Thunthy K H, Weinberg R
Oral Surg Oral Med Oral Pathol. 1982 Dec;54(6):691-5. doi: 10.1016/0030-4220(82)90086-x.
This investigation evaluated changes in the contrast of duplicated radiographs made at different ultraviolet light exposures. Increasing ultraviolet light exposure had different effects on the duplicates of originals of different "background" densities. When correctly exposed, a duplicate radiograph enhanced contrast. When originals had the same contrast but different "background" densities, their duplicates did not have the same contrast. It was not possible to duplicate accurately all the different contrasts measured on an original. It was possible, however, to produce duplicates with all contrasts greater than those of the original.
本研究评估了在不同紫外线照射下制作的重复X光片的对比度变化。增加紫外线照射对不同“背景”密度原件的复制品有不同影响。正确曝光时，重复X光片会增强对比度。当原件具有相同对比度但“背景”密度不同时，它们的复制品对比度并不相同。不可能精确复制原件上测量的所有不同对比度。然而，有可能制作出对比度高于原件的复制品。
