An imaging device according to one aspect of the present invention has a
CCD, a mechanical shutter which prevents transmission of incident light
beams to the CCD, a main CPU which sequentially reads stored electric
charges obtained by the CCD in a plurality of field cycles and calculates
a signal amplification rate based on an image signal which relies on the
stored electric charge read to the last field of the plurality of field
cycles, and a non-volatile memory which stores the signal amplification
rate. The above-described calculation may be executed by an external PC.