A distance determining apparatus includes a distance calculating unit and a signal processor. The distance calculating unit calculates a distance to an object on the basis of a first signal corresponding to a light flux that has passed through a first pupil region of an exit pupil of an imaging optical system and a second signal corresponding to a light flux that has passed through a second pupil region of the exit pupil of the imaging optical system. The second pupil region is different from the first pupil region. The signal processor filters either one signal by using a filter based on an optical transfer function corresponding to the first pupil region and an optical transfer function corresponding to the second pupil region. The either one signal is one of the first signal and the second signal.
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