Measured S/N (enclosed flux) as a function of aperture radius for a set of sources given in upper (lower panel). For the upper panel, the mean of these curves is shown as a black solid line, while the maximum S/N of each source is indicated as per the colour bar. We note that this is consistent with the theoretical expectation from Naylor (1998). Lower panel shows the enclosed flux for a given aperture radius. We note the majority of the flux is enclosed by an aperture radius of ~2.5 × FWHM.