The present invention allows detection of an exposure time of an image that has already been captured. A motion detector 102 detects an amount of inter-frame movement of a foreground object in a designated frame based on the designated frame and a frame preceding or subsequent to the designated frame. A mixture-ratio calculator 104 detects a mixture ratio indicating the ratio of mixture of a foreground component and a background component in a mixed area of the designated frame. In accordance with the mixture ratio, the mixture-ratio calculator 104 detects the amount of movement of the foreground object within an exposure time in which pixel data is obtained. A shutter-time calculator 106 detects a ratio of a time interval between frames to the exposure time based on the amount of inter-frame movement and the amount of movement within the exposure time of the foreground object. The present invention is applicable to an image processing apparatus.