A control apparatus includes a storage circuit that stores first data containing a plurality of coefficient data obtained by approximating an optical transfer function of an optical system to an approximation function having a predetermined order. An input circuit inputs information of an image processing apparatus that is different from the control apparatus and performs image processing on an image captured by using the optical system. A determination circuit determines second data, that are coefficient data corresponding to an order lesser than the predetermined order of the approximation function, from the first data, based on the information of the image processing apparatus. An output circuit outputs the second data to the image processing apparatus.