This International Standard specifies the procedure to be used for determining the whiteness of papers and boards. The values obtained correspond to the visual appearance of white papers and boards with or without fluorescent whitening agents when they are viewed under the CIE D65 daylight illuminant. It is based on reflectance data obtained over the full visible spectral range (VIS) in contrast to the measurement of ISO brightness which is limited to the blue region of VIS. In addition, it specifies a method for adjustment of the UV-content to correspond to the D65 daylight illuminant[8] [9], insofar as results obtained when fluorescent whitening agents are present are dependent upon the UV-content of the radiation falling upon the sample. It is specific for the measurement of fluorescence in the blue region of the spectrum. This method is not applicable to coloured papers containing fluorescent dyes. This International Standard should be read in conjunction with ISO 2469. NOTE A related standard, ISO 11476[4], specifying the procedure for obtaining values corresponding to the appearance of these products under indoor illumination, has also been published.