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Dependence on orientation of relative UVB exposure for a cylindrical body with (top) a white integument and (bottom) a countershaded coloration. Time of the day, time of the year, geographical location match those of Fig. 3, top panel. The thickness of the melanin layer Δ was set to (top) 0 m, that is no melanin at all, and (bottom) 0·001 m for the computations. Both plots are normalized jointly to have an overall maximum irradiation of 1.
