As the name suggests, Filters are selective to wavelengths. There are color glass filters (used for pulse attenuation, long and short pass), neutral density filters (wavelength impartial), linear and circular variable density filters and interference filters (for wavelength selection). The critical parameters for selecting a filter are transmittance and opacity at the wavelengths of interest.
Agniroth OPTIK provides a wide range of filters: monochromatic, dichroic, infrared, ultraviolet, neutral and variable density and long and short wavelength pass filters.