Paper and board -- Determination of colour by diffuse reflectance -- Part 3: Indoor illumination conditions (D50/2 degrees)
ISO 5631-3:2008 specifies a method for measuring the colour of paper and board by the diffuse reflectance method with the elimination of specular gloss.
ISO 5631-3:2008 is primarily intended for measuring the colour of paper and board to be used in the graphic arts industry where that industry specifies the measurement of colour under D50/2° conditions in accordance with ISO 13655.
The method may be used to determine the colour of papers or boards that contain fluorescent whitening agents, provided the UV content of the illumination on the test piece has been adjusted to conform to that in the CIE illuminant C, using a fluorescent reference standard provided by an authorized laboratory, as described in ISO 2470-1.
ISO 5631-3:2008 is not applicable to coloured papers or boards that incorporate fluorescent dyes or pigments.