Fig. 8. Removing the ß-peak from the GFRKD visual pigment template optimization allows for a much better fit in both eye types (gray lines; correlations=0.984, lower eye; 0.968, upper eye). With invertebrate levels of self-screening (k=0.0067; A,B, black lines) the curves are indistinguishable from the no screening case (A,B, gray lines). However, these fits can be improved further by adding vertebrate level self-screening to the optimization (C,D, black lines); where k= 0.035 µm^-1, and l=50 µm for the lower eye photoreceptors and l=35 µm for the upper eye photoreceptors. Here, self-screening has the effect of broadening the absorption curve. For the lower eye (C) the half-width increases to 112.1 nm with the addition of screening, compared to 82.0 nm without screening. For the upper eye (D) the half-width increases to 111.2 nm from 82.8 nm. Correspondingly the correlation values increase to 0.991 and 0.980 for the lower and upper eyes, respectively.