An imaging apparatus includes a pixel region having a plurality of unit pixels arranged in a matrix, each of the unit pixels including first and second photoelectric conversion units, a reading controller configured to read first signals obtained by mixing signals output from the first and second photoelectric conversion units in rows of a first reading mode and read second signals at least including signals of the first photoelectric conversion units and third signals at least including signals of the second photoelectric conversion units in rows of a second reading mode, and an OB clamp processor configured to correct signals in the unit pixels included in an opening region in the pixel region based on signals output from the unit pixels included in a light shielding region in the pixel region. The OB clamp processor performs one of various correction processes depending on an imaging condition.