1. An image-processing device to acquire recovery image data by performing a restoration process for original image data, the original image data being acquired from an image-capturing element by an image taking of an object image using an optical system, the restoration process using a restoration filter that is based on a point spread function for the optical system, the image-processing device comprising: a gradation correction section to perform a gradation correction by a logarithmic process, for the original image data; and a restoration processing section to perform the restoration process, for color data of the original image data after the gradation correction, wherein the restoration filter has a filter coefficient corresponding to image data before the logarithmic process.