PROBLEM TO BE SOLVED: To provide an imaging apparatus etc., capable of detecting irradiation with X rays more accurately and synchronizing the irradiation with the X rays with the operation of the imaging device more accurately.SOLUTION: The imaging apparatus includes a detection part 101 including a plurality of pixels 201, each including a conversion element which converts radiation or light into electric charges and a switch element which outputs an electric signal corresponding to the electric charges, in a matrix a driving circuit part 102 which places the switch elements in an electrically conductive state, row by row, and controlling the electrically conductive state of the switch elements so that switch elements in a plurality of discontinuous rows are in the electrically conductive state at the same time a signal processing part 106 which generates a signal 115 for detection by summing up or averaging electric signals output by the switch elements in the discontinuous rows a comparison part 501 which compares the signal 115 for detection with a threshold to determine whether the irradiation with the radiation or light starts or ends and a control circuit part 108 which controls the driving circuit part 102 or signal processing part 106 according to the determination by the comparison part 501.
