We present an analytical method to analyze, from a theoretical point of view, the influence of color-matching functions on the perception of luminance thresholds. We show that the thresholds depend on the spectral responsivities of each observer. We also analyze the influence of luminance level on the thresholds: a strong inter-observer variability is found at low or moderate luminance levels (0.02 < Y < 1 ft-L) whereas at high intensities (1 < Y < 7 ft-L) the thresholds are observer-independent. (C) 2006 Wiley Periodicals, Inc.