Recovery of Einstein radius (top), total image-plane-lensed flux (middle), and magnification (bottom) for simulated lenses fitted with sl_fit in fast-modeling mode. We distinguish the case of ground-based CFHTLS-wide-like g-band observations (left) and the case of HST WFPC2/F606W observations (right). In both cases, the deflector light has been subtracted with galfit before modeling the residuals. In this case, oversubtracted background emission or undersubtraction or inaccurate modeling of the deflector produces larger errors and biases on fitted important parameters of the lens models. In each panel, the red error bars show the binned median values for guidance.