply the limit on the camera body side by referencing the allowable range. In other words, a number of pulses exceeding the allowable range is not transmitted. Furthermore, not only when performing the contrast AF, but also when performing phase difference AF, specifically when performing a tracking mode to track a subject, the camera body control section  3318  may transmit the response information in association with the control command designating the drive of the focus lens unit  3212 . In this way, tracking of the subject can be performed within the focus limit. 
     The replacement lens, the imaging device, and the imaging device control program according to the embodiments described above realize at least a portion of the features described below. 
     A replacement lens attached to an imaging device includes a focus lens unit and a transmitting section that transmits to the imaging device first information relating to a first range that is a range in which the focus lens unit is allowed to move and second information relating to a second range that is a different range from the first range. 
     The replacement lens comprises a storage section that stores a set of first pulse information indicating the first range and second pulse information indicating the second range, an actuator that drives the focus lens, and a drive control section that controls the drive of the actuator by supplying pulses to the actuator, wherein the transmitting section transmits the set of the first pulse information and the second pulse information. 
     In the replacement lens, even when the range in which the focus lens unit is allowed to move is switched to the first range, the drive control section drives the actuator in the second range according to instructions from the imaging device, and even when the range in which the focus lens unit is allowed to move is switched to the second range, the drive control section drives the actuator in the first range according to the instructions from the imaging device. 
     The replacement lens includes a zoom lens unit, and in the replacement lens, the storage section stores a plurality of the sets corresponding to the focal distance and the transmitting section transmits the set corresponding to the selected focal distance. 
     The replacement lens includes a switching section that switches the range in which the focus lens unit is allowed to move, and in the replacement lens, the transmitting section transmits setting information that indicates which range is the range in which the focus lens unit is allowed to move. 
     In the replacement lens, the transmitting section changes the second information that is transmitted when autofocus is performed using a contrast method and when autofocus is performed using a phase difference method. 
     An imaging device includes a receiving section that receives first information relating to a first range that is a range in which a focus lens unit is allowed to move and second information indicating a second range that is a different range from the first range, a selecting section that selects the first information or the second information based on setting information relating to image capturing, and a control section that controls drive of the focus lens unit according to the selected first information or second information. 
     In the imaging device, the selecting section acquires the setting information indicating which range is the range in which the focus lens unit is allowed to move and, even when the setting information indicates the second range, selects the first information if the setting information fulfills a predetermined condition. 
     In the imaging device, the selecting section selects the first information when an image capturing mode is set to a full auto mode. 
     In the imaging device, the selecting section selects the first information when a focus mode is set to a manual mode. 
     The imaging device includes a display control section that changes the display of an indicator relating to the movement range of the focus lens unit when the range in which the focus lens unit is allowed to move is the first range and when the range in which the focus lens unit is allowed to move is the second range. 
     In the imaging device, when the range in which the focus lens unit is allowed to move is switched, the display control section displays at least a portion of the marker relating to the indicator in a different manner, while maintaining the display range of the position of the focus lens unit. 
     A control program used by a replacement lens attached to an imaging device causes a computer to perform an acquisition step of acquiring first information relating to a first range that is a range in which a focus lens unit is allowed to move and second information relating to a second range that is a different range from the first range and a transmission step of transmitting the first information and the second information to the imaging device. 
     A control program causes a computer to perform a reception step of receiving first information relating to a first range that is a range in which a focus lens unit is allowed to move and second information relating to a second range that is a different range from the first range, a selection step of selecting the first information or the second information based on setting information relating to image capturing, and a control step of controlling the drive of the focus lens unit according to the selected first information or second information. 
     While the embodiments of the present invention have been described, the technical scope of the invention is not limited to the above described embodiments. It is apparent to persons skilled in the art that various alterations and improvements can be added to the above-described embodiments. It is also apparent from the scope of the claims that the embodiments added with such alterations or improvements can be included in the technical scope of the invention. 
