Errors In Color Calculations Due to Fluorescence When Using the Neugebauer Equations.

When tristimulus values of colors formed by halftone combinations are calculated by the Neugebauer equations, it is necessary to measure certain colors used as constants in these equations. If any fluorescence is present either in the printing inks or the paper substrates, as is usually the case, these measurements should be made by illumination with white light as opposed to monochromatic or filtered illumination. If this is not done, a mean color error as large as 12-15 units may occur with fluorescent inks, with individual errors up to 36 units. For the graphic arts, the recommended standard white light illumination is D50000. It was found that a single glass filter in conjunction with a xenon arc lamp can produce an acceptable D50000 source.