1. An image processing apparatus comprising: image-capturing-mode selecting portion configured to select one image-capturing mode from a plurality of image-capturing modes; and noise-reduction processing portion configured to perform noise reduction processing on input image signals by employing, in the case in which an image-capturing mode selected by the image-capturing-mode selecting portion is a specific image-capturing mode, an applied noise model in which a noise model for a predetermined signal-value region differs from a reference noise model determined on the basis of properties of an image-acquisition element.