Patent ID: 7847264

Claim:
A method for measuring the colour of samples printed on substrates containing brightener, the method comprising the steps of: a) determining the total spectral reflection factor R i (λ) of a sample printed on a substrate; and b) calculating values characterising the colour of the sample using the total spectral reflection factor R i (λ); wherein the total spectral reflection factor R i (λ) is obtained as the sum of a first spectral proportion R UVblock (λ) and a spectral correction factor R iUVpass (λ); wherein the first spectral proportion R UVblock (λ) represents the spectral reflection factor of the sample as determined during illumination with essentially UV-free light; wherein the spectral correction factor R iUVpass (λ) represents the proportion of the total spectral reflection factor R i (λ) of the sample which is determined by the effect of the fluorescence of the brightener only; wherein the spectral correction factor R iUVpass (λ) is calculated from given or measured characterisation data R iWUVpass (λ), R WUVblock (λ) of the substrate and/or given or measured characterisation data of the brightener contained in the substrate and from a given spectrum of a freely selectable, virtual type of lighting E i (λ) from the first spectral proportion R UVblock (λ); and wherein a relative spectral weighting of the spectrum of the selected type of lighting E i (λ) is used to calculate the spectral correction factor R iUVpass (λ).