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Standard: |
ISO |
Method: |
ISO 11476 |
Title: |
Paper and board — Determination of CIE whiteness, C/2 degrees |
ISO 11476 Whiteness specifies the procedure to be used for determining the CIE whiteness of papers and boards, in order to obtain values which correspond to the visual appearance of white papers and boards, with or without fluorescent whitening agents, when they are viewed indoors. It is based on radiance factor 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. This International Standard also specifies the procedures for the determination of CIE tint values and the fluorescent component of CIE whiteness.
In addition, it specifies a method for adjustment of the UV content to correspond to that of CIE illuminant C, since the results obtained when fluorescent whitening agents are present are dependent upon the UV content of the radiation falling upon the sample. The CIE illuminant C is taken to be representative of indoor illumination conditions because it contains a suitable proportion of UV radiation. This method is not applicable to colored papers containing fluorescent dyes. It is specific to the situation where the fluorescence occurs in the blue region of the visible spectral range.
The diffuse radiance factor of the material is determined under standardized conditions after adjustment of the instrument so that the relative UV content of the illumination corresponds to that of the CIE illuminant C, and the CIE whiteness and tint are calculated. The fluorescence component of the CIE whiteness is calculated from the difference between the diffuse radiance factor value and the 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.
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