An x-ray energies, filters consist of material placed in the useful beam to absorb, preferentially, radiation based on energy level or to modify the spatial distribution of the beam. Filtration is required to absorb the lower-energy x-ray photons emitted by the tube before they reach the target
. The use of filters produce a cleaner image by absorbing the lower energy x-ray photons that tend to scatter more.
The total filtration of the beam includes the inherent filtration (composed of part of the x-ray tube and tube housing) and the added filtration (thin sheets of a metal
inserted in the x-ray beam). Filters are typically placed at or near the x-ray port in the direct path of the x-ray beam. Placing a thin sheet of copper between the part and the film cassette has also proven an effective method of filtration.