Spectral Reflectance Modification of Neugebauer Equations

This paper presents a spectral reflectance modification of Neugebauer equations which is based on the elementary optical reflectance of the eight primary printing colors. These modified Neugebauer equations include all of the optical effects of color printing: absorption of ink layers, first surface reflectance, multiple internal reflectance and scattering. Since the spectral reflectance is the most fundamental property of printing color, using the spectral reflectance instead of optical density is the advantage of this method. The spectral reflectance can be transferred to any other values of previous color printing theories. The modified Neugebauer equations are more accurate of wavelength analysis for printing color prediction and dot area ratios prediction. This paper presents equations derived directly from modified Neugebauer equations both or printing color prediction and for dot area ratio prediction. The equivalent spectral reflectance (ESR) is introduced to represent the optical effect of ink layer only. The reflectance of overlay ink color is equal to the product of ESR's of its components. The application of ESR can theoretically solve the disagreement between the Neugebauer equations and measurable results.