1. An imaging device comprising: an imaging lens; an image sensor to output an image signal in accordance with an image of a subject captured via the imaging lens; a lens driver to move the imaging lens; an autofocus detector to determine a focal point according to image data obtained from the image signal; a point source detector to determine whether or not a subject is a point source subject on the basis of a brightness component included in the image data; and a driving mode setter to change a driving condition of the image sensor when the subject is determined to be a point source subject.