Unfortunately, large maximum errors in the approximation of the sedimentation boundaries are an unavoidable consequence of coarse radial discretization. In fact, the errors in the sedimentation boundaries shown in Fig. 2 are similar in magnitude to those of Figs. 8b and 9b in Cao and Demeler (2005) . Remarkably, none of the examples provided by Cao and Demeler (2005) led to maximum errors below 0.001, and in most cases it was a factor of 10 or more above this mark. Such errors can be expected to significantly impact the result of the size-and-shape distribution analysis.