Vacuum roll-to-roll coating of plastic substrates with thin film nanomaterials is widely used in industry to manufacture e.g. packaging films with a gas barrier performance against water or oxygen. Metallized films are used to manufacture colour pigments for lacquers or conductive surfaces. Other examples are “low-E” coatings / “window films” that are laminated between two glass sheets and there used as heat mirror to save energy in buildings or automotive application. Optical coatings on web provide decorative or optical filter functionality. Most of the applications have in common that they require the deposition of multiple layers on a substrate, ideally – to maximise productivity – in a single deposition run in multiple stations of the same machine. The demand on high productivity, however, is complemented by a strong demand for a very high homogeneity (often < ±2%) of the layer properties over the width of a roll (“cross-web homogeneity”) and during the duration of a continuous deposition run (“down-web homogeneity”) which may accumulate to several hours (>10) in an industrial scenario.