Completeness-corrected PNLF for the whole catalogue of M 31 PNe (black points) is shown fitted by the Ciardullo et al. (1989) analytical LF (black dotted line). The LMC (Reid & Parker 2010), SMC (Jacoby & De Marco 2002), and MW Bulge PNe (Kovacevic et al. 2011) shifted to the distance of M 31 are shown in blue, orange, and green, respectively. The region beyond the limiting magnitude of the shallowest field (Field# 33_4) is shown in grey. The grey dotted line shows the 90% completeness limit of the shallowest field.