T.O. 33B-1-16-68Figure 6-33. Radiation Transmission versus Thickness for Various Densities at 150 kVp.6.7.3.6.1For materials of approximately uniform thickness where the range of transmitted X-ray intensities is small, thetechnique producing high contrast will show all portions of the area of interest with an increased radiographicsensitivity. If, however, the part radiographed transmits a wide range of X-ray intensities, then a technique producinglower contrast will be necessary to record the detail in all portions of the radiograph, probably with some decrease inradiographic sensitivity. In cases where an extreme range of intensities is transmitted, high radiographic contrast maybe obtained by loading the film holder with two high contrast films of different speeds. The kilovoltage and exposureare so chosen that the thick portions of the object be satisfactorily recorded on the faster film and the thin portions onthe slower film.6.7.3.7 FilmContrast.Film contrast has been covered in Section III. In general, films of the no-screen type give higher contrast with orwithout lead screens than screen type films with or without lead screens. Screen type films with calcium tungstatescreens, however, produce maximum contrast with sacrifice of detail due to the grain size of the screens. The contrastof a film can be seen from the slope of the characteristic curves.
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