Understanding Neutron Radiography Reading V-Kodak Part 2 of 3

3. The use of a different type of film can be corrected for by comparing the
difference in the amount of exposure necessary to give the same density
on both films from relative exposure charts such as those shown in Figure
47.
• For example, to obtain a density of 1.5 using Film Y, 0.6 more exposure is
required than for Film X.
• This log exposure difference is found on the L scale and corresponds to an
exposure factor of 3.99 on the D scale. (Read directly below the log E
difference.) Therefore, in order to obtain the same density on Film Y as on
Film X, multiply the original exposure by 3.99 to get the new exposure.
Conversely, if going from Film Y to Film X, divide the original exposure by
3.99 to obtain the new exposure.
• You can use these procedures to change densities on a single film as well.
Simply find the log E difference needed to obtain the new density on the
film curve; read the corresponding exposure factor from the chart; then
multiply to increase density or divide to decrease density.
Charlie Chong/ Fion Zhang
Radiography in Modern Industry. Rochester, NY: Eastman Kodak Co. 1980