Research on Optimization of Colour Tone Value (CTV) Formula Based on CIE XYZ

The Colour Tone Value (CTV) is defined as a new measure of the printing tone value in the second edition of the ISO/TS 10128, and the calculation formula is specified in ISO 20654. However, in 4-colour process printing, the ∆CTV target curve varies greatly compared to the ∆TV target curve and some values may be negative, which is not convenient in practical applications. In this study, the optimization of Colour Tone Value (CTV) formula based on CIE XYZ is proposed. It is found that the results are more consistent with conventional expectations for printing tone values, and no negative values occur when the new formula is used to calculate the colour tone values of typical offset printing condition datasets. The structure of this formula is basically the same as the original formula, and it can be widely applied to calculate the colour tone values of all colours.