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This part of ISO 2470 specifies a method for measuring the D65 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, particularly those exhibiting fluorescence which promotes the appearance of whiteness. 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 standard illuminant D65 using a fluorescent reference standard. The source employed in this part of ISO 2470 excites almost twice as much fluorescence as the illuminant in ISO 2470-1. Consequently, this part of ISO 2470 is better suited for measuring the fluorescent contribution to the brightness. However, D65 brightness should not be confused with ISO brightness which closely approximates the brightness of papers viewed under indoor conditions. NOTE The property called ISO brightness is measured with an instrument adjusted to a much lower UV content than that specified in this part of ISO 2470. The measurement of ISO brightness is described in ISO 2470-1.