1. A composition determination device comprising: subject detection means configured to detect a subject in an image based on acquired image data; still detection means configured to detect a still state, with an image based on said image data, or a subject detected by said subject detection means, as an object thereof; and composition determination means configured to determine a composition, with only real subjects or only unreal subjects, of subjects detected by said subject detection means, as the object thereof, based on detection results of said still detection means, wherein determining a composition comprises changing the position of a subject or subjects within an image frame, wherein when there are one or more real subjects in an image, determining a composition comprises determining a face direction for each of the real subjects and automatically shifting a total center of gravity for the real subjects according to the determined face directions and the number of real subjects in the image, wherein the amount of shift is calculated by adding the centers of gravity for the real subjects and dividing by the number of subjects.