ISO 11475 Whiteness (D65 Illuminant)

ISO 11475 Whiteness test 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, 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.

Principle

The diffuse radiance factor of the material is determined under standardized conditions after the instrument has been adjusted so that a reference standard has the same CIE whiteness value as it would have under CIE standard D65 Illumination, and the CIE whiteness value and the tint value are calculated. The fluorescence component of the whiteness is calculated from the difference between this whiteness value and the whiteness value obtained when the fluorescence emission from the material is eliminated, for instance by the introduction into the light beams of a sharp cut-off UV-absorbing filter.