A high dynamic range image can be recovered from a full-resolution lower-dynamic-range image and a reduced-resolution higher-dynamic-range image. Consequently, a space A between the inlet side orifice 23 and the intermediate orifice 25 is set to be small without damaging the fluidity of a molten metal 11 between the inlet side orifice 23 and the intermediate orifice 25 in a bath container 22. An earthen fill zone is arranged in spaced apart relationship to the rear surface of the wall and clean granular back-fill is interposed between the wall and the earthen fill zone.