Patent ID: 8848096

Claim:
An image-pickup apparatus capable of mounting a removable lens unit with an image-pickup optical system including a focus lens thereon, comprising: an image sensor in which an image-pickup pixel to receive a light beam passed through an exit pupil of the image-pickup optical system and a focus detecting pixel to receive a light beam passed through the exit pupil, partially shielded, of the image-pickup optical system, are arrayed; focus detection means for detecting a shift amount of said focus lens from a focus position based on a phase difference in an output signal from said focus detecting pixel; and acquisition means for acquiring ray vignetting information of said image-pickup optical system, wherein, when a position detection resolution of said focus lens is lower than a drive resolution of said focus lens, said focus detection means detects the shift amount of said focus lens from the focus position using the ray vignetting information in a predetermined position of said focus lens specified based on information from said lens unit.