Schematic of the isophote map fitting procedure. Top left: Example g-band DESI-LS image of an elliptical host galaxy, with neighbouring field sources. Top right: The galaxy image sampled before mean-kernel convolution, at 24 ± 0.1 mag/arcsec². Bottom left: The image sampled after mean-kernel convolution, with the target galaxy pixels highlighted in blue, external sources in red and a fitted 24 mag/arcsec² isophote in black. The target galaxy pixels are isolated by running a connected-component labelling algorithm. Bottom right: The constructed g-band isophote map for this host galaxy, showing isophotes at every 0.2 mag/arcsec².