An imaging apparatus 100 includes a detector 104 having a plurality of pixels arranged in a matrix and performing an imaging operation of outputting image data according to the radiation or light emitted in a predetermined irradiation field and a controller unit 106, and performs a first imaging operation for outputting image data according to the radiation in a narrower irradiation field A corresponding to part of pixels and a second imaging operation for outputting image data according to the radiation in a wider irradiation field B, under controlling the detector to perform an accumulation operation during the second imaging operation so that a step of image is a preliminarily set tolerable quantity.
