A measurement system has a camera with a lens and a separate sensor mounted so that their planes intersect at an object plane according to the Scheimpflug principle. In the work-up by distillation of cleavage product mixtures, the hydroxyacetone can be removed from the cleavage product mixture together with a phenol fraction from which the hydroxyacetone has to be removed. In exemplary implementation, a client device detects discontinuities at or near block boundaries, determines which discontinuities are artificial, and smooths at least those discontinuities that are determined to be artificial.