Five basic densities seen on an X ray
These include air, fat, soft tissue, bone, and metal. Air appears black on a radiograph, because it minimally attenuates the x-ray beam. Bone appears white and metal appears even more white on a radiograph, because they both markedly attenuate the x-ray beam. Fat and soft tissue attenuate intermediate amounts of the x-ray beam and appear dark gray and brighter gray, respectively.