Brill and Carter [Color Res Appl (DOI:10.1002/col21777)] rekindle the question of whether brightness scaling is better approximated by a log or power function, proposing on theoretical and empirical grounds that the log function is the correct choice. This note provides a new twist to this debate in terms of a recently introduced theory of brightness and lightness perception, called gamut relativity. The theory reconciles the log and power function formulations and approximately predicts the weight/exponent values associated with these functions. The theory provides, moreover, a unified and testable approach to human performance in brightness magnitude estimation, discrimination and matching tasks. (C) 2013 Wiley Periodicals, Inc.