1. An image processing method comprising: acquiring an input image produced by an image pickup system including at least one imaging optical system and causing light rays from a same point in an object space to respectively enter different image pickup pixels depending on, of a pupil plane of the at least one imaging optical system, light ray passing areas through which the respective light rays pass; performing a shaping process including at least one of an image restoration process to restore a restoration target image on a basis of an optical transfer function of the image pickup system and a luminance estimation process to estimate a luminance value in a luminance saturated area in an estimation target image; performing a reconstruction process to reconstruct a new image different from the input image; and performing a blur addition process to add an image blur component to an addition target image, wherein the method performs the shaping process before the reconstruction process and the blur addition process.