To avoid localized MTF degradation when a subject with periodic patterns is photographed.

In an image sensor used for photographing, two pixels differing in pixel aperture which are formed in different lengths between row and column directions in at least one of the row and the column directions of a pixel array are disposed alternately. The image sensor has its reference position moved in minute steps smaller in size than one pixel from the reference position. Then pixel data of each pixel is retrieved at the reference position of the image sensor, and also pixel data of each pixel is retrieved at a position to which the image sensor has been moved from the reference position in minute steps smaller in size than one pixel. Finally, for each pixel position individually, pixel data is retrieved from two pixels differing in pixel aperture.