1. An imaging apparatus, comprising: imaging means configured to receive subject light passing through imaging optics having an aperture mechanism, and generate an acquired image corresponding to the subject; luminance information acquiring means configured to meter a predetermined light meter area and acquire luminance information regarding the subject; detecting means configured to detect the luminance range of the subject on the basis of high-intensity luminance information and low-intensity luminance information acquired by the luminance information acquiring means; imaging controlling means configured to set a range of exposure control values having a step that corresponds to a value obtained by multiplying the luminance range detected by the detecting means by a predetermined coefficient k (where 0<k<1), and then use the imaging means to take multiple shots (i.e., multiple imagings) set with respectively different exposure control values within the range of exposure control values; and image compositing means configured to generate a composite image by compositing image portions extracted from the plurality of images obtained as a result of the imaging means taking the multiple shots; wherein when just one shot is taken, the single exposure control value set for the one shot is contained within the range of the exposure control values.