1. An imaging apparatus comprising: a light exposure condition determining unit for determining a plurality of exposure conditions based on histogram of a luminance distribution of an imaging scene; an imaging unit for imaging, at plural times, an imaging scenes under the plurality of exposure conditions determined by the light exposure condition determining unit, and generating first and second raw image signals before synthesizing; and an image synthesizing unit for synthesizing first and second raw image signals using, as a boundary, a reference value contained in the first raw image signal to generate a synthesized image signal, wherein the light exposure condition determining unit determines at least one of the plurality of exposure conditions so that the reference value contained in the first raw image signal corresponds to a luminance value at a bottom of a ravine of the histogram of the luminance distribution of the imaging scene.