New Narrow-Band Color Responses for Pressroom Densitometry.

The major sources of reproducibility problems in densitometers, when measuring process inks, are variations in the spectral characteristics of light sources, color filters, light sensors, and infrared blocking filters. The use of narrow-band filters (20 nm) vs. wide-band filters (50-75 nm) reduces these variations. A computer investigation using SWOP inks, was conducted to evaluate the improvement in reproducibility resulting from the use of narrow-band filters. It is shown that the total instrument reproducibility and the reproducibility attributed to the individual optical components is substantially enhanced by narrow-band filters for the blue and green regions of the spectrum. For the red region, the total reproducibility resulting from variations in the components is very good for both narrow- and wide-band filters. A second investigation was conducted to identify the optimum wave-lengths for the narrow-band responses.