1. An image sensing apparatus comprising: an image sensor which generates an electrical signal commensurate with an amount of incident light, and has a photoelectric conversion characteristic comprised of a linear characteristic area where the electrical signal is outputted after being linearly converted in relation to the amount of incident light, and a logarithmic characteristic area where the electrical signal is outputted after being logarithmically converted in relation to the amount of incident light; an exposure evaluation value detector which detects an exposure evaluation value based on luminance information acquired from a subject in sensing an image of the subject; and an exposure controller which acquires a setting value for exposure based on the exposure evaluation value detected by the exposure evaluation value detector to control exposure of the image sensing apparatus, the exposure controller determining a subject luminance for exposure setting based on the exposure evaluation value, and controlling the exposure in such a manner that an output of the image sensor corresponding to the subject luminance for exposure setting is obtained from the linear characteristic area of the image sensor.