Appendix 5—figure 2. Theoretical ways to neurally improve the optical image resolution in the fly compound eyes.

Left, neural superposition with overlapping photoreceptor receptive fields. Middle, same type photoreceptors (here R2s) in the neighboring ommatidia (∆φ ~ 4.5 ^o) collect light from neighboring visual areas, but their receptive fields (RFs) overlap, having twice as large acceptance angles, ∆ρ ~ 9.5 ^o. Right, neighboring photoreceptors in the same ommatidium collect light from neighboring visual areas with their RFs overlapping. By comparing the resulting variable photoreceptor outputs from a small visual object (0.5 ^o vertical grey bar), neural circuitry may resolve objects finer than the inter-ommatidial angle (∆φ).