Filters absorb the low energy photons from the x-ray spectrum. These low energy photons will not contribute to the image formation. In dental x-ray units, the glass of the tube acts like a filter (inherent filtration) and, in addition, a piece of aluminum is added in front of the x-ray tube for additional filtration. The total filtration is expressed as an equivalent to millimeter of aluminum. If the kVp of the tube increases, the total filtration should increase.3,6,11 chat Let's get started!