I-band-derived sharpness versus I₀ magnitudes of the mock stars recovered in both I and V filters (see also Fig. 5) as described in Sect. 3.4. Left panel: mock star sharpnesses against I₀ band magnitude, and Right panel: zoomed version of the same plane. The great majority of the mock stars in the magnitude range 24 <I₀ < 25 lie in the region −0.10 < sharpness < 0.03, which we use to select our point sources.