Spitzer IRAC 3.6 μm image from SERVS (Mauduit et al. 2012) of the XMM-LSS field. The cyan polygon traces the footprint of the VIDEO survey (Jarvis et al. 2013). The black square region denotes the location of the CFHTLS-D1 square-degree footprint (Gwyn 2012) over which we have tested the implementation of forced photometry with The Tractor.