Understanding Neutron Radiography Reading V-Kodak Part 2 of 3

■ Example 1: Suppose a radiograph made on Film Z with an exposure of 12
mA-min has a density of 0.8 in the region of maximum interest. It is desired to
increase the density to 2.0 for the sake of the increased contrast there
available. Locate the intersection of the line for the original density of 0.8 with
the characteristic curve of Film Z (Point A in Figure 51). Superimpose the
transparent overlay on the curve, so that the vertical line for the original
exposure--12 mA-min--passes through point A and the horizontal line overlies
the line for the desired final density of 2.0. The new exposure, 50 mA-min, is
read at the intersection of the characteristic curve with the horizontal line of
the overlay (Point B in Figure 51). The method of solution would be the same
if the new density were lower rather than higher than the old. The vertical line
corresponding to the old exposure would pass through the characteristic
curve at the point of the old density. The horizontal line of the overlay would
pass through the desired new density. The new exposure would be read at
the intersection of the characteristic curve and the horizontal line of the
overlay.
Charlie Chong/ Fion Zhang
Radiography in Modern Industry. Rochester, NY: Eastman Kodak Co. 1980