Understanding Neutron Radiography Reading V-Kodak Part 2 of 3

Estimating Exposures For Multithickness Specimens
A minimum acceptable density for radiographs is often specified, not because
of any virtue in the particular density, but because the slope of the
characteristic curve (and hence the film contrast) below a certain point is too
low for adequate rendition (rendering: expressing) of detail. Similarly, a
maximum acceptable density is often designated because either the film
contrast is lower at high densities or detail cannot be seen on the available
illuminators if the density is above a certain value. The problem of
radiographing a part having several thicknesses is one of using the available
density range most efficiently. In other words, the kilovoltage and exposure
should be adjusted so that the image of the thinnest part has the maximum
acceptable density, and the thickest has the minimum. Exposure charts alone,
although adequate for the radiography of uniform plates, can serve only as
rough guides for articles having considerable variation in thickness.
Charlie Chong/ Fion Zhang
Radiography in Modern Industry. Rochester, NY: Eastman Kodak Co. 1980