In viewing a moving image taken by an image taking apparatus, contents of that moving image are easily understood. A feature quantity extraction block 150 extracts a feature quantity associated with a taken image. A conversion information correction block 160 corrects conversion information if the feature quantity is over a threshold value. A synthesized image division decision block 170 determines that a taken image and a log image are not to be synthesized if the feature quantity is over a threshold level. If the conversion information was corrected, an image conversion block 180 converts a taken image by the corrected conversion information; if the conversion information was not corrected, the image conversion block corrects a taken image by the conversion information. If a taken image and a log image are determined to be synthesized, a image synthesis block 190 synthesizes the converted taken image with the log image in a image memory 220; if a taken image and a log image are determined not to be synthesized, the image synthesis block erases the log image in the image memory 220 and holds the converted taken image in the image memory 220.