The purpose of the present invention is to reduce the exposure amount of radiation to a subject without adversely affecting the identification of a region-of-interest mainly in the shooting of a moving image. In a radiographic image shooting system, when a moving image is to be shot, the exposure of radiation to a subject is continued for a longer period compared with that in the shooting of a still image, and therefore it is needed to have the exposure amount of radiation to a subject under consideration. Then, during the setting of a region-of-interest (ROI) which is to be performed before image shooting, the amount of radiation from a radiation source (22A) is reduced as possible (at a level lower than a level in a stationary time), and the compression rate of a dynamic range is increased compared with that in a stationary time in accordance with the distribution of a histogram of an QL value on the basis of the reduced amount of radiation. Consequently, even when the distribution of the QL value is unbalanced, it becomes possible to utilize the dynamic range with economy and it also becomes possible to achieve both the reduction in exposure amount of radiation to a subject through the reduction in the amount of radiation and the highly accurate setting of an ROI.La présente invention vise à réduire la quantité de rayonnement à laquelle est exposé un sujet sans affecter de manière néfaste lidentification dune région dintérêt principalement dans la prise dune image en mouvement. Dans un système de prise dimage radiographique en mouvement, lorsquune image doit être prise, lexposition dun sujet aux rayons dure plus longtemps que lors de la prise dune image fixe, et il est par conséquent nécessaire de prendre en considération la quantité de rayonnement à laquelle un sujet est exposé. Ensuite, durant la définition dune région dintérêt (ROI) qui doit être réalisée avant la prise dimage, la quantité de rayonnement dune source de rayonnement (22A) est réduite autant que
