In addition, X-ray generators usually have a filter along the beam path (placed at or
near the x-ray port). Filters consist of a thin sheet of material (often high atomic
number materials such as lead, copper, or brass) placed in the useful beam 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 in order to produce a
cleaner image (since lower energy X-ray photons tend to scatter more).