Comparison of various film densitometers

A total of 27 densitometers of 10 different models were included in the study. There were two models for which four or more instruments were available, namely the RMI QA sensidensitometer (four instruments) and the RMI/X-Rite 331 (14 instruments). The results are summarized and the deviations of the density values from the mean are shown. On the whole, the results indicate good agreement between the densitometers, with the greatest difference between any two being 0.45 (step 9: densitometer number 14 reading 3.38, densitometer number 27 reading 2.93). The variation between densitometers of the same model was smaller than that for the group as a whole. The data for variation from the mean value should be treated with some caution, because the sample is heavily biased towards one model of densitometer (RMI/X-Rite 331). However, two densitometers do seem to stand apart from the others, namely number 1 (RMS deviation 0.10) and number 27 (RMS deviation 0.15), the remaining 25 having RMS deviations of 0.06 or less. (author)