What happens when a filter is tilted?

For filters in general, 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, this typically means the transmission will steadily drop and the slopes in the curve will start to change. A similar effect is noticed as temperature increases. Interference filters are the most sensitive to angle of incidence and temperature.