Fig. 4. (A) Left, equilateral red-green-blue colour triangle filled with the isoluminant colour shades used; middle, real colours of Campsis radicans in Figs 2, 3A-C, as perceived by a polarization-blind retina with polarization sensitivity P_R=P_G=P_B=1 and microvillar directions ß_R, ß_G, ß_B = arbitrary (number of pixels = 560x736=412160); right, relative frequency distribution of perceived colours (M_R, M_G and M_B) within the colour triangle calculated for the full rectangular picture. Note that the colours used in the white triangles at the right-hand side code the relative frequencies alone and have nothing to do with the perceived colours shown in the rectangular patterns painted by the colours of the colour triangle at the left-hand side in part A. (B-E) Polarization-induced false colours of C. radicans perceived by a polarization-sensitive retina with P_R=P_G=P_B=2, ß_R=145°, ß_G=35° and ß_B=0°, and their relative frequency distribution in the colour triangle as a function of the alignment of the eye's dorso-ventral symmetry plane (indicated by red arrows in the circular insets) measured from the vertical. Note that the isoluminant rectangular images and the isoluminant colour triangle on the left in part A give information on colour alone; intensity information is missing.

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