Ratios between measured extents as function of luminosity. The shaded area is the one-sigma uncertainty of the ratio measured from the (u,v)-plane. The (u,v)-range used for calculating the extent of R_{CO,5 × Lcur} is shown in the upper left of each panel. The number in the upper right corner of each panel indicate how large a fraction of the ratios measured from the (u,v)-plane are within 20 % of the ratios measured from the abundance profiles.