Fig. 5. Absorption spectra for different states of light adaptation, given by the pupil distance, h (Fig. 4A, inset). At all wavelengths, a uniform light source with radiance 1 W sr^-1 µm^-2 illuminates a 25 µm facet lens (F=2.2) with, in its focal plane, the distal end of a rhabdomere with diameter 2.0 µm. (A) Pure rhodopsin (R). Pupil closure causes an overall reduced absorption spectrum. (B) One sensitizing pigment molecule per rhodopsin (R+S). A distinct UV peak remains upon pupil closure. (C) Two sensitizing pigment molecules per rhodopsin (R+2S). The UV peak is only slightly higher than that in B due to self-screening.