Color Control by Image Color Measurement (A Progress Report)

In the two years since our first announcement of having achieved color control by direct image color measurement, we have learned that sheetfed offset presses generally show random variations in color over a visually detectable range determined by process variables. Visually significant trends of change can be identified quickly and reliably, using direct image color measurement and applying statistical process control methods. Indicated corrective actions are effective and, when performed in a timely manner, they provide superior color control to purely visual or densitometric methods. The records produced are suitable for certification of conformity to color uniformity requirements, and they provide the basis for statistical quality control analysis. The tools are now available to establish standards for color uniformity within a run and for visually acceptable limits to differences between a sample and its target color.