High Quality Content by WIKIPEDIA articles! An X-ray filter is a device to block or filter out some or all wavelengths in the X-ray spectrum. X-ray filters are used to block low-energy X-rays during medical x-ray imaging. Low energy X-rays are more likely to be absorbed by the patient's soft tissues. This causes non-stochasic radioactive effects, and does not contribute to image quality. X-ray filters are used in X-ray crystallography, where crystalline lattice spacings can be determined using Bragg diffraction. The filters allow only a single X-ray wavelength to penetrate through to a target crystal, allowing the resulting scattering to determine the diffraction distance.