Using moireto Study Certain Problems of Misregister.

As part of the PIA-GATF web offset research program, a moire pattern was tried as a means to study certain problems of misregister. This was done on both the laboratory sheet fed press and production web offset presses. Preliminary trials indicated that the moire would be useful in studying and identifying the causes of local image distortion. When used with fan-out targets, the two methods are complementary since two targets measure the relative displacement of two points with no information on the area between while the moire reveals the pattern of distortion over the whole sheet. Major local distortions as revealed by the moire are obtained with changes in packing and impression. Fan-out targets showed that extreme changes in the amount of water from the first fountain on the laboratory two color press changed the size of an offset paper but did not change the size of a heavily coated seventy pound paper.