ISO brightness : A more complete definition

Over the years, several methods for measuring brightness have been developed and used as standards. New instrumentation and an increase in the use of fluorescent whitening agents added to the difficulty of developing universally accepted standards. One variable has simply been the quality of light. The paper, board and pulps' optical properties working group of the International Organization for Standardization (ISO) recently accepted CIE-illuminant C within the revised standard for determining ISO brightness, to be published as the new Standard ISO 2470:1999. This article explains why the illuminant has been a concern and covers the provisions of the revised standard. As mills and laboratories adapt their testing routines to the new requirements, it will serve as a more uniform standard for measurement.