3D grid of recovery rates for the J0430 filter shown as an example. Left and right panels respectively show the projections of recovery rates in the Lyα flux vs. r plane and Lyα flux vs. g​ − ​r plane. We note that the recovery rates show noisy values at r​ <  ​17 and g​ − ​r​ <  ​ − 1.25 due to the low number of sources in these magnitude and colour bins. Nevertheless, these regions of the 3D parameter space are excluded from the LF computation by the purity weight (Sect. 4.3).