     The operations, procedures, steps, and stages of each process performed by an apparatus, system, program, and method shown in the claims, embodiments, or diagrams can be performed in any order as long as the order is not indicated by “prior to,” “before,” or the like and as long as the output from a previous process is not used in a later process. Even if the process flow is described using phrases such as “first” or “next” in the claims, embodiments, or diagrams, it does not necessarily mean that the process must be performed in this order. 
     LIST OF REFERENCE NUMERALS 
     
         
         
           
               1011 : optical axis,  1021 : arrow,  1022 : arrow,  1100 : camera system,  1200 : replacement lens,  1201 : focus limit switching switch,  1202 : focus ring,  1209 : lens marker,  1210 : image capturing lens,  1211 : zoom lens unit,  1212 : focus lens unit,  1220 : replacement lens control section,  1221 : lens mount,  1230 : system memory,  1240 : zoom lens drive section,  1250 : lock pin,  1251 : drive motor,  1252 : encoder,  1260 : detecting section,  1300 : camera body,  1307 : AF sensor,  1308 : imaging element,  1309 : A/D converter,  1310 : internal memory,  1311 : image processing section,  1312 : storage medium IF,  1313 : display control section,  1314 : display section,  1315 : manipulation member,  1316 : power supply control section,  1317 : system memory,  1318 : camera body control section,  1321 : camera mount,  1323 : power supply switch,  1340 : body marker,  1350 : lock pin,  1400 : storage medium,  1401 : display bar,  1402 : focus lens unit position,  1403 : MF manipulation guide,  1404 : marker,  1405 : marker,  1406 : far end,  1407 : close end,  1408 : movement-prohibited region,  1410 : power supply,  2011 : optical axis,  2021 : arrow,  2022 : arrow,  2100 : camera system,  2200 : replacement lens,  2201 : focus limit switching switch,  2202 : focus ring,  2203 : AF/MF switching switch,  2209 : lens marker,  2210 : image capturing lens,  2211 : zoom lens unit,  2212 : focus lens unit,  2220 : replacement lens control section,  2221 : lens mount,  2230 : system memory,  2240 : zoom lens drive section,  2250 : focus lens drive section,  2251 : drive motor,  2252 : first encoder,  2260 : second encoder,  2300 : camera body,  2307 : AF sensor,  2308 : imaging element,  2309 : A/D converter,  2310 : internal memory,  2311 : image processing section,  2312 : storage medium IF,  2313 : display control section,  2314 : display section,  2315 : manipulation member,  2316 : power supply control section,  2317 : system memory,  2318 : camera body control section,  2319 : external communication section,  2321 : camera mount,  2323 : power supply switch,  2340 : body marker,  2350 : lock pin,  2360 : release switch,  2400 : storage medium,  2401 : display bar,  2402 : close side marker,  2403 : far side marker,  2404 : limit marker,  2405 : MF icon,  2406 : movement-prohibited region,  2410 : power supply,  2411 : lens icon,  2412 : lens icon,  2420 : indicator image,  2430 : live view image,  2500 : tablet terminal,  2501 : display section,  2502 : display bar,  2503 : lens icon,  2504 : close side marker,  2505 : far side marker,  2600 : finger,  2700 : scenery,  3011 : optical axis,  3021 : arrow,  3022 : arrow,  3100 : camera system,  3200 : replacement lens,  3201 : focus limit switching switch,  3202 : focus ring,  3203 : AF/MF switching switch,  3209 : lens marker,  3210 : image capturing lens,  3211 : zoom lens unit,  3212 : focus lens unit,  3220 : replacement lens control section,  3221 : lens mount,  3230 : system memory,  3240 : zoom lens drive section,  3250 : focus lens drive section,  3251 : drive motor,  3252 : first encoder,  3260 : second encoder,  3300 : camera body,  3307 : AF sensor,  3308 : imaging element,  3309 : A/D converter,  3310 : internal memory,  3311 : image processing section,  3312 : storage medium IF,  3313 : display control section,  3314 : display section,  3315 : manipulation member,  3316 : power supply control section,  3317 : system memory,  3318 : camera body control section,  3321 : camera mount,  3323 : power supply switch,  3340 : body marker,  3350 : lock pin,  3360 : release switch,  3400 : storage medium,  3410 : power supply