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ISO 2470-2 Brightness (D65 illuminant)

Standard:

ISO

Method:

ISO 2470-2

Title:

Measurement of diffuse blue reflectance factor — Part 2: Outdoor daylight conditions

Scope

ISO 2470-2 Brightness 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 illuminant 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.

Principle

A test piece is illuminated diffusely in a standard instrument and the light reflected normal to the surface is either allowed to pass through a defined optical filter and then measured by a photodetector or measured by an array of photosensitive diodes, where each diode responds to a different effective wavelength. The brightness is then determined directly from the output from the photodetector or by calculation from the photosensitive diode outputs using the appropriate weighting function.

 

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