Influence of the number of SOM clusters on the resulting tomographic bin redshifts and the recovered photometric misrepresentation for the MICE2 simulation dataset. We show three statistics as a function of cluster number. Panel a: change in the tomographic mean estimate. Panel b: change in the representation of the spectroscopic catalogue. Panel c: change in the tomographic mean bias. The inset of panel a shows the distribution of PDFs estimated for the third tomographic bin with 10 000 and 2500 clusters. The black curve shows the distribution of the unweighted spec-z sample. Panel a demonstrates that, with increasing cluster number, our estimate of the tomographic redshift distribution mean changes significantly. Middle panel: demonstrates why: with more clusters there is more fragmentation of the photometric data and significant decreases in the spectroscopic representation, such that the “gold” sample decreases in size. However, crucially, panel c demonstrates that the loss of representation does not change the low level of bias in the recovered redshift distribution.