Examples of bandpass filters are Lyot filters and Fabry P é rot interferometers. These two filters can also be made into tunable filters, making the central wavelength selectable by the user. Bandpass filters are commonly used in astronomy to facilitate the observation of spectral lines with correlation.

Light filters are devices that selectively transmit light of different wavelengths, typically planar glass or plastic devices in the optical path, which are dyed or have interference coatings. The optical characteristics of filters are completely described by their frequency response, which specifies that the amplitude and phase of each frequency component of the input signal are modified by the filter.