Fit of a Sérsic profile to the r-band image of a simulated galaxy. Left panel: r-band image. Middle panel: image of the minimum-χ² model. Right panel: residual. The galaxy is taken from simulation set A, with spiral arm parameters A = 16″, B = 1, N = 10, and f_spi = 0.1 and smooth component parameters n_smo = 4, R_e = 2.52″, and m_r, smo = 17.5. The true values of the total r-band magnitude and half-light radius are m_r, tot = 17.40 and R_e = 3.06″. The parameters of the best-fit Sérsic model are reported in the middle panel.