An Evaluation of Errors in Reflection Densitometry

The use of reflection densitometers is widespread in the Graphic Arts industry. These instruments are relatively inexpensive and simple to operate. They produce numbers which represent the thickness of ink on a substrate or a derived function such as dot gain. These and other related parameters determine the final acceptability of a printed job. Thus, judgements about the acceptability of a printed job are often made on the basis of densitometer numbers. Despite their widespread use and importance, relatively few studies have been made of the factors affecting the accuracy and precision of densitometers. (2), (3), (7), (8), (10), (12) Densitometers, like other instruments, are subject to errors which fall into a few principle categories. The effect of these errors can become critical when the quality level of printing is near the borderline between acceptable and rejectable. Control of error sources is also important when information is obtained from, and transferred among different locations. Densitometers, like other instruments, are subject to errors which fall into a few principle categories. The effect of these errors can become critical when the quality level of printing is near the borderline between acceptable and rejectable. Control of error sources is also important when information is obtained from, and transferred among different locations. This paper examines common sources of errors in reflection densitometry. The results of a staggered nested designed experiment are discussed and recommendations are made for minimizing the effects of these errors.