Recovery of characteristic radii across size-flux space. Each panel shows the map of the average absolute difference (in arcsec) between the measured and reference values of a given radius - R₂₀ (a), R₅₀ (b), R₈₀ (c), R_P (d) in the apparent magnitude vs. R_e. The dashed red lines define the approximate average surface brightness when assuming a circular (q = 1) Sérsic profile. The hatched region above the 〈μ_2Re〉 denotes the adopted threshold in this work. Galaxies with a surface brightness smaller than 26 mag s⁻² can yield unreliable shape parameters and characteristic radii. In particular, the hatched region overlaps significantly with the region in which the error in R_P exceeds 1 arcsec (∼4 pixels). This effect is more visible in R_P due to it having the outermost radii in comparison to the others, and thus being more prone to background contamination.