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 only 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.