Nocturnal Vision: Bees in the Dark Michael F Land  Current Biology  Volume 14, Issue 15, Pages R615-R616 (August 2004) DOI: 10.1016/j.cub.2004.07.043

Figure 1 Ways of increasing an eye's sensitivity. (A) Typical diurnal eye with a small lens. D, aperture diameter; f, focal length; d, receptor diameter; Δρ, receptor acceptance angle=d/f. (B) Increase in size of lens aperture. (C) Increasing Δρ, which coarsens resolution. (D) To improve on (B) without loss of resolution requires an increase in all dimensions, and a bigger eye. Current Biology 2004 14, R615-R616DOI: (10.1016/j.cub.2004.07.043)