Evolution of the normalized ray-traced flux at ν = 210 GHz with increasing field of view for three values of screen resolution, N = 51 (red), N = 101 (blue), and N = 201 (green). The optimal value of field of view for a given resolution is the beginning of the plateau-phase of the curve (see text for details). The plateaus of the N = 101 and N = 201 curves are identical to within 0.1%, which shows that N = 101 is the smallest resolution that ensures accurate flux values, associated to F = 3 mas.