1. An image processing apparatus comprising: an input unit configured to input a plurality of digital image data obtained by a plurality of image capturing units, wherein a pixel aperture characteristic provided for at least some of the image capturing units differs from a pixel aperture characteristic provided for the other image capturing units; an obtaining unit configured to obtain design parameters including the pixel aperture characteristics for the plurality of image capturing units; and a generation unit configured to synthesize the plurality of digital image data input by the input unit using the obtained designed parameters to generate developed image data, wherein the developed image data represents an image consisting of a greater number of pixels than each image represented by the digital image data obtained by the each image capturing unit.