An imager is provided having an imaging sensor and a focusing detector. The imaging sensor reads stored charges in a positive or negative direction and outputs image data created from the read charges. The comparator calculates a differential between first image data output by said imaging sensor and second image data output by the imaging sensor immediately after the first image data is output, and determines whether the differential is larger than a first threshold value. The composer creates composite image data from the data of two images output by the imaging sensor. When the comparator determines that the differential is larger than the first threshold value, the composer creates composite image data from the second image data and negatively scanned image data that is obtained by scanning the second image in a direction that is opposite to the scanning direction of the second image data.