Illustration of our surface-fitting and source-blanking algorithms. Left panel: H-band 2MASS image of UGC 4555. The galaxy itself is toward the bottom of the frame; black ellipses mark radii of 2.5, 3.5, and 6.5r₁. Second panel: same image but with neighboring sources blanked and the estimated galaxy profile subtracted. Third panel: 9th-order surface fit using our iterative scheme, which was chosen to be the “best” fit to the image. Right panel: residual image after surface subtraction. All images have the same dynamic range of 3DN, where 1DN corresponds to 20.7 mag arcsec^-2. They have been smoothed by a Gaussian with a FWHM of 9 pixels (1″/pix) to enhance low-signal structure.