 Retinal receptor pitch and angular sampling

For a roughly square array of retinal receptors with surface density $n$ and image distance $f$, the pitch is $s\simeq n^{-1/2}$ and its angular scale is $s/f$. Reconstructing a periodic spatial pattern requires at least two samples per period under the Nyquist–Shannon sampling theorem. Receptor density alone does not specify lattice geometry, contrast sensitivity or a unique point-source resolution criterion.