. The principles and practice of roentgenological technique . and distance being constant, the blackeningproduced in the plate increases with the timeof exposure. The blackness of the deposit onthe plate is expressed in terms of density. SENSITIVENESS OF PLATE 199 This density is judged by the transinissibil-ity of light or its inverse opacity. If the un-affected part of a plate, having an oj^acity ofzero, transmits a certain arbitrary amount oflight. 100%, an area transmitting half asmuch, 50%, would be said to have an opacityof 2. Thus density is proportional to theamount of silver reduced p
. The principles and practice of roentgenological technique . and distance being constant, the blackeningproduced in the plate increases with the timeof exposure. The blackness of the deposit onthe plate is expressed in terms of density. SENSITIVENESS OF PLATE 199 This density is judged by the transinissibil-ity of light or its inverse opacity. If the un-affected part of a plate, having an oj^acity ofzero, transmits a certain arbitrary amount oflight. 100%, an area transmitting half asmuch, 50%, would be said to have an opacityof 2. Thus density is proportional to theamount of silver reduced per unit of platearea. The plate, which gives the maximumdensity for the same unit of exposure is theplate which has the greatest speed. Thedensity of two plates may be the same, butthe chemical change throughout the emulsionmay not be similar. Contrast depends on the quality of theradiation. It diminishes as the penetrationof the ray increases. For the differentiationof tissues of similar density, therefore, raysof low penetration must be used while, if the. Fig. 286 the density increases with increase of develop-ment. Fogging contributes its quota to thedensity of the affected emulsion and the extentof fogging varies with the particular emulsionbeing greater where the concentration of silverin the gelatine emulsion is hitrh. The shorter
Size: 1396px × 1791px
Photo credit: © Reading Room 2020 / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1920, booksubjectradiogr, bookyear1920
