Two photography operations are performed without emitting flash during a second photography operation, to obtain image signals P1 and P2. A flash influence signal value F1 is calculated in image signal P1. A flash influence signal value F2, which is the amount of influence due to flash in the case that flash was emitted during the second photography operation, is calculated based on the differences between the imaging conditions of the first photography operation and the second photography operation and the flash influence signal value F1. An image signal P2″, which is an image signal which is estimated to be obtained in the case that flash was emitted during the second photography operation, is obtained by adding flash influence signal value F2 to image signal P2 obtained by the second photography operation. A dynamic range expanded image signal Pc is calculated based on image signal P1 and image signal P2″.