Densitometric and Planimetric Measurement Techniques for Newspaper Printing

Two types of measurement technologies are used for process control in newspaper printing, namely densitometric and planimetric technologies. Densitometric measurements are done with densitometers or spectrophotometers, while planimetric measurements are typically done with CCD image sensor-based instruments called dot meters. Although these two technologies are fundamentally different, they are often used interchangeably in print calibration and process control. In this paper we investigate the statistical relationship between densitometric and planimetric measurements on newspaper print. The aim of our project was to investigate whether it was possible to estimate halftone values measured by a densitometer, from the halftone values measured by different dot meters. The applied model is based on regression analysis using second order polynomials. The results are given as estimates of the polynomial parameters, i.e. the polynomials give the relation between halftone measurements with one of the dot meters and halftone measurements with the densitometer. Our statistical analysis showed that due to the large uncertainty of the estimated parameters, the model does not accurately describe the relationship between the two measurement technologies. This can be explained in part by the poor repeatability performance for dot meters applied to newspaper print. Moreover the measurement results also have shown significant variations within the three dot meters used in this experiment. Factors affecting the repeatability and determining the performance of the model are considered and discussed in this work.