Erratum to the paper J. Luo, K. Ying. P. He and J. Bai, Properties of Savitzky-Golay digital differentiators, Digital Signal Processing 15 (2005), 122-136. Observed by Tom Koornwinder, February 8, 2011. On p.128, in the first line below Fig. 4, "higher" should be replaced by "lower".