ISO 2471:2008规定了通过漫反射测定纸张不透明度（纸张背衬）的方法。 它可用于测定含有荧光增白剂的纸张或纸板的不透明度，前提是已使用ISO/TC 6授权实验室提供的荧光参考标准（如ISO 2470-1所述）将入射到试样上的辐射的UV含量调整为符合CIE光源C中的UV含量。 ISO 2471:2008不适用于含有荧光染料或颜料的彩色纸或纸板。

ISO 2471:2008 specifies a method for the determination of the opacity (paper backing) of paper by diffuse reflectance. It can be used to determine the opacity of papers or boards which contain fluorescent whitening agents, provided the UV content of the radiation incident on the test piece has been adjusted to conform to that in the CIE illuminant C using a fluorescent reference standard provided by an ISO/TC 6 Authorized Laboratory as described in ISO 2470-1. ISO 2471:2008 is not applicable to coloured papers or boards which incorporate fluorescent dyes or pigments.