Thin-film coatings, which for example have alternating layers of high and low refractive index materials, are shown to function as both positive and negative C-plates, in dependence upon the incident radiation. In particular, the shape of the retardance versus angle of incidence profile is found to be determined, at least in part, by the phase thickness of the thin film coating (i.e., the optical thickness in terms of the wavelength of the incident radiation, which may, for example, be expressed in degrees, radians, or as the number of quarter wavelengths). These thin film coatings are optionally integrated into anti-reflection coatings, thin film interference filters and/or other components to improve efficiency and/or functionality.