T.O. 33B-1-16-54conditions. An example of its use follows, but note that 3 out of 4 terms in the equation must be known before it can beused.Figure 6-24. Nomogram to Assist in Solving Equation Ug= Ft/d.6.7.2.5.2Suppose that a specimen having a maximum thickness of 1.5-inch (t) is to be radiographed at 20-inch source-to-filmdistance (d) using a source of effective focal size 6mm. The need is to establish an approximate value for Ug. Thesteps in using the nomogram are:a. Plot the points A and C that represent the known value of F and t. The pivot line is intersected at B.b. Plot a line joining point D (the value of d) and B. The extension of this line at E gives the value of Ug(0.47mm).6.7.2.5.3It should be remembered that unsharpness of the radiographic image is also affected by the characteristics of the X-rayfilm. Therefore, the total image sharpness may be controlled by either geometrical unsharpness or film unsharpness.Whichever unsharpness value is the greater will control the total image unsharpness. In a given situation, the