Pixel values are read out of an OB pixel region under a predetermined exposure condition, and predetermined processing is performed on the pixel values to derive a dark current component value. The dark current component value of a segmented pixel region is estimated from the OB dark current component value by taking into account the difference between the exposure conditions of the OB pixel region and the segmented pixel region. Specifically, a conversion ratio for calculating the dark current component value from the OB dark current component value is derived based on the ratios between exposure time and gain in the exposure conditions of the two pixel regions. This conversion ratio is applied to the pixel values of the OB pixel region or the OB dark current component value calculated from them to thereby calculate an estimated dark current component value for the exposure condition of the segmented pixel region.