Radiography in Modern Industry - Kodak

Figure 63: Advantage of higher radiographic contrast (left) is largely offset by poordefinition. Despite lower contrast (right), better rendition of detail is obtained by improveddefinition.Radiographic contrast between two areas of a radiograph is the difference between the densitiesof those areas. It depends on both subject contrast and film contrast. Subject contrast is the ratioof x-ray or gamma-ray intensities transmitted by two selected portions of a specimen. (See Figure64.) Subject contrast depends on the nature of the specimen, the energy (spectral composition,hardness, or wavelengths) of the radiation used, and the intensity and distribution of the scatteredradiation, but is independent of time, milliamperage or source strength, and distance, and of thecharacteristics or treatment of the film.Figure 64: With the same specimen, the lower-kilovoltage beam (left) produces highersubject contrast than does the higher-kilovoltage beam (right).Radiography in Modern Industry 88