PURPOSE: To decide the distance from a subject and the lowering of reflectance based on a received light quantity and to selectively switch a battery and the main capacitor of a stroboscope based on the decided result lest range-finding accuracy in AF should by deteriorated by always performing stable light projection for AF without being affected by battery voltage.

CONSTITUTION: A power source switching part 13 selectively switches either the battery 10 or the main capacitor of a stroboscopic light emission part 12. A decision part 14 decides, based on a subject luminance decision signal from the outside, which of the battery 10 and the main capacitor is to be supplied to a light projection part 15. The light projection part 15 receives output from the switching part 13 switched and selected by the decision of the decision part 14 and allows an infrared light LED to emit light with the power source selected by the switching part 13 as a driving source according to a control signal outputted from a range-finding arithmetic part 16. Then, range-finding is performed by receiving reflected light from the subject by a light receiving part 17.