WL FoM as a function of exposure time by pointing for a primary mirror diameter of 1.2 m, 1.5 m, and 1.8 m with a pixel scale varying in order to have the same optimal effective PSF sampling using a 8-filter set with a resolution of ℛ = 3.2. The FOV is fixed at 0.5 deg², which implies that the number of pixels decrease when the pixel scale is larger. The dashed curves represent the number of galaxies  ×1e7 for all configurations.