Digital camera, lens unit, and camera system having the same

A lens unit loadable on a camera body having a lens mount portion and a camera contact, comprising:

• a lens barrel for mounting a photographic lens;
• an image pickup device for image pickup by detecting object light from said photographing lens;
• a lens unit coupling portion, formed on said lens barrel, engageable with said lens mount portion, for removable loading on said camera body;
• a lens connection contact, located on said lens barrel, for touching said camera contact when said lens mount portion is engaged with said lens unit coupling portion, for electrical connection;
• and
• a circuit board, contained in said lens barrel, connected with said image pickup device, having a first surface opposed to said camera body, wherein said lens connection contact is mounted on said first surface.

A camera system comprising:

• a camera body for loading in a removable manner with an interchangeable unit selected from plural interchangeable units including a lens unit;
• a detector for detecting completion of loading of said interchangeable unit;
• and
• a signal generator, positioned on said camera body, for notifying state information of said completion of said loading by generating a signal upon detection of said detector.

A camera system comprising:

• a camera body for loading in a removable manner with an interchangeable unit selected from plural interchangeable units including a lens unit;
• a first detector for detecting a start of loading of said interchangeable unit;
• a second detector for detecting completion of said loading of said interchangeable unit;
• and
• a timer for measuring time elapsed after said first detector detects said start of said loading;
• a partial loading signal generator, positioned on said camera body, for, after detection of said start of said loading in said first detector, monitoring said second detector for detection of said completion of said loading, and for, in case of lack of detection of said completion of said loading in said second detector upon lapse of a predetermined time after said start of measurement in said timer, notifying state information of an incomplete state of said loading of said interchangeable unit.