1. An imaging apparatus that can drive an image sensor to capture a series of image frames time-sequentially, said imaging apparatus comprising: a feature point extracting device that extracts a plurality of feature points from a first image frame captured through said image sensor; a feature points tracking device for tracking the feature points extracted by said feature point extracting device, said feature point tracking device identifying corresponding points to the extracted feature points in a second image frame captured before or after the first image frame; and a movement judging device that judges whether the speed of movement of a common subject contained in the first and second image frames is high or low, depending upon the number of traceable feature points to which said feature point tracking device can identify the corresponding points, or the number of untraceable feature points to which said feature point tracking device cannot identify the corresponding points, wherein said movement judging device judges that the speed of movement of the subject is high when the number of traceable feature points is not more than a predetermined value.