This part of ISO 2470 specifies a method for measuring the diffuse blue reflectance factor (ISO brightness) of pulps, papers and boards.
This part of ISO 2470 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]
NOTE The property called D65 brightness is measured with an instrument adjusted to correspond with CIE standard illuminant D65,[4] which has a much higher UV content than that specified in this part of ISO 2470. The measurement of D65 brightness is described in ISO 2470-2.[2]