Details:
Summary:
Control of color during printing production involves two stages: (a) producing the image colors achievable by making optimum settings of press controls and (b) maintaining constant image colors throughout the run. Acquiring and maintaining specified ink densities for color bars outside the image area to achieve these conditions is usually not sufficient. Almost invariably, the operator must exercise visual color comparison skills and make additional adjustments accordingly throughout the production process to assure satisfactory output product color. This stage in the process is subjective and often exhibits a wide range of variation. Acquiring and maintaining specified ink densities for color bars outside the image area to achieve these conditions is usually not sufficient. Almost invariably, the operator must exercise visual color comparison skills and make additional adjustments accordingly throughout the production process to assure satisfactory output product color. This stage in the process is subjective and often exhibits a wide range of variation. We at Hunter Lab have developed and reported previously a manually positioned system using direct measurement of color within selected areas of the image to provide: objectivity and consistency in the actions taken, and a useful record for analysis and characterization of the process performance regarding color. This paper described the PICCS 4000 system which now employs a solid state full range spectrophotometer with preprogrammed computer controlled positioning of up to 32 readings over the sheet, in addition to features previously reported. These combine to provide an immediate indication of color errors detected and the objective ink adjustments needed to maintain target color. Indicated ink feed adjustments can be statistically based for maintaining color periodically sampled during an extended run, or individual readings can be used in achieving target color during makeready. Reports of process performance derived from statistical analysis (SPC) are prepared directly from the data collected.