Luminosity functions of the matched PN samples from this survey (filled circles), from C98 (top panel, green squares), and from F03 (bottom panel, cyan triangles). The error bars show the 1σ uncertainty from counting statistics. Data are binned into 0.2 mag intervals. The solid red line represents the analytical PNLF model using a distance modulus of 30.8, convolved with photometric errors. The magnitude range is driven by the magnitude limit of the C98 sample (top panel) and F03 sample (bottom panel). A zero point shift Δ = 0.3 mag relative to our sample was applied to both survey.