1. An image processing apparatus comprising an image processor configured to: obtain a first optical transfer function which is different depending on a shooting condition and on a position in an image; generate a corrected image from the image using the first optical transfer function, the corrected image including a shift-invariant region larger than a shift-invariant region of the image; convert the first optical transfer function to a second optical transfer function corresponding to the corrected image; and perform blind deconvolution processing using the corrected image and the second optical transfer function to generate a restored image, wherein the second optical transfer function has a shift-invariant characteristic compared with the first optical transfer function.