A method for calculating a shift amount of a microlens from a position of a light receiving element arranged in a pixel of an image pickup element is provided. The microlens collects incident light from an image pickup lens. The method comprises: acquiring an incident angle characteristic value indicating a relation between an arranged position of the pixel and an incident angle of the incident light to the pixel; calculating a sampled shift amount of the microlens from the position of the light receiving element corresponding the incident angle characteristic value based on light collection efficiency of the incident light; approximating the sampled shift amount by a second or higher order function to calculate a shift amount characteristic function indicating a relation between the arranged position and the shift amount; and calculating the shift amount of the pixel using the shift amount characteristic function.