Three- and four-dimensional signals can be replaced by two-dimensional sequences of sectional images if sampling in one or two dimensions is practicable. The convolution of such sequences yields, under certain conditions, the sequence representation of the three- or four-dimensional convolution result. Thus higher-dimensional filter operations can be performed by means of two-dimensional filter methods, e.g. coherent optics, whose parallel computing power matches the usually high space-bandwidth products (SBP) of such sequences. The possible throughput of coherent-optical setups is estimated. Experimental results for three-dimensional filter operations are shown.