A display apparatus includes a display; an optical sensor; and a processor configured to: obtain a current illumination value detected by the optical sensor while the display displays an image, identify a first illumination level corresponding to the obtained current illumination value, the first illumination level being previously obtained at a time when the display is displaying a preset image, identify an ambient brightness based on a second illumination level, the second illumination level corresponding to the identified first illumination level and being previously obtained at a time when the display is not displaying any image, and perform an operation based on the identified ambient brightness.