What happens when an optical filter is tilted?

Generally, as the angle of incidence increases a filter's transmission curve will shift to lower wavelengths. The effect of large angles from the center of the optical system is the same as tilting a filter from a perpendicular position to an optical system. As the angle of tilt gets larger, the curve will start to change shape, causing the transmission to steadily drop and the transmission curve slope to change. A similar effect is noticed as temperature increases. Interference filters are the most sensitive to angle of incidence and temperature.