1. An image processing method of producing, based on information on positions and angles of light rays obtained from a first image, a second image, the first image being produced by using an image pickup apparatus that introduces the light rays from an image capturing optical system to an image sensor through an optical element array, the method comprising the steps of: acquiring the first image and information on an image capturing condition at a time of producing the first image; acquiring an image restoration filter corresponding to the information on the image capturing condition and corresponding to respective optical transfer functions of the image capturing optical system and the optical element array; performing an image restoration process on the first image by using the image restoration filter to produce a restored first image; and producing the second image by performing an image reconstruction process on the restored first image, wherein the first image is a defocused image captured at a position away from an imaging position of the image capturing optical system, and wherein the image restoration filter is a filter to correct degradation of the first image due to an aberration generated in the image capturing optical system and optical element array without correcting a PSF having spread in the first image to a point image.