A device which is used to modify, by transmission, the radiant or luminous flux, or the spectral distribution, or both, of the radiation passing through it.
Note: A distinction is made between Selective Filters and Non-Selective Filters according as they do or do not alter the relative spectral distribution of the radiation.
Reference: C.I.E. (modified)
Please note that this is the term as it stands in the original IALA Dictionary edition (1970-1989)
Celsius (previously Centigrade)
International Association of Marine Aids to Navigation and Lighthouse Authorities - AISM