Illustration of the morphology and radial structure of typical Milky Way-sized LTGs in the local Universe. Left: SDSS true-color thumbnails of galaxies from the sample analyzed by Breda & Papaderos (2018) with their inner reddish zone and surrounding blue star-forming disk. From top left to bottom-right: NGC 0309, NGC 0234, NGC 3811, NGC 0873, UGC 4256, NGC 2543, NGC 0171, and UGC 4308. Right: schematic representation of the bulge (shaded red area) and the disk (light blue) in a face-on late-type galaxy. The surface brightness profile of the disk results from the projection of an exponential stellar surface density Σ_⋆ (dark blue), whereby the ℳ/ℒ ratio in the inner SF-quenched zone of the disk (iD) within the bulge radius R_B is higher than that in the outer (R^⋆ > R_B) star-forming zone of the disk (oD). A consequence of this is that the central surface brightness μ₀ of the disk is fainter by δμ₀ mag than the value implied by inward extrapolation of the exponential fit to the outer disk (dashed line) and that the standard bulge-disk decomposition overestimates the integrated magnitude of the disk within R_B by δ_io (mag). This in turn entails an oversubtraction of the disk, thus a systematic underestimation of the luminosity of the bulge.