Thin film optical coatings tailor light reflected or transmitted from an optical element in a desired way. An optical coating chamber is a complex system in which multiple subsystems operate together to fabricate such coatings. For physical vapor deposition processes, such as evaporation and sputtering, the active parts of the subsystems are located within a vacuum chamber. One example is the source system that provides vapor from which films are formed. A gas delivery subsystem may add process gases either in their ground or excited states. Rotary motion and masking subsystems may be used to achieve better uniformity. In addition, a subsystem that ensures accurate layer thickness control may be utilized. Precision optical coatings require that individual layer thicknesses be controlled to within a few percent of the design target or less to achieve accurate placement of a spectral feature. Systems for manufacturing precision optical coatings demand the use of the subsystems that operate within tight tolerances. In this letter, we illustrate subsystem requirements by examining three examples in detail. We then discuss spectral placement impact resulting from height variations of the substrate mounting, thermal gradients on a substrate, and process instabilities from a moving anode. Finally, we conclude by providing a few examples of the performance attainable using a precision coating platform, when all subsystems work properly.