The radiation spectrum can also be optimized with the use of filters, made of aluminum, tin, or gold, at the output window of the X-ray tube.  The  use  of  such filters,  however, results in lower radiation intensities, which must be compensated for with longer measurement times or increased power (worsening the resolution). Because the measurement results can be affected by filtering different artifact behavior, the filter selection should be controlled by software.  The 2D X-ray image should be set as bright as possible to obtain the optimal signal to noise ratio in the areas of the work piece that are difficult to penetrate.  However, over exposure of the image must be avoided for all pixels of the image. When selecting the voltage and current, care should be taken that the power of the X-ray tubes is not too great. This is to achieve a sufficiently small focal spot for the selected magnification and thus the desired voxel size.  For measuring machines with cone angle adjustment, the user can optimize the cone for the application. For high precision applications, a small cone angle minimizes cone beam artifacts. Conversely, for rapid measurements, a short distance between the X-ray source and the sensor is preferred. A reduction in measurement accuracy must be accepted or corrected if greater cone angles are selected.

Seen in image above: The X-ray spectra when using various filters (X-ray voltage 100 kV): Filtering reduces low frequencies, which lowers the overall intensity. (Source: Viscom AG, Hannover, Germany)