Understanding Neutron Radiography Reading V-Kodak Part 2 of 3

Photographic Density
Photographic density refers to the quantitative measure of film blackening.
When no danger of confusion exists, photographic density is usually spoken
of merely as density. Density is defined by the equation:
D = log I o /I t
where D is density, I o is the light intensity incident on the film and I t is the light
intensity transmitted. The tabulation below illustrates some relations between
transmittance, percent transmittance, opacity, and density. This table shows
that an increase in density of 0.3 reduces the light transmitted to one-half its
former value. In general, since density is a logarithm, a certain increase in
density always corresponds to the same percentage decrease in
transmittance.
Charlie Chong/ Fion Zhang
Radiography in Modern Industry. Rochester, NY: Eastman Kodak Co. 1980