Radiographic contrast is the degree of density (darkness)
difference between two areas on a radiograph. Contrast makes
it easier to distinguish features of interest, such as defects, from
the surrounding area. The image to the right shows two
radiographs of the same stepwedge. The upper radiograph has a
high level of contrast and the lower radiograph has a lower level
of contrast. While they are both imaging the same change in
thickness, the high contrast image uses a larger change in
radiographic density to show this change. In each of the two
radiographs, there is a small dot, which is of equal density in
both radiographs. It is much easier to see in the high contrast
radiograph.