A New Ink-Trap Formula For Newsprint

When printing color on newsprint, the ink-trap calculations often produce numbers that are much lower than expected. Color overprints, however, look better than the numbers would indicate. An analysis of the GATF ink-trap formula which accounts for the lower trap values and provides a modified formula based on realistic assumptions about reflection densities is presented. The standard GATF ink-trap calculation currently in use is examined. A common definition of ink-trap is given. The new equation is used to relate the thickness of an ink-layer to its intrinsic density. The intrinsic density is computed both on paper and on the first ink. A new ink-trap formula for newsprint is then derived.