1. An image processing method comprising: acquiring an input image produced by image capturing through an image capturing optical system; storing image restoration filters to be used for an image restoration process to a memory; acquiring information showing an image capturing state that is a state of the image capturing optical system for the image capturing; determining whether or not to perform the image restoration process on the input image depending on the image capturing state; acquiring the image restoration filter corresponding to the image capturing state from the memory when a determination to perform the image restoration process is made; and performing the image restoration process on the input image by using the acquired image restoration filter, and not performing the image restoration process on the input image, even in a case where the input image includes an image degradation due to an aberration of the image capturing optical system, when a determination to not perform the image restoration process is made, wherein the image restoration process is a process for correcting the input image by using information on an optical transfer function of the image capturing optical system, and the image restoration filters stored to the memory are provided only for a specific image capturing state for which a determination to perform the image restoration process is made.