1. A system comprising: an imaging apparatus configured to have a plurality of pixels which are arranged in pixel groups, each of the pixel groups having at least two pixels; and one or more processors configured to: generate an image based on each pixel signal from each pixel group of the pixel groups, wherein each pixel group of the pixel groups has different exposure times; input the image which has been shot with different exposure times set by region; generate a plurality of exposure pattern images corresponding to the different exposure times based on the input image; generate, from the plurality of exposure pattern images, a plurality of difference images; and generate a corrected image by synthesizing the plurality of difference images having different exposure starting times within a set interval.