Abstract

The speed of intensifying screens was measured at three arbitrary densities by a sensitometric method. The screen factor was found to increase with shortened development time; to increase with increase of tube potential; to be independent of the tube current from 2 to 35 ma; to be independent of the target film distance from 0.5 to 2.5 meters; to increase as more filtering medium was interposed between the tube and screens; and to vary considerably with the photographic emulsion used. The increase with increasing potential is explained as the effect of the varying energy losses of x-rays of different wave lengths when passing through the front screen, and also by the different relative abilities of x-rays of different wave lengths to excite fluorescence, and to expose silver bromide. The variation of the speed factors with different emulsions is due to different relative sensitivity of the screens to x-rays and to the fluorescent light from the screens.

© 1930 Optical Society of America

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