An apparatus for vapor deposition of thin film coatings, including: a process controller; a plurality of precursor containers into which a plurality of coating precursors, each in the form of a liquid or a solid, are respectively placed; a plurality of precursor vapor reservoirs, each in communication with a respective one of said precursor containers; a plurality of in-line devices which control a vapor flow of a coating precursor vapor from one of said precursor containers into one of said precursor vapor reservoirs with which said precursor container is in communication upon receipt of a signal from said process controller; a plurality of precursor control valves which control vapor flow from said precursor vapor reservoir upon receipt of a signal from said process controller; and a process chamber for vapor deposition of said coating on a substrate when present in said process chamber.