<title>Using improved spectral Neugebauer equations to construct color LUT</title>

Abstract

Neugebauer equations are basic formulas to calculate colors of print. But there is obvious deviation between calculation and measurement due to the complexity of printing process. Some methods of improving its precision are reviewed and an improved spectral Neugebauer method is proposed in this paper, which is based on spectral dot gain correction. There are two kinds of dot gains, one is mechanical dot gain and another is optical dot gain. Both of them are the key factors affecting calculated results of Neugebauer equations. It is found that the optical dot gain is a function of wavelength, so that the correction should also be a function of wavelength. After measuring spectral curves of paper substrate, primaries and their mixture, spectral dot gain can be calculated and Neugebauer equations can be corrected with it. The forwards color lookup table is got directly from the improved Neugebauer equations, the reverse color lookup table is calculated by interpolation from forwards color lookup table (LUT).