To reliably obtain a captured image expected by a user, such as an image precisely showing the shades of a blue sky or a flower, or an image captured under flat illumination and having high contrast, an apparatus comprises an aperture, shutter, CCD, and an AGC, and applies gamma correction to an image signal using gamma correction values. Maximum reflectance, being an index of the amount of incident light according to the maximum output from the CCD, is increased or decreased in multiple levels depending on the subject being photographed, and the exposure amount is accordingly adjusted, thereby changing a dynamic range. A microcomputer revises the gamma correction values in response to changes in maximum reflectance so as to substantially maintain a relationship between an incident light reference amount being a reference for appropriate exposure and the corresponding gamma corrected output value.