We show that the entrance aperture of the foveal cone is about 80% of the 3 micron center-to-center spacing. Reduction in contrast caused by averaging of illumination over this aperture prompts us to predict detection with aliasing between the Nyquist limit of 60 c/deg (where contrast reduction is 63%) and 150 c/deg (where contrast is zero) when the eye's optics are bypassed by impressing interference fringes directly on the fovea.