Precision of a rotating-drum film scanner

Precession X-ray films were scanned with a rotating-drum microdensitometer. It is necessary to correct for non-linearity between the scanner input and output. Reliability factors for estimating the precision of scanner measurements are compared. The values of the symmetry-averaged reliability factor, R_sym, vary between 3.9 and 12% and depend strongly on the quality of films, while the values of the scanning reproducibility factor, R_rept (3.5-4%), and the film-scaling reliability factor, R_scale (4.5-5.5%), depend more on the quality of scanner software and electronics than on films.