TAPPI Brightness is often used as a measure of the reflectance of papers. The spectral and geometric conditions for TAPPI Brightness are specified in TAPPI Method of Test T452, 'Brightness of pulp, paper and paperboard (directional reflectance at 457 nm).' The instrument specified is a directional geometry 'brightness tester.' A brightness filter is used so that the values measured by the instrument will match those on a set of opal glass and paper standards within set tolerances.
Conditions for Measurement
Instrumental: D25A with TAPPI filter
Standard Observer Function: 2 degree
Transmittance and/or Reflectance: Reflectance.
Mathematical formulas for this index do not exist. The TAPPI filter makes the required adjustment to the reflected light from which the TAPPI brightness values are output directly.
This index is typically used as a measure of the brightness of paper and related products.
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