A Masking Technic for Photographic Reproduction of Roentgenograms

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ROENTGENOGRAPH detail that ordinarily cannot be reproduced by conventional photographic methods may at times be preserved by means of a masking technic. The method described here is not entirely original, but is a modification of several previously described technics aimed at development of a simple yet effective process.

The basic problem with which radiologists and medical photographers are faced is the difference in contrast between roentgen film, which is viewed in transmitted light, and photographic paper, which is viewed in reflected light. The brightness range of a roentgenogram may run from 1 to 1000 or more; whereas, that of a photographic print may run from less than 1 to 50.1 To offset this wide difference in contrast ranges, it has been common practice in making prints of roentgenograms to use a dodging or blocking procedure that decreases the exposure of the less dense areas of the roentgenogram. Dodging usually is accomplished by passing the hand or other opaque object between the source of light and the printing easel. Dodging is a type of masking procedure; in photographic terminology a mask is a device for screening light to secure visualization of details of contrast that otherwise would be lost in the process of reproduction. We currently are using a positive film mask. Exposure is made simultaneously through both a negative film and a positive film (mask) of the roentgenogram. This preserves details that otherwise would be beyond the range of contrast of the paper.

The technic of using a positive mask,. . .



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