To convert a pixel value obtained from a non-reference photoelectric conversion characteristic into a pixel value obtained from a reference photoelectric conversion characteristic without variation, and to prevent generation of fixed pattern noise in an image. An image sensor 3 is constituted of pixels having photoelectric conversion characteristics, in which a linear characteristic is on the low luminance side with respect to an inflection point, and a logarithmic characteristic is on the high luminance side with respect to the inflection point. A conversion information storage 68 stores, as conversion information, coefficients “c”, “d”, “e”, and “f” of two kinds of linear functions (y=c·log(x)+d, and y=e·log(x)+f), which are approximation equations expressing the logarithmic characteristic of each of the pixels, where y designates a pixel value, and x designates a luminance value of incident light. A linear converter 64 converts a pixel value obtained from the logarithmic characteristic into a pixel value obtained from the linear characteristic by using the approximation equations specified by the coefficients.