Studios are moving to stop distributing 35-millimeter film prints. Converting to digital is an expense many theaters in the fading drive-in industry can't afford.As the night grew darker, a cold wind whipped across the asphalt expanse of the vintage Rubidoux Drive-In Theatre in Riverside. A howling gust banged open the door to the snack bar, where hot dogs glistened on metal spits and the black-and-white linoleum floor gleamed.