Conversion of Solid Ink Density and Dot Gain Specifications into Colorimetric Specifications

Traditionally, printing standards and tolerances are defined in terms of solid density and dot gain. These standards have served the purpose quite well, as long as densitometers are used for quality control. The recent availability of reasonably priced, portable spectrophotometers and colorimeters gives the printing industry the option of using colorimetric methods for quality control. This makes it possible to use a single 3-color gray patch for controlling a printing press. Now the question arises, what color tolerances should be used in terms of CIELAB? Such tolerances can of course be obtained by simply observing a pressrun that is in statistical control. However, it would also be interesting to know how the old dot gain and solid density tolerances would translate to colorimetric units. This paper describes such a conversion. Such tolerances can of course be obtained by simply observing a pressrun that is in statistical control. However, it would also be interesting to know how the old dot gain and solid density tolerances would translate to colorimetric units. This paper describes such a conversion. Because it would be impossible to accurately print all possible combinations of high and low values of solid density and dot gain tolerances for all colors, a mathematical model, utilizing n-modified, spectral Neugebauer equations, is used to do the conversion. The results are plotted in 3 dimensional CIELAB space.