ISO 2470-1:2016 specifies a method for measuring the diffuse blue reflectance factor (ISO brightness) of pulps, papers and boards.

ISO 2470-1:2016 is limited in its scope to white and near-white pulps, papers and boards. The measurement can only be made in an instrument in which the ultraviolet energy level of the illumination has been adjusted to correspond to the CIE illuminant C[6] using a fluorescent reference standard. The CIE illuminant C is taken to be representative of indoor daylight conditions because it contains a suitable proportion of UV radiation.[9]