Appendix 4—figure 1. Classic theories of compound eye optics.

(A) It is assumed that the minimum angle a compound eye can resolve is its interommatidial angle, ∆φ. (B) The effective interommatidial angle of an eye with a hexagonal layout, ∆φ_e, is smaller than its actual interommatidial angle, ∆φ. Equation A4.1 gives their geometrical relation. (C) Light diffraction at the ommatidial lens and the rhabdomere tip strongly affects the optical quality of the image pixel that a photoreceptor samples. D = ommatidial lens diameter; d = rhabdomere tip diameter; f = focal length; λ = wavelength. Redrawn from (Land, 1997).