The n-value is a factor which allows the Murray-Davies equation to be correctly solved for physical dot area or tint density. This equation becomes known as the Yule-Nielsen equation when the n-value is used.

Many variables affect the value of n; paper characteristics, screen ruling, even the equation variables themselves. The level of solid ink density may have a very significant effect on the n-value. This fact, although suspected, has not been investigated until now.

A study into this variance was undertaken in Appendix II with a method for adjusting the value of n to a standard solid ink density given in the body of the paper.

If screen ruling is held constant, the only other significant factor affecting the n-value is the light-scattering properties of the substrate. This light-scattering may be inferred through TAPPI opacity measurements. This opacity figure may then be adjusted to a sheet of "standard" caliper to discount the influence of various thicknesses.

If the measurements can be made accurate enough, a mathematical relationship between the adjusted n-value and TAPPI opacity may be discovered through regression analysis.

The attempt made in this paper may be considered unsuccessful because of the low reliability of the opacity readings and other factors. More accurate measurements may establish a better correlation.

Library of Congress Subject Headings

Paper--Printing properties; Paper--Optical properties; Photoengraving--Halftone process--Analysis

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Julius Silver


Physical copy available from RIT's Wallace Library at Z247.A765 1988


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