Optical filters carefully transfer light in a specific range of wavelengths or colors while obstructing what remains. These dyed plastic or glass devices are placed in the optical path. They are described by their frequency response, and this identifies how the scale and stage of each frequency component

Optical filters carefully transfer light in a specific range of wavelengths or colors while obstructing what remains. These dyed plastic or glass devices are placed in the optical path. They are described by their frequency response, and this identifies how the scale and stage of each frequency component of an incoming signal is altered by the filter